The multiple sex chromosomes of platypus and echidna are not completely identical and several share homology with the avian Z

Rens, Willem, O'Brien, Patricia C. M., Grutzner, Frank, Clarke, Oliver, Graphodatskaya, Daria, Tsend-Ayush, Enkhjargal, Trifonov, Vladimir A., Skelton, Helen, Wallis, Mary C., Johnston, Steve, Veyrunes, Frederic, Graves, Jennifer A. M. and Ferguson-Smith, Malcolm A. (2007) The multiple sex chromosomes of platypus and echidna are not completely identical and several share homology with the avian Z. Genome Biology, 8 11: R243.1-R243.21. doi:10.1186/gb-2007-8-11-r243


Author Rens, Willem
O'Brien, Patricia C. M.
Grutzner, Frank
Clarke, Oliver
Graphodatskaya, Daria
Tsend-Ayush, Enkhjargal
Trifonov, Vladimir A.
Skelton, Helen
Wallis, Mary C.
Johnston, Steve
Veyrunes, Frederic
Graves, Jennifer A. M.
Ferguson-Smith, Malcolm A.
Title The multiple sex chromosomes of platypus and echidna are not completely identical and several share homology with the avian Z
Journal name Genome Biology   Check publisher's open access policy
ISSN 1474-760X
Publication date 2007-11-16
Sub-type Article (original research)
DOI 10.1186/gb-2007-8-11-r243
Open Access Status DOI
Volume 8
Issue 11
Start page R243.1
End page R243.21
Total pages 21
Place of publication London, United Kingdom
Publisher BioMed Central
Collection year 2008
Language eng
Formatted abstract
Background
Sex-determining systems have evolved independently in vertebrates. Placental mammals and marsupials have an XY system, birds have a ZW system. Reptiles and amphibians have different systems, including temperature-dependent sex determination, and XY and ZW systems that differ in origin from birds and placental mammals. Monotremes diverged early in mammalian evolution, just after the mammalian clade diverged from the sauropsid clade. Our previous studies showed that male platypus has five X and five Y chromosomes, no SRY, and DMRT1 on an X chromosome. In order to investigate monotreme sex chromosome evolution, we performed a comparative study of platypus and echidna by chromosome painting and comparative gene mapping.

Results

Chromosome painting reveals a meiotic chain of nine sex chromosomes in the male echidna and establishes their order in the chain. Two of those differ from those in the platypus, three of the platypus sex chromosomes differ from those of the echidna and the order of several chromosomes is rearranged. Comparative gene mapping shows that, in addition to bird autosome regions, regions of bird Z chromosomes are homologous to regions in four platypus X chromosomes, that is, X1, X2, X3, X5, and in chromosome Y1.

Conclusion

Monotreme sex chromosomes are easiest to explain on the hypothesis that autosomes were added sequentially to the translocation chain, with the final additions after platypus and echidna divergence. Genome sequencing and contig anchoring show no homology yet between platypus and therian Xs; thus, monotremes have a unique XY sex chromosome system that shares some homology with the avian Z.
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

 
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Created: Mon, 12 May 2008, 09:55:55 EST by Keryn Eaton on behalf of School of Animal Studies