Mercer Marianne, Dasgupta Anirban, Pawłowski Krzysztof, Buszczak Michael
Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390.
Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390.
Proc Natl Acad Sci U S A. 2025 Apr 15;122(15):e2426524122. doi: 10.1073/pnas.2426524122. Epub 2025 Apr 11.
In ovaries, germ cells differentiate through several stages of cyst development before entering meiosis. This early differentiation program depends on both the stepwise deployment of specific regulatory mechanisms and on maintenance of germline sexual identity. The study of female sterile mutations that result in formation of germ cell tumors has been invaluable in identifying the mechanisms that control these developmental events. Here, we characterize the germ cell-enriched gene null mutants of which cause the formation of a mixture of agametic ovarioles and cystic germ cell tumors. We performed proteomic analysis and found Bbn forms a complex with Ovarian tumor (Otu), a protein previously linked with regulation of the sex determination factor (), and the ortholog of c-Myc binding protein (Mycbp). Loss of also results in the formation of cystic germ cell tumors. Bbn promotes the stability of Otu and fosters interactions between Otu and Mycbp. Germ cells from and mutants display a loss of Sxl expression specifically in the germline. Transgenic rescue experiments show the sterile phenotype is independent from splicing defects. Further evidence suggests Otu physically interacts with and promotes Sxl protein stability. This function does not depend on Otu's deubiquitinase activity. Last, we find the human orthologs of Otu and Mycbp, OTUD4, and MYCBP, also physically interact, suggesting conservation of function. Together these data provide insights into how a conserved complex promotes the germline expression of Sxl protein and the differentiation of germ cells.
在卵巢中，生殖细胞在进入减数分裂之前会通过几个囊肿发育阶段进行分化。这种早期分化程序既依赖于特定调控机制的逐步展开，也依赖于生殖系性别的维持。对导致生殖细胞肿瘤形成的雌性不育突变的研究，在确定控制这些发育事件的机制方面具有重要价值。在这里，我们对富含生殖细胞的基因无效突变体进行了表征，这些突变体导致形成无配子卵巢管和囊性生殖细胞肿瘤的混合物。我们进行了蛋白质组学分析，发现Bbn与卵巢肿瘤（Otu）形成复合物，Otu是一种先前与性别决定因子（）调控相关的蛋白质，也是c-Myc结合蛋白（Mycbp）的直系同源物。的缺失也会导致囊性生殖细胞肿瘤的形成。Bbn促进Otu的稳定性，并促进Otu与Mycbp之间的相互作用。和突变体的生殖细胞在生殖系中特异性地表现出Sxl表达缺失。转基因拯救实验表明，不育表型与剪接缺陷无关。进一步的证据表明，Otu与Sxl蛋白物理相互作用并促进其稳定性。该功能不依赖于Otu的去泛素酶活性。最后，我们发现Otu和Mycbp的人类直系同源物OTUD4和MYCBP也存在物理相互作用，这表明功能具有保守性。这些数据共同为一个保守复合物如何促进Sxl蛋白在生殖系中的表达以及生殖细胞的分化提供了见解。
