Atikukke Govindaraja, Albosta Paul, Zhang Huamei, Finley Russell L
Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, MI 48201, USA.
Mech Dev. 2014 Aug;133:64-76. doi: 10.1016/j.mod.2014.06.001. Epub 2014 Jun 16.
Cyclin J (CycJ) is a poorly characterized member of the Cyclin superfamily of cyclin-dependent kinase regulators, many of which regulate the cell cycle or transcription. Although CycJ is conserved in metazoans its cellular function has not been identified and no mutant defects have been described. In Drosophila, CycJ transcript is present primarily in ovaries and very early embryos, suggesting a role in one or both of these tissues. The CycJ gene (CycJ) lies immediately downstream of armitage (armi), a gene involved in the Piwi-associated RNA (piRNA) pathways that are required for silencing transposons in the germline and adjacent somatic cells. Mutations in armi result in oogenesis defects but a role for CycJ in oogenesis has not been defined. Here we assessed oogenesis in CycJ mutants in the presence or absence of mutations in armi or other piRNA pathway genes. CycJ null ovaries appeared normal, indicating that CycJ is not essential for oogenesis under normal conditions. In contrast, armi null ovaries produced only two egg chambers per ovariole and the eggs had severe axis specification defects, as observed previously for armi and other piRNA pathway mutants. Surprisingly, the CycJ armi double mutant failed to produce any mature eggs. The double null ovaries generally had only one egg chamber per ovariole and the egg chambers frequently contained an overabundance of differentiated germline cells. Production of these compound egg chambers could be suppressed with CycJ transgenes but not with mutations in the checkpoint gene mnk, which suppress oogenesis defects in armi mutants. The CycJ null showed similar genetic interactions with the germline and somatic piRNA pathway gene piwi, and to a lesser extent with aubergine (aub), a member of the germline-specific piRNA pathway. The strong genetic interactions between CycJ and piRNA pathway genes reveal a role for CycJ in early oogenesis. Our results suggest that CycJ is required to regulate egg chamber production or maturation when piRNA pathways are compromised.
细胞周期蛋白J（CycJ）是细胞周期蛋白依赖性激酶调节因子的细胞周期蛋白超家族中一个特征尚不明确的成员，其中许多调节因子调控细胞周期或转录。尽管CycJ在多细胞动物中是保守的，但其细胞功能尚未确定，也未描述过突变缺陷。在果蝇中，CycJ转录本主要存在于卵巢和极早期胚胎中，表明其在这些组织中的一种或两种中发挥作用。CycJ基因（CycJ）紧邻阿米蒂奇（armi）基因下游，armi基因参与了Piwi相关RNA（piRNA）途径，该途径对于沉默生殖系和相邻体细胞中的转座子是必需的。armi突变会导致卵子发生缺陷，但CycJ在卵子发生中的作用尚未明确。在这里，我们评估了在有或没有armi或其他piRNA途径基因突变的情况下CycJ突变体中的卵子发生。CycJ基因敲除的卵巢看起来正常，这表明在正常条件下CycJ对于卵子发生不是必需的。相比之下，armi基因敲除的卵巢每个卵巢管仅产生两个卵室，并且卵子具有严重的轴规格缺陷，这与之前观察到的armi和其他piRNA途径突变体的情况一样。令人惊讶的是，CycJ armi双突变体未能产生任何成熟卵子。双基因敲除的卵巢通常每个卵巢管只有一个卵室，并且卵室中经常含有过多分化的生殖系细胞。这些复合卵室的产生可以用CycJ转基因抑制，但不能用检查点基因mnk的突变抑制，mnk突变可抑制armi突变体中的卵子发生缺陷。CycJ基因敲除与生殖系和体细胞piRNA途径基因Piwi表现出相似的遗传相互作用，并且在较小程度上与生殖系特异性piRNA途径的成员茄子（aub）表现出遗传相互作用。CycJ与piRNA途径基因之间强烈的遗传相互作用揭示了CycJ在早期卵子发生中的作用。我们的结果表明，当piRNA途径受损时，CycJ是调节卵室产生或成熟所必需的。
