Cytogenetic and molecular characterization of Y isochromosome in a 63XO/64Xi(Yq) mosaic karyotype of an intersex horse

P. J. Das, S. K. Lyle, D. Beehan, B. P. Chowdhary, Terje Raudsepp

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12 Citations (Scopus)


Sex chromosome aberrations commonly lead to abnormal sexual development. Here we cytogenetically and molecularly characterized Y isochromosome in an intersex horse. Blood lymphocyte analysis showed a mosaic karyotype with 96% 63,XO and 4% 64,Xi(Y) cells. Molecular analysis of the isochromosome was carried out by fluorescence in situ hybridization and polymerase chain reaction with male-specific and pseudoautosomal markers from the horse Y chromosome. We found that the isochromosome was monocentric, composed of 2 long arms, carrying 2 sets of genes of the pseudoautosomal region (PAR) and the male-specific region of the Y (MSY), including the SRY - thus being genetically equivalent to Y disomy. Sequence analysis of a 1,955-bp region including the SRY exon, the promoter and the UTRs, revealed no mutations in the aberrant Y. The presence of an intact SRY in a small proportion of cells is the proposed cause for the intersex phenotype. Given that the i(Yq) was present in a mosaic form, both post-zygotic and meiotic mechanisms of its origin were proposed. We speculated that nonmosaic 64,Xi(Yq) karyotypes might be rare or absent because of the likely instability of the i(Yq) during cell division. Genetic and phenotypic implications of Y isochromosome formation in other mammals are discussed in the light of the diversity of Y chromosome organization between species.

Original languageEnglish
Pages (from-to)117-127
Number of pages11
JournalSexual Development
Issue number1-3
Publication statusPublished - Feb 2012
Externally publishedYes


  • FISH
  • Horse
  • Intersex
  • Mosaicism
  • PCR
  • Y isochromosome

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Embryology
  • Developmental Biology


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