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Seasonal alterations in the daily rhythms in hypothalamic expression of genes involved in the photoperiodic transduction and neurosteroid‐dependent processes in migratory blackheaded buntings
Author(s) -
Mishra I.,
Singh D.,
Kumar V.
Publication year - 2017
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/jne.12469
Subject(s) - medicine , endocrinology , biology , rhythm , circadian rhythm , photoperiodism , gene , neuroactive steroid , signal transduction , gene expression , receptor , microbiology and biotechnology , genetics , gabaa receptor
The present study investigated seasonal alterations in the daily rhythms of hypothalamic expression of genes involved in the photoperiodic regulation of annual cycles in birds. We measured the 4‐hourly mRNA expression of genes involved in the photoperiodic transduction ( OPN 5 , EYA 3 , CGA , TSH β, DIO 2 , DIO 3 ) and neurosteroid‐dependent processes ( AR , CYP 19 , ER α, ER β) in the hypothalamus of migratory blackheaded buntings photoinduced with photosensitive, photostimulated (early and late stimulated) and photorefractory seasonal states. There were significant differences in daily mRNA profiles between the photoperiodic states. Particularly, increased CGA , TSH β and DIO 2 and decreased DIO 3 mRNA levels in the early photostimulated state, compared to the photosensitive state, suggest that thyroid hormones have a role in photostimulation in buntings. Similar differences in the expression of genes coding for the aromatase enzyme ( CYP 19 ) and receptors for oestrogen ( ER α, ER β) (but not androgen; AR ) indicate that there is seasonal alteration in the neuro‐oestrogen‐mediated functions. Furthermore, peak expression times of CGA , TSH β and DIO 2 genes at hours 14‐15 of the day in the early stimulated state indicated molecular regulation of the daily rhythm of photoinducibility in buntings. Most significantly, however, we found an attenuated daily rhythm in thyroid hormone modulatory genes and a switch of peak expression time from day to night in CYP 19 mRNA rhythm in the subsequent late photostimulated state, although testicular maturation still persisted. These alterations in daily rhythms may have signalled the initiation of processes underlying other seasonal phenologies in parallel with the gonadal response, such as a manifestation of the night‐time flight in buntings. These results show alterations in daily rhythms underlying the transcriptional regulation of the photoperiod‐induced seasonal states in migratory blackheaded buntings.