Lauren Gerard Koch

Functional Genomics Laboratory

Medical College of Ohio

Toledo, Ohio

A Genome Scan for Aerobic Running Capacity QTLs in Rats

Rat Genetic Models of Aerobic Running Capacity

“A Parallel Strategy”

Identify already-available inbred strains that widely differ in aerobic capacity to serve as genetic models.

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DA PVG AUG SR F344 ACI LEW WKY BUF MNS COP

STRAIN

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*

Aerobic Capacity was Assessed By Treadmill Running To Exhaustion In 11 Inbred Rat Strains

DA and COP showed the widest divergence

[Barbato et al, J. Appl. Physiol., 1998]

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Langendorff-Neely Working Heart Preparation

Cardiac Performance as a Likely Determinant Phenotype for Differences in Aerobic Capacity

PRE-LOAD

15 mm Hg

AFTER-LOAD

70 mm Hg

Cardiac Output Versus Distance Run

y = 19.03X - 290.39r = 0.868

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ISOLATED CARDIAC OUTPUT (ml/min/g Heart Weight)

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F344ACILEW

WKYBUF

MNS

COP

[Barbato et al, J. Appl. Physiol., 1998]

Based on these data, we propose that COP and DA strains could serve as parentals for developing a segregating population for the evaluation of the genetic basis of low and high exercise capacity.

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Distance Run to Exhaustion (m)

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Test for Aerobic Running Capacity

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COPDA

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Distance Run to Exhaustion (m)

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COP F1 DA

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Position (cM)

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core

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D3Rat56

D7Rat74D8Rat23

D16Rat17 D16Rat55

D20Rat5

Significant linkage

Suggestive linkage

Genome-Wide Scan for Aerobic Capacity QTLs.Phase I: Selective Genotyping of F2 (COP X DA) Population

D16Rat90

D16Rat48D16Rat13

D16Rat55D16Rat36

D16Rat16

D16Rat56

D16Rat42

D16Arb3

D16Rat109

D16Rat12

D16Rat32

D16Rat19

D16Rat17

D16Rat95

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Lpl Npy5r Cpe Adrb3

LOD Plot for Chromosome 16Phase II: Entire F2 (COP X DA) Population

Significant QTL

D3Rat132D3Rat114

D3Rat61

D3Rat150

D3Rat21D3Rat25D3Rat31

D3Rat42D3Rat44

D3Rat98

D3Rat277

D3Rat56

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Cel Rxra

Suggestive QTL

LOD Plot for Chromosome 3Phase II: Entire F2 (COP X DA) Population

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COP/COP COP/DA DA/DA

D16Rat55

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D3Rat56

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Interaction Effect Between Markers D16Rat55 and D3Rat56 on Distance Run

Additional interval mapping was done to determine whether heart weight and body weight QTLs co-localize to aerobic capacity regions.

D7Rat66D7Rat34

D7Rat27

D7Rat147D7Rat51

D7Rat69

D7Rat74

D7Rat86

D7Rat100D7Rat67D7Rat11

D7Rat123D7Rat81 D7Rat101

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reRelative Heart Weight QTL

Chromosome 7

Aerobic Capacity-

Phase I

D8Rat71D8Rat5D8Rat59D8Rat16

D8Rat23

D8Rat158

D8Rat99

D8Rat49D8Rat54D8Rat77

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Aerobic Capacity-

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Total Heart Weight QTLChromosome 8

D8Rat71

D8Rat5

D8Rat59

D8Rat16

D8Rat23

D8Rat158

D8Rat99

D8Rat49

D8Rat54D8Rat77

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Body Weight QTLChromosome 8

Aerobic Capacity-Phase I

QTL Regions contain genes related to Lipid Metabolism and Energy Homeostasis

Chromosome 16

• Lipoprotein Lipase (Lpl)

• Neuropeptide Y5 (Npy5r)

• Adrenergic Beta 3 (Adrb3)

• Carboxypeptidase E (Cpe)

Chromosome 7

• Peroxisome Proliferator- Activated Receptors (Ppara)

Chromosome 3

• Carboxyl Ester Lipase (Cel)

• Retinoid X Receptor (Rxra)

Chromosome 8

• Apolipoprotein

(Apoc3, Apoa1, APoa4)

• Hepatic Lipase (Lipc)

• 5´Nucleotidase (Nt5)

• There are at least two aerobic capacity QTLs present on rat chromosome 16. A QTL near D16Rat17 had effects on running capacity independent of other putative QTLs whereas the aerobic capacity QTL located near D16Rat55 interacted with a QTL located near D3Rat56.

• Possible associated relative heart weight, total heart weight, and average body weight QTLs were found on chromosomes 7 (D7Rat74) and 8 (D8Rat23) respectively.

• Candidate genes within the identified QTL regions include enzymes and transcription factors involved in energy balance and lipid metabolism.

Summary

Significance

• These findings represent the first known identification of aerobic capacity QTLs in animal genetic models.

This work will be appear as the cover article in the June issue of Genomics.

END

Phenotype by Genotype(meters run)

Chromosome Locus Model COP/COP COP/DA DA/DA LOD

Score

P Value

(ANOVA)

3 D3Rat56 Dominant 486 18 560 13 592 19 2.2* 0.008

7 D7Rat74 Dominant 493 20 562 14 572 20 1.6 0.035

8 D8Rat23 Additive 588 24 549 18 505 25 1.5 0.041

16 D16Rat17 Dominant 466 19 568 14 601 22 4.0** <0.0001

16 D16Rat55 Dominant 488 19 567 15 597 23 2.9* 0.0007

20 D20Rat5 Recessive 570 29 565 18 494 28 1.6 0.032

* markers above the suggestive LOD threshold for respective models

** markers above the significant LOD threshold for respective models

Putative Aerobic Capacity QTLs for F2 (COP x DA) Population

We found other Likely Determinant Phenotypes where DA is Significantly Greater than COP:

1. Maximal developed tension in isolated papillary muscles (38%) (Chen et al., J. Physiol., 2001).

2. Fractional Shortening (50%) and amplitude of calcium transients (78%) in ventricular myocytes (Chen et al., J.

Physiol., 2001).

3. Wider range for sympathetic and parasympathetic control of heart rate and blood pressure (Koch et al., Physiol.

Genomics, 1999).

4. Heart weight to body weight ratio (27%) (Koch et al., Physiol.

Genomics, 1999).

5. Cardiac adenosine production (46%) (Walker et al., Am J.

Physiol., 2002).

Sensorimotor Capacity in 11 Inbred Rat Strains Assessed by Rotarod Performance

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PVG BUF SR/Jr ACI WKY F344 AUG LEW COP DA MNS

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PVG and MNS showed the widest divergence

Biesiadecki et al., Am J. Physiol.,1999