Natural Exceptions to Normal Gonad Development in Mammals

  title={Natural Exceptions to Normal Gonad Development in Mammals},
  author={Rafael Jim{\'e}nez and Francisco J. Barrionuevo and Miguel Burgos},
  journal={Sexual Development},
  pages={147 - 162}
Gonads are the only organs with 2 possible developmental pathways, testis or ovary. A consequence of this unique feature is that mutations in genes controlling gonad development give rise not only to gonadal malformation or dysfunction but also to frequent cases of sex reversal, including XY females, XX males and intersexes. Most of our current knowledge on mammalian sex determination, the genetic process by which the gonadal primordia are committed to differentiate as either testes or ovaries… 

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Known cases of XY and XX sex reversals described in mammals are reviewed, focusing mostly on domestic animals where sex reversal pathologies occur and on wild species in which deviations from the usual XX/XY system have been documented.
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It is reported that enforced expression of Dmrt1 in XX mouse fetal gonads using a Wt1-BAC transgene system is sufficient to drive testicular differentiation and male secondary sex development, suggesting that it has retained sex-determining function.
Inherited Sex-Reversal Mutations in SRY Define a Functional Threshold of Gonadogenesis: Biochemical and Evolutionary Implications of a Rare Monogenic Syndrome
The known inherited mutations in SRY provide experiments of nature that unmask multi-faceted molecular functions of this specific DNA-bending protein and architectural transcription factor, suggesting that wild-type SRY functions just above a critical transcriptional threshold required for testis formation.
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Cell fate commitment during mammalian sex determination.
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It is proposed that the balance of endocrine had broken in the XX-DSD pigs, and new insight is provided into coding and non-coding RNAs that may be associated with DSD in pigs.
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It is shown that M. oregoni has lost an independently segregating Y chromosome and that the male-specific sex chromosome is a second X chromosome that is largely homologous to the maternally transmitted X.
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Genetics of sexual differentiation and anomalies in dogs and cats.
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Current studies support the hypothesis that target organ resistance, possibly a mutation in the gene for the MIS receptor, is responsible for abnormalities of genetic sex in the dog and cat, such as the XXY and XO syndromes, chimaeras and mosaic.
XX sex reversal in the American cocker spaniel dog: phenotypic expression and inheritance
The distribution of testicular tissue within ovotestes of true hermaphrodites was consistent with the hypothesis that testicular differentiation is initiated in the center of the gonad and spreads outward.
On Sex-Intergrade Pigs: Their Anatomy, Genetics, and Developmental Physiology
It is not improbable that all sex-intergrades were true hermaphrodites in embryonic or early post-natal stages and a tendency to sexual abnormality in pigs is inherited.
Epididymides of sex-reversed XX mice lack the initial segment.
It is found that the initial segment of XXSxr pseudomales is truly absent, the first report of a mutant genotype causing absence of a segment of the epididymis, showing that, even in full androgenization, male phenotype may not always be independent of chromosomal sex.
Male sexual differentiation in mice lacking H–Y antigen
It is reported here that H–Y is absent from certain mice that develop testes and are of indisputably male phenotype, hence this transplantation antigen is unlikely to be responsible for testis determination.
Abnormal sex-duct development in female moles: the role of anti-Müllerian hormone and testosterone.
RT-PCR demonstrated that the gene governing this hormone begins to be expressed in males coinciding with testis differentiation, and expression continues until shortly after birth, thus suggesting that testosterone produced by the ovotestes is responsible for masculinisation of female moles.
The evolution of female mole ovotestes evidences high plasticity of mammalian gonad development.
Parsimony reconstruction on alternative phylogenetic hypotheses clearly indicates that reversal(s) must have occurred and suggests that a relatively simple genetic mechanism must be associated with the evolution of female hermaphroditism in moles.
Meiosis Onset Is Postponed to Postnatal Stages during Ovotestis Development in Female Moles
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SOX9 is not required for the cellular events of testicular organogenesis in XX mole ovotestes.
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