Department of Pediatrics, Keio University School of Medicine, Tokyo, Japan.
Circ J. 2012;76(7):1703-11. doi: 10.1253/circj.cj-11-1389. Epub 2012 Apr 13.
The genetic basis of most congenital heart defects (CHDs), especially non-syndromic and non-familial conditions, remains largely unknown.
DNA samples were collected from immortalized cell lines and original genomes of 256 non-syndromic, non-familial patients with cardiac outflow tract (OFT) defects. Genes encoding NKX2.5, GATA4, GATA6, MEF2C, and ISL1, essential for heart development, were analyzed using PCR-based bidirectional sequencing. The transcriptional activity of proteins with identified sequence variations was analyzed using a luciferase assay. A novel sequence variant (A103V in MEF2C) was identified, in addition to 4 unreported non-synonymous sequence variants in 3 known causative genes (A6V in NKX2.5, T330R and S339R in GATA4, and E142K in GATA6) in 5 individuals. None of these was found in 500 controls without CHDs. In vitro functional assay showed that all proteins with identified sequence variations exhibited significant changes in transcriptional activity and/or synergistic activity with other transcription factors. Furthermore, overexpression of the A103V MEF2C variant in a fish system disturbed early cardiac development.
New mutations in the transcription factors NKX2.5, GATA4, GATA6, and MEF2C that affect their protein function were identified in 2.3% (6/256) of patients with OFT defects. Our results provide the first demonstration of MEF2C mutation and suggest that disturbances in the regulatory circuits involving these cardiac transcription factors may cause a subset of non-syndromic and non-familial CHDs.
大多数先天性心脏病（CHD）的遗传基础，尤其是非综合征性和非家族性病例，仍然很大程度上未知。
从 256 例非综合征性、非家族性心脏流出道（OFT）缺陷患者的永生化细胞系和原始基因组中收集 DNA 样本。使用基于 PCR 的双向测序分析编码心脏发育所必需的 NKX2.5、GATA4、GATA6、MEF2C 和 ISL1 的基因。使用荧光素酶测定分析具有鉴定出的序列变异的蛋白质的转录活性。除了在 3 个已知致病基因（NKX2.5 的 A6V、GATA4 的 T330R 和 S339R 以及 GATA6 的 E142K）中发现的 5 个个体中的 4 个未报道的非同义序列变异外，还鉴定出 MEF2C 中的一个新的序列变异（A103V）。在没有 CHD 的 500 名对照中均未发现这些序列变异。体外功能测定显示，所有具有鉴定出的序列变异的蛋白质在转录活性和/或与其他转录因子的协同活性方面均发生了显著变化。此外，在鱼类系统中过表达 A103V MEF2C 变体扰乱了早期心脏发育。
在 256 例 OFT 缺陷患者中的 2.3%（6/256）中发现了影响其蛋白功能的转录因子 NKX2.5、GATA4、GATA6 和 MEF2C 的新突变。我们的结果首次证明了 MEF2C 突变，并提示涉及这些心脏转录因子的调节回路的干扰可能导致一部分非综合征性和非家族性 CHD。
