Sexual differentiation of the zebra finch song system: potential roles for sex chromosome genes.
BACKGROUND
Recent evidence suggests that some sex differences in brain and behavior might result from direct genetic effects, and not solely the result of the organizational effects of steroid hormones. The present study examined the potential role for sex-biased gene expression during development of sexually dimorphic singing behavior and associated song nuclei in juvenile zebra finches.


RESULTS
A microarray screen revealed more than 2400 putative genes (with a false discovery rate less than 0.05) exhibiting sex differences in the telencephalon of developing zebra finches. Increased expression in males was confirmed in 12 of 20 by qPCR using cDNA from the whole telencephalon; all of these appeared to be located on the Z sex chromosome. Six of the genes also showed increased expression in one or more of the song control nuclei of males at post-hatching day 25. Although the function of half of the genes is presently unknown, we have identified three as: 17-beta-hydroxysteroid dehydrogenase type IV, methylcrotonyl-CoA carboxylase, and sorting nexin 2.


CONCLUSIONS
The data suggest potential influences of these genes in song learning and/or masculinization of song system morphology, both of which are occurring at this developmental stage.
Tomaszycki
Michelle L
ML
Department of Psychology & Program in Neuroscience, Michigan State University, East Lansing, MI, USA. tomaszy1@msu.edu
Peabody
Camilla
C
Replogle
Kirstin
K
Clayton
David F
DF
Tempelman
Robert J
RJ
Wade
Juli
J
D015067:17-Hydroxysteroid Dehydrogenases / Q000378:metabolism; D000818:Animals; D015139:Blotting, Southern; D019735:Carbon-Carbon Ligases / Q000378:metabolism; D005260:Female; D046369:Finches / Q000235:genetics / Q000502:physiology*; D015870:Gene Expression; D017403:In Situ Hybridization; D008297:Male; D020411:Oligonucleotide Array Sequence Analysis; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger; D012727:Sex Characteristics; D012730:Sex Chromosomes; D012733:Sex Differentiation / Q000235:genetics* / Q000502:physiology; D013687:Telencephalon / Q000502:physiology*; D033921:Vesicular Transport Proteins / Q000378:metabolism; D014828:Vocalization, Animal / Q000502:physiology*
D012333:RNA, Messenger; D033921:Vesicular Transport Proteins; D015067:17-Hydroxysteroid Dehydrogenases; D019735:Carbon-Carbon Ligases; C021573:methylcrotonoyl-CoA carboxylase