Parametric linkage analysis was performed using the CHST3 variant genotype, which resulted in a two-point LOD score of 10. 5 at =0. this family provides new insights into phenotypic spectrum ofCHST3alleles and disease progression with age. == Introduction == Genetic disorders that result in deficits of skeletal systems are collectively termed as skeletal dysplasias (SDs) or Osteochondrodysplasias. Their prevalence has been estimated to be 1: 5000 (1). However , in children with congenital birth defects, SD prevalence is approximately 5% (2). SD has been classified into 40 sub-groups primarily on the basis of clinical, molecular, biochemical and radiological findings (3). In some cases, SD leads to lethality due to small chest, pulmonary hypoplasia, and respiratory problems (4). Genetically, SD can manifest under a variety of inheritance models including autosomal dominant or recessive, and X-linked dominant or recessive (2, 3). Hundreds of genes have been found that subserve a variety of functions in bone development, mineralization and growth in humans. Deciphering the genetic causes of SDs often help in comprehending basic bone biology, disease prognosis and treatment options. For instance, in some cases of monogenic SDs, novel targeted therapies including Cathepsin K inhibitors and anti-sclerostin monoclonal antibodies are now in late phases of clinical trials (57). Here, we describe a six-generation Pakistani family (LUAB01) with autosomal recessively inherited congenital skeletal dysplasia and hearing loss. Whole exome sequencing (WES) revealed a nonsense (p. Glu268*) mutation in theCHST3(OMIM 603799) gene segregating with the phenotype. C6ST-1 enzyme, encoded byCHST3, belongs to the carbohydrate sulfotransferase family of fifteen enzymes that is involved in the transfer of sulfate groups to carbohydrates in glycoprotein and glycolipids. C6ST-1 catalyzes sulfation of chondroitin containing proteoglycan, an essential constituent of connective tissues (8). Previously, mutations inCHST3have been associated with a rare phenotype of skeleton dysplasia, known as Spondyloepiphyseal dysplasia with congenital joint dislocations (OMIM 143095) (9, 10). The phenotypic presentation of the disease varies among ethnically and geographically divergent populations (912). Common features include large joint contractures, progressive kyphosis, clubfoot, and dislocation of hip joints (912). Hearing loss incidence in patients withCHST3mutations has been anecdotal. Intriguingly, all IACS-8968 R-enantiomer the affected individuals of the family LUAB01 have bilateral symmetric mild-to-severe hearing impairment and thus provided statistically significant evidence of linkage of hearing loss phenotype with theCHST3allele. == Subject and Methods == == Enrollment and clinical evaluation == This study was approved by the Ethical Rabbit polyclonal to AFP (Biotin) Review Committees of the participating institutes. After obtaining written informed consent, blood samples were collected from the participating members of the family LUBA01. Anthropological measurements and earlier developmental milestone were recorded. Detailed IACS-8968 R-enantiomer clinical investigations including X-rays, echocardiograms, and audiometry were performed on available affected individuals. == Whole exome sequencing (WES) == WES was performed using genomic DNA samples from one affected and one normal individual and NimbleGen SeqCap EX Exome v2. 0 kit (Roche Diagnostics, San Francisco, CA). Sequencing data analysis, alignment, variants calling, and filteration were performed as described previously (13). == Sanger sequencing and LOD score calculation == Sequencing reaction was carried out by using a Big Dye Terminator v3. 1 (Applied Biosystems) as described previously (14). To IACS-8968 R-enantiomer confirm the association with the phenotype, two point LOD score for theCHST3variant was calculated with Superlink by EasyLinkage 5. 02 IACS-8968 R-enantiomer v GUI (15). An autosomal recessive inheritance and a disease allele frequency of 0. 001 were used for linkage analysis. == Molecular modeling == Molecular modeling for CHST3 was performed using Phyre2 (16) with the Sulfotransferase domain from the Curacin biosynthetic pathway as the template (Protein Data Bank (PDB), 4GBM). == Results == == Clinical findings == We enrolled a six-generation family (LUAB01) from Sindh province of Pakistan with fourteen individuals in ten sibships who were affected with recessively inherited congenital skeletal dysplasia (Fig. 1a). The neonatal clinical records of the affected individuals were not available at the time of enrollment. According to the family history, the affected individuals exhibited restricted movement at the elbow and knee joints at birth and progressively.
Parametric linkage analysis was performed using the CHST3 variant genotype, which resulted in a two-point LOD score of 10
