Identification of a Novel De Novo Heterozygous Deletion in the SOX10 Gene in Waardenburg Syndrome Type II Using Next-Generation Sequencing

Frameshift variant in MITF gene in a large family with Waardenburg syndrome type II and a co-segregation of a C2orf74 variant

Waardenburg syndrome (WS) is a hereditary disorder affecting the auditory system and pigmentation of hair, eyes, and skin. Different variants of the disease exist with the involvement of mutation in six genes. The aim of the study is to identify the genetic defects underlying Waardenburg syndrome in a large family with multiple affected individuals. Here, in this study, we recruited a large family with eleven affected individuals segregating WS type 2. We performed whole genome SNP genotyping, whole exome sequencing and segregation analysis using Sanger approach. Whole genome SNP genotyping, whole exome sequencing followed by Sanger validation of variants of interest identified a novel single nucleotide deletion mutation (c.965delA) in the MITF gene. Moreover, a rare heterozygous, missense damaging variant (c.101T>G; p.Val34Gly) in the C2orf74 has also been identified. The C2orf74 is an uncharacterized gene present in the linked region detected by DominantMapper. Variants in MITF and C2orf74 follows autosomal dominant segregation with the phenotype, however, the variant in C2orf74 is incompletely penetrant. We proposed a digenic inheritance of variants as an underlying cause of WS2 in this family.

Comprehensive analysis of syndromic hearing loss patients in Japan

More than 400 syndromes associated with hearing loss and other symptoms have been described, corresponding to 30% of cases of hereditary hearing loss. In this study we aimed to clarify the mutation spectrum of syndromic hearing loss patients in Japan by using next-generation sequencing analysis with a multiple syndromic targeted resequencing panel (36 target genes). We analyzed single nucleotide variants, small insertions, deletions and copy number variations in the target genes. We enrolled 140 patients with any of 14 syndromes (BOR syndrome, Waardenburg syndrome, osteogenesis imperfecta, spondyloepiphyseal dysplasia congenita, Stickler syndrome, CHARGE syndrome, Jervell and Lange-Nielsen syndrome, Pendred syndrome, Klippel-Feil syndrome, Alport syndrome, Norrie disease, Treacher-Collins syndrome, Perrault syndrome and auditory neuropathy with optic atrophy) and identified the causative variants in 56% of the patients. This analysis could identify the causative variants in syndromic hearing loss patients in a short time with a high diagnostic rate. In addition, it was useful for the analysis of the cases who only partially fulfilled the diagnostic criteria.

The Rare Neurocutaneous Disorders: Update on Clinical, Molecular, and Neuroimaging Features

Phakomatoses, also known as neurocutaneous disorders, comprise a vast number of entities that predominantly affect structures originated from the ectoderm such as the central nervous system and the skin, but also the mesoderm, particularly the vascular system. Extensive literature exists about the most common phakomatoses, namely neurofibromatosis, tuberous sclerosis, von Hippel-Lindau and Sturge-Weber syndrome. However, recent developments in the understanding of the molecular underpinnings of less common phakomatoses have sparked interest in these disorders. In this article, we review the clinical features, current pathogenesis, and modern neuroimaging findings of melanophakomatoses, vascular phakomatoses, and other rare neurocutaneous syndromes that may also include tissue overgrowth or neoplastic predisposition.

Locus and allelic heterogeneity and phenotypic variability in Waardenburg syndrome

Waardenburg syndrome (WS) is a disorder of neural crest cell migration characterized by auditory and pigmentary abnormalities. We investigated a cohort of 14 families (16 subjects) either by targeted sequencing or whole-exome sequencing. Thirteen of these families were clinically diagnosed with WS and one family with isolated non-syndromic hearing loss (NSHL). Intra-familial phenotypic variability and non-penetrance were observed in families diagnosed with WS1, WS2 and WS4 with pathogenic variants in PAX3, MITF and EDNRB, respectively. We observed gonosomal mosaicism for a variant in PAX3 in an asymptomatic father of two affected siblings. For the first time, we report a biallelic pathogenic variant in MITF in a subject with WS2 and a biallelic variant in EDNRB was noted in a subject with WS2. An individual with isolated NSHL carried a pathogenic variant in MITF. Blended phenotype of NSHL and albinism was observed in a subject clinically diagnosed to have WS2. A phenocopy of WS1 was observed in a subject with a reported pathogenic variant in GJB2, known to cause isolated NSHL. These novel and infrequently reported observations exemplify the allelic and genetic heterogeneity and show phenotypic diversity of WS.