Institute of Reproductive and Child Health, National Health Commission Key Laboratory of Reproductive Health, Peking University, Beijing 100191, China.
Center for Precision Environmental Health, Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77031, USA.
Hum Mol Genet. 2020 Nov 4;29(18):3132-3144. doi: 10.1093/hmg/ddaa211.
Neural tube defects (NTDs) are a group of severe congenital malformations caused by a failure of neural tube closure during early embryonic development. Although extensively investigated, the genetic etiology of NTDs remains poorly understood. FKBP8 is critical for proper mammalian neural tube closure. Fkbp8-/- mouse embryos showed posterior NTDs consistent with a diagnosis of spina bifida (SB). To date, no publication has reported any association between FKBP8 and human NTDs. Using Sanger sequencing on genomic DNA samples from 472 SB and 565 control samples, we identified five rare (MAF ≤ 0.001) deleterious variants in SB patients, while no rare deleterious variant was identified in the controls (P = 0.0191). p.Glu140* affected FKBP8 localization to the mitochondria and created a truncated form of the FKBP8 protein, thus impairing its interaction with BCL2 and ultimately leading to an increase in cellular apoptosis. p.Ser3Leu, p.Lys315Asn and p.Ala292Ser variants decreased FKBP8 protein level. p.Lys315Asn further increased the cellular apoptosis. RNA sequencing on anterior and posterior tissues isolated from Fkbp8-/- and wildtype mice at E9.5 and E10.5 showed that Fkbp8-/- embryos have an abnormal expression profile within tissues harvested at posterior sites, thus leading to a posterior NTD. Moreover, we found that Fkbp8 knockout mouse embryos have abnormal expression of Wnt3a and Nkx2.9 during the early stage of neural tube development, perhaps also contributing to caudal specific NTDs. These findings provide evidence that functional variants of FKBP8 are risk factors for SB, which may involve a novel mechanism by which Fkbp8 mutations specifically cause SB in mice.
神经管缺陷（NTDs）是一组严重的先天性畸形，由早期胚胎发育中神经管闭合失败引起。尽管已经进行了广泛的研究，但 NTDs 的遗传病因仍知之甚少。FKBP8 对于哺乳动物神经管的正常闭合至关重要。Fkbp8-/- 小鼠胚胎表现出与脊柱裂（SB）一致的后部 NTD。迄今为止，尚无文献报道 FKBP8 与人类 NTDs 之间存在任何关联。我们使用 Sanger 测序对来自 472 名 SB 患者和 565 名对照患者的基因组 DNA 样本进行了分析，在 SB 患者中发现了 5 个罕见的（MAF≤0.001）有害变异，而在对照组中没有发现罕见的有害变异（P=0.0191）。p.Glu140* 影响 FKBP8 向线粒体的定位，并产生 FKBP8 蛋白的截断形式，从而破坏其与 BCL2 的相互作用，最终导致细胞凋亡增加。p.Ser3Leu、p.Lys315Asn 和 p.Ala292Ser 变异降低了 FKBP8 蛋白水平。p.Lys315Asn 进一步增加了细胞凋亡。在 E9.5 和 E10.5 时从 Fkbp8-/-和野生型小鼠的前、后组织中进行 RNA 测序，结果表明 Fkbp8-/- 胚胎在采集后部组织时具有异常的组织表达谱，从而导致后部 NTD。此外，我们发现 Fkbp8 敲除小鼠胚胎在神经管发育早期 Wnt3a 和 Nkx2.9 的表达异常，这也可能导致尾部特异性 NTDs。这些发现为 FKBP8 的功能变异是 SB 的风险因素提供了证据，这可能涉及 Fkbp8 突变特异性导致小鼠 SB 的新机制。
