Sex determination in mammals — Before and after the evolution of SRY

  title={Sex determination in mammals — Before and after the evolution of SRY},
  author={M. C. Wallis and Paul D. Waters and Jennifer A. Marshall Graves},
  journal={Cellular and Molecular Life Sciences},
Abstract.Therian mammals (marsupials and placentals) have an XX female: XY male sex chromosome system, which is homologous to autosomes in other vertebrates. The testis-determining gene, SRY, is conserved on the Y throughout therians, but is absent in other vertebrates, suggesting that the mammal system evolved about 310 million years ago (MYA). However, recent work on the basal monotreme mammals has completely changed our conception of how and when this change occurred. Platypus and echidna… 

Lessons from an unusual vertebrate sex-determining gene

‘limited options’ for the emergence of new master sex-determining genes could be more constrained by their need to tightly interact with a conserved sex differentiation regulatory network rather than by being themselves ‘usual suspects’, already inside this sex regulatory network.

Molecular Mechanisms of Sex Determination in Reptiles

The molecular, cellular, morphological, and physiological changes associated with sex determination in reptiles are reviewed and a prospectus on various techniques that promise to reveal new sex-determining genes and regulatory interactions among these genes is provided.

Marsupial Sex Chromosome Behaviour During Male Meiosis

Comparison of the meiotic mechanism present in marsupials with those present in some eutherian mammals opens new perspectives concerning the origin of sex chromosomes and sex chromosome segregation in the ancestor of marsupial and placental mammals.

Evolution of mammalian sex chromosomes and sex determination genes: insights from monotremes.

The results suggest that negative selection might act against X-bearing sperm carrying the chromosome 6 with the large NOR region in females but not in males, providing a possible mechanism that may have influenced the evolution of chromosome 6 as a sex chromosome in therian mammals.

Sox9 gene regulation and the loss of the XY/XX sex-determining mechanism in the mole vole Ellobius lutescens

This work proposes a model whereby Δ14 may have triggered up-regulation of Sox9 in XX gonads leading to destabilization of the XY/XX sex-determining mechanism in Ellobius, indicating that testicular Sox9 expression in E. lutescens might still be regulated via TESCO.

Brain Sexual Differentiation and Requirement of SRY: Why or Why Not?

The evidence from various taxa disputing the requirement of Sry for brain sexual differentiation in mammals (therians and prototherians) and certain fish and reptilian species will be examined.

Identification of SOX3 as an XX male sex reversal gene in mice and humans.

SOX3 and SRY are functionally interchangeable in sex determination and support the notion that SRY evolved from SOX3 via a regulatory mutation that led to its de novo expression in the early gonad.

Identification of SOX 3 as an XX male sex reversal gene in mice and humans

SOX3 and SRY are functionally interchangeable in sex determination and support the notion that SRY evolved from SOX3 via a regulatory mutation that led to its de novo expression in the early gonad.

Genome Analysis of the Platypus

Key findings to emerge from the genome project include the complex evolution of mammalian sex chromosomes, the transition from egg-laying to live birth in mammals, and the evolution of immune genes and venom molecules in this unique species.

Putative Mitochondrial Sex Determination in the Bivalvia: Insights From a Hybrid Transcriptome Assembly in Freshwater Mussels

The sex-biased transcriptome in gonads of two closely-related freshwater mussel species with different reproductive and mitochondrial transmission modes is analyzed and identified common male and female-specific genes, as well as SMI and DUI-related genes that are probably involved in sex determination and mitochondrial inheritance in this animal group.



Sex determination in platypus and echidna: autosomal location of SOX3 confirms the absence of SRY from monotremes

The autosomal localization of SOX3 in monotreme mammals, as well as non-mammal vertebrates, implies that SRY is absent in Prototheria and evolved later in the therian lineage 210-180 million years ago, implying sex determination in platypus and echidna must therefore depend on another male-determining gene(s) on the Y chromosomes, or on the different dosage of a gene on the X chromosomes.

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 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.

Autosomal location of genes from the conserved mammalian X in the platypus (Ornithorhynchus anatinus): implications for mammalian sex chromosome evolution

It is demonstrated that part of the therian X chromosome was lost from the platypus X1 to an autosome, which included genes flanking the XIST locus, and also genes with Y-linked homologues that are important to male reproduction in therians.

Evolution of the human X – a smart and sexy chromosome that controls speciation and development

The origin of the human X, and the evolution of dosage compensation and gene content, is discussed, in the light of recent demonstrations that particular functions in sex and reproduction and cognition have accumulated on it.

Evolution: Conservation of a sex-determining gene

It is shown that a gene implicated in human testis differentiation, DMRT1, has a gonad-specific and sexually dimorphic expression profile during embryogenesis in mammals, birds and a reptile (Alligator mississippiensis).

Sequences homologous to ZFY, a candidate human sex-determining gene, are autosomal in marsupials

Using the ZFY probe, it is found that the Zfy homologous sequences are not on either the X or the Y chromosome in marsupials, but map to the auto-somes, which implies ZFY is not the primary sex-determining gene in mars upials.

Evolution of sex determination and the Y chromosome: SRY-related sequences in marsupials

Comparisons of eutherian and metatherian Y-located SRY sequences suggest rapid evolution of these genes, especially outside the region encoding the DNA-binding HMG box.

Interactions between SRY and SOX genes in mammalian sex determination.

  • J. Graves
  • Biology
    BioEssays : news and reviews in molecular, cellular and developmental biology
  • 1998
This hypothesis makes testable predictions of the phenotypes of XX and XY individuals with deficiencies or overproduction of any of the three genes, and is able to account for the difficult cases of XX(SRY-) males and transdifferentiation in the absence of SRY.