Giri Dinesh, Vignola Maria Lillina, Gualtieri Angelica, Scagliotti Valeria, McNamara Paul, Peak Matthew, Didi Mohammed, Gaston-Massuet Carles, Senniappan Senthil
Department of Paediatric Endocrinology, Alder Hey Children's Hospital NHS Foundation Trust, Liverpool, UK.
Department of Women and Children's Health, Institute in the Park, University of Liverpool, Liverpool L12 2AP, UK.
Hum Mol Genet. 2017 Nov 15;26(22):4315-4326. doi: 10.1093/hmg/ddx318.
Congenital hypopituitarism (CH) is characterized by the deficiency of one or more pituitary hormones and can present alone or in association with complex disorders. Congenital hyperinsulinism (CHI) is a disorder of unregulated insulin secretion despite hypoglycaemia that can occur in isolation or as part of a wider syndrome. Molecular diagnosis is unknown in many cases of CH and CHI. The underlying genetic etiology causing the complex phenotype of CH and CHI is unknown. In this study, we identified a de novo heterozygous mutation in the developmental transcription factor, forkhead box A2, FOXA2 (c.505T>C, p.S169P) in a child with CHI and CH with craniofacial dysmorphic features, choroidal coloboma and endoderm-derived organ malformations in liver, lung and gastrointestinal tract by whole exome sequencing. The mutation is at a highly conserved residue within the DNA binding domain. We demonstrated strong expression of Foxa2 mRNA in the developing hypothalamus, pituitary, pancreas, lungs and oesophagus of mouse embryos using in situ hybridization. Expression profiling on human embryos by immunohistochemistry showed strong expression of hFOXA2 in the neural tube, third ventricle, diencephalon and pancreas. Transient transfection of HEK293T cells with Wt (Wild type) hFOXA2 or mutant hFOXA2 showed an impairment in transcriptional reporter activity by the mutant hFOXA2. Further analyses using western blot assays showed that the FOXA2 p.(S169P) variant is pathogenic resulting in lower expression levels when compared with Wt hFOXA2. Our results show, for the first time, the causative role of FOXA2 in a complex congenital syndrome with hypopituitarism, hyperinsulinism and endoderm-derived organ abnormalities.
先天性垂体功能减退症（CH）的特征是一种或多种垂体激素缺乏，可单独出现或与复杂疾病相关。先天性高胰岛素血症（CHI）是一种尽管存在低血糖但胰岛素分泌不受调控的疾病，可单独发生或作为更广泛综合征的一部分出现。在许多CH和CHI病例中，分子诊断尚不清楚。导致CH和CHI复杂表型的潜在遗传病因尚不清楚。在本研究中，我们通过全外显子测序在一名患有CHI和CH且伴有颅面畸形特征、脉络膜缺损以及肝脏、肺和胃肠道等内胚层衍生器官畸形的儿童中，鉴定出发育转录因子叉头框A2（FOXA2）中的一个新生杂合突变（c.505T>C，p.S169P）。该突变位于DNA结合域内一个高度保守的残基处。我们使用原位杂交技术证明了Foxa2 mRNA在小鼠胚胎发育中的下丘脑、垂体、胰腺、肺和食管中强烈表达。通过免疫组织化学对人类胚胎进行表达谱分析显示，hFOXA2在神经管、第三脑室、间脑和胰腺中强烈表达。用野生型（Wt）hFOXA2或突变型hFOXA2瞬时转染HEK293T细胞，结果显示突变型hFOXA2的转录报告活性受损。使用蛋白质印迹分析的进一步分析表明，与Wt hFOXA2相比，FOXA2 p.(S169P)变体具有致病性，导致表达水平降低。我们的结果首次表明FOXA2在伴有垂体功能减退、高胰岛素血症和内胚层衍生器官异常的复杂先天性综合征中的致病作用。
