Discovery and Delineation of Dermatan 4O-Sulfotransferase-1 ( D 4 ST 1 )-Deficient Ehlers-Danlos Syndrome

© 2013 Kosho, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Discovery and Delineation of Dermatan 4-O-Sulfotransferase-1 (D4ST1)-Deficient Ehlers-Danlos Syndrome


Adducted thumb-Clubfoot syndrome
The original report of ATCS was written by Dündar et al. [8] from Erciyes University, Turkey, presenting two cousins, a boy aged 3.5 years and a girl aged 1.5 years, from a consanguineous Turkish family.In common, they had moderate to severe psychomotor developmental delay, ocular anterior chamber abnormality, facial characteristics, generalized joint laxity, arachnodactyly, camptodactyly, and distal arthrogryposis with adducted thumbs and clubfeet.They reported another patient with ATCS, a boy aged 3 months, from a consanguineous Turkish family including three affected siblings who died of unknown etiology between the ages of 1 and 4 months [9].The patient also had bilateral nephrolithiasis, a unilateral inguinal hernia, and bilateral cryptorchidism.The authors suggested that two brothers, aged 22 months and 7 months, from a Japanese consanguineous family reported by Sonoda and Kouno [10] would also fit the diagnosis of ATCS.The brothers had multiple distal arthrogryposis, characteristic facial features, cleft palates, short stature, hydronephrosis, cryptorchidism, and normal intelligence.Dündar et al. [9] also showed follow-up observations of the original patients: the intelligence quotient (IQ) was roughly 90 in one subject at age 7 years and 2 months and the other died of unknown cause at 5 years of age.Janecke et al. [11] from Innsbruck Medical University, Austria, reported two brothers with ATCS from a consanguineous Austrian family, one of whom died shortly after birth because of respiratory failure.The authors concluded that all these patients represented a new type of arthrogryposis with central nervous system involvement, congenital heart defects, urogenital defects, myopathy, connective tissue involvement (generalized joint laxity), and normal or subnormal mental development.In 2009, Dündar et al. reported that CHST14 w a s t h e c a u s a l g e n e f o r A T C S t h r o u g h homozygosity mapping using samples from four previously published consanguineous families.The authors mentioned some follow-up clinical findings including generalized joint laxity, delayed wound healing, ecchymoses, hematomas, and osteopenia/osteoporosis; and categorized ATCS as a generalized connective tissue disorder [5].

EDS, Kosho type
We encountered the first patient with a specific type of EDS in 2000 and the second with parental consanguinity in 2003.They were Japanese girls with strikingly similar symptoms: characteristic craniofacial features; skeletal features including multiple congenital contractures, malfanoid habitus, pectus excavatum, generalized joint laxity, recurrent dislocations, and progressive talipes and spinal deformity; skin hyperextensibility, bruisability, and fragility with atrophic scars; recurrent hematomas; and hypotonia with mild motor developmental delay [12].These symptoms overlapped those in the kyphoscoliosis type EDS (previously known as EDS type VI), which is typically associated with deficiency of lysyl hydroxylase (EDS type VIA) [13].A rare condition with the clinical phenotype of the kyphoscoliosis type EDS but with normal lysyl hydroxylase activity were reported and named as EDS type VIB [13].Therefore, we tentatively proposed that the two patients represented a clinically recognizable subgroup of EDS type VIB [12].Through their long-term clinical evaluation as well as four additional unrelated Japanese patients including one with parental consanguinity and another reported by Yasui et al. [14], we concluded that they-four female patients and two male patients aged 4-32 years, represented a new clinically recognized type of EDS with distinct craniofacial characteristics, multiple congenital contractures, progressive joint and skin laxity, and multisystem fragility-related manifestations [15].The disorder has been registered as EDS Kosho Type (EDSKT) in the London Dysmorphology Database (http://www.lmdatabases.com/index.html) and in POSSUM (http://www.possum.net.au/).In 2009, we identified CHST14 as causal for the disorder through homozygosity mapping using samples from two consanguineous families and all the other patients were also found to have compound heterozygous CHST14 mutations [6].

Musculocontractural EDS
Malfait et al. [7] from Ghent University, Belgium have found mutations in CHST14 through homozygosity mapping of two Turkish sisters and an Indian girl both presenting clinically with EDS VIB and with parental consanguinity.They had distinct craniofacial features, joint contractures, and wrinkled palms in addition to common features of kyphoscoliosis type EDS including kyphoscoliosis, muscular hypotonia, hyperextensible, thin, and bruisable skin, atrophic scarring, joint hypermobility, and variable ocular involvement.Malfait et al. [7] concluded that their series and ATCS, as well as EDSKT, formed a phenotypic continuum based on their clinical observations and identification of an identical mutation in both conditions; and proposed to coin the disorder as "musculocontractural EDS" (MCEDS).

Glycobiological abnormalities in D4ST1-deficient EDS
D4ST1 is a regulatory enzyme in the glycosaminoglycan (GAG) biosynthesis that transfers active sulfate to position 4 of the N-acetyl-D-galactosamine residues of dermatan sulfate (DS) (Fig. 1) [16,17].DS, together with chondroitin sulfate (CS) and heparan sulfate, constitutes GAG chains of proteoglycans and is implicated in cardiovascular disease, tumorigenesis, infection, wound repair, and fibrosis via DS-containing proteoglycans such as decorin and biglycan [18].
Sulfotransferase activity toward dermatan in the skin fibroblasts derived from the patients was significantly decreased to 6.7% (patient 1 with a compound heterozygous mutation: P281L/Y293C) and 14.5% (patient 3 with a homozygous mutation: P281L) of each age-and sex-matched control) (Fig. 2A).Disaccharide composition analysis of CS/DS chains isolated from the skin fibroblasts showed a negligible amount of DS and a slight excess of CS (Fig. 2B).Subsequently, we focused on a major DS proteoglycan in the skin, decorin, consisting of core protein and one GAG chain and playing an important role in assembly of collagen fibrils (Nomura, 2006).No DS disaccharides were detected in the GAG chains of decorin from the patients, whereas the GAG chains of decorin from the controls were mainly composed of DS disaccharides (approximately 95%) (Fig. 2C) [6].

Pathological abnormalities in D4ST1-deficient EDS
Hematoxylin and eosin (H&E)-stained light microscopy on patients' skin specimens showed that fine collagen fibers were present predominantly in the reticular to papillary dermis with marked reduction of normally thick collagen bundles (Fig. 3a, b).Electron microscopy showed that collagen fibrils were dispersed in the reticular dermis, compared with the regularly and tightly assembled ones observed in the control; whereas each collagen fibril was smooth and round, not varying in size and shape, similar to each fibril of the control (Fig. 3c, d) [6].In view of these glycobiological and pathological findings, skin fragility in this disorder is suggested to be caused by impaired assembly of collagen fibrils resulting from loss of DS in the GAG chain of decorin [6].Decorin DS regulates the interfibrillar distance in collagen fibrils and permits the extracellular matrix to resist physical stress, possibly through electrostatic interaction between decorin DS chains and adjacent collagen fibrils (Fig. 4A) [19].Collagen fibrils are dispersed in patients' skin tissues where the decorin GAG chains are exclusively composed of CS (Fig. 4B), whereas collagen fibrils in controls' skin specimens are tightly assembled through the GAG chains of decorin exclusively composed of DS (Fig. 4A).
Possible relationship between collagen fibrils and decorin in skin specimens of normal control subjects (A) and of patients (B).

Delineation of D4ST1-deficient EDS
Independently identified three conditions, ATCS, EDSKT, and MCEDS caused by loss-offunction mutations in CHST14, were supposed to be a single clinically recognizable type of connective tissue disorder [7,21].Shimizu et al. [22] presented detailed clinical information of two additional unrelated patients and a comprehensive review of all reported 20 patients, which could definitely unite the three conditions named as "D4ST1deficient EDS (DD-EDS)".Kosho et al. [23] concluded that categorization of the disorder into a form of "EDS" was appropriate clinically because the disorder satisfied all the hallmarks of EDS including skin hyperextensibility, joint hypermobility, and tissue fragility affecting the skin, ligaments, joints, blood vessels, and internal organs [1] and etiologically because multisystem fragility in the disorder was illustrated to be caused by impaired assembly of collagen fibrils resulting from loss of DS in the decorin GAG chains [6].
Recurrent large subcutaneous hematomas are the most serious complication , which sometimes progress acutely and massively to be treated intensively (admission, blood transfusion, surgical drainage) and are supposed to be caused by rupture of subcutaneous arteries or veins (Fig. 5X) [12. 15, 22].

Conclusion
DD-EDS is a newly recognized and delineated form of EDS, characterized by progressive multisystem fragility-related manifestations (skin hyperextensibilty and fragility, progressive spinal and foot deformities, large subcutaneous hematoma) and various malformations (facial features, congenital eye/heart/gastrointestinal defects, congenital multiple contractures).The cause of multisystem connective tissue fragility is supposed to be impaired assembly of collagen fibrils resulting from loss of DS in the decorin GAG chains.It is the first human disorder affecting biosynthesis of DS, which emphasize a role for DS in human development and extracellular matrix maintenance [27].
A. Sulfotransferase activity of skin fibroblasts: A patient (a compound heterozygous mutation, P281L/Y293C; patient 1), her heterozygous mother, and her age-matched control (control 1); another patient (a homozygous mutation, P281L; patient 3) and his age-matched control (control 2).B. The total amounts of CS and DS derived from skin fibroblasts.The total disaccharide contents of CS and DS are shown in a black box and a white box, respectively.C. Proportion of the disaccharide units in the CS/DS hybrid chains in decorin secreted by the fibroblasts.A white box and a light gray box indicate GlcUA-GalNAc (4S) and GlcUA-GalNAc (6S), respectively, both composing CS.A dark gray box and a black box indicate IdoUA-GalNAc(4S) and IdoUA-GalNAc (6S), respectively, both composing DS.