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Selection for Scrapie resistance based on PrP polymorphism

Selection for Scrapie resistance based on PrP polymorphism. A simulation study. Vitezica Zulma, Palhière Isabelle, Manfredi Eduardo, Elsen Jean Michel SAGA-INRA, Toulouse, France. Selection for Scrapie resistance…. Importance of Scrapie Simulation description

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Selection for Scrapie resistance based on PrP polymorphism

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  1. Selection for Scrapie resistance based on PrP polymorphism A simulation study Vitezica Zulma, Palhière Isabelle, Manfredi Eduardo, Elsen Jean Michel SAGA-INRA, Toulouse, France IWMGQSG, Toulouse, France, 2003.

  2. Selection for Scrapie resistance… • Importance of Scrapie • Simulation description • Population structure • Selection and mating schemes • Comparison criteria • Results • Conclusions IWMGQSG, Toulouse, France, 2003.

  3. Selection for Scrapie resistance… • Importance of Scrapie • Simulation description • Population structure • Selection and mating schemes • Comparison criteria • Results • Conclusions IWMGQSG, Toulouse, France, 2003.

  4. Introduction • Scrapie, TSE that affect animals and humans • Resistance/susceptibility  PrP gene • Selection based on PrP polymorphism • Genotyping a subset of animals for PrP gene …use of the estimation of genotype probabilities in a selection program IWMGQSG, Toulouse, France, 2003.

  5. Selection for Scrapie resistance… • Importance of Scrapie • Simulation description • Population structure • Selection and mating schemes • Comparison criteria • Results • Conclusions IWMGQSG, Toulouse, France, 2003.

  6. 13900 females 1040 males Male’s sires Male’s dams 25% 25% Female’s sires Female’s dams 25% 75% Terminal dams 50% 2-7 years 2-4 years Population structure IWMGQSG, Toulouse, France, 2003.

  7. 1275 ♂ born Culling 600 ♂ 2550 ♀ born PrP genotype 200 ♂ 2000 ♀ Production trait 80 ♂ 1700 ♀ Selection and mating IWMGQSG, Toulouse, France, 2003.

  8. Male’s dams Male’s sires PrP x PrP Female’s dams Female’s sires yix PrP Terminal dams Selection and mating 40 females / male IWMGQSG, Toulouse, France, 2003.

  9. Compared selection schemes PrP gene: R allele, S allele Three R frequencies (0.15 - 0.40 - 0.85) Genotype frequencies -> 15 years of selection Estimation of genotypes IWMGQSG, Toulouse, France, 2003.

  10. Estimation de genotypes Peeling equations (Fernando et al. 1993) Information from - parents - mates and progeny - animal itself P(SS)=0.999 Genotype probabilities: P(RR), P(RS), P(SS) Ii= P(RR)i +½ P(RS)i IWMGQSG, Toulouse, France, 2003.

  11. Selection for Scrapie resistance… • Importance of Scrapie • Simulation description • Population structure • Selection and mating schemes • Comparison criteria • Results • Conclusions IWMGQSG, Toulouse, France, 2003.

  12. Results Females, ♀ + ♂ known, freq(R)=0.15 Genotype frequencies IWMGQSG, Toulouse, France, 2003.

  13. Results Males, ♀ + ♂ known, freq(R)=0.15 Genotype frequencies IWMGQSG, Toulouse, France, 2003.

  14. ♀ + ♂ known ♂ known ♂ known + ♀ estimated Results Females, freq(R)=0.40 Frequency of RR genotype IWMGQSG, Toulouse, France, 2003.

  15. ♀ + ♂ known ♂ known ♂ known + ♀ estimated Results Females, freq(R)=0.15 Frequency of RR genotype IWMGQSG, Toulouse, France, 2003.

  16. ♀ + ♂ known ♂ known ♂ known + ♀ estimated Results Females, freq(R)=0.85 Frequency of RR genotype IWMGQSG, Toulouse, France, 2003.

  17. Selection for Scrapie resistance… • Importance of Scrapie • Simulation description • Population structure • Selection and mating schemes • Comparison criteria • Results • Conclusions IWMGQSG, Toulouse, France, 2003.

  18. Conclusions • Using female genotype probabilities yielded better results than ignoring PrP information for females • Allele frequency a long-term processes • Extension of this preliminary study … the interest of estimating genotype probabilities for selection purposes IWMGQSG, Toulouse, France, 2003.

  19. Acknowledgements INRA, France Universidad de Buenos Aires, Argentina IWMGQSG, Toulouse, France, 2003.

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