Gonadotropin-releasing hormone (GnRH) is a highly conserved neuroendocrine decapeptide that is essential for the onset of puberty and the maintenance of the reproductive state. In addition to its role as hypothalamic releasing hormone, GnRH has multiple functions including modulator of neural activity within the nervous system and of resulting behaviors. These multiple functions are reflected by the existence of multiple isoforms. Despite its importance as a critical hypothalamic releasing hormone, the gnrh1 gene has been lost in zebrafish, and its reproductive function is not compensated for by other GnRH isoforms (GnRH2 and GnRH3), suggesting that, surprisingly, zebrafish do not use any of the GnRH peptides to control reproduction and fertility. Previously we proposed that Phoenixin/SMIM20, a novel peptide identified in mammals and the ligand for the orphan GPR173, is a potential candidate to control the initiation of sexual development and fertility in the zebrafish. Here we confirm the sequence of the zebrafish phoenixin/smim20 gene and by RT-PCR show that it is expressed early in development through adulthood. Subsequently we show that phoenixin/smim20 is expressed in the adult brain including the regions of the hypothalamus important in the control of fertility and reproduction.

促性腺激素释放激素 (GnRH) 是一种高度保守的神经内分泌十肽，对青春期的开始和生殖状态的维持至关重要。除了作为下丘脑释放激素的作用外，GnRH 还具有多种功能，包括调节神经系统内的神经活动和由此产生的行为。这些多重功能通过多种异构体的存在来体现。尽管它作为一种关键的下丘脑释放激素很重要，但gnrh1基因在斑马鱼中已经丢失，并且其生殖功能没有被其他 GnRH 同种型（GnRH2 和 GnRH3）补偿，这表明，令人惊讶的是，斑马鱼不使用任何 GnRH 肽来控制繁殖和生育能力。此前，我们提出 Phoenixin/SMIM20，一种在哺乳动物中发现的新型肽和孤儿 GPR173 的配体，是控制斑马鱼性发育和生育能力开始的潜在候选者。在这里，我们确认了斑马鱼phoenixin/smim20基因的序列，并通过 RT-PCR 显示它在成年期的早期发育中表达。随后我们表明，phoenixin/smim20在成人大脑中表达，包括对控制生育和繁殖很重要的下丘脑区域。