MAPK Signaling Contributes to Primary Follicle Development in Zebrafish (Danio rerio)

Folliculogenesis is essential for fish reproduction, but the role of ERK signaling during early primary follicle development in teleosts remains unclear. Here, we reanalyzed and integrated previously published transcriptomic and DNA methylation datasets from four primary follicle subtypes in zebrafish to identify MAPK-related candidate genes. No new sequencing was performed. Additional qRT-PCR and immunohistochemical analyses examined gene expression and the localization of total ERK and JNK proteins, respectively. Zebrafish were also exposed to the ERK inhibitor SCH772984 from 25 to 60 days post-fertilization to assess changes in ovarian development. The reanalysis identified MAPK-related genes with stage-associated differences in expression and DNA methylation. SCH772984 exposure was associated with reduced ovarian ERK phosphorylation and a lower proportion of advanced follicles. These results support a role for ERK signaling in the progression of early ovarian follicles in zebrafish. These observations derive from a single ERK inhibitor at nominal exposure; complementary assays could strengthen the evidence for target specificity.