Synteny conservation of the Z chromosome in 14 avian species (11 families) supports a role for Z dosage in avian sex determination.
In order to determine synteny conservation of the avian Z chromosome, a chicken (Gallus gallus, GGA) Z chromosome painting probe was hybridized to the chromosomes of 14 bird species belonging to 11 different families. The GGAZ painted the Z chromosomes in all species analyzed, suggesting strong conservation of its gene content among the different avian lineages. This was confirmed by the mapping of five GGAZ-orthologous genes (DMRT1, GHR, CHRNB3, ALDOB, B4GALT1) to the Z chromosomes of eight other species. The shuffled order of these genes on different Z chromosomes can be explained by the prevalence of intrachromosomal rearrangements during avian evolution. Synteny conservation of the mammalian X is generally thought to be the result of X chromosome inactivation. The absence of Z chromosome inactivation implies sex-specific dosage differences of a highly conserved array of Z-linked genes in birds. The evolutionary conservation of the entire Z chromosome among avian lineages supports the idea that avian sex determination and/or sex-specific functions are largely based on sex chromosome dosage. We propose that the accumulation of male-specific genes on the Z chromosome confers selective pressure on the Z to conserve its synteny.
Nanda
I
I
Institute of Human Genetics, University of Wurzburg, Wurzburg, Germany.
Schlegelmilch
K
K
Haaf
T
T
Schartl
M
M
Schmid
M
M
D000818:Animals; D001717:Birds / Q000145:classification / Q000235:genetics*; D002478:Cells, Cultured; D017124:Conserved Sequence / Q000235:genetics*; D012730:Sex Chromosomes / Q000235:genetics*; D019849:Sex Determination Processes; D026801:Synteny / Q000235:genetics*