B Senthilkumaran

University of Hyderabad, Hyderabad

B Senthilkumaran is a Professor, DBT-TATA Innovation Fellow, and faculty in the Department of Animal Biology, School ofLife Sciences, University of Hyderabad. He works in the area of fish reproductive biology and molecular endocrinology research. His group is known for identifying the shift in steroidogenesis during meiotic maturation and unravelling the molecular mechanisms underlying sexual development and gamete maturation in fishes. His group has also identified sexually dimorphic transcripts and proteins from the gonads and brain to define sex differentiation that leads to identifying biomarkers of gamete maturation and brain sex differentiation in fishes. He is a recipient of the DBT-TATA innovation Fellowship (2014--2019) from DBT India, visiting STA and JSPS fellowships from the Government of Japan, Global Ambassador Fellowship, University of Saskatchewan, Canada (2021-2022) and J C Bose Fellowship (2023) from SERB, India. He is a Fellow of the National Academy of Agricultural Sciences (2022) and an elected Fellow of all three major science academies in India. Elected as Fellow in 2020.

B Senthilkumaran

Session 3A - Lectures by Fellows and Associates

E Krishnakumar, RRI, Bengaluru

'Brain sex differentiation' in bony fishes

The mammalian brain depicts structural and functional changes during brain sex differentiation wherein responses of a fetal brain to sex steroid hormones impart diverse variations as specified by gonadal sex, leading to a gender-centric pattern. Later, the influence of sex steroids sensitizes the brain through a steroid-mediated feedback mechanism. Consequentially, gender-based brain differences are evident, driven by various molecules with structure-based differences. On the other hand, the 'brain sex differentiation' mediated impact on gonads seems intriguing in lower vertebrates. Such a mechanism seems consequential rather than causative, yet distinguished gender-based mechanisms have been recognized. Bony fishes exhibit sexual plasticity during gonadal development. Incidentally, our research on this line identified novel brain-specific biomarkers concerning brain-gonadal interaction during sexual development in fish. Sex-specific differences in a variety of transcripts or molecules ranging from tryptophan hydroxylase, tyrosine hydroxylase, cyp19al, serotonin, catecholamines, glial cell-line derived neurotropic factor, and its receptor, gfra-1 are evident in the fish brain during early gonadal development. Incidentally, gonadotropin-releasing hormone but not gonadotropins showed a brief phase of sexual dimorphism. In line with this, the controlled release of sex steroids via an osmotic pump imparted hormone-mediated influence on several brain biomarkers, indicating a contributory gonadal influence. In general, the brain serotonergic system explicitly directs male sex development, while the catecholaminergic system shows higher activity during female sex development. Overall, our study warrants the existence of brain sex differentiation in fish, leading to the identification of the most reliable novel gene biomarkers from the brain to detect reproductive well-being or endocrine disruption.

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