Sex determination and differentiation are complex processes. As a juvenile hermaphrodite or undifferentiated gonochorist, zebrafish undergoes a special phase of juvenile ovary during sex differentiation, making it an excellent model for studying early oogenesis and folliculogenesis. In this study, we provided lines of evidence at morphological, molecular, and genetic levels for roles of Figla (Factor in the Germline Alpha), an oocyte-specific transcription factor, in early zebrafish gonadogenesis. As in mammals, Figla/figla was also expressed in the gonads and its expression in the ovary was also restricted to early oocytes. Disruption of figla gene by CRISPR/Cas9 led to all-male phenotype in the mutant. Detailed analysis of early gonadal development showed that the germ cells in the mutant were clustered in cysts and underwent meiosis, forming oocytes at pre-follicular chromatin nucleolar (CN) stage (stage IA). However, the subsequent transition from cystic CN oocytes to individual follicular perinucleolar (PN) oocytes (stage IB) was blocked, resulting in all-male phenotype of the mutant. The phenotype of figla could not be rescued by estrogen treatment, in contrast to cyp19a1a mutant, and introduction of tp53 mutation had no effect either, unlike fancd1 and fancl mutants. Transcriptome analysis revealed that a large number of biological processes and pathways related to germ cell development especially oogenesis were up-regulated in the presence of Figla, and that the regulation of figla expression may involve heat shock proteins. In conclusion, our results strongly suggest important roles for Figla in juvenile ovary development, especially the formation of individual follicles from cystic oocytes.

Sex determination and differentiation are complex processes controlled by many different factors; however, the relationships among these factors are poorly understood. Zebrafish gonadal differentiation exhibits high plasticity involving multiple factors and pathways, which provides an excellent model for investigating the interactions among them. Ovarian aromatase (cyp19a1a) and dmrt1 are key factors in directing vertebrate ovary and testis differentiation, respectively. Knockout of zebrafish cyp19a1a led to all-male offspring, whereas the loss of dmrt1 resulted in a female-biased sex ratio. In the present study, we established dmrt1^−/−;cyp19a1a^−/− double mutant zebrafish and discovered that the introduction of the dmrt1 mutation into the cyp19a1a mutant could rescue the all-male phenotype of the latter. Interestingly, despite the lack of aromatase/estrogens, the follicles in the ovary of the rescued cyp19a1a mutant could develop normally up to the previtellogenic stage (PV). Further evidence suggested the ovarian aromatase directed ovarian differentiation by suppressing dmrt1 expression via nuclear estrogen receptors (nERs). Our results provide solid evidence for an interaction between cyp19a1a and dmrt1 in zebrafish gonadal differentiation and for the dispensability of estrogens in controlling early folliculogenesis.

Exposure to the antibacterial agent triclosan (TCS) is associated with abnormal placenta growth and fetal development during pregnancy. Peroxisome proliferator-activated receptor γ (PPARγ) is crucial in placenta development. However, the mechanism of PPARγ in placenta injury induced by TCS remains unknown. Herein, we demonstrated that PPARγ worked as a protector against TCS-induced toxicity. TCS inhibited cell viability, migration, and angiogenesis dose-dependently in HTR-8/SVneo and JEG-3 cells. Furthermore, TCS downregulated expression of PPARγ and its downstream viability, migration, angiogenesis-related genes HMOX1, ANGPTL4, VEGFA, MMP-2, MMP-9, and upregulated inflammatory genes p65, IL-6, IL-1β, and TNF-α in vitro and in vivo. Further investigation showed that overexpression or activation (rosiglitazone) alleviated cell viability, migration, angiogenesis inhibition, and inflammatory response caused by TCS, while knockdown or inhibition (GW9662) of PPARγ had the opposite effect. Moreover, TCS caused placenta dysfunction characterized by the significant decrease in weight and size of the placenta and fetus, while PPARγ agonist rosiglitazone alleviated this damage in mice. Taken together, our results illustrated that TCS-induced placenta dysfunction, which was mediated by the PPARγ pathway. Our findings reveal that activation of PPARγ might be a promising strategy against the adverse effects of TCS exposure on the placenta and fetus.