EFS, Univ Brest, INSERM, UMR 1078, GGB, Brest, France.
Department of Gastroenterology, Changhai Hospital, Second Military Medical University, Shanghai, China.
Hum Mutat. 2020 Aug;41(8):1358-1364. doi: 10.1002/humu.24029. Epub 2020 May 12.
In the human genome, most 5' splice sites (99%) employ the canonical GT dinucleotide whereas a small minority (1%) use the noncanonical GC dinucleotide. The functionality and pathogenicity of 5' splice site GT>GC (+2T>C) variants have been extensively studied but we know very little about 5' splice site GC>GT (+2C>T) variants. Herein, we have addressed this deficiency by performing a meta-analysis of reported +2C>T "pathogenic" variants together with a functional analysis of engineered +2C>T substitutions using a cell culture-based full-length gene splicing assay. Our results establish proof of concept that +2C>T variants are qualitatively different from +2T>C variants in terms of their functionality and suggest that, in sharp contrast to +2T>C variants, most if not all +2C>T variants have no pathological relevance. Our findings have important implications for interpreting the clinical relevance of +2C>T variants and understanding the evolutionary switching between GT and GC 5' splice sites in mammalian genomes.
在人类基因组中，大多数 5' 剪接位点（99%）使用典型的 GT 二核苷酸，而一小部分（1%）使用非典型的 GC 二核苷酸。5' 剪接位点 GT>GC（+2T>C）变体的功能和致病性已得到广泛研究，但我们对 5' 剪接位点 GC>GT（+2C>T）变体知之甚少。在此，我们通过对报道的+2C>T“致病性”变体进行荟萃分析，并使用基于细胞培养的全长基因剪接测定法对工程化的+2C>T 取代进行功能分析，解决了这一不足。我们的结果证明了概念，即+2C>T 变体在功能方面与+2T>C 变体存在质的差异，并表明与+2T>C 变体形成鲜明对比的是，大多数（如果不是全部）+2C>T 变体与病理无关。我们的发现对于解释+2C>T 变体的临床相关性以及理解哺乳动物基因组中 GT 和 GC 5' 剪接位点之间的进化转换具有重要意义。
