Identification of six novel mutations in EDA from 20 hypohidrotic ectodermal dysplasia families

OBJECTIVE: To investigate the genetic causes of 22 patients with clinically high suspicion of X-linked hypohidrotic ectodermal dysplasia from 20 unrelated Chinese families, expand the spectrum of ectodysplasin-A mutations, and provide more evidence for variants of uncertain significance. SUBJECTS AND METHODS: Whole-exome sequencing was performed and potentially pathogenic variants were verified by Sanger sequencing. Western blotting, real-time PCR and immunofluorescence analyses were performed to investigate the preliminary functions of the candidate variants. RESULTS: Nineteen ectodysplasin-A variants were identified, six of which were not previously reported. Among these variants, we identified a patient who carried two mutations in ectodysplasin-A and exhibited more severe phenotypes. Additionally, mutant protein expression levels decreased, whereas mRNA transcription levels increased. Cellular sublocalisation of the variants located in the tumour necrosis factor homologous domain showed that the proteins accumulated in the nucleus, whereas wild-type proteins remained in the cell membrane. A rare indel variant and two classical splicing variants that lead to exon 7 skipping were detected. CONCLUSIONS: This study provides definitive diagnoses for 20 families with suspected X-linked hypohidrotic ectodermal dysplasia and additional information on clinical heterogeneity and genotype-phenotype relationships.