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Sex determination: insights from the chicken
Craig A Smith1, Andrew H Sinclair
1Murdoch Childrens Research Institute and Department of Paediatrics, Royal Childrens Hospital, Parkville, Victoria, Australia. craig.smith@mcri.edu.au
Summary
Avian sex determination differs from mammals, using a ZZ:ZW system. Research in chickens reveals conserved and divergent genetic elements, with candidate genes like DMRT1, ASW, and FET1 emerging as key players in this process.
Area of Science:
- Comparative genomics
- Developmental biology
- Evolutionary genetics
Background:
- Vertebrate sex determination varies, with mammals using XX:XY and birds using ZZ:ZW chromosome systems.
- Gonadal development in chickens offers insights into the evolution of sex determination pathways.
- Estrogens are crucial for sex differentiation in chicken embryos, similar to lower vertebrates.
Purpose of the Study:
- To investigate the molecular genetics of sex determination in chickens.
- To compare avian sex determination with mammalian systems and identify conserved/divergent elements.
- To explore candidate genes involved in triggering avian sex determination.
Main Methods:
- Comparative analysis of sex determination pathways across vertebrates.
- Examination of gene expression patterns in developing chicken gonads.
- Identification and evaluation of candidate sex-determining genes in birds.
Main Results:
- Chicken sex determination involves both conserved and divergent genetic elements compared to mammals.
- Estrogen signaling plays a significant role in chicken gonadal differentiation.
- Candidate genes DMRT1 (Z-linked) and ASW, FET1 (W-linked) show potential roles in avian sex determination.
Conclusions:
- Avian sex determination pathways exhibit functional plasticity, with differing gene expression compared to mammals.
- The Z-dosage model is supported by the Z-linked gene DMRT1.
- Novel W-linked genes ASW and FET1 are identified as potential female determinants in birds.