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1: Chromosome Res. 2007;15(6):777-85. Epub 2007 Aug 29.

Search for the sex-determining switch in monotremes: Mapping WT1, SF1, LHX1,
LHX2, FGF9, WNT4, RSPO1 and GATA4 in platypus.

Grafodatskaya D, Rens W, Wallis MC, Trifonov V, O'brien PC, Clarke O, Graves JA, 
Ferguson-Smith MA.

Cambridge Resource Centre for Comparative Genomics, Department of Veterinary
Medicine, University of Cambridge, Cambridge, CB3 OES, UK, [e-mail].

The duck-billed platypus has five pairs of sex chromosomes, but there is no
information about the primary sex-determining switch in this species. As there is
no apparent SRY orthologue in platypus, another gene must acquire the function of
a key regulator of the gonadal male or female fate. SOX9 was ruled out from being
this key regulator as it maps to an autosome in platypus. To check whether other 
genes in mammalian gonadogenesis could be the primary switch in monotremes, we
have mapped a number of candidates in platypus. We report here the autosomal
location of WT1, SF1, LHX1, LHX9, FGF9, WNT4 and RSPO1 in platypus, thus
excluding these from being key regulators of sex determination in this species.
We found that GATA4 maps to sex chromosomes Y(1) and X(2); however, it lies in
the pairing region shown by chromosome painting to be homologous, so is unlikely 
to be either male-specific or differentially dosed in male and female.

PMID: 17717721 [PubMed - in process]

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