Open access peer-reviewed chapter

Paternal Effects on Embryonic, Fetal and Offspring Health: The Role of Epigenetics in the ICSI and ROSI Era

Written By

Jan Tesarik

Submitted: 06 December 2018 Reviewed: 15 July 2019 Published: 23 October 2019

DOI: 10.5772/intechopen.88589

From the Edited Volume

Innovations In Assisted Reproduction Technology

Edited by Nidhi Sharma, Sudakshina Chakrabarti, Yona Barak and Adrian Ellenbogen

Chapter metrics overview

791 Chapter Downloads

View Full Metrics

Abstract

Paternal effects on the developmental potential of human embryos have been studied since the early 1990s, particularly with respect to newly emerging assisted reproduction technologies. Both genetic and epigenetic paternal effects can influence postfertilization development and cause implantation failure or miscarriage. However, it is only over the last few years that issues related to paternal effects associated with different assisted reproduction techniques on the health status of newborn and adult progeny have been focused. At the same time, new findings point out different, yet unexplored, areas of research into the potentially responsible factors, including the activity of the sperm-derived oocyte-activating factor and the oocyte signaling pathways mediating its action, the methylation status of both imprinted and non-imprinted genes, correct replacement of sperm nuclear protamines with oocyte-derived histones, the histone acetylation status, and the function of sperm-borne small RNAs. It is increasingly important to know how these developmentally important epigenetic regulators can be altered in the context of the current micromanipulation-assisted fertilization techniques, intracytoplasmic sperm injection (ICSI) and round spermatid injection (ROSI). Last but not least, transgenerational transmission of acquired, environmentally conditioned disorders from fathers to offspring is a newly emerging issue which warrants further research.

Keywords

  • paternal effects
  • embryonic health
  • fetal health
  • offspring health
  • epigenetics
  • ICSI
  • ROSI
  • assisted reproduction
  • epigenetic inheritance

1. Introduction

There are two types of paternal factors involved in problems of embryonic, fetal and offspring health: the genetic ones and the epigenetic ones. The terms “hard” and “soft” inheritance, first introduced in 1980 [1], are increasingly used to refer to the genetic and epigenetic inheritance, respectively [2, 3]. These terms reflect very nicely the nature of the two kinds of inheritance. The genetic inheritance, the hard one, is based on transmission of DNA sequences, and it is this type of inheritance which has been the main subject of human genetic studies for the past 60 years. On the other hand, a number of studies carried out over the past 20 years have revealed that phenotypes are affected by more complex layers of information besides DNA sequences. These factors, interposed between the DNA sequence of a gene and its phenotypic expression, are termed epigenetic marks and can be modified by environmental exposures [4].

This chapter reviews the current knowledge about the factors affecting epigenetic marks in human gametes and embryos and about the ways how improper function of the male gametes during the process of fertilization can influence further embryonic and fetal development, with particular attention to possible adverse epigenetic effects related to the new micromanipulation-assisted fertilization technologies, intracytoplasmic sperm injection (ICSI) and round spermatid injection (ROSI).

Advertisement

2. Hard and soft hereditary elements

Hard hereditary elements are stable DNA sequences constituting specific genes that can only be modified by mutations or deletions. The system of soft hereditary elements is made up by a variety of molecules (epigenetic factors) that interact with each other and determine if, and to what extent, individual genes will be expressed at any given time of life. Early studies into epigenetic regulations in mammals largely focused on two constitutive events: genomic imprinting [5, 6] and X chromosome inactivation [7, 8]. However, later studies have pointed out that epigenetic regulation is a much more ample phenomenon than thought previously, involving a number of both imprinted and non-imprinted genes, and their role is particularly important in developmental processes, such as embryogenesis and organogenesis [9].

DNA methylation at the 5′ position of cytosin in CpG dinucleotides [2, 10] and histone acetylation are the two most widely known processes involved in epigenetic regulations. However, more recent studies have revealed other players in these complex processes, especially non-coding RNAs (siRNAs, microRNAs, and piRNAs) [11, 12, 13, 14, 15, 16, 17, 18], some of which have been detected in the germline [14, 15, 17, 18], as well as factors regulating higher-level organization of chromatin [19, 20]. Some of these elements can be modified by environmental factors leading to alternate gene expression [18, 19, 20].

Advertisement

3. Gamete and embryo epigenetics

In spite of the ample knowledge about epigenetic mechanisms involved in gene expression control during the early embryogenesis fetal development and adult life [9], the environmental epigenetic inheritance through gametes was initially thought impossible because of the belief that all epigenetic marks, including DNA methylation, histone acetylation status and small RNAs, are completely erased and subsequently reset during germline reprogramming [21]. In mammals, these events take place both in the germline and in zygote immediately after fertilization [21, 22]. However, it is now known that this reset is not complete, and some parental imprinted loci can resist the global demethylation after fertilization, owing to the action of different mechanisms [23, 24, 25, 26]. These findings explain previous observations on transgenerational transmission of environmentally conditioned disorders. For instance, the incidence of effects of parental ionizing irradiation on genomic instability in the offspring is too high to be explained by radiation-induced mutations which occur at a substantially lower rate [27]. Epigenetic inheritance through gametes can also explain transgenerational transmission of obesity [28, 29], diabetes [30, 31], and some types of cancer [32, 33].

All these data converge to suggest that epigenetic marks carried by the fertilizing spermatozoon are important for a variety of physiological and pathological processes that can affect offspring throughout life.

Advertisement

4. Potential sources of paternal epigenetic issues

It has been known since the early 2000 that human embryonic development is subject to paternal effects that can affect not only the early postfertilization events but also later phases of preimplantation and postimplantaion development [34, 35, 36]. Two types of paternal effects were distinguished: the early paternal effect and the late paternal effect [35]. The early paternal effect was reflected by an impairment of postfertilization development as early as the 1-cell zygote stage and subsequently was often associated with irregular cleavage divisions and blastomere fragmentation [34]. The late paternal effect was not detectable during the early cleavage stages, but became manifest after the 8-cell stage [35, 36]. Unlike the early paternal effect, the late paternal effect was often, though not always, associated with abnormally increased levels of DNA fragmentation in the father’s sperm [35]. Both types of paternal effect reduced the chance of pregnancy [36].

In view of more recent data about sperm epigenetics, the meaning of these early observations can now be extended and reinterpreted. Since both the early and the late paternal effect were evaluated only in patients treated by intracytoplasmic sperm injection (ICSI), facilitating fertilization with spermatozoa carrying different morphological and functional abnormalities, which would not be capable of fertilizing oocytes by their proper means, the analysis of the resulting embryos can yield valuable information about the impact of sperm abnormalities and immaturity on fertilization and early development.

4.1 Fertilization with abnormal spermatozoa

ICSI has made it possible to achieve fertilization, embryonic and fetal development and childbirth by using spermatozoa with severe morphological and functional abnormalities. However, these abnormalities cannot be blamed for most of the negative paternal effects observed in ICSI-derived embryos. In fact, data have shown that fertilization with spermatozoa from certain individuals consistently leads to the formation of embryos with developmental abnormalities detectable as early as the 1-cell zygote stage [34]. Interestingly, these abnormalities almost always included abnormal pattern of the formation of nucleolar precursor bodies (NPBs) in the zygote pronuclei [34], as characterized previously [37]. The process of NPB assembly in human zygotes requires an early onset of RNA synthesis activity in the adjacent chromatin regions [38, 39]. The nature of the RNA molecules synthesized at this stage is unknown, but they are likely to be non-coding ones, since the first signs of embryonic gene expression can only be detected between the 4-cell and the 8-cell stage of the human preimplantation development [40, 41, 42]. These non-coding RNA species may be involved in the early epigenetic events that condition further embryonic development. Interestingly, the assembly of NPBs and the accompanying pronuclear RNA synthesis coincide with the assembly of microtubule organizing centers in human zygotes [43], and abnormalities of NPB assembly are associated with abnormal development of human preimplantation embryos [37, 44] and an increased risk of embryo aneuploidy [45].

Some conditions potentially responsible for sperm epigenetic abnormalities, such as advanced paternal age [46], tobacco smoking [47], and various lifestyle factors including dietary habits, physical activity or alcohol consumption [48], have been pointed out. However, a more comprehensive analysis of factors involved in these phenomena remains a big challenge for future research.

4.2 Fertilization with immature male germ cells

The final stage of sperm maturation is achieved during sperm passage through the epididymis. However, spermatozoa recovered directly from the testis [49, 50] and even round spermatids [51, 52, 53, 54, 55] are able to fertilize human oocytes and generate normal offspring when incorporated into oocytes via ICSI and ROSI, respectively. Moreover, live offspring was born in mice after fertilization with secondary spermatocytes [56], and in humans after fertilization with round spermatids developed in vitro from germ cells of men with spermatogenic arrest at the primary spermatocyte stage [57, 58].

Recent reports on the postnatal development of 108 babies born after fertilization of oocytes by round spermatid injection (ROSI), 90 of them in Japan and 18 in Spain [59], did not show any significant differences as compared with naturally conceived babies in either physical or cognitive development during the first 2 years after birth, and none of them developed any of the syndromes associated with genomic imprinting defects [59]. Thus, the use of immature male germ cells for fertilization, in spite of the still relatively low success rates, does not appear to be associated with an increased risk of epigenetic abnormalities in the offspring.

4.3 Disorders of paternally induced oocyte activation

As discussed in the previous sections, human embryonic development appears to be particularly sensitive to epigenetic events taking place during an early phase of the fertilization process, referred to as oocyte activation. Oocyte activation has been extensively studied since the mid-1990s, especially in relation with the new technologies. Both ICSI and ROSI avoid the initial contact between the surfaces of the fertilizing spermatozoon and the oocyte preceding their fusion during natural fertilization. Yet, this contact activates a series of signal transduction events that participate in physiological oocyte activation [60, 61].

These early signal transduction events are obviously by-passed when oocytes are fertilized by ICSI. This shortcut, however, does not prevent fertilization in most mammalian species. In fact, sperm-induced oocyte activation is driven by repeated rises of free cytosolic Ca2+ ions, referred to as calcium oscillations, mediated by periodic release and uptake of calcium by two types of calcium stores (basically endoplasmic reticulum), one opened by inositol trisphosphate (IP3) and the other by the very increase in free cytosolic calcium in its vicinity [62, 63]. In order to sustain the periodic calcium oscillations, the oocyte’s calcium stores have to be sensitized by a soluble factor released from the fertilizing spermatozoon, initially called “oscillin” and later identified as a special form of phospholipase C (PLC) referred to as PLCζ [64]. Even in the absence of the initial contact between the sperm and oocyte surfaces, the release of PLCζ from the injected spermatozoon to the oocyte cytoplasm, together with an early extracellular calcium influx produced by the ICSI procedure itself, is sufficient to sustain calcium oscillations needed for proper oocyte activation [65]. However, the temporal pattern of the oscillations after ICSI (Figure 1) is slightly different from that following sperm-oocyte fusion (Figure 2). The release of PLCζ from the spermatozoon to the oocyte cytoplasm marks the spatial pattern of the first calcium rise, which propagates in a wave-like manner from the sperm position site across the oocyte (Figure 3).

Figure 1.

Oscillations of free cytosolic Ca2+ concentration induced by sperm-oocyte fusion, recorded by confocal microscopy in a living human oocyte loaded with fluorescent calcium indicator Fluo-3 as described [65].

Figure 2.

Oscillations of free cytosolic Ca2+ concentration after ICSI (arrow), recorded by confocal microscopy in a living human oocyte loaded with fluorescent calcium indicator Fluo-3 as described [65].

Figure 3.

Spatial propagation of the first sperm-induced increase in free cytosolic Ca2+ concentration, recorded by confocal microscopy in a living human oocyte loaded with fluorescent calcium indicator Fluo-3 as described [65].

In spite of the fact that the slight difference in the temporal pattern of the first sperm-induced calcium rise does not appear to have any impact on zygote and embryo development, the frequency and duration of the ongoing calcium rises have been shown to affect embryo development in different mammalian species [66, 67, 68] including the human [69]. Recent findings have pointed out the possibility that inherent abnormalities of the sperm-born PLCζ, but also in the oocyte response mechanisms, including steps downstream of the calcium releasing machinery, may influence mitotic divisions and gene expression during subsequent development and have to be considered an additional epigenetic risk factors to be taken into consideration in relation with the current-assisted fertilization technologies [70].

Advertisement

5. Current clinical experience

Several studies have suggested that both IVF and ICSI may increase the risk of certain types of birth defects in general [71, 72, 73] and heart defects in particular [74, 75]. However, there does not appear to exist a significant difference between the children conceived by conventional IVF and by ICSI [76, 77]. During the early years of its use, ICSI was preferentially employed in cases of poor sperm quality, while conventional IVF was used in cases with normal or nearly normal sperm, and the lack of significant differences between the outcomes of conventional IVF and ICSI suggests that sperm quality, as reflected by spermogram, spermocytogram and other standard sperm evaluation methods, has little, if any, impact on the health of offspring. Hence, the trend toward a higher risk of birth defects after IVF and ICSI as compared with natural conception is likely to be related to different, largely sperm-independent factors, such as the underlying cause of infertility, higher maternal age or a higher incidence of twin pregnancies [75, 78].

Even though there is no strong correlation between the conventional sperm parameters and ICSI outcome, sperm abnormalities, especially morphological ones, were shown to be associated with different genetic and epigenetic abnormalities [79], such as increased sperm DNA fragmentation [80] or abnormal patterns of DNA methylation [81]. Morphological abnormalities of the human sperm head have been shown to be associated with different types of genetic abnormalities [79], increased sperm DNA fragmentation [80] and different potentially harmful epigenetic factors, such as abnormal patterns of DNA methylation [81] and the absence or defective function of the sperm-derived oocyte-activating factor [82]. These observations explain the findings of increased implantation and pregnancy rate and decreased miscarriage rate [83, 84, 85], as well as a significantly decreased risk of major birth defects [86, 87], with the use of high-magnification ICSI (IMSI) as compared with conventional ICSI, although some studies failed to confirm these differences [88, 89].

As to fertilization by ICSI with immature (testicular) spermatozoa and by round spermatid injection (ROSI), the initial fears that incomplete or defective DNA methylation and chromatin configuration of these immature germ cells might cause syndromes related to genomic imprinting abnormalities [90] were not confirmed. In fact, no increase in the frequency of health problems caused by genomic imprinting abnormalities, such as Beckwith-Wiedemann, Prader-Willi, and Angelman syndromes, has been detected in children born after ICSI with testicular spermatozoa [91] and ROSI [59]. A recent study [92] has suggested that the supposed increase of imprinting errors, present in the sperm of infertile patients, does not have an obvious influence on assisted reproduction outcome or the imprinting of offspring, probably because the imprinting errors in sperm are selectively discarded or corrected during development [20, 93].

In contrast to the reassuring clinical data concerning the potential epigenetic risk of using abnormal and immature male germ cells for fertilization, there is increasing concern about the possible transmission of epigenetic abnormalities and diseases acquired during the father’s life via his spermatozoa. This risk is difficult to evaluate with the use of currently available diagnostic methods because it is not necessarily associated either with sperm morphology or with its DNA integrity. It was actually demonstrated in humans that nutritional status and physical activity levels were associated with dynamic epigenetic changes in spermatozoa, including DNA methylation patterns and small RNA expression [94, 95, 96, 97]. This kind of acquired epigenetic changes in spermatozoa is suspected to mediate transgenerational epigenetic inheritance of neurological disorders [95] and susceptibility to diabetes [31] and obesity [96, 97], and this list does not appear to be definitive, since new evidence of environmentally driven sperm-borne epigenetic factors, which are capable of altering the phenotype of the next generation, is emerging on a large scale. Paternal aging [46] and smoking [47] were also shown to affect sperm DNA methylation patterns, with still ill-defined developmental and health consequences for the offspring.

Advertisement

6. Future prospects for paternal epigenetic diagnosis and treatment

Abnormal patterns of sperm DNA methylation, small RNA expression, and chromatin configuration can now be detected with a relative ease. However, many of these abnormalities lack clinical significance because they might be corrected during fertilization and postfertilization development. The mechanisms responsible for this repair are still largely hypothetical and poorly understood. However, they are very likely to exist because a recent publication, based on the analysis of 1280 IVF-related treatment cycles, did not show any influence of either male age or sperm parameters on clinical pregnancy and live birth outcomes [92], in spite of the existence of data suggesting that there are very clear consequences of aging in the sperm epigenome that can be directly detected in DNA methylation patterns [46]. Obviously, further studies are needed to assess whether any effects of male age and sperm parameters on the offspring health status can be detected later in life.

In order to be able to distinguish between “benign” paternal epigenetic alterations that can be repaired spontaneously, on the one hand, and clinically relevant alterations that can cause negative effects on the embryonic, fetal and offspring health, studies are needed to relate DNA methylation status of specific genes and the expression pattern of specific small RNAs with specific developmental abnormalities. This work can be done by analyzing nucleic acids extracted directly from sperm cells or by using the “liquid biopsy” approach, based on the use of soluble nucleic acids isolated from blood plasma or seminal fluid. This latter approach is particularly interesting in azoospermic men so as to avoid the need for testicular biopsy to obtain a sample.

The identification of the developmentally relevant sperm epigenetic abnormalities is a necessary pre-requisite to design possible therapeutic interventions. These may go from relatively simple to more complex ones. It has been shown in the mouse that several waves of microRNAs and tRNA fragments are shipped to sperm during post-testicular maturation in the epididymis [98]. If some pathogenic paternal epigenetic signals are conveyed to sperm essentially during epididymal passage, ICSI with spermatozoa retrieved surgically from the testis, the technique already used with success in men with elevated levels of sperm DNA fragmentation [99, 100], might be a relatively simple and immediately available solution. If this approach is not possible, other, more sophisticated technologies, such as injecting specific microRNA molecules, capable of repairing specific epigenetic defects, into the early zygote [98] or induction of DNA methylation of the genes of interest by a Dnmt3-type de novo DNA methyltransferase targeted to the corresponding sperm DNA sequence by a nuclease-inactivated CRISPR variant (dCas9) [101], may be explored.

Advertisement

7. Conclusions

Since the availability of cell micromanipulation technologies enabling fertilization of human oocytes by ICSI with immature (testicular) spermatozoa and by round spermatid injection (ROSI), the role of paternal factors on embryonic, fetal, and offspring health needed a profound revision. While genetic abnormalities contributed by injected spermatozoa or spermatids can be controlled by preimplantation genetic testing and usually lead to a miscarriage, sperm-borne epigenetic abnormalities are much more difficult to detect and may be at the origin of different health problems throughout the offspring life. The current knowledge of the origin, nature, and mechanism of action of these sperm-borne epigenetic factors is outlined in this chapter. Surprisingly, in spite of multiple types of sperm epigenetic abnormalities associated with defective spermatogenesis and male aging, the current clinical experience is reassuring. In fact, no significant increase in the prevalence of diseases attributable to abnormal genomic imprinting was detected in children conceived by testicular spermatozoa or spermatids, probably because of the existence of efficient repair mechanisms acting in postfertilization stages of development.

By contrast, there is increasing evidence suggesting that transgenerational inheritance of paternally acquired epigenetic abnormalities via spermatozoa is more frequent than previously thought and can occur even in cases with normal conventional sperm parameters and during natural conception. The known pathologies transmitted in this way include neurological disorders, obesity, and diabetes, and their list is in continuous expansion. Future diagnostic and therapeutic possibilities applicable in these cases are discussed.

Advertisement

Conflict of interest

The author declares no conflict of interest related to this chapter.

References

  1. 1. Mayr E, Provine WB. The Evolutionary Synthesis: Perspectives on the Unification of Biology. Cambridge, MA: Harvard University Press; 1980
  2. 2. Richards EJ. Inherited epigenetic variation—revisiting soft inheritance. Nature Reviews. Genetics. 2006;7:395-401. DOI: 10.1038/nrg1834
  3. 3. Wei Y, Schatten H, Sun Q-Y. Environmental epigenetic inheritance through gametes and implications for human reproduction. Human Reproduction Update. 2015;21:194-208. DOI: 10.1093/humupd/dmu061
  4. 4. Duffie R, Ajjan S, Greenberg MV, Zamudio N, Escamilla del Arenal M, Iranzo J, et al. The Gpr1/Zdbf2 locus provides new paradigms for transient and dynamic genomic imprinting in mammals. Genes & Development. 2014;28:463-478. DOI: 10.1101/gad.232058.113
  5. 5. Falls JG, Pulford DJ, Wylie AA, Jirtle RL. Genomic imprinting: Implications for human disease. The American Journal of Pathology. 1999;154:635-647
  6. 6. Reik W, Walter J. Genomic imprinting: Parental influence on the genome. Nature Reviews. Genetics. 2001;2:21-32. DOI: 10.1038/35047554
  7. 7. Huynh KD, Lee JT. X-chromosome inactivation: A hypothesis linking ontogeny and phylogeny. Nature Reviews. Genetics. 2005;6:410-418. DOI: 10.1038/nrg1604
  8. 8. Thorvaldsen JL, Verona RI, Bartolomei MS. X-tra! X-tra! News from the mouse X chromosome. Developmental Biology. 2006;298:344-353. DOI: 10.1016/j.ydbio.2006.07.011
  9. 9. Christophersen NS, Helin K. Epigenetic control of embryonic stem cell fate. The Journal of Experimental Medicine. 2010;207:2287-2295. DOI: 10.1084/jem.20101438
  10. 10. Klose RJ, Bird AP. Genomic DNA methylation: The mark and its mediators. Trends in Biochemical Sciences. 2006;31:89-97. DOI: 10.1016/j.tibs.2005.12.008
  11. 11. Fire A, Xu S, Montgomery MK, Kostas SA, Driver SE, Mello CC. Potent and specific genetic interference by double-stranded RNA in Caenorhabditis elegans. Nature. 1998;391:806-811. DOI: 10.1038/35888
  12. 12. Rassoulzadegan M, Grandjean V, Gounon P, Vincent S, Gillot I, Cuzin F. RNA-mediated non-mendelian inheritance of an epigenetic change in the mouse. Nature. 2006;441:469-474. DOI: 10.1038/nature04674
  13. 13. Grandjean V, Gounon P, Wagner N, Martin L, Wagner KD, Bernex F, et al. The miR-124-Sox9 paramutation: RNA-mediated epigenetic control of embryonic and adult growth. Development. 2009;136:3647-3655. DOI: 10.1242/dev.041061
  14. 14. Watanabe T, Takeda A, Tsukiyama T, Mise K, Okuno T, Sasaki H, et al. Identification and characterization of two novel classes of small RNAs in the mouse germline: Retrotransposon-derived siRNAs in oocytes and germline small RNAs in testes. Genes & Development. 2006;20:1732-1743. DOI: 10.1101/gad.1425706
  15. 15. Ashe A, Sapetschnig A, Weick EM, Mitchell J, Bagijn MP, Cording AC, et al. piRNAs can trigger a multigenerational epigenetic memory in the germline of C. elegans. Cell. 2012;150:88-99. DOI: 10.1016/j.cell.2012.06.018
  16. 16. Bagijn MP, Goldstein LD, Sapetschnig A, Weick EM, Bouasker S, Lehrbach NJ, et al. Function, targets, and evolution of Caenorhabditis elegans piRNAs. Science. 2012;337:574-578. DOI: 10.1126/science.1220952
  17. 17. Lee HC, Gu W, Shirayama M, Youngman E, Conte D Jr, Mello CC. C. elegans piRNAs mediate the genome-wide surveillance of germline transcripts. Cell. 2012;150:78-87. DOI: 10.1016/j.cell.2012.06.016
  18. 18. Shirayama M, Seth M, Lee HC, Gu W, Ishidate T, Conte D Jr, et al. piRNAs initiate an epigenetic memory of nonself RNA in the C. elegans germline. Cell. 2012;150:65-77. DOI: 10.1016/j.cell.2012.06015
  19. 19. Becker JS, McCarthy RL, Sidoli S, Donahue G, Kaeding KE, He Z, et al. Genomic and proteomic resolution of heterochromatin and its restriction of alternate fate genes. Molecular Cell. 2017;68:1023-1037.e15. DOI: 10.1016/j.molcel.2017.11.030
  20. 20. Wang C, Liu X, Gao Y, Yang L, Li C, Liu W, et al. Reprogramming of H3K9me3-dependent heterochromatin during mammalian embryo development. Nature Cell Biology. 2018;20:620-631. DOI: 10.1038/s41556-018-0093-4
  21. 21. Hackett JA, Surani MA. Beyond DNA: Programming and inheritance of parental methylomes. Cell. 2013;153:737-739. DOI: 10.1016/j.cell.2013.04.044
  22. 22. Hackett JA, Sengupta R, Zylicz JJ, Murakami K, Lee C, Down TA, et al. Germline DNA demethylation dynamics and imprint erasure through 5-hydroxymethylcytosine. Science. 2013;339:448-452. DOI: 10.1126/science.1229277
  23. 23. Nakamura T, Liu YJ, Nakashima H, Umehara H, Inoue K, Matoba S, et al. PGC7 binds histone H3K9me2 to protect against conversion of 5mC to 5hmC in early embryos. Nature. 2012;486:415-419. DOI: 10.1038/nature11093
  24. 24. Messerschmidt DM. Should I stay or should I go: Protection and maintenance of DNA methylation at imprinted genes. Epigenetics. 2012;7:969-975. DOI: 10.4161/epi.21337
  25. 25. Messerschmidt DM, de Vries W, Ito M, Solter D, Ferguson-Smith A, Knowles BB. Trim28 is required for epigenetic stability during mouse oocyte to embryo transition. Science. 2012;335:1499-1502. DOI: 10.1126/science.1216154
  26. 26. Jiang L, Zhang J, Wang JJ, Wang L, Zhang L, Li G, et al. Sperm, but not oocyte, DNA methylome is inherited by zebrafish early embryos. Cell. 2013;153:773-784. DOI: 10.1016/j.cell.2013.04.041
  27. 27. Dubrova YE. Radiation-induced transgenerational instability. Oncogene. 2003;22:7087-7093. DOI: 10.1038/sj.onc.1206993
  28. 28. Gluckman PD, Hanson MA, Bateson P, Beedle AS, Law CM, Bhutta ZA, et al. Towards a new developmental synthesis: Adaptive developmental plasticity and human disease. Lancet. 2009;373:1654-1657. DOI: 10.1016/S0140-6736(09)60234-8
  29. 29. Li L, Law C, Lo Conte R, Power C. Intergenerational influences on childhood body mass index: The effect of parental body mass index trajectories. The American Journal of Clinical Nutrition. 2009;89:551-557. DOI: 10.3945/ajcn.2008.26759
  30. 30. Whitaker RC, Wright JA, Pepe MS, Seidel KD, Dietz WH. Predicting obesity in young adulthood from childhood and parental obesity. The New England Journal of Medicine. 1997;337:869-873. DOI: 10.1056/NEJM199709253371301
  31. 31. Wei Y, Yang CR, Wei YP, Zhao ZA, Hou Y, Schatten H, et al. Paternally induced transgerenational inheritance of susceptibility to diabetes in mammals. Proceedings of the National Academy of Sciences of the United States of America. 2014;111:1873-1878. DOI: 10.1073/pnas.1321195111
  32. 32. Suter CM, Martin DL, Ward RL. Germline epimutation of MLH1 in individuals with multiple cancers. Nature Genetics. 2004;36:497-501. DOI: 10.1038/ng1342
  33. 33. Chan TL, Yuen ST, Kong CK, Chan YW, Chan YS, NG WF, et al. Heritable gernline epimutation of MSH2 in a family with hereditary nonpolyposis colorectal cancer. Nature Genetics. 2006;37:1178-1183. DOI: 10.1038/ng1866
  34. 34. Tesarik J, Mendoza C, Greco E. Paternal effects acting during the first cell cycle of human preimplantation development after ICSI. Human Reproduction. 2002;17:184-189. DOI: 10.1093/humrep/17.1.184
  35. 35. Tesarik J, Greco E, Mendoza C. Late, but not early, paternal effect on human embryo development is related to sperm DNA fragmentation. Human Reproduction. 2004;19:611-615. DOI: 10.1093/humrep/deh127
  36. 36. Tesarik J. Paternal effects on cell division in the preimplantation embryo. Reproductive Biomedicine Online. 2005;10:370-375. DOI: 10.1016/S1472-6483(10)61798-1
  37. 37. Tesarik J, Greco E. The probability of abnormal preimplantation development can be predicted by a single static observation on pronuclear stage morphology. Human Reproduction. 1999;14:1318-1323. DOI: 10.1093/humrep/14.5.1318
  38. 38. Tesarik J, Kopecny V. Nucleic acid synthesis and development of human male pronucleus. Journal of Reproduction and Fertility. 1989;86:549-558. DOI: 10.1530/jrf.0.0860549
  39. 39. Tesarik J, Kopecny V. Assembly of the nucleolar precursor bodies in human male pronuclei is correlated with an early RNA synthetic activity. Experimental Cell Research. 1990;191:153-156. DOI: 10.1016/0014-4827(90)90050-K
  40. 40. Tesarik J, Kopecny V, Plachot M, Mandelbaum J. Activation of nucleolar and extranucleolar RNA synthesis and changes in the ribosomal content of human embryos developing in vitro. Journal of Reproduction and Fertility. 1986;78:463-470. DOI: 10.1530/jrf.0.0780463
  41. 41. Braude P, Bolton V, Moore S. Human gene expression first occurs between the four- and eight-cell stages of preimplntation development. Nature. 1988;332:459-461. DOI: 10.1038/332459a0
  42. 42. Tesarik J, Kopecny V, Plachot M, Mandelbaum J. Early morphological signs of embryonic genome expression in human preimplantation development as revealed by quantitative electron microscopy. Developmental Biology. 1988;128:15-20. DOI: 10.1016/0012-1606(88)90261-8
  43. 43. Sathananthan AH, Ratnam SS, Ng SC, Tarín JJ, Gianaroli L, Trounson A. The sperm centriole: Its inheritance, replication and perpetuation in early human embryos. Human Reproduction. 1996;11:345-356
  44. 44. Balaban B, Urman B, Isiklar A, Alatas C, Aksoy S, Mercan R, et al. The effect of pronuclear morphology on embryo quality parameters and blastocyst transfer outcome. Human Reproduction. 2001;16:2357-2361. DOI: 10.1093/humrep/16.11.2357
  45. 45. Balaban B, Yakin K, Urman B, Isiklar A, Tesarik J. Pronuclear morphology predicts embryo development and chromosome constitution. Reproductive Biomedicine Online. 2004;8:695-700. DOI: 10.1016/S1472-6483(10)61651-3
  46. 46. Jenkins TG, Aston KI, Carrell DT. Sperm epigenetics and aging. Translational Andrology and Urology. 2018;7(Suppl. 3):S328-S335. DOI: 10.21037/tau.2018.06.10
  47. 47. Hamad MF, Abu Dayyih WA, Laqqan M, AlKhaled Y, Montenarh M, Hammadeh ME. The status of global DNA methylation in the spermatozoa of smokers and non-smokers. Reproductive Biomedicine Online. 2018;37:581-589. DOI: 10.1016/j.rbmo.2018.016
  48. 48. Donkin I, Barrès R. Sperm epigenetics and influence of environmental factors. Molecular Metabolism. 2018;14:1-11. DOI: 10.1016/j.molmet.2018.02.006
  49. 49. Schoysman R, Vanderzwalmen P, Nijs M, Segal L, Segal-Bertin G, Geerts L, et al. Pregnancy after fertilisation with human testicular spermatozoa. Lancet. 1993;342:1237
  50. 50. Silber SJ, Van Steirteghem AC, Liu J, Nagy Z, Tournaye H, Devroey P. High fertilization and pregnancy rate after intracytoplasmic sperm injection with spermatozoa obtained from testicular biopsy. Human Reproduction. 1995;10:148-152
  51. 51. Tesarik J, Mendoza C, Testart J. Viable embryos from injection of round spermatids into oocytes. The New England Journal of Medicine. 1995;333:525. DOI: 10.1056/NEJM199508243330819
  52. 52. Tesarik J, Mendoza C. Spermatid injection into human oocytes. I. Laboratory techniques and special features of zygote development. Human Reproduction. 1996;11:772-779
  53. 53. Tesarik J, Rolet F, Brami C, Sedbon E, Thorel J, Tibi C, et al. Spermatid injection into human oocytes. II. Clinical application in the treatment of infertility due to non-obstructive azoospermia. Human Reproduction. 1996;11:780-783
  54. 54. Barak Y, Kogosowski A, Goldman S, Soffer Y, Gonen Y, Tesarik J. Pregnancy and birth after transfer of embryos that developed from single-nucleated zygotes obtained by injection of round spermatids into oocytes. Fertility and Sterility. 1998;70:67-70
  55. 55. Tanaka A, Nagayoshi M, Takemoto Y, Tanaka I, Kusunoki H, Watanabe S, et al. Fourteen babies born after round spermatid injection into human oocytes. Proceedings of the National Academy of Sciences of the United States of America. 2015;112:14629-14634. DOI: 10.1073/pnas.1517466112
  56. 56. Kimura Y, Yanagimachi R. Development of normal mice from oocytes injected with secondary spermatocyte nuclei. Biology of Reproduction. 1995;53:855-862
  57. 57. Tesarik J, Guido M, Mendoza C, Greco E. Human spermatogenesis in vitro: Respective effects of follicle-stimulating hormone and testosterone on meiosis, spermiogenesis, and Sertoli cell apoptosis. The Journal of Clinical Endocrinology and Metabolism. 1998;83:4467-4473. DOI: 10.1210/jcem.83.12.5304
  58. 58. Tesarik J, Bahceci M, Ozcan C, Greco E, Mendoza C. Restoration of fertility by in-vitro spermatogenesis. Lancet. 1999;353:555-556. DOI: 10.1016/S0140-6736(98)04784-9
  59. 59. Tanaka A, Suzuki K, Nagayoshi M, Tanaka A, Takemoto Y, Watanabe S, et al. Ninety babies born after round spermatid injection into oocytes: Survey of their development from fertilization up to 2 years old. Fertility and Sterility. 2018;110:443-451. Comment by Tesarik J, Mendoza C, Mendoza-Tesarik R. https://www.fertstertdialog.com/users/16110-fertility-and-sterility/posts/32485-25452. DOI: 10.1016/j.fertnstert.2018.04.033
  60. 60. Tesarik J, Mendoza C. In vitro fertilization by intracytoplasmic sperm injection. BioEssays. 1999;21:791-801. DOI: 10.1002/(SICI)1521-1878(199909)21:9<791::AID-BIES11>3.0.CO;2-Z
  61. 61. Machaty Z. Signal transduction in mammalian oocytes during fertilization. Cell and Tissue Research. 2016;363:169-183. DOI: 10.1007/s00441-015-2291-8
  62. 62. Miyazaki S. Inositol 1,4,5-trisphosphate-induced calcium release and guanine nucleotide-binding protein-mediated periodic calcium rises in golden hamster eggs. The Journal of Cell Biology. 1988;106:345-353
  63. 63. Tesarik J, Sousa M. Mechanism of calcium oscillations in human oocytes: A two-store model. Molecular Human Reproduction. 1996;2:383-386
  64. 64. Saunders CM, Larman MG, Parrington J, Cox LJ, Royse J, Blayney LM, et al. PLCζ: A sperm specific trigger of Ca2+ oscillations in eggs and embryo development. Development. 2002;129:3533-3544
  65. 65. Tesarik J, Sousa M. Comparison of Ca2+ responses in human oocytes fertilized by subzonal insemination and by intracytoplasmic sperm injection. Fertility and Sterility. 1994;62:1197-1204. DOI: 10.1016/S0015-0282(16)57185-4
  66. 66. Ozil JP, Huneau D. Activation of rabbit oocytes: The impact of the Ca2+ signal regime on development. Development. 2001;128:917-928
  67. 67. Ozil JP, Markoulaki S, Toth S, Matson S, Banrezes B, Knott JG, et al. Egg activation events are regulated by the duration of a sustained [Ca2+]cyt signal in the mouse. Developmental Biology. 2005;282:39-54. DOI: 10.1016/j.ydbio.2005.02.035
  68. 68. Ozil JP, Banrezes B, Tóth S, Pan H, Schultz RM. Ca2+ oscillatory pattern in fertilized mouse eggs affects gene expression and development to term. Developmental Biology. 2006;300:534-544. DOI: 10.1016/j.ydbio.2006.08.041
  69. 69. Tesarik J. Calcium signaling in human preimplantation development: A review. Journal of Assisted Reproduction and Genetics. 1999;16:216-220. DOI: 10.1023/A:1020321024973
  70. 70. Ferrer-Buitrago M, Bonte D, Dhaenens L, Vermogen S, Lu Y, De Sutter P, et al. Assessment of the calcium releasing machinery in oocytes that failed to fertilize after conventional ICSI and assisted oocyte activation. Reproductive Biomedicine Online. 2019;38(4):497-507. DOI: 10.1016/j.rbmo.2018.12.035
  71. 71. Hansen M, Kurinczuk JJ, Bower C, Webb S. The risk of major birth defects after intracytoplasmic sperm injection and in vitro fertilization. The New England Journal of Medicine. 2002;346:725-730. DOI: 10.1056/NEJMoa010035
  72. 72. Reefhuis J, Honein MA, Schieve LA, Correa A, Hobbs CA, Rasmussen SA. National birth defects prevention study. Assisted reproductive technology and major structural birth defects in the United States. Human Reproduction. 2009;24:360-366. DOI: 10.1093/humrep/den387
  73. 73. Davies MJ, Moore VM, Willson KJ, Van Essen P, Priest K, Scott H, et al. Reproductive technologies and the risk of birth defects. The New England Journal of Medicine. 2012;366:1803-1813. DOI: 10.1056/NEJMoa1008095
  74. 74. Tararbit K, Houyel L, Bonnet D, De Vigan C, Lelong N, Goffinet F, et al. Risk of congenital heart defects associated with assisted reproductive technologies: A population-based evaluation. European Heart Journal. 2011;32:500-508. DOI: 10.1093/eurheartj/ehq440
  75. 75. Giorgione V, Parazzini F, Fesslova V, Cipriani S, Candiani M, Inversetti A, et al. Congenital heart defects in IVF/ICSI pregnancy: Systematic review and meta-analysis. Ultrasound in Obstetrics & Gynecology. 2017;51:33-42. DOI: 10.1002/uog.18932
  76. 76. Lie RT, Lyngstadaas A, Ørstavik KH, Bakketeig LS, Jacobsen G, Tanbo T. Birth defects in children conceived by ICSI compared with children conceived by other IVF-methods; a meta-analysis. International Journal of Epidemiology. 2005;34:696-701. DOI: 10.1093/ije/dyh363
  77. 77. Wen J, Jiang J, Ding C, Dai J, Liu Y, Xia Y, et al. Birth defects in children conceived by in vitro fertilization and intracytoplasmic sperm injection: A meta-analysis. Fertility and Sterility. 2012;97:1331-1337.e4. DOI: 10.1016/j.fertnstert.2012.02.053
  78. 78. Pendina AA, Efimova OA, Chiryaeva OG, Tikhonov AV, Petrova LI, Dudkina VS, et al. A comparative cytogenetic study of miscarriages after IVF and natural conception in women aged under and over 35 years. Journal of Assisted Reproduction and Genetics. 2014;31:149-155. DOI: 10.1007/s10815-013-0148-1
  79. 79. Ray PF, Toure A, Metzler-Guillemain C, Mitchell MJ, Arnoult C, Coutton C. Genetic abnormalities leading to qualitative defects of sperm morphology or function. Clinical Genetics. 2017;91:217-232. DOI: 10.1111/cge.12905
  80. 80. Cassuto NG, Hazout A, Hammoud I, Balet R, Bouret D, Barak Y, et al. Correlation between DNA defect and sperm-head morphology. Reproductive Biomedicine Online. 2012;24:211-218. DOI: 10.1016/j.rbmo.2011.10.006
  81. 81. Cassuto NG, Montjean D, Siffroi J-P, Bouret D, Marzouk F, Copin H, et al. Different levels of DNA methylation detected in human sperms after morphological selection usinf high magnification microscopy. BioMed Research International. 2016;2016:6372171. DOI: 10.1155/2016/6372171
  82. 82. Rybouchkin A, Dozortsev D, Pelinck MJ, De Sutter P, Dhont M. Analysis of the oocyte activating capacity and chromosomal complement of round-headed human spermatozoa by their injection into mouse oocytes. Human Reproduction. 1996;11:2170-2175
  83. 83. Bartoov B, Berkovitz A, Eltes F, Kogosovsky A, Yagoda A, Lederman H, et al. Pregnancy rates are higher with intracytoplasmic morphologically selected sperm injection than with conventional intracytoplasmic injection. Fertility and Sterility. 2003;80:1413-1419
  84. 84. Berkovitz A, Eltes F, Yaari S, Katz N, Barr I, Fishman A, et al. The morphological normalcy of the sperm nucleus and pregnancy rate of intracytoplasmic sperm injection with morphologically selected sperm. Human Reproduction. 2005;20:185-190. DOI: 10.1093/humrep/deh545
  85. 85. Hazout A, Dumont-Hassan M, Junca AM, Cohen Bacrie P, Tesarik J. High-magnification ICSI overcomes paternal effect resistant to conventional ICSI. Reproductive Biomedicine Online. 2006;12:19-25
  86. 86. Cassuto NG, Hazout A, Bouret D, Balet R, Larue L, Benifla JL, et al. Low birth defects by deselecting abnormal spermatozoa before ICSI. Reproductive Biomedicine Online. 2014;28:47-53. DOI: 10.1016/j.rbmo.2013.08.01
  87. 87. Hershko-Klement A, Sukenik-Halevy R, Biron Shental T, Miller N, Berkovitz A. Intracytoplasmic morphologically selected sperm injection and congenital birth defects: A retrospective cohort study. Andrology. 2016;4:887-893. DOI: 10.1111/andr.12221
  88. 88. Gatimel N, Parinaud J, Leandri RD. Intracytoplasmic morphologically selected sperm injection (IMSI) does not improve outcome in patients with two successive IVF-ICSI failures. Journal of Assisted Reproduction and Genetics. 2016;33:349-355. DOI: 10.1007/s10815-015-0645-5
  89. 89. Gaspard O, Vanderzwalmen P, Wirleitner B, Ravet S, Wenders F, Eichel V, et al. Impact of high magnification sperm selection on neonatal outcomes: A retrospective study. Journal of Assisted Reproduction and Genetics. 2018;35:1113-1121. DOI: 10.1007/s10815-018-1167-8
  90. 90. Tesarik J, Mendoza C. Genomic imprinting abnormalities: A new potential risk of assisted reproduction. Molecular Human Reproduction. 1996;2:295-298
  91. 91. Tsai CC, Huang FJ, Wang LJ, Lin YJ, Kung FT, Hsieh CH, et al. Clinical outcomes and development of children born after intracytoplasmic sperm injection (ICSI) using extracted testicular sperm or ejaculated extreme oligo-astheno-teratozoospermia sperm: A comparative study. Fertility and Sterility. 2011;96:567-571. DOI: 10.1016/j.fertnstert.2011.06.080
  92. 92. Mariappen U, Keane KN, Hinchliffe PM, Dhaliwal SS, Yovich JL. Neither male age nor semen parameters influence clinical pregnancy or live birth outcomes from IVF. Reproductive Biology. 2018;18:324-329. DOI: 10.1016/j.repbio.2018.11.003
  93. 93. Tang L, Liu Z, Zhang R, Su C, Yang W, Yao Y, et al. Imprinting alterations in sperm may not significantly influence ART outcomes and imprinting patterns in the cord blood of offspring. PLoS One. 2017;12:e0187869. DOI: 10.1371/journal.pone.0187869
  94. 94. Denham J, O’Brien BJ, Harvey JT, Charchar FJ. Genome-wide sperm DNA methylation changes after 3 months of exercise training in humans. Epigenomics. 2015;7:717-731. DOI: 10.2217/epi.15.29
  95. 95. Donkin I, Versteyhe S, Ingerslev LR, Qian K, Mechta M, Nordkap L, et al. Obesity and bariatric surgery drive epigenetic variation of spermatozoa in humans. Cell Metabolism. 2016;23:369-378. DOI: 10.1016/j.cmet.2015
  96. 96. Ingerslev LR, Donkin I, Fabre O, Versteyhe S, Mechta M, Pattamaprapanont P, et al. Endurance training remodels sperm-borne small RNA expression and methylation at neurological gene hotspots. Clinical Epigenetics. 2018;10:12. DOI: 10.1186/s13148-018-0446-7
  97. 97. Öst A, Lempradl A, Casas E, Weigert M, Tiko T, Deniz M, et al. Paternal diet defines offspring chromatin state and intergenerational obesity. Cell. 2014;159:1352-1364. DOI: 10.1016/j.cell.2014.11.005
  98. 98. Conine CC, Sun F, Song L, Rivera-Pérez JA, Rando OJ. Small RNAs gained during epididymal transit of sperm are essential for embryonic development in mice. Developmental Cell. 2018;46:1-11. DOI: 10.1016/j.devcel.2018.06.024
  99. 99. Greco E, Scarselli F, Iacobelli M, Rienzi L, Ubaldi F, Ferrero S, et al. Efficient treatment of infertility due to sperm DNA damage by ICSI with testicular spermatozoa. Human Reproduction. 2005;20:226-230. DOI: 10.1093/humrep/deh590
  100. 100. Tesarik J, Galán-Lázaro M. Clinical scenarios of unexplained sperm DNA fragmentation and their management. Translational Andrology and Urology. 2016;5:935-950. DOI: 10.21037/tau.2017.03.70
  101. 101. Stepper P, Kungulovski G, Jurkowska RZ, Chandra T, Krueger F, Reinhardt R, et al. Efficient targeted DNA methylation with chimeric dCas9-Dnmt3a-Dnmt3L methyltransferase. Nucleic Acids Research. 2017;45(4):1703-1713

Written By

Jan Tesarik

Submitted: 06 December 2018 Reviewed: 15 July 2019 Published: 23 October 2019