title: Additional copies of CBX2 in the genomes of males of mammals lacking SRY, the Amami spiny rat (Tokudaia osimensis) and the Tokunoshima spiny rat (Tokudaia tokunoshimensis).
abstract: Tokudaia osimensis (the Amami spiny rat) and Tokudaia tokunoshimensis (the Tokunoshima spiny rat) have a sex chromosome composition of XO/XO, no Y chromosome. The mammalian sex-determining gene, SRY, is also absent in these species, which indicates that these spiny rats exhibit a novel sex-determining mechanism that is independent of SRY. To identify a candidate gene that controls this mechanism, the copy numbers and chromosomal locations of 10 genes with important functions in gonadal differentiation were determined: ATRX, CBX2 (M33), DMRT1, FGF9, NR0B1 (DAX1), NR5A1 (Ad4BP/SF1), RSPO1, SOX9, WNT4, and WT1. Multiple bands were detected for NR0B1 in Southern blot analysis, which suggested the presence of multiple copies of the gene in the genomes of these two species. CBX2 was localized to two loci in both sexes of the two species by fluorescence in situ hybridization mapping: 3q24 and 6p11.2 in T. osimensis and 10q25-q26 and 14q12-q13.1 in T. tokunoshimensis. Quantification of copy numbers in the two species by quantitative real-time PCR indicated that there were two or three more copies of CBX2 per haploid genome in males (T. osimensis, n = 3; T. tokunoshimensis, n = 2) than in females (T. osimensis, n = 4; T. tokunoshimensis, n = 2), whereas NR0B1 was present as a single copy in both. The results suggest that additional copies of CBX2 in males might be involved in a novel sex-determining mechanism in species that lack SRY.
authors.affiliation: Graduate School of Life Science, Hokkaido University, Kita 10 Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan. asatok@cris.hokudai.ac.jp
authors.forename: Asato
authors.initials: A
authors.lastname: Kuroiwa
authors.forename: Sanae
authors.initials: S
authors.lastname: Handa
authors.forename: Chigusa
authors.initials: C
authors.lastname: Nishiyama
authors.forename: Eriko
authors.initials: E
authors.lastname: Chiba
authors.forename: Fumio
authors.initials: F
authors.lastname: Yamada
authors.forename: Shintaro
authors.initials: S
authors.lastname: Abe
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Matsuda
mesh_terms: D000818:Animals; D015139:Blotting, Southern; D002874:Chromosome Mapping; D033481:Chromosomes, Mammalian / Q000235:genetics; D057137:DAX-1 Orphan Nuclear Receptor / Q000235:genetics*; D005260:Female; D018628:Gene Dosage; D016678:Genome / Q000235:genetics*; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D051189:Murinae / Q000145:classification / Q000235:genetics*; D063146:Polycomb-Group Proteins; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics*; D019849:Sex Determination Processes; D051876:Sex-Determining Region Y Protein / Q000235:genetics; D013045:Species Specificity
chemical_list: D057137:DAX-1 Orphan Nuclear Receptor; D063146:Polycomb-Group Proteins; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; D012097:Repressor Proteins; D051876:Sex-Determining Region Y Protein; C077885:XIST non-coding RNA