Enhanced at Puberty-1 (Eap1) Expression Critically Regulates the Onset of Puberty Independent of Hypothalamic Kiss1 Expression

Background/aims: Enhance at puberty-1 (Eap1) is an intronless gene that regulates the onset of puberty through a network of hypothalamic genes. However, precise mechanistic events essential for Eap1-regulation of puberty have not been fully elucidated. Eap1 is thought to promote the initiation of puberty through regulation of the hypothalamic metastasis-suppressor KiSS1. We aim to investigate this hypothesis by genetically perturbing Eap1 through RNA interference in vivo.

Methods: We first engineered and optimized four sets of shRNAs that target rat Eap1 mRNA as well as one negative control shRNA. After generating lentiviral (LV) particles, we examined the suppression of Eap1 in NRK-54E cell line to select the most efficient one. Sequencelly, LV-Eap1-shRNA or controls including LV-eGFP and saline were intraventricular microinjected into 21-day-old rats. Rats were raised in appropriate conditions and we examined the time of vaginal opening, ovary physiology as well as hypothalamic puberty-regulatory genes at three developmental stages: juvenile (postnatal day PND25), early puberty (PND35), adult (PND42).

Results: Hypothalamic suppression of Eap1 delayed the onset of rat vaginal opening. Hematoxylin and eosin (H&E) staining revealed a significant reduction of corpus luteum (CL) at PND35, but at PND42 CL levels were normal relative to control. In conjunction with differences in phenotype and ovary morphology, GnRH expression and transcripts were also reduced at PND25 and PND35, while their levels were similar to control at PND42. KiSS1 mRNA and protein levels were not significantly different at all three developmental stages.

Conclusion: Eap1 expression critically regulates puberty as well as GnRH expression. However, Eap1-regulation of puberty may not necessitate KiSS1/GPR54 signaling.