Journal article
Non-homologous sex chromosomes of birds and snakes share repetitive sequences
Chromosome Research, Vol.18(7), pp.787-800
2010
Abstract
Snake sex chromosomes provided Susumo Ohno with the material on which he based his theory of how sex chromosomes differentiate from autosomal pairs. Like birds, snakes have a ZZ male/ZW female sex chromosome system, in which the snake Z is a macrochromosome much the same size as the bird Z. However, the gene content shows clearly that the snake and bird Z chromosomes are completely non-homologous. The molecular aspect of W chromosome degeneration in snakes remains largely unexplored. We used comparative genomic hybridization to identify the female-specific region of the W chromosome in representative species of Australian snakes. Using this approach, we show that an increasingly complex suite of repeats accompanies the evolution of W chromosome heteromorphy. In particular, we found that while the python Liasis fuscus exhibits no sex-specific repeats and indeed, no cytologically recognizable sex-specific region, the colubrid Stegonotus cucullatus shows a large domain on the short arm of the W chromosome that consists of female-specific repeats, and the large W of Notechis scutatus is composed almost entirely of repetitive sequences, including Bkm and 18S rDNA-related elements. FISH mapping of both simple and complex probes shows patterns of repeat amplification concordant with the size of the female-specific region in each species examined. Mapping of intronic sequences of genes that are sex-linked in both birds (DMRT1) and snakes (CTNNB1) reveals massive amplification in discrete domains on the W chromosome of the elapid N. scutatus. Using chicken W chromosome paint, we demonstrate that repetitive sequences are shared between the sex chromosomes of birds and derived snakes. This could be explained by ancestral but as yet undetected shared synteny of bird and snake sex chromosomes or may indicate functional homology of the repeats and suggests that degeneration is a convergent property of sex chromosome evolution. We also establish that synteny of snake Z-linked genes has been conserved for at least 166 million years and that the snake Z consists of two conserved blocks derived from the same ancestral vertebrate chromosome. © 2010 Springer Science + Business Media B.V.
Details
- Title
- Non-homologous sex chromosomes of birds and snakes share repetitive sequences
- Authors
- Denis O'Meally (Author) - Australian National UniversityH R Patel (Author) - Australian National UniversityR Stiglec (Author) - Australian National UniversityS D Sarre (Author) - University of CanberraA Georges (Author) - University of CanberraJ A Marshall Graves (Author) - Australian National UniversityT Ezaz (Author) - Australian National University
- Publication details
- Chromosome Research, Vol.18(7), pp.787-800
- Publisher
- Springer Netherlands
- Date published
- 2010
- DOI
- 10.1007/s10577-010-9152-9
- ISSN
- 0967-3849
- Organisation Unit
- University of the Sunshine Coast, Queensland
- Language
- English
- Record Identifier
- 99451177502621
- Output Type
- Journal article
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