In the platypus a meiotic chain of ten sex chromosomes shares genes with the bird Z and mammal X chromosomes

  title={In the platypus a meiotic chain of ten sex chromosomes shares genes with the bird Z and mammal X chromosomes},
  author={Frank Gr{\"u}tzner and Willem Rens and Enkhjargal Tsend-Ayush and Nisrine El-Mogharbel and P. C. M. O’Brien and Russell C. Jones and Malcolm Andrew Ferguson-Smith and Jennifer A. Marshall Graves},
Two centuries after the duck-billed platypus was discovered, monotreme chromosome systems remain deeply puzzling. Karyotypes of males, or of both sexes, were claimed to contain several unpaired chromosomes (including the X chromosome) that form a multi-chromosomal chain at meiosis. Such meiotic chains exist in plants and insects but are rare in vertebrates. How the platypus chromosome system works to determine sex and produce balanced gametes has been controversial for decades. Here we… 

How did the platypus get its sex chromosome chain? A comparison of meiotic multiples and sex chromosomes in plants and animals

It is concluded that the evolutionary conservation of the chain in monotremes, the structural properties of the translocated chromosomes and the highly accurate segregation at meiosis make the platypus system remarkably different from meiotic multiples in other species.

Bird-like sex chromosomes of platypus imply recent origin of mammal sex chromosomes.

In therian mammals (placentals and marsupials), sex is determined by an XX female: XY male system, in which a gene (SRY) on the Y affects male determination. There is no equivalent in other amniotes,

The unique sex chromosome system in platypus and echidna

Search for the platypus testis-determining gene continues, and the extension of comparative mapping between platypUS and birds and reptiles may shed light on the ancestral origin of monotreme sex chromosomes.

The Status of Dosage Compensation in the Multiple X Chromosomes of the Platypus

While some genes on the platypus X are not dosage compensated, other genes do show some form of compensation via stochastic transcriptional inhibition, perhaps representing an ancestral system that evolved to be more tightly controlled in placental mammals such as human and mouse.

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

A comparative study of platypus and echidna by chromosome painting and comparative gene mapping shows that monotremes have a unique XY sex chromosome system that shares some homology with the avian Z.

Platypus chain reaction: directional and ordered meiotic pairing of the multiple sex chromosome chain in Ornithorhynchus anatinus.

This work has analysed the pairing dynamics of specific sex chromosome pseudoautosomal regions in platypus spermatocytes during prophase of meiosis I and shows a highly coordinated pairing process that begins at the terminal Y5 chromosome and completes with the union of sex chromosomes X1Y1.

Chromosome chains and platypus sex: kinky connections.

  • T. Ashley
  • Biology
    BioEssays : news and reviews in molecular, cellular and developmental biology
  • 2005
Gutzner et al. find no recognizable SRY sequence and question whether the mammalian X was even the original sex chromosome in the platypus, suggesting that the original platypUS sex chromosomes were derived from the ZW chromosome system of birds and reptiles.

More sex chromosomes than autosomes in the Amazonian frog Leptodactylus pentadactylus

Heteromorphic sex chromosomes are common in eukaryotes and largely ubiquitous in birds and mammals. The largest number of multiple sex chromosomes in vertebrates known today is found in the monotreme

Analysis of SINE and LINE repeat content of Y chromosomes in the platypus, Ornithorhynchus anatinus.

This work isolates, sequencing and analysis of approximately 700 kb of sequence of the non-recombining regions of Y2, Y3 and Y5, which revealed differences in base composition and repeat content between autosomes and sex chromosomes, and within the sex chromosomes themselves.

Convergent Evolution of Chicken Z and Human X Chromosomes by Expansion and Gene Acquisition

It is concluded that the avian Z and mammalian X chromosomes followed convergent evolutionary trajectories, despite their evolving with opposite (female versus male) systems of heterogamety.



Resolution and evolution of the duck-billed platypus karyotype with an X1Y1X2Y2X3Y3X4Y4X5Y5 male sex chromosome constitution.

The preparation of chromosome-specific probes from flow-sorted chromosomes and their application in the identification and classification of all platypus chromosomes are reported on, revealing that the male karyotype has 21 pairs of chromosomes and 10 unpaired chromosomes (E1-E10), which are linked by short regions of homology to form a multivalent chain in meiosis.

A unique cytogenetic system in monotremes

All 3 extant genera of monotremes show a unique kind of cytogenetic system involving the formation of a structurally heterozygous chain multiple apparently coupled with a system of complementary

Unusual sex chromosome inheritance in mammals.

  • K. Fredga
  • Biology
    Philosophical transactions of the Royal Society of London. Series B, Biological sciences
  • 1970
The present contribution will mainly deal with unusual sex chromosome inheritance, that is the groups (ii), (iii) and (iv) above, but the other two groups will also be briefly discussed and examples will be given.

Meiotic behavior of the X1X2Y1Y2 quadrivalent of the primateAlouatta caraya

Thin sections of the quadrivalent body show that the chromatin packing in the sex chromosome region is different from that of the autosomal region and this X1X2Y1Y2/X1X1XX2 sex chromosome system may be extended among other members of the genusAlouatta.

The origin and function of the mammalian Y chromosome and Y‐borne genes – an evolving understanding

  • J. Graves
  • Biology
    BioEssays : news and reviews in molecular, cellular and developmental biology
  • 1995
The addition–attrition hypothesis predicts that the pseudoautosomal region of the human X is merely the last relic of the latest addition, and evolved functions in male sex determination and differentiation distinct from the general functions of their X‐linked partners.

A duplicated copy of DMRT1 in the sex-determining region of the Y chromosome of the medaka, Oryzias latipes

  • I. NandaM. Kondo M. Schartl
  • Biology
    Proceedings of the National Academy of Sciences of the United States of America
  • 2002
It is found that in the fish medaka the Y chromosome-specific region spans only about 280 kb and contains a duplicated copy of the autosomal DMRT1 gene, named D MRT1Y, which is the only functional gene in this chromosome segment and maps precisely to the male sex-determining locus.

Karyotypic conservation in the mammalian order monotremata (subclass Prototheria)

The order Monotremata, comprising the platypus and two species of echidna (Australian and Nuigini) is the only extant representative of the mammalian subclass Prototheria, which diverged from

DMRT1 in a ratite bird: evidence for a role in sex determination and discovery of a putative regulatory element

Part of the candidate bird sex-determining gene DMRT1 is cloned from the emu, a ratite bird, and it is shown that it is expressed during the stages of development corresponding to gonadal differentiation in the chicken and an unexpressed 270-bp region in intron 3 showed 90% homology with a sequence in the corresponding intron of human D MRT1.

Z and W chromosomes of chickens: studies on their gene functions in sex determination and sex differentiation

The purpose of this review is to summarize the present knowledge of these sex chromosome-linked genes in chickens and to give perspectives and point out questions concerning the mechanisms of avian sex determination.

The monotreme genome: a patchwork of reptile, mammal and unique features?