Hypothalamic and liver transcriptome from two crucial life‐history stages in a migratory songbird

Abstract

Very little is understood about genetic mechanisms underlying the onset of spring migration in latitudinal avian migrants. To gain insight into the genetic architecture of the hypothalamus and liver tissues of a long-distance migrant, we examined and compared the transcriptome profile of captive night-migratory black-headed buntings (Emberiza melanocephala) between photoperiod-induced winter non-migratory (WnM) and spring migratory (SM) life-history states under short and long days, respectively. High-throughput 454 pyrosequenced transcripts were mapped initially with reference to the genome of two phylogenetically close species, Taeniopygia guttata and Ficedula albicollis. The F. albicollis genome gave higher annotation results and was used for further analysis. A total of 216 (78 in hypothalamus; 138 in liver) genes were found to be expressed differentially between the WnM and SM life-history states. These genes were enriched for physiological pathways that might be involved in the regulation of seasonal migrations in birds. For example, genes for the ATP binding pathway in the hypothalamus were expressed at a significantly higher level in SM than in the WnM life-history state. Likewise, upregulated genes associated with the myelin sheath and focal adhesion were enriched in the hypothalamus, and those with cell-to-cell junction, intracellular protein transport, calcium ion transport and small GTPase-mediated signal transduction were enriched in the liver. Many of these genes are a part of physiological pathways potentially involved in the regulation of seasonal migration in birds. These results show molecular changes at the regulatory and metabolic levels associated with seasonal transitions in a long-distance migrant and provide the basis for future studies aimed at unravelling the genetic control of migration in birds.

Transcriptome Analyses of Heart and Liver Reveal Novel Pathways for Regulating Songbird Migration

“…31 and Sharma et al . 21 found general downregulation of genes involved in cell adhesion and cell motility, consistent with our results 31 . We hypothesize that this downregulation of extracellular matrix proteins may help modulate cell to cell communication, cell adhesion and cellular differentiation.…”

“…20 and Sharma et al . 21 who also found wide scale changes in gene transcripts regulating metabolic pathways for lipids, carbohydrates and protein in the black headed bunting. Previous behavioral data show that prior to migration, birds become hyperphagic and increase fat stores, and that failure to do so restricts the ability to enter the migratory state 22,23 .…”

Exploration of tissue-specific gene expression patterns underlying timing of breeding in contrasting temperature environments in a song bird

“…In addition, MAPK pathway being important in the ovary, MAPK1 is estrogen activated in the brain and is important in female sexual behaviour [97]. Both MAPK1 and HSPA8 have been found to be differentially expressed in hypothalamus during spring migration in black-headed buntings ( Emberiza melanocephala ) [98]. ADCYC2 in hypothalamus and SNAP25 in liver are important genes in insulin secretion and four genes are important in temperature detection (two in hypothalamus: MAPK1, HSPA8 and two in ovary: AKT1, HSP90AA1 ).…”

Mapping Molecular Datasets Back to the Brain Regions They are Extracted from: Remembering the Native Countries of Hypothalamic Expatriates and Refugees

“…Despite the intensive investigations of chicken hypothalamus for molecular mining and extraction, these studies have not contextualized sub-regional changes in expression for molecules in relation to published stereotaxic atlases of the chicken that include illustrations, maps and drawings of the hypothalamus with stereotaxic coordinates [112, 444, 471]. Seasonal changes in hypothalamic gene expression have also been documented in the black-headed bunting, a migratory songbird [394, 438]. …”