Shawki Hossam H, Oishi Hisashi, Usui Toshiaki, Kitadate Yu, Basha Walaa A, Abdellatif Ahmed M, Hasegawa Kazunori, Okada Risa, Mochida Keiji, El-Shemy Hany A, Muratani Masafumi, Ogura Atsuo, Yoshida Shosei, Takahashi Satoru
Department of Anatomy and Embryology, Graduate School of Comprehensive Human Science, University of Tsukuba, Tsukuba, Japan.
Department of Animal Genetic Resources, National Gene Bank, Giza, Egypt.
PLoS One. 2018 Jan 11;13(1):e0190800. doi: 10.1371/journal.pone.0190800. eCollection 2018.
The transcription factor MAFB is an important regulator of the development and differentiation of various organs and tissues. Previous studies have shown that MAFB is expressed in embryonic and adult mouse testes and is expected to act as the downstream target of retinoic acid (RA) to initiate spermatogenesis. However, its exact localization and function remain unclear. Here, we localized MAFB expression in embryonic and adult testes and analyzed its gene function using Mafb-deficient mice. We found that MAFB and c-MAF are the only large MAF transcription factors expressed in testes, while MAFA and NRL are not. MAFB was localized in Leydig and Sertoli cells at embryonic day (E) 18.5 but in Leydig cells, Sertoli cells, and pachytene spermatocytes in adults. Mafb-deficient testes at E18.5 showed fully formed seminiferous tubules with no abnormal structure or differences in testicular somatic cell numbers compared with those of control wild-type mice. Additionally, the expression levels of genes related to development and function of testicular cells were unchanged between genotypes. In adults, the expression of MAFB in Sertoli cells was shown to be stage specific and induced by RA. By generating Mafbfl/fl CAG-CreER™ (Mafb-cKO) mice, in which Cre recombinase was activated upon tamoxifen treatment, we found that the neonatal cKO mice died shortly upon Mafb deletion, but adult cKO mice were alive upon deletion. Adult cKO mice were fertile, and spermatogenesis maintenance was normal, as indicated by histological analysis, hormone levels, and germ cell stage-specific markers. Moreover, there were no differences in the proportion of seminiferous stages between cKO mice and controls. However, RNA-Seq analysis of cKO Sertoli cells revealed that the down-regulated genes were related to immune function and phagocytosis activity but not spermatogenesis. In conclusion, we found that MAFB is dispensable for fetal testis morphogenesis and spermatogenesis maintenance in adult mice, despite the significant gene expression in different cell types, but MAFB might be critical for phagocytosis activity of Sertoli cells.
转录因子MAFB是多种器官和组织发育及分化的重要调节因子。以往研究表明，MAFB在胚胎期和成年小鼠睾丸中均有表达，有望作为视黄酸（RA）的下游靶点启动精子发生。然而，其确切定位和功能仍不清楚。在此，我们定位了MAFB在胚胎期和成年睾丸中的表达，并利用Mafb基因缺陷小鼠分析了其基因功能。我们发现MAFB和c-MAF是睾丸中仅有的两个表达的大型MAF转录因子，而MAFA和NRL则不表达。MAFB在胚胎第18.5天（E18.5）定位于睾丸间质细胞和支持细胞，但在成年小鼠中定位于睾丸间质细胞、支持细胞和粗线期精母细胞。E18.5的Mafb基因缺陷睾丸显示生精小管完全形成，与对照野生型小鼠相比，睾丸体细胞数量无异常结构或差异。此外，不同基因型之间与睾丸细胞发育和功能相关的基因表达水平没有变化。在成年小鼠中，支持细胞中MAFB的表达具有阶段特异性，并由RA诱导。通过构建Mafbfl/fl CAG-CreER™（Mafb-cKO）小鼠，其中Cre重组酶在他莫昔芬处理后被激活，我们发现新生cKO小鼠在Mafb基因缺失后不久死亡，但成年cKO小鼠在基因缺失后存活。成年cKO小鼠可育，组织学分析、激素水平和生殖细胞阶段特异性标志物表明精子发生维持正常。此外，cKO小鼠和对照小鼠之间生精阶段的比例没有差异。然而，对cKO支持细胞的RNA测序分析显示，下调的基因与免疫功能和吞噬活性有关，而与精子发生无关。总之，我们发现MAFB对于成年小鼠胎儿睾丸形态发生和精子发生维持并非必需，尽管在不同细胞类型中有显著的基因表达，但MAFB可能对支持细胞的吞噬活性至关重要。
