Transcriptome analysis of bovine preantral follicles during early folliculogenesis

Primordial (PMF), primary (PF), and secondary follicles (SF) were mechanically isolated from the ovarian cortex of 12- to 24-month-old heifers and analyzed by bulk RNA sequencing. The PMF dataset is available under accession number GSE283263 and was sequenced in the same batch as the PF-SF dataset.

Differential expression analysis of these datasets identified 689 significant genes in PF vs. PMF and 3,206 in SF vs. PF (FDR<0.05), with enrichment in pathways such as PI3K-Akt, Wnt, mTOR, and ECM-receptor interaction. Furthermore, a Likelihood Ratio Test across all stages (using DESeq2, padj<0.05), followed by hierarchical clustering, recognized four main expression clusters enriched in processes like cell cycle regulation and extracellular matrix organization.