Cristo Fernando, Inácio José M, de Almeida Salomé, Mendes Patrícia, Martins Duarte Saraiva, Maio José, Anjos Rui, Belo José A
Stem Cells and Development Laboratory, CEDOC, NOVA Medical School / Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisboa, Portugal.
Center for Biomedical Research (CBMR), Universidade do Algarve, Faro, Portugal.
BMC Med Genet. 2017 Jul 24;18(1):77. doi: 10.1186/s12881-017-0444-1.
Perturbations on the Left-Right axis establishment lead to laterality defects, with frequently associated Congenital Heart Diseases (CHDs). Indeed, in the last decade, it has been reported that the etiology of isolated cases of CHDs or cases of laterality defects with associated CHDs is linked with variants of genes involved in the Nodal signaling pathway.
With this in mind, we analyzed a cohort of 38 unrelated patients with Congenital Heart Defects that can arise from initial perturbations in the formation of the Left-Right axis and 40 unrelated ethnically matched healthy individuals as a control population. Genomic DNA was extracted from buccal epithelial cells, and variants screening was performed by PCR and direct sequencing. A Nodal-dependent luciferase assay was conducted in order to determine the functional effect of the variant found.
In this work, we report two patients with a DAND5 heterozygous non-synonymous variant (c.455G > A) in the functional domain of the DAND5 protein (p.R152H), a master regulator of Nodal signaling. Patient 1 presents left isomerism, ventricular septal defect with overriding aorta and pulmonary atresia, while patient 2 presents ventricular septal defect with overriding aorta, right ventricular hypertrophy and pulmonary atresia (a case of extreme tetralogy of Fallot phenotype). The functional analysis assay showed a significant decrease in the activity of this variant protein when compared to its wild-type counterpart.
Altogether, our results provide new insight into the molecular mechanism of the laterality defects and related CHDs, priming for the first time DAND5 as one of multiple candidate determinants for CHDs in humans.
左右轴建立过程中的扰动会导致身体左右不对称缺陷，常伴有先天性心脏病（CHD）。事实上，在过去十年中，有报道称孤立性CHD病例或伴有CHD的左右不对称缺陷病例的病因与参与Nodal信号通路的基因变体有关。
考虑到这一点，我们分析了一组38例先天性心脏缺陷患者，这些缺陷可能源于左右轴形成初期的扰动，并以40例种族匹配的健康个体作为对照人群。从颊上皮细胞中提取基因组DNA，通过聚合酶链反应（PCR）和直接测序进行变体筛选。进行了一项依赖Nodal的荧光素酶测定，以确定所发现变体的功能效应。
在这项研究中，我们报告了两名患者，他们在DAND5蛋白（一种Nodal信号的主要调节因子）的功能域中存在DAND5杂合非同义变体（c.455G>A，导致p.R152H）。患者1表现为左位异构、室间隔缺损伴主动脉骑跨和肺动脉闭锁，而患者2表现为室间隔缺损伴主动脉骑跨、右心室肥厚和肺动脉闭锁（法洛四联症极端表型病例）。功能分析试验表明，与野生型对应物相比，该变体蛋白的活性显著降低。
总之，我们的结果为左右不对称缺陷和相关CHD的分子机制提供了新的见解，首次将DAND5作为人类CHD的多个候选决定因素之一。
