Chromosome Research

, Volume 19, Issue 5, pp 635–644

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)

  • Asato Kuroiwa
  • Sanae Handa
  • Chigusa Nishiyama
  • Eriko Chiba
  • Fumio Yamada
  • Shintaro Abe
  • Yoichi Matsuda
Article

DOI: 10.1007/s10577-011-9223-6

Cite this article as:
Kuroiwa, A., Handa, S., Nishiyama, C. et al. Chromosome Res (2011) 19: 635. doi:10.1007/s10577-011-9223-6

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.

Keywords

sex determination sex differentiation XO Y chromosome 

Abbreviations

AP

Alkaline phosphatase

ASA

American Standards Association

BSA

Bovine serum albumin

BrdU

Bromodeoxyuridine

cDNA

Complementary DNA

CDP

Cytidine diphosphate

DIG

Digoxygenine

dUTP

Deoxyuridine 5-triphosphate

FISH

Fluorescence in situ hybridization

IgG

Immunoglobulin G

IUCN

International Union for Conservation of Nature

kb

Kilo base pairs

KO

Knockout

MEM

Minimal essential medium

qRT-PCR

Quantitative real-time PCR

RACE

Rapid amplification of cDNA ends

SD

Standard deviation

SDS

Sodium dodecyl sulfate

SSC

Saline sodium citrate

UTR

Untranslated region

UV

Ultraviolet

Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  • Asato Kuroiwa
    • 1
    • 5
  • Sanae Handa
    • 1
  • Chigusa Nishiyama
    • 1
  • Eriko Chiba
    • 1
  • Fumio Yamada
    • 2
  • Shintaro Abe
    • 3
  • Yoichi Matsuda
    • 4
  1. 1.Graduate School of Life ScienceHokkaido UniversitySapporoJapan
  2. 2.Forestry and Forest Products Research InstituteTsukubaJapan
  3. 3.Naha Nature Conservation Office, Ministry of the EnvironmentNahaJapan
  4. 4.Laboratory of Animal Genetics, Department of Applied Molecular Biosciences, Graduate School of Bioagricultural SciencesNagoya UniversityNagoyaJapan
  5. 5.Laboratory of Animal Cytogenetics, Faculty of ScienceHokkaido UniversitySapporoJapan

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