Seasonal differences of gene expression profiles in song sparrow (Melospiza melodia) hypothalamus in relation to territorial aggression.
BACKGROUND
Male song sparrows (Melospiza melodia) are territorial year-round; however, neuroendocrine responses to simulated territorial intrusion (STI) differ between breeding (spring) and non-breeding seasons (autumn). In spring, exposure to STI leads to increases in luteinizing hormone and testosterone, but not in autumn. These observations suggest that there are fundamental differences in the mechanisms driving neuroendocrine responses to STI between seasons. Microarrays, spotted with EST cDNA clones of zebra finch, were used to explore gene expression profiles in the hypothalamus after territorial aggression in two different seasons.


RESULTS
Free-living territorial male song sparrows were exposed to either conspecific or heterospecific (control) males in an STI in spring and autumn. Behavioral data were recorded, whole hypothalami were collected, and microarray hybridizations were performed. Quantitative PCR was performed for validation. Our results show 262 cDNAs were differentially expressed between spring and autumn in the control birds. There were 173 cDNAs significantly affected by STI in autumn; however, only 67 were significantly affected by STI in spring. There were 88 cDNAs that showed significant interactions in both season and STI.


CONCLUSIONS
Results suggest that STI drives differential genomic responses in the hypothalamus in the spring vs. autumn. The number of cDNAs differentially expressed in relation to season was greater than in relation to social interactions, suggesting major underlying seasonal effects in the hypothalamus which may determine the differential response upon social interaction. Functional pathway analyses implicated genes that regulate thyroid hormone action and neuroplasticity as targets of this neuroendocrine regulation.
Mukai
Motoko
M
Department of Neurobiology, Physiology, and Behavior, University of California Davis, Davis, California, United States of America. momukai@ucdavis.edu
Replogle
Kirstin
K
Drnevich
Jenny
J
Wang
Gang
G
Wacker
Douglas
D
Band
Mark
M
Clayton
David F
DF
Wingfield
John C
JC
D000374:Aggression; D000818:Animals; D001947:Breeding; D016000:Cluster Analysis; D018076:DNA, Complementary / Q000235:genetics; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D053263:Gene Regulatory Networks / Q000235:genetics; D007031:Hypothalamus / Q000378:metabolism*; D008297:Male; D008954:Models, Biological; D020411:Oligonucleotide Array Sequence Analysis; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012621:Seasons; D012984:Software; D046370:Sparrows / Q000235:genetics*; D013731:Territoriality; D013963:Thyroid Hormones / Q000378:metabolism; D014828:Vocalization, Animal
D018076:DNA, Complementary; D013963:Thyroid Hormones