Identification of genes in the testis determination pathway has increased our understanding of the complexity of this decision pathway and provided molecular diagnosis and prevention for inherited disorders affecting sexual development. Sry is accepted as the gene encoding the testis-determining factor in mammals, yet genes directly affected by Sry are unknown. One such gene may be responsible for Sry-negative XX sex reversal, wherein an autosomal gene induces testis development in individuals lacking Sry and the Y chromosome. It is unlikely that these genes will be identified in humans because small family sizes and genetic heterogeneity are severe impediments to linkage analysis. Animal models lack these disadvantages and provide the means to study molecular events in embryonic tissue. Sex determination is expected to be similar among eutherian mammals, and steps common to all mammals should be applicable to humans. Sry-negative XX sex reversal in the canine model is inherited as an autosomal recessive trait. Affected individuals have a female karyotype (78,XX) and either testes (XX males) or ovotestes (XX true hermaphrodites). The canine syndrome is strikingly similar to familial Sry-negative XXSR in humans, in which XX males and XX true hermaphrodites occur as full siblings. The genetic etiology is unknown in both species. Characterization of the testis induction mechanism in the absence of Siy would greatly increase our understanding of testis induction at the molecular level. Our long term goal is to dissect the testis determination pathway, by characterizing genes having a testis induction role and explaining the molecular mechanism of their actions.
The specific aims of this proposal are: (1) Identify the autosomal gene responsible for canine Sry-negative XXSR, through linkage analysis and screening a BAC library. (2) Compare the gene expression pattern in gonads of affected embryos and controls during the normal period of testis determination (d28-32). (3) Compare the gene expression pattern in gonads of affected embryos and controls after the normal period of testis determination (d32-40).
For Aims 2 and 3 we will use quantitative reverse transcriptase polymerase chain reaction and whole mount in situ hybridization to compare embryonic gonadal expression of Sox9, MIS/AMh, Sf1, Daxl, Wt-1 and Sry. At the end of this grant period, we will have identified the gene causing this disorder and the step in the testis pathway that is altered by the mutation in timing, quantity, or location of gene expression.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
5R01HD040351-04
Application #
6711165
Study Section
Reproductive Biology Study Section (REB)
Program Officer
Taymans, Susan
Project Start
2001-04-01
Project End
2006-03-31
Budget Start
2004-04-01
Budget End
2005-03-31
Support Year
4
Fiscal Year
2004
Total Cost
$250,425
Indirect Cost
Name
Cornell University
Department
Veterinary Sciences
Type
Schools of Veterinary Medicine
DUNS #
872612445
City
Ithaca
State
NY
Country
United States
Zip Code
14850
Meyers-Wallen, V N (2012) Gonadal and sex differentiation abnormalities of dogs and cats. Sex Dev 6:46-60
Meyers-Wallen, V N (2009) Review and update: genomic and molecular advances in sex determination and differentiation in small animals. Reprod Domest Anim 44 Suppl 2:40-6
De Lorenzi, L; Groppetti, D; Arrighi, S et al. (2008) Mutations in the RSPO1 coding region are not the main cause of canine SRY-negative XX sex reversal in several breeds. Sex Dev 2:84-95
Kim, YeunHee; Travis, Alexander J; Meyers-Wallen, Vicki N (2007) Parturition prediction and timing of canine pregnancy. Theriogenology 68:1177-82
Meyers-Wallen, V N (2007) Unusual and abnormal canine estrous cycles. Theriogenology 68:1205-10
Pujar, S; Kothapalli, K S D; Goring, H H H et al. (2007) Linkage to CFA29 detected in a genome-wide linkage screen of a canine pedigree segregating Sry-negative XX sex reversal. J Hered 98:438-44
Kothapalli, K S D; Kirkness, E F; Vanwormer, R et al. (2006) Exclusion of DMRT1 as a candidate gene for canine SRY-negative XX sex reversal. Vet J 171:559-61
Meyers-Wallen, Vicki N (2006) Genetics, genomics, and molecular biology of sex determination in small animals. Theriogenology 66:1655-8
Kothapalli, K; Kirkness, E; Pujar, S et al. (2005) Exclusion of candidate genes for canine SRY-negative XX sex reversal. J Hered 96:759-63
Meyers-Wallen, Vicki N (2005) Sf1 and Mis expression: molecular milestones in the canine sex determination pathway. Mol Reprod Dev 70:383-9

Showing the most recent 10 out of 14 publications