Abstract
Due to its exceptionally small genome size and protogynous hermaphroditism, Monopterus albus has been proposed as a model for vertebrate sexual development. The Kiss/GPR54 system is a central regulator of sexual development in most vertebrates, but its role in sex reversal remains hypothetical. In contrast to mammals, fishes often possess more than one copy of the kiss and gpr54 genes. Our objectives were to identify all kiss/gpr54 genes in the genome of M. albus and to assess their involvement in sex reversal via their expression patterns (qPCR) in females, males, and intersex specimens. We identified only two genes: kiss2 and gpr54‐2. kiss2 expression was extremely high in the gonads of males, intermediate in females, and low in intersex; and reduced in all tissues of intersex. gpr54 expression was also extremely high in the gonads of males, high in intersex, but low in females. gpr54 expression in brain was high in all three sexes. In conclusion, (a) kiss1 has been functionally replaced in M. albus; (b) the functions of gpr54‐2 in brain are not sex‐specific; (c) kiss2 appears to undergo a ‘reset’ in the expression during the sex change; and (d) sex‐specific expression patterns in the gonads indicate that these two genes may play a role in sex reversal in fish.
Highlights
Due to its exceptionally small genome size and protogynous hermaphroditism, Monopterus albus has been proposed as a model for vertebrate sexual development
(a) kiss1 has been functionally replaced in M. albus; (b) the functions of gpr54-2 in brain are not sexspecific; (c) kiss2 appears to undergo a ‘reset’ in the expression during the sex change; and (d) sex-specific expression patterns in the gonads indicate that these two genes may play a role in sex reversal in fish
Using M. albus as a model, this study aimed to improve the understanding of Kisspeptin/GPR54 axis functioning in the sex reversal in fish
Summary
Due to its exceptionally small genome size and protogynous hermaphroditism, Monopterus albus has been proposed as a model for vertebrate sexual development. Among these is a freshwater teleost species Asian swamp eel Monopterus albus (Zuiew, 1793; Synbranchiformes: Synbranchidae) native to SouthEast Asia It is protogynous: It starts its sexual life history as a female, undergoes an intersex stage, and develops into the final male stage [3,4]. Sex reversal of this fish has received some scientific attention in recent years, for example, [3,5,6], the control and molecular mechanisms of this process remain poorly understood As this species has an exceptionally small genome, it has been proposed as a model system for sexual development in vertebrates [3,4]. As there is evidence that kiss and kiss paralogues have different functions [12,14,15], this variability in the number of kiss genes is rather intriguing
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