Nonrandom representation of sex-biased genes on chicken Z chromosome.
Several lines of evidence suggest that the X chromosome of various animal species has an unusual complement of genes with sex-biased or sex-specific expression. However, the study of the X chromosome gene content in different organisms provided conflicting results. The most striking contrast concerns the male-biased genes, which were reported to be almost depleted from the X chromosome in Drosophila but overrepresented on the X chromosome in mammals. To elucidate the reason for these discrepancies, we analysed the gene content of the Z chromosome in chicken. Our analysis of the publicly available expressed sequence tags (EST) data and genome draft sequence revealed a significant underrepresentation of ovary-specific genes on the chicken Z chromosome. For the brain-expressed genes, we found a significant enrichment of male-biased genes but an indication of underrepresentation of female-biased genes on the Z chromosome. This is the first report on the nonrandom gene content in a homogametic sex chromosome of a species with heterogametic female individuals. Further comparison of gene contents of the independently evolved X and Z sex chromosomes may offer new insight into the evolutionary processes leading to the nonrandom genomic distribution of sex-biased and sex-specific genes.
Storchová
R
R
Institute of Molecular Genetics, Academy of Sciences of Czech Republic and Center for Applied Genomics, Vídenská 1083, CZ-142 20, Prague 4, Czech Republic. radkas@biomed.cas.cz
Divina
P
P
D000818:Animals; D002645:Chickens / Q000235:genetics*; D002874:Chromosome Mapping; D004303:Dosage Compensation, Genetic; D020224:Expressed Sequence Tags; D005260:Female; D020869:Gene Expression Profiling; D008040:Genetic Linkage; D008297:Male; D012730:Sex Chromosomes / Q000235:genetics*; D012737:Sex Factors