Expression profile of kisspeptin2 and gonadotropin-releasing hormone2 mRNA during photo-thermal and melatonin treatments
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Expression profile of kisspeptin2 and gonadotropin-releasing hormone2 mRNA during photo-thermal and melatonin treatments in the female air-breathing catfish Heteropneustes fossilis R. Chaube & S. Sharma & B. Senthilkumaran & S. G. Bhat & K. P. Joy Received: 13 June 2020 / Accepted: 1 October 2020 # Springer Nature B.V. 2020
Abstract In seasonally breeding vertebrates, extrinsic factors like photoperiod and temperature are major determinants, controlling the annual reproductive cycle. In teleosts, kisspeptin, which occurs in two molecular forms: kisspeptin1 (Kiss1) and kisspetin2 (Kiss2), has been reported to alter gonadotropin (Lh and Fsh) secretion but its effect on gonadotropin-releasing hormone (Gnrh) secretion is not unequivocally proved. In the catfish Heteropneustes fossilis, we isolated and characterized kiss2 and gnrh2 cDNAs and the present work reports effects of altered photo-thermal conditions and melatonin (MT, a pineal hormone) on their expressions in the brain. The exposure of the catfish to long photoperiod (LP, 16 h light) at normal temperature (NT) or high temperature (HT, 28 °C) at normal photoperiod (NP) for 14 or 28 days stimulated both kiss2 and gnrh2 expression in both gonad resting and preparatory phases with the combination of LP + HT eliciting maximal effects. Short photoperiod (SP, 8 h light) under NT or
R. Chaube and S. Sharma contributed equally to this work. R. Chaube : S. Sharma Department of Zoology, Institute of Science, Banaras Hindu University, Varanasi 221005, India B. Senthilkumaran Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India S. G. Bhat : K. P. Joy (*) Centre for Neuroscience, Department of Biotechnology, Cochin University of Science and Technology, Kochi 682022, India e-mail: [email protected]
HT altered the gene expression according to the reproductive phase and temperature. MT that mediates photothermal signals to the brain inhibited brain kiss2 and gnrh2 gene expression in the NP + HT, LP + NT, and SP + NT groups. The altered photo-thermal conditions elicited changes in steroidogenic pathway as evident from changes in plasma E2, progesterone, and testosterone levels. The results show that brain kiss2-gnrh2 signaling is involved in photo-thermal-mediated mechanisms controlling reproduction. Keywords kiss2 . gnrh2 . Expression . Catfish . Brain
Introduction In teleosts, as in other vertebrates, gametogenesis and spawning are regulated by hormones of the brainpituitary-gonadal (BPG) endocrine axis in a hierarchical manner. The primary regulators of the BPG axis are kisspeptin (Kiss), gonadotropin-releasing hormone (Gnrh), and Gnrh-inhibiting hormone (Gnih) in the brain, gonadotropins (Gth: Lh and Fsh) in the pituitary, and steroid hormones in the gonads (Zohar et al. 2010; Chang and Pemberton 2018; Ohga et al. 2018; Somoza et al. 2020; Muñoz-Cueto et al. 2020). Kisspeptin-10 with its cognate receptor GPR54 was first identified in mammals as the upstream regulator of Gnrh. Mutations of the receptor led to reproducti
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