The ZW micro-sex chromosomes of the Chinese soft-shelled turtle (Pelodiscus sinensis, Trionychidae, Testudines) have the same origin as chicken chromosome 15.
The Chinese soft-shelled turtle (Pelodiscus sinensis, Trionychidae, Testudines) has ZZ/ZW-type micro-sex chromosomes where the 18S-28S ribosomal RNA genes (18S-28S rDNA) are located. The W chromosome is morphologically differentiated from the Z chromosome by partial deletion and amplification of 18S-28S rDNA and W-specific repetitive sequences. We recently found a functional gene (TOP3B) mapped on the P. sinensis Z chromosome, which is located on chicken (Gallus gallus, GGA) chromosome 15. Then we cloned turtle homologues of 4 other GGA15-linked genes (GIT2, NF2, SBNO1, SF3A1) and localized them to P. sinensis chromosomes. The 4 genes all mapped on the Z chromosome, and 2 of them (SBNO1, SF3A1) were also localized to the W chromosome. Our mapping data suggest that at least one large inversion occurred between GGA15 and the P. sinensis Z chromosome, and that there are homologous regions in the distal portions of both the short and long arms between the Z and W chromosomes. W chromosomal differentiation in P. sinensis probably proceeded by the deletion of the proximal chromosomal region followed by 18S-28S rDNA amplification, after a paracentric inversion occurred at the breakpoints between the distal region of 18S-28S rDNA and the proximal region of SBNO1 on the Z chromosome.
Kawagoshi
T
T
Laboratory of Animal Cytogenetics, Biosystems Science Course, Graduate School of Life Science, Sapporo, Japan.
Uno
Y
Y
Matsubara
K
K
Matsuda
Y
Y
Nishida
C
C
D000818:Animals; D002478:Cells, Cultured; D002645:Chickens / Q000235:genetics*; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D012730:Sex Chromosomes; D014426:Turtles / Q000235:genetics*
D018076:DNA, Complementary