Developmental stage-specific localization of CK1α protein in the mouse ovary.

Casein kinase 1 alpha (CK1α), a conserved serine/threonine kinase, regulates diverse cellular processes including signal transduction, cell cycle progression, and DNA replication. To define its spatiotemporal dynamics during mammalian ovarian development, we systematically analyzed CK1α protein expression from embryonic day (E) 14.5 to postnatal day (P) 56 in the mouse ovary using Western blotting, immunofluorescence (IF) on tissue sections, and IF on isolated primary granulosa cells and oocytes. Reanalysis of published single-cell RNA sequencing data revealed progressive upregulation of Csnk1a1 transcripts from E9.5 through early postnatal stages. At the protein level, CK1α expression significantly increased from E14.5 to P56, with stabilization after P28. Immunofluorescence showed CK1α localized predominantly to oocytes within primordial follicles from E14.5 to P7. Starting at P7, CK1α expression expanded to include granulosa cells of developing primary and secondary follicles. Quantitative fluorescence analysis confirmed that CK1α signal in granulosa cells increased significantly from P7 onward, while the signal in the oocytes gradually decreased throughout development process. In vitro validation confirmed robust CK1α localization in both isolated granulosa cells and oocytes, co-localizing with FSHR and DDX4, respectively. This study provides the first comprehensive spatiotemporal atlas of CK1α expression in the wild-type developing mouse ovary, revealing stage-specific localization patterns that suggest distinct roles in oocyte maintenance and granulosa cell differentiation during folliculogenesis.