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Evidence for three sex determining loci in Atlantic salmon.

Evidence for three sex determining loci in Atlantic salmon. June 18, 2012. William D. Eisbrenner, Natasha Botwright, Mathew Cook, Evelyn Davidson, Sonja Dominik, Nick Elliott, John Henshall, Stacy Jones, Krzysztof P. Lubieniecki , Peter Kube, Sigrid Lehnert and William S. Davidson.

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Evidence for three sex determining loci in Atlantic salmon.

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  1. Evidence for three sex determining loci in Atlantic salmon. June 18, 2012 William D. Eisbrenner, Natasha Botwright, Mathew Cook, Evelyn Davidson, Sonja Dominik, Nick Elliott, John Henshall, Stacy Jones, Krzysztof P. Lubieniecki, Peter Kube, Sigrid Lehnert and William S. Davidson

  2. Salmonids are diverse – 70 species from 11 genera Genome duplication

  3. Salmonids have genetically determined sex • Cytogenetic Evidence: • Heteromorphic chromosomes in some species • Linkage Map Evidence: • Male specific markers • Crosses between sex reversed females (XX males) and normal females yields all female progeny. • Crossing sex reversed males (XY females) and normal males yield a 3:1 ratio male: female progeny. • Male are the heterogametic sex (XX/XY system)

  4. Why do we care? • SalTas Broodstock program • 3 Year class families, 2004, 2005, 2006 • Originate from East coast of Canada • Economic benefits • Problem: Males are not marketable • Want to develop a genetic marker to identify males • Early removal of males prevents waste of feed and tank space. 1. Pool of males and sex reversed females Misidentification Males 2. Sex reversed females Removed males 3. Cross with normal females 50% males in stock (i.e. 50% waste) All female stock

  5. A chromosome (Ssa02) harboring the sex determining gene has been identified

  6. Marker Selection • Choose markers from Ssa02 • Markers must be informative to be useful. Homologous chromosomes in one individual. Left comes from father. Right comes from mother. B A 1. Grandsire 2. Sire 3.Dam 1 2 3 1 2 3 1 2 3 C B A Informative Not informative

  7. Analysis 1. Grandsire 2. Sire 3.Dam 1 2 3 C B A

  8. An unexpected surprise • 7 families derived from 4 males screened using Ssa02 markers. • These markers did not predict sex in any of these families • Sex is not on chromosome 2? • So where is it?

  9. Fishing for SEX • A Taq-Man 64 SNP genome wide scan suggested SEX was on chromosome 6. • Microsatellite markers mapping to this chromosome confirm this result.

  10. Family history shows the 4 males giving rise to the tested families all share one father. i.e. they are brothers • Therefore expand testing to include more families from more founding sires

  11. Another Surprise SEX is not on Chromosome 6 for this family SEX is on Chromosome 2 in the same family

  12. What does this mean… • Tasmanian Atlantic salmon and Arctic charr both have two sex loci one of which is common between these two species. • This will have economic consequences for management of the Tasmanian breeding population. • Therefore…

  13. Survey of Current Tasmanian breeding population • 40x ½ sib families chosen from the 2009YC • These represent 33 out of 40 Founding sires • Adding in previously obtained data this covers 38 of the 40 Sires. • All offspring sexed phenotypically • Markers from both Ssa02 and Ssa06 used to screen representative families to identify a lineage as either Ssa02 or Ssa06.

  14. Are there more than 2 SEX Loci? • Markers from both chromosome 2 and chromosome 6 did not predict sex well in this family. • Two families show this pattern • Ssa03 has been identified in European salmon. • Markers from this chromosome predict sex much more accurately

  15. Only one representative family in this lineage • This was the case for the other family as well (2009182) • Therefore more families in these lineages need to be identified to validate this third locus.

  16. Summary • Three sex loci in Tasmanian Atlantic salmon • Ssa02 – 24/38 Lineages • Ssa06 – 12/38 Lineages • Ssa03 – 2/38 Lineages • Are there more than 3?

  17. What’s Next • Screen additional families from lineage with SEX predicted to be on Ssa03 • Screen remaining 2 lineages so that all 40 lineages can be accounted for • Collaborate with CIGENE and Koop lab to examine the sex-determining pathway in Atlantic salmon

  18. The Atlantic salmon sex team. Simon Fraser University, BC Evelyn Davidson Willie Davidson Will Eisbrenner Stacy Jones Jieying Li Song Lin Krzysztof Lubieniecki CSIRO, Australia Natasha Botwright Mat Cook Sonja Dominik Nick Elliott John Henshell Peter Kube Sigrid Lehnert CIGENE, Norway Sigbjorn Lien Matthew Kent University of Victoria, BC Ben Koop Kris von Schalburg

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