Concurrent hypothalamic gene expression under acute and chronic long days: Implications for initiation and maintenance of photoperiodic response in migratory songbirds

Ila Mishra, Sanjay K. Bhardwaj, Shalie Malik, Vinod Kumar

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


Hypothalamic expression of the thyroid hormone (TH) responsive gonadostimulatory (eya3, cga, tshβ, dio2, dio3, gnrh, gnih) and neurosteroid pathway genes (androgen receptor [ar], aromatase [cyp19], estrogen receptor [er] α and β) was examined in photosensitive redheaded buntings exposed to 2 (acute, experiment 1) or 12 (chronic, experiment 2) long days (16L:8D). Experiment 2 also included a photorefractory group. Acute long days caused a significant increase in eya3, cga, tshβ, dio2 and gnrh and decrease in dio3 mRNA levels. eya3, cga and tshβ expressions were unchanged after the chronic long days. We also found increased cyp19, erα and erβ mRNA levels after acute, and increased cyp19 and decreased erβ levels after the chronic long-day exposure. Photorefractory buntings showed expression patterns similar to that in the photosensitive state, except for high gnrh and gnih and low dio3 mRNA levels. Consistent with gene expression patterns, there were changes in fat deposition, body mass, testis size, and plasma levels of testosterone, tri-iodothyronine and thyroxine. These results show concurrent photostimulation of the TH-signalling and neurosteroid pathways, and extend the idea, based on differences in gene expression, that transitions in seasonal photoperiodic states are accomplished at the transcriptional levels in absolute photorefractory species.

Original languageEnglish
Pages (from-to)81-94
Number of pages14
JournalMolecular and Cellular Endocrinology
StatePublished - Jan 5 2017

Bibliographical note

Funding Information:
A research grant to VK by the Department of Biotechnology, New Delhi through a research grant ( BT/PR4984/MED/30/752/2012 ) supported all analyses and gene expression study. The experiment was carried out using the facility built with the support under IRHPA center for excellence research grant from the Science and Engineering Research Board, New Delhi.

Funding Information:
We thank Professor Michael R. Gorman, University of California, San Diego, CA, USA for critically reading of the manuscript. The help rendered by Dr. Amit Kumar Trivedi in sampling and by Prof. Sangeeta Rani during the experimentation is acknowledged. IM receives a Senior Research Fellowship from the Council of Scientific and Industrial Research, New Delhi.

Publisher Copyright:
© 2016 Elsevier Ireland Ltd


  • Bird
  • Bunting
  • Gene expression
  • Neurosteroid
  • Photoperiod
  • Thyroid hormone

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Endocrinology


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