BACKGROUND: Three mutations in the DFNA5 gene have been described in three families with autosomal dominant non-syndromic hearing impairment. Although these mutations are different at the genomic DNA level, they all lead to skipping of exon 8 at the mRNA level. We hypothesise that hearing impairment associated with DFNA5 is caused by a highly unusual mechanism, in which skipping of one specific exon leads to disease that is not caused by other mutations in this gene. We hypothesise that this represents a very specific "gain of function" mutation, with the truncated protein exerting a deleterious new function. METHODS: We performed transfection experiments in mammalian cell lines (HEK293T and COS-1) with green fluorescent protein (GFP) tagged wildtype and mutant DFNA5 and analysed cell death with flow cytometry and fluorescence microscopy. RESULTS: Post-transfection death of HEK293T cells approximately doubled when cells were transfected with mutant DFNA5-GFP compared with wildtype DFNA5-GFP. Cell death was attributed to necrotic events and not to apoptotic events. CONCLUSION: The transfection experiments in mammalian cell lines support our hypothesis that the hearing impairment associated with DFNA5 is caused by a "gain of function" mutation and that mutant DFNA5 has a deleterious new function.
BACKGROUND: Three mutations in the DFNA5 gene have been described in three families with autosomal dominant non-syndromic hearing impairment. Although these mutations are different at the genomic DNA level, they all lead to skipping of exon 8 at the mRNA level. We hypothesise that hearing impairment associated with DFNA5 is caused by a highly unusual mechanism, in which skipping of one specific exon leads to disease that is not caused by other mutations in this gene. We hypothesise that this represents a very specific "gain of function" mutation, with the truncated protein exerting a deleterious new function. METHODS: We performed transfection experiments in mammalian cell lines (HEK293T and COS-1) with green fluorescent protein (GFP) tagged wildtype and mutant DFNA5 and analysed cell death with flow cytometry and fluorescence microscopy. RESULTS: Post-transfection death of HEK293T cells approximately doubled when cells were transfected with mutant DFNA5-GFP compared with wildtype DFNA5-GFP. Cell death was attributed to necrotic events and not to apoptotic events. CONCLUSION: The transfection experiments in mammalian cell lines support our hypothesis that the hearing impairment associated with DFNA5 is caused by a "gain of function" mutation and that mutant DFNA5 has a deleterious new function.
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Authors: Kevin T Booth; Hela Azaiez; Kimia Kahrizi; Donghong Wang; Yuzhou Zhang; Kathy Frees; Carla Nishimura; Hossein Najmabadi; Richard J Smith Journal: Hum Mutat Date: 2018-01-11 Impact factor: 4.878
Authors: Lut Van Laer; Nicole C Meyer; Mahdi Malekpour; Yasser Riazalhosseini; Mahdi Moghannibashi; Kimia Kahrizi; Ann Vandevelde; Fatemeh Alasti; Hossein Najmabadi; Guy Van Camp; Richard J H Smith Journal: J Hum Genet Date: 2007-04-11 Impact factor: 3.172