A variant in long noncoding RNA NORSF affects granulosa cells response to transcription factor RFX7

NORSF is a nuclear long noncoding RNA (lncRNA) that contributes to the follicular atresia and restrains 17β-estradiol (E₂) release by granulosa cells (GCs). Importantly, it is also a potential candidate gene in the quantitative trait locus (QTLs) for sow fertility traits. We identified NORSF as a candidate (causal) gene affecting sow fertility traits. A novel G–A variant was discovered at −478 nt of the NORSF promoter and termed as g.−478G>A. Association analysis revealed that this variant was associated with sow fertility traits (e.g., the total number of piglets born, the total number of piglets born alive, and the number of healthy piglets). Mechanistically, the g.−478G>A variant reduced the binding activity of the NORSF promoter to its transcription activator regulatory factor X7 (RFX7), leading to decreased NORSF promoter activity and transcription levels in sow GCs (sGCs), and weakened inhibitory effects on the transcription of CYP19A1, which encodes a rate-limiting enzyme for E₂ synthesis and E₂ release by sGCs. In addition, RFX7 is transcriptionally activated by P53, which restrains E₂ release from sGCs via the RFX7/NORSF/CYP19A1 pathway. These findings indicate that the lncRNA NORSF is a causal gene in QTLs for sow fertility traits and define the P53/NORSF/CYP19A1 pathway as a new signaling pathway affecting sow reproduction, which provides a new target for improving female fertility.