Qian Guang, Bao Yongbo, Song Danli, Chen Na, Lin Zhihua
Zhejiang Key Laboratory of Aquatic Germplasm Resources, College of Biological and Environmental Sciences, Zhejiang Wanli University, Ningbo, China.
School of Marine Sciences, Ningbo University, Ningbo, China.
Front Physiol. 2019 May 15;10:594. doi: 10.3389/fphys.2019.00594. eCollection 2019.
The self-renewal and differentiation of germ cells are essential for gametogenesis and reproduction. In mammals, the transcription factors SOHLH1 and SOHLH2, two members of the bHLH family, are specifically expressed in the gonads, and play an important role in spermatocyte and oocyte differentiation. In our previous study, we performed a phylogenetic analysis of the Lophotrochozoa bHLH genes, and two were identified in the Pacific oyster . Based on the genomes of other species that have complete genomic information, we further analyzed the phylogenetics of the in this study. The results indicate that the are ancient genes that were lost in many species during evolution, including in some invertebrates, and lower vertebrates. The phylogenetic tree shows that Sohlh1 and Sohlh2 are located in different scaffolds and that they have low similarity, suggesting early separation in invertebrates. We used RNA-seq and RT-PCR to examine the mRNA expression of the in (termed ), we found that , and are specifically expressed in the gonads. During gonadal development, the mRNA expression levels of both genes increased from the proliferative stage and reached the highest level at the growth stage ( < 0.05). Then, the expression level decreased until the resting stage. In addition, immunohistochemistry was used to determine that the Cg-SOHLH1 protein was specifically expressed in the spermatogonia and spermatocytes. mRNA was expressed in both the male and female gonads, while mRNA was highly expressed in the female gonads at all developmental stages except for the resting stage. These data indicate that Cg-SOHLH might be gonad-specific regulatory factors, similar to mammalian SOHLH, and that Cg-SOHLH1 might be involved in spermatogonial differentiation. This study lays the foundation to further determine the functional role of SOHLH in mollusk gametogenesis and provides a foundation to better understand the regulatory mechanism of gametogenesis in invertebrates.
生殖细胞的自我更新和分化对于配子发生和繁殖至关重要。在哺乳动物中，bHLH家族的两个成员转录因子SOHLH1和SOHLH2在性腺中特异性表达，并在精母细胞和卵母细胞分化中发挥重要作用。在我们之前的研究中，我们对冠轮动物bHLH基因进行了系统发育分析，并在太平洋牡蛎中鉴定出两个。基于其他具有完整基因组信息的物种的基因组，我们在本研究中进一步分析了它们的系统发育。结果表明，它们是古老的基因，在进化过程中在许多物种中丢失，包括一些无脊椎动物和低等脊椎动物。系统发育树显示，Sohlh1和Sohlh2位于不同的支架上，并且它们的相似性较低，表明在无脊椎动物中早期分离。我们使用RNA测序和RT-PCR检测了太平洋牡蛎（称为Cg-SOHLH）中它们的mRNA表达，我们发现Cg-SOHLH1和Cg-SOHLH2在性腺中特异性表达。在性腺发育过程中，这两个基因的mRNA表达水平从增殖期开始增加，并在生长阶段达到最高水平（P<0.0
