The KiSS1/GPR54 system in fish.

The KiSS1/GPR54 system has now been identified in non-mammalian vertebrates. Transcripts encoding for KiSS1 and its receptor, GPR54, have been isolated from a number of fish species. The expression of their genes was characterized in the context of temporal and spatial expression and in response to endocrine manipulations. GPR54 sequence is conserved between mammals and fish, with a second receptor sequence identified in zebrafish. The KiSS1 gene sequence is highly divergent between mammals and fish, yet the human kisspeptin is capable of activating the fish GPR54. As in mammals, the fish KiSS1/GPR54 system appears to be partially regulated by gonadal steroids. The data available for fish are fragmented, yet indicate that the KiSS1/GPR54 system is functionally conserved in non-mammalian vertebrates and supports the notion that it has a role in pubertal development and reproduction in piscine systems.