A Recurrent Nonsense Mutation in NECTIN4 Underlying Ectodermal Dysplasia-Syndactyly Syndrome with a Novel Phenotype in a Consanguineous Kashmiri Family.

EDSS1, a syndrome characterized by ectodermal dysplasia-syndactyly, is inherited in an autosomal recessive manner due to mutations in the NECTIN4/PVRL4 gene. Clinical manifestations of the syndrome include defective nail plate, sparse to absent scalp and body hair, spaced teeth with enamel hypoplasia, and bilateral cutaneous syndactyly in the fingers and toes. Here, we report a consanguineous family of Kashmiri origin presenting features of EDSS1. Using whole exome sequencing, we found a recurrent nonsense mutation (NM_030916: c.181C > T, p.(Gln61 ∗)) in the NECTIN4 gene. The variant segregated perfectly with the disorder within the family. The candidate variant was absent in 50 in-house exomes pertaining to other disorders from the same population. In addition to the previously reported clinical phenotype, an upper lip cleft was found in one of the affected members as a novel phenotype that is not reported by previous studies in EDSS1 patients. Therefore, the study presented here, which was conducted on the Kashmiri population, is the first to document a NECTIN4 mutation associated with the upper lip cleft as a novel phenotype. This finding broadens the molecular and phenotypic spectrum of EDSS1.

Identification of a Novel Homozygous Missense (c.443A>T:p.N148I) Mutation in BBS2 in a Kashmiri Family with Bardet-Biedl Syndrome.

BACKGROUND: Bardet-Biedl syndrome (BBS) is a rare autosomal recessive inherited disorder with distinctive clinical feature such as obesity, degeneration of retina, polydactyly, and renal abnormalities. The study was aimed at finding out the disease-causing variant/s in patients exhibiting clinical features of BBS. METHODS: The identification of disease-causing variant was done by using whole exome sequencing on Illumina HiSeq 4000 platform involving the SeqCap EZ Exome v3 kit (Roche NimbleGen). The identified variant was further validated by Sanger sequencing. RESULTS: WES revealed a novel homozygous missense mutation (NM_031885: c.443A>T:p.N148I) in exon 3 of the BBS2 gene. Sanger sequencing confirmed this variant as homozygous in both affected subjects and heterozygous in obligate parents, demonstrating autosomal recessive inheritance pattern. To the best of our knowledge, this variant was not present in literature and all publically available databases. The candidate variant is predicted to be pathogenic by a set of in-silico softwares. CONCLUSION: Clinical and genetic spectrum of BBS and BBS-like disorders is not completely defined in the Pakistani as well as in Kashmiri population. Therefore, more comprehensive genetic studies are required to gain insights into genotype-phenotype associations to facilitate carrier screening and genetic counseling of families with such disorders.

Identification of a recurrent nonsense mutation in HR gene responsible for atrichia with papular lesions in two Kashmiri families.

BACKGROUND: Congenital atrichia (CA) is a rare form of irreversible alopecia with an autosomal recessive mode of inheritance. This form of hair loss is mainly associated with mutations in the human hairless (HR) gene located at chromosome 8p21.3. An additional unique feature atrichia with papular lesions (APL) comprises keratin-filled cysts known as papules. The present study aimed to uncover the underlying genetic causes of APL in two consanguineous Kashmiri families. METHODS: In the present study, two consanguineous families of Kashmiri origin with APL displaying an autosomal recessive mode of inheritance were investigated. Whole exome and Sanger sequencing followed by bioinformatic studies, variant prioritization, Sanger validation and segregation analysis was performed to find the mutation. RESULTS: A recurrent nonsense (NM_005144: c.2818C > T:p.Arg940*) mutation was detected in exon 13 of the human HR gene. CONCLUSIONS: Whole exome sequencing analysis has widely been used in the screening of single gene disorders mutations, both in research and diagnostic laboratories. Sanger sequencing alone for genes such as HR becomes expensive and time consuming. Instead, it is recommended that a patient is to screen by whole exome sequencing and then special attention first focuses on known genes of the APL phenotype. This is helpful for intime diagnosis, being more efficient and economic. The results obtained in the present study may contribute to prenatal diagnosis, carrier secreening and the genetic counseling of families with the APL phenotype in Kashmiri poplution.