title: The molecular basis of chromosome orthologies and sex chromosomal differentiation in palaeognathous birds.
abstract: Palaeognathous birds (Struthioniformes and Tinamiformes) have morphologically conserved karyotypes and less differentiated ZW sex chromosomes. To delineate interspecific chromosome orthologies in palaeognathous birds we conducted comparative chromosome painting with chicken (Gallus gallus, GGA) chromosome 1-9 and Z chromosome paints (GGA1-9 and GGAZ) for emu, double-wattled cassowary, ostrich, greater rhea, lesser rhea and elegant crested tinamou. All six species showed the same painting patterns: each probe was hybridized to a single pair of chromosomes with the exception that the GGA4 was hybridized to the fourth largest chromosome and a single pair of microchromosomes. The GGAZ was also hybridized to the entire region of the W chromosome, indicating that extensive homology remains between the Z and W chromosomes on the molecular level. Comparative FISH mapping of four Z- and/or W-linked markers, the ACO1/IREBP, ZOV3 and CHD1 genes and the EE0.6 sequence, revealed the presence of a small deletion in the proximal region of the long arm of the W chromosome in greater rhea and lesser rhea. These results suggest that the karyotypes and sex chromosomes of palaeognathous birds are highly conserved not only morphologically, but also at the molecular level; moreover, palaeognathous birds appear to retain the ancestral lineage of avian karyotypes.
authors.affiliation: Laboratory of Animal Cytogenetics, Division of Genome Dynamics, Creative Research Initiative Sousei, Hokkaido University, North 10 West 8, Kita-ku, Sapporo, 060-0810, Japan.
authors.forename: Chizuko
authors.initials: C
authors.lastname: Nishida-Umehara
authors.forename: Yayoi
authors.initials: Y
authors.lastname: Tsuda
authors.forename: Junko
authors.initials: J
authors.lastname: Ishijima
authors.forename: Junko
authors.initials: J
authors.lastname: Ando
authors.forename: Atushi
authors.initials: A
authors.lastname: Fujiwara
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Matsuda
authors.forename: Darren K
authors.initials: DK
authors.lastname: Griffin
mesh_terms: D000818:Animals; D001717:Birds; D018929:Cell Culture Techniques; D002871:Chromosome Banding; D002874:Chromosome Mapping; D020223:Chromosome Painting; D002875:Chromosomes / Q000235:genetics / Q000648:ultrastructure*; D005347:Fibroblasts / Q000378:metabolism; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D012335:RNA, Ribosomal / Q000737:chemistry; D012730:Sex Chromosomes / Q000648:ultrastructure*; D012733:Sex Differentiation; D013045:Species Specificity
chemical_list: D012335:RNA, Ribosomal