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Sex-dependent gene expression in early brain development of chicken embryos

Birger Scholz1*, Kim Kultima1, Anna Mattsson2, Jeanette Axelsson2, Björn Brunström2, Krister Halldin3, Michael Stigson1 and Lennart Dencker1

Author Affiliations

1 Department of Pharmaceutical Biosciences, Division of Toxicology, The Biomedical Center, Husargatan 3, Box 594, SE-75124 Uppsala, and Centre for Reproductive Biology in Uppsala, Uppsala University, Sweden

2 Department of Environmental Toxicology, Uppsala University, Norbyvägen 18A, SE-75236 Uppsala, and Centre for Reproductive Biology in Uppsala, Uppsala University, Sweden

3 Institute of Environmental Medicine, Karolinska Institutet, P.O. Box 210, SE-171 77 Stockholm, Sweden

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BMC Neuroscience 2006, 7:12  doi:10.1186/1471-2202-7-12

Published: 15 February 2006



Differentiation of the brain during development leads to sexually dimorphic adult reproductive behavior and other neural sex dimorphisms. Genetic mechanisms independent of steroid hormones produced by the gonads have recently been suggested to partly explain these dimorphisms.


Using cDNA microarrays and real-time PCR we found gene expression differences between the male and female embryonic brain (or whole head) that may be independent of morphological differentiation of the gonads. Genes located on the sex chromosomes (ZZ in males and ZW in females) were common among the differentially expressed genes, several of which (WPKCI-8, HINT, MHM non-coding RNA) have previously been implicated in avian sex determination. A majority of the identified genes were more highly expressed in males. Three of these genes (CDK7, CCNH and BTF2-P44) encode subunits of the transcription factor IIH complex, indicating a role for this complex in neuronal differentiation.


In conclusion, this study provides novel insights into sexually dimorphic gene expression in the embryonic chicken brain and its possible involvement in sex differentiation of the nervous system in birds.