Clinical Research Center for Reproduction and Genetics in Hunan Province, Reproductive and Genetic Hospital of CITIC-Xiangya, Changsha, 410078, China.
Institute of Pediatrics, Children's Hospital of Fudan University and the Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism, Ministry of Science and Technology and Institutes of Biomedical Sciences, State Key Laboratory of Genetic Engineering, Fudan University, Shanghai, 200032, China.
Am J Hum Genet. 2020 Jul 2;107(1):24-33. doi: 10.1016/j.ajhg.2020.05.010. Epub 2020 Jun 4.
Zygotic cleavage failure (ZCF) is a unique early embryonic phenotype resulting in female infertility and recurrent failure of in vitro fertilization (IVF) and/or intracytoplasmic sperm injection (ICSI). With this phenotype, morphologically normal oocytes can be retrieved and successfully fertilized, but they fail to undergo cleavage. Until now, whether this phenotype has a Mendelian inheritance pattern and which underlying genetic factors play a role in its development remained to be elucidated. B cell translocation gene 4 (BTG4) is a key adaptor of the CCR4-NOT deadenylase complex, which is involved in maternal mRNA decay in mice, but no human diseases caused by mutations in BTG4 have previously been reported. Here, we identified four homozygous mutations in BTG4 (GenBank: NM_017589.4) that are responsible for the phenotype of ZCF, and we found they followed a recessive inheritance pattern. Three of them-c.73C>T (p.Gln25Ter), c.1A>G (p.?), and c.475_478del (p.Ile159LeufsTer15)-resulted in complete loss of full-length BTG4 protein. For c.166G>A (p.Ala56Thr), although the protein level and distribution of mutant BTG4 was not altered in zygotes from affected individuals or in HeLa cells, the interaction between BTG4 and CNOT7 was abolished. In vivo studies further demonstrated that the process of maternal mRNA decay was disrupted in the zygotes of the affected individuals, which provides a mechanistic explanation for the phenotype of ZCF. Thus, we provide evidence that ZCF is a Mendelian phenotype resulting from mutations in BTG4. These findings contribute to our understanding of the role of BTG4 in human early embryonic development and provide a genetic marker for female infertility.
合子卵裂失败（ZCF）是一种独特的早期胚胎表型，导致女性不孕以及体外受精（IVF）和/或胞浆内单精子注射（ICSI）的反复失败。具有这种表型的形态正常的卵母细胞可以被取出并成功受精，但它们无法进行卵裂。到目前为止，这种表型是否具有孟德尔遗传模式以及哪些潜在的遗传因素在其发育中起作用仍有待阐明。B 细胞易位基因 4（BTG4）是 CCR4-NOT 脱腺苷酸酶复合物的关键衔接子，该复合物参与了小鼠的母体 mRNA 降解，但以前没有报道过由 BTG4 突变引起的人类疾病。在这里，我们鉴定了 BTG4 中的四个纯合突变（GenBank：NM_017589.4），这些突变负责 ZCF 的表型，我们发现它们遵循隐性遗传模式。其中三个突变（c.73C>T [p.Gln25Ter]、c.1A>G [p.?]和 c.475_478del [p.Ile159LeufsTer15]）导致全长 BTG4 蛋白完全缺失。对于 c.166G>A（p.Ala56Thr），尽管受影响个体的合子或 HeLa 细胞中突变 BTG4 的蛋白水平和分布没有改变，但 BTG4 和 CNOT7 之间的相互作用被消除。体内研究进一步表明，受影响个体的合子中母体 mRNA 降解过程被破坏，这为 ZCF 的表型提供了机制解释。因此，我们提供了证据表明 ZCF 是由 BTG4 突变引起的孟德尔表型。这些发现有助于我们理解 BTG4 在人类早期胚胎发育中的作用，并为女性不孕提供了遗传标记。
