Autosomal recessive ichthyosis with hypotrichosis (ARIH; MIM 602400) syndrome is characterized by diffused congenital ichthyosis and generalized non-scarring hypotrichosis. The underlying genetic cause of ARIH syndrome has been associated with sequence variants of the gene ST14, encoding type II transmembrane serine protease matriptase, which maps to chromosome 11q24.3. The current report aimed to investigate the clinical features and genetic cause of ARIH syndrome in a large consanguineous family of Pakistani origin. The technique of homozygosity mapping with highly polymorphic microsatellite markers was employed to establish linkage within the family. Sanger sequencing of exons and intron-exon boundaries of ST14 was performed to identify the potential pathogenic sequence variants, followed by structural analysis of the mutated protein. Linkage was established to chromosome 11q24.3, comprising the gene ST14. Sequence analysis led to the identification of a novel homozygous missense variant (c.1315G>A, p.Gly439Ser) in the ST14 gene that co-segregated with the disease phenotype in all affected members. Homology modelling and molecular docking analysis of ST14 with wild-type TMEFF1 protein was performed which revealed that glycine at position 439 is crucial for maintaining normal structural confirmation and interaction with the EGF domain of TMEFF1 protein. Taken together, the data strongly advocate this ST14 variant as the underlying genetic cause of ARIH syndrome in this first reported affected family from Pakistan. Moreover, the present study adds to the spectrum of mutations in the ST14 gene, implicating them in the pathogenesis of ARIH syndrome.
Keywords: ST14 gene; autosomal recessive ichthyosis with hypotrichosis syndrome; novel missense variant.