Biomedical Sciences Graduate Program, Department of Reproductive Medicine, University of California San Diego, La Jolla, California, USA.
Endocrinology. 2012 Apr;153(4):1827-40. doi: 10.1210/en.2011-2049. Epub 2012 Feb 21.
Arginine-phenylalanine-amide (RFamide)-related peptide 3 (RFRP-3, encoded by the Rfrp gene) is the mammalian ortholog of gonadotropin-inhibiting hormone and can inhibit GnRH neuronal activity and LH release. However, the development and regulation of the RFRP-3 system in both sexes is poorly understood. Using in situ hybridization, we examined changes in Rfrp-expressing neurons in mice of both sexes during development and under different adulthood hormonal milieus. We found no sex differences in Rfrp expression or cell number in adult mice. Interestingly, we identified two interspersed subpopulations of Rfrp cells (high Rfrp-expressing, HE; low Rfrp-expressing, LE), which have unique developmental and steroidal regulation characteristics. The number of LE cells robustly decreases during postnatal development, whereas HE cell number increases significantly before puberty. Using Bax knockout mice, we determined that the dramatic developmental decrease in LE Rfrp cells is not due primarily to BAX-dependent apoptosis. In adults, we found that estradiol and testosterone moderately repress Rfrp expression in both HE and LE cells, whereas the nonaromatizable androgen dihydrotestosterone has no effect. Using double-label in situ hybridization, we determined that approximately 25% of Rfrp neurons coexpress estrogen receptor-α in each sex, whereas Rfrp cells do not readily express androgen receptor in either sex, regardless of hormonal milieu. Lastly, when we looked at RFRP-3 receptors, we detected some coexpression of Gpr147 but no coexpression of Gpr74 in GnRH neurons of both intact and gonadectomized males and females. Thus, RFRP-3 may exert its effects on reproduction either directly, via Gpr147 in a subset of GnRH neurons, and/or indirectly, via upstream regulators of GnRH.
精氨酸-苯丙氨酸酰胺（RFamide）相关肽 3（RFRP-3，由 Rfrp 基因编码）是促性腺激素抑制激素的哺乳动物同源物，可抑制 GnRH 神经元活性和 LH 释放。然而，RFRP-3 系统在两性中的发育和调节知之甚少。我们通过原位杂交技术研究了两性小鼠在发育过程中和不同成年激素环境下 Rfrp 表达神经元的变化。我们发现成年小鼠的 Rfrp 表达或细胞数量没有性别差异。有趣的是，我们鉴定出两个交错的 Rfrp 细胞亚群（高 Rfrp 表达，HE；低 Rfrp 表达，LE），它们具有独特的发育和类固醇调节特征。LE 细胞的数量在出生后发育过程中急剧减少，而 HE 细胞数量在青春期前显著增加。使用 Bax 基因敲除小鼠，我们确定 LE Rfrp 细胞数量的急剧减少主要不是由于 BAX 依赖性细胞凋亡。在成年期，我们发现雌二醇和睾酮适度抑制 HE 和 LE 细胞中的 Rfrp 表达，而非芳香化雄激素二氢睾酮没有影响。通过双重原位杂交，我们确定在两性中，大约 25%的 Rfrp 神经元共表达雌激素受体-α，而无论激素环境如何，Rfrp 细胞在两性中都不易表达雄激素受体。最后，当我们观察 RFRP-3 受体时，我们在两性的完整和去势雄性和雌性 GnRH 神经元中检测到一些 Gpr147 的共表达，但没有 Gpr74 的共表达。因此，RFRP-3 可能通过 GnRH 神经元中的 Gpr147（在一部分 GnRH 神经元中）直接或通过 GnRH 的上游调节剂间接发挥其对生殖的作用。
