Application of CRISPR /Cas9 for GDF9 Gene Editing in Caprine Granulosa Cells: Effects on Receptor Signalling and FGF2 Response

ABSTRACT Fecundity‐related genes, such as GDF9, play a critical role in regulating ovulation, fertilisation and early embryonic development. This study aimed to elucidate the functional role of GDF9 in caprine granulosa cells by employing CRISPR/Cas9‐mediated gene editing. The CRISPR/Cas9 system, incorporating single guide RNA (sgRNA) and Cas9 endonuclease, was used to specifically disrupt the GDF9 gene. Successful GDF9 knockout was confirmed via the T7 Endonuclease I (T7E1) cleavage assay. Subsequent analyses assessed the impact of GDF9 disruption on the expression of GDF9 and its associated receptors—BMPR‐1A, BMPR‐1B and BMPR‐II. Additionally, the study examined the modulatory effects of fibroblast growth factor 2 (FGF2) on receptor expression. FGF2 treatment led to increased mRNA expression of BMPR‐1A, BMPR‐1B and BMPR‐II in wild‐type granulosa cells. Furthermore, follicle‐stimulating hormone receptor (FSHR) levels were significantly upregulated, whereas luteinising hormone receptor (LHR) expression decreased following FGF2 stimulation in wild‐type cells. In contrast, GDF9‐knockout cells showed elevated expression of both FSHR and LHR. The study also investigated the impact of GDF9 deletion on the expression of key steroidogenic genes, particularly StAR. The combined presence of GDF9 and FGF2 synergistically enhanced StAR expression. Cellular responses to FGF2 included a downregulation of CASPASE 3, indicating reduced apoptosis and an upregulation of PCNA, suggesting increased cell proliferation. In conclusion, this study provides novel insights into the regulatory role of GDF9 in ovarian granulosa cell function and highlights the utility of CRISPR/Cas9 technology for functional genomics in caprine species. The findings have significant implications for enhancing reproductive performance through targeted gene modulation.