TY - JOUR
T1 - In the platypus a meiotic chain of ten sex chromosomes shares genes with the bird Z and mammal X chromosomes
AU - Grützner, Frank
AU - Rens, Willem
AU - Tsend-Ayush, Enkhjargal
AU - El-Mogharbel, Nisrine
AU - O'Brien, Patricia C.M.
AU - Jones, Russell C.
AU - Ferguson-Smith, Malcolm A.
AU - Marshall Graves, Jennifer A.
PY - 2004/12/16
Y1 - 2004/12/16
N2 - Two centuries after the duck-billed platypus was discovered, monotreme chromosome systems remain deeply puzzling. Karyotypes of males1, or of both sexes2-1, were claimed to contain several unpaired chromosomes (including the X chromosome) that form a multi-chromosomal chain at meiosis. Such meiotic chains exist in plants5 and insects6 but are rare in vertebrates7. How the platypus chromosome system works to determine sex and produce balanced gametes has been controversial for decades1-4. Here we demonstrate that platypus have five male-specific chromosomes (Y chromosomes) and five chromosomes present in one copy in males and two copies in females (X chromosomes). These ten chromosomes form a multivalent chain at male meiosis, adopting an alternating pattern to segregate into XXXXX-bearing and YYYYY-bearing sperm. Which, if any, of these sex chromosomes bears one or more sex-determining genes remains unknown. The largest X chromosome, with homology to the human X chromosome, lies at one end of the chain, and a chromosome with homology to the bird Z chromosome lies near the other end. This suggests an evolutionary link between mammal and bird sex chromosome systems, which were previously thought to have evolved independently.
AB - Two centuries after the duck-billed platypus was discovered, monotreme chromosome systems remain deeply puzzling. Karyotypes of males1, or of both sexes2-1, were claimed to contain several unpaired chromosomes (including the X chromosome) that form a multi-chromosomal chain at meiosis. Such meiotic chains exist in plants5 and insects6 but are rare in vertebrates7. How the platypus chromosome system works to determine sex and produce balanced gametes has been controversial for decades1-4. Here we demonstrate that platypus have five male-specific chromosomes (Y chromosomes) and five chromosomes present in one copy in males and two copies in females (X chromosomes). These ten chromosomes form a multivalent chain at male meiosis, adopting an alternating pattern to segregate into XXXXX-bearing and YYYYY-bearing sperm. Which, if any, of these sex chromosomes bears one or more sex-determining genes remains unknown. The largest X chromosome, with homology to the human X chromosome, lies at one end of the chain, and a chromosome with homology to the bird Z chromosome lies near the other end. This suggests an evolutionary link between mammal and bird sex chromosome systems, which were previously thought to have evolved independently.
UR - http://www.scopus.com/inward/record.url?scp=11144346999&partnerID=8YFLogxK
U2 - 10.1038/nature03021
DO - 10.1038/nature03021
M3 - Article
SN - 0028-0836
VL - 432
SP - 913
EP - 917
JO - Nature
JF - Nature
IS - 7019
ER -