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QUANTITATIVE TRAIT LOCI FOR PARASITE RESISTANCE

Sonja Dominik

CSIRO Livestock Industries

Armidale

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BONJOUR!!!

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KEY MESSAGES

Parasite resistance is….a prime trait to investigate on a

molecular level

….a very complex trait

….difficult to collect phenotypes for

….evidently influenced by major genes

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INTRODUCTION

Parasite resistance is a prime trait to investigate

on a molecular level!

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ECONOMIC IMPACT

Direct cost~ AUS$ 50 Million = EURO 30 Million

+ Indirect Cost~ AUS$ 250 Million = EURO 150 Million

Total Cost

~ AUS$ 300 Million = EURO 180 Million

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GENETIC VARIATION

Between breed variation

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GENETIC VARIATION

Within-breed variation allows genetic progress

1990 1992 1994 1996 1998 2000

-0.4

-0.2

0.0

0.2

Ruby Hills genetic trends: 1990 to 2000

Year

Sta

nd

ard

de

via

tion

un

its

CFWMFDFEC

SELECT Breeding Services

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THE TECHNOLOGY…

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PARASITE OF MAJOR IMPORTANCE

• Haemonchus contortus

(Barbers pole)

• Trichostrongylus colubriformis / vitrinus (Black scour worm)

• Teladorsagia circumcincta (syn Ostertagia or Brown stomach worm)

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DIAGRAM OF IMMUNE RESPONSE

EXPULSION OF WORMS

Gut mucosa

Th

B-cells Clonal expansionPlasma cells AB

Clonal expansion

Processing / RecognitionMesenteric lymph nodes

Antigens

Behnke et al. 2003

StemcellsMastcellsEosinophilsNeutrophils

RecruitmentBone marrow

Th2 activation

CytokinesIL-3, IL-4, IL-5,IL-6,IL-9, IL-10, IL13

MemoryB-cells

IgG,IgM,IgE Inflammatorymediators

Plasmacells

Goblet cells

IgA IgG1 IgEMucus

Peristalsis

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• Large allelic variation

• Dominant

• Heritability 0.2 – 0.4

• MHC genes responsible for some genetic variation between strains

• Interaction between MHC and non-MHC genes

INSIGHTS FROM MOUSE EXPERIMENTS

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• FEC• TWC

• Serum antibody• Circulating eosinophils

• Packed cell volume• Plasma pepsinogen• Dag score• Faecal consistency score

PHENOTYPIC INDICATORS

Worm burden

Physiological host response

Clinical symptoms

(Beh and Maddox 1996)

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QTL FOR PARASITE RESISTANCE TRAITS IN SHEEP

Segregation analysis

H. contortus– Evidence for two QTL based on FEC in

ITT x Merino (Raadsma et al. 2002)

– Evidence from segregation analysis for QTL based on FEC in Merino (Meszaros et al. 2001)

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347 cM

Chromosome 1

T.colubriformisEPCDV010 – ILSTS044(Diez-Tascon et al. 2002)

T. colubriformisMcM130 – McM257(Beh et al. 2001)

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Chromosome 3

308.8 cM

T. colubriformisTGLA67 – OarVH130(Beh et al. 2001)

Multiple speciesIFNG region(Paterson et al. 2002)

Te. circumcinctaIFNG region(Coltman et al. 2001)

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Chromosome 6

148.7 cM

T. colubriformisMcM140 – McM257(Beh et al. 2001)

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89.6 cM

Chromosome 20

Te. circumcinctaDY locus(Buitkamp et al. 1996)

H. contortusOarCP73BM1815DYMS1(Janssen et al. 2002) Te. circumcincta

MHC-DRB1(Schwaiger et al. 1995)

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QTL FOR PARASITE RESISTANCE TRAITS IN SHEEP

Summary

– Evidence of QTL for parasite resistance

– Difficult to compare studies – wide range of phenotypes

– Most findings do not overlap, but IFNG is a very likely candidate

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CSIRO GENE MAPPING FLOCK

2 1 1 2 3 4 5 .....

1997HS Progeny

229 animals genotyped

FS-1 FS-4 FS-5 FS-6 FS-7 FS-8FS-2 FS-3

1994 - 1996Total of 15 fullsib groups172 animals genotyped

♀♂ ♂ ♀ ♀ ♀ ♀ ♀ ♀♀

Romney Grandsires

Merino Granddams

F1

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MATERIALS & METHODSPhenotypic data

• FEC 3, 4 and 5• FEC3, FEC4, FEC5 -> total FEC• crFEC3, crFEC4, crFEC5 -> total

crFEC

• 160 records

• Between 28% and 86% of animals infected

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MATERIALS & METHODSProtocol

• Check phenotypes for possible errors

• Check genotype data

• Test fixed effects

• Check residuals for normality

• QTL Express / Rqtl

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DISTRIBUTION OF RESIDUALS

Residual FEC3

FEC3

Fre

quen

cy

-2000 0 1000 3000

010

2030

4050

60

Residual cube root FEC3

cube root FEC3

Fre

quen

cy

-15 -5 0 5 10 15 20

010

2030

4050

60

Residual FEC4

FEC4

Fre

quen

cy

-10000 0 10000 30000

010

2030

4050

6070

Residual cube root FEC4

cube root FEC4

Fre

quen

cy

-20 -10 0 10 20 30 40

05

1015

2025

30

FEC5

FEC5

Fre

quen

cy

-10000 0 10000 30000

010

2030

4050

6070

cube root FEC5

cube root FEC5

Fre

quen

cy

-30 -10 0 10 20 30 40

010

2030

4050

Residual FEC3

FEC3

Fre

quen

cy

-2000 0 1000 3000

010

2030

4050

60

Residual cube root FEC3

cube root FEC3

Fre

quen

cy

-15 -5 0 5 10 15 20

010

2030

4050

60

Residual FEC4

FEC4

Fre

quen

cy

-10000 0 10000 30000

010

2030

4050

6070

Residual cube root FEC4

cube root FEC4

Fre

quen

cy

-20 -10 0 10 20 30 400

510

1520

2530

FEC5

FEC5

Fre

quen

cy

-10000 0 10000 30000

010

2030

4050

6070

cube root FEC5

cube root FEC5

Fre

quen

cy

-30 -10 0 10 20 30 40

010

2030

4050

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RESULTS

crFECtotal

FECtotal

crFEC5

FEC5

crFEC4

FEC4

crFEC3

FEC3

HKNPMLHKNPML

Chr. BChr. A

LOD scores for parasite resistance traits

5.6

5.75.53.5

4.9

2.4

3.78.3 2.8

2.8 2.5

4.6 3.1

2.1 2.73.17.0

3.22.85.63.8

3.8

3.8

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KEY POINTS FROM CSIRO MAPPING FLOCK

• Some evidence for QTL for parasite resistance

• Data Analysis

• Extension of the CSIRO mapping flock will provide more data for closer investigation

• Binomial analysis as an alternative analysis approach

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KEY MESSAGES

Parasite resistance is….a prime trait to investigate on a

molecular level

….a very complex trait

….difficult to measure

….evidently influenced by major genes

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THE FUTURE

• More work on the effects of data quality and analysis method on findings

• Combination of candidate gene approaches and mapping studies

• Comparative genomics plays an important role

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