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.

合子分裂失败（ZCF）是一种独特的早期胚胎表型，导致女性不育和体外受精（IVF）和/或胞浆内精子注射（ICSI）的复发失败。通过这种表型，可以恢复形态正常的卵母细胞并成功受精，但是它们无法进行切割。直到现在，该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尚待阐明。B细胞易位基因4（BTG4）是CCR4-NOT腺苷酸酶复合物的关键衔接子，它与小鼠母体mRNA降解有关，但没有人类疾病由BTG4突变引起先前已有报道。在这里，我们确定了BTG4（GenBank：NM_017589.4）中的四个纯合突变，这些突变与ZCF的表型有关，我们发现它们遵循隐性遗传模式。其中三个-c.73C> T（p.Gln25Ter），c.1A> G（p。？）和c.475_478del（p.Ile159LeufsTer15）-导致全长BTG4蛋白完全丢失。对于c.166G> A（p.Ala56Thr），尽管突变BTG4的蛋白水平和分布在受影响个体的受精卵或HeLa细胞中没有改变，但BTG4与CNOT7之间的相互作用被消除了。体内研究进一步表明，母体mRNA衰变的过程在受影响个体的受精卵中被破坏，这为ZCF表型提供了机械解释。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，并为女性不育症提供了遗传标记。