title: Sex bias and dosage compensation in the zebra finch versus chicken genomes: general and specialized patterns among birds.
abstract: We compared global patterns of gene expression between two bird species, the chicken and zebra finch, with regard to sex bias of autosomal versus Z chromosome genes, dosage compensation, and evolution of sex bias. Both species appear to lack a Z chromosome-wide mechanism of dosage compensation, because both have a similar pattern of significantly higher expression of Z genes in males relative to females. Unlike the chicken Z chromosome, which has female-specific expression of the noncoding RNA MHM (male hypermethylated) and acetylation of histone 4 lysine 16 (H4K16) near MHM, the zebra finch Z chromosome appears to lack the MHM sequence and acetylation of H4K16. The zebra finch also does not show the reduced male-to-female (M:F) ratio of gene expression near MHM similar to that found in the chicken. Although the M:F ratios of Z chromosome gene expression are similar across tissues and ages within each species, they differ between the two species. Z genes showing the greatest species difference in M:F ratio were concentrated near the MHM region of the chicken Z chromosome. This study shows that the zebra finch differs from the chicken because it lacks a specialized region of greater dosage compensation along the Z chromosome, and shows other differences in sex bias. These patterns suggest that different avian taxa may have evolved specific compensatory mechanisms.
authors.affiliation: Department of Integrative Biology and Physiology, University of California, Los Angeles, CA 90095-1606, USA.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Itoh
authors.forename: Kirstin
authors.initials: K
authors.lastname: Replogle
authors.forename: Yong-Hwan
authors.initials: YH
authors.lastname: Kim
authors.forename: Juli
authors.initials: J
authors.lastname: Wade
authors.forename: David F
authors.initials: DF
authors.lastname: Clayton
authors.forename: Arthur P
authors.initials: AP
authors.lastname: Arnold
mesh_terms: D000818:Animals; D001717:Birds / Q000235:genetics / Q000378:metabolism; D002645:Chickens / Q000235:genetics* / Q000378:metabolism; D002874:Chromosome Mapping; D055028:Comparative Genomic Hybridization; D004303:Dosage Compensation, Genetic / Q000235:genetics; D019143:Evolution, Molecular; D005260:Female; D046369:Finches / Q000235:genetics* / Q000378:metabolism; D016678:Genome / Q000235:genetics*; D006657:Histones / Q000378:metabolism; D008297:Male; D020411:Oligonucleotide Array Sequence Analysis; D012727:Sex Characteristics; D012730:Sex Chromosomes / Q000737:chemistry / Q000235:genetics; D013045:Species Specificity; D026801:Synteny / Q000235:genetics
chemical_list: D006657:Histones