# Presentation: 376467

## Finding Genes Controlling Complex Phenotypes

- Elaine Ostrander, PhD
- National Human Genome Research Institute
- National Institutes of Health

## Methodology and Approaches

- Whole Genome Association Studies
- Human Height
- Obesity
- Behavior
- Others
- Animal Models
- Skin Color
- Skeletal Size
- Leg length
- Racing Speed

## WGA Association Studies Associated with Height

- GWA scan data
- Multiple SNPs in strong LD with each other reached genome wide levels of significance
- Mice with with homozygous deletions at this locus are short in stature

## In whole genome association studies encompassing over 38,000 subjects, common set of variants in FTO gene were found to be associated with increased BMI. 
Result grew out of study of diabetes and represents increased risk for both disease and obesity.
No mechanistic data.  Appears that risk is mediated through changes in fat mass.
16% of adults who are homozygous for the risk allele weigh 3 Kg more and had 1.67 fold increased risk of obesity than those without risk allele. 

- In whole genome association studies encompassing over 38,000 subjects, common set of variants in *FTO* gene were found to be associated with increased BMI.
- Result grew out of study of diabetes and represents increased risk for both disease and obesity.
- No mechanistic data.  Appears that risk is mediated through changes in fat mass.
- 16% of adults who are homozygous for the risk allele weigh *3 Kg more* and had *1.67 fold increased risk* of obesity than those without risk allele.

*Genetics of Obesity*

##  Implications for Society are Enormous

- Societal traits perceived to be advantageous or desirable:
- tall and thin
- Discrimination--obesity predisposes to variety of health problems diabetes, heart disease, blood pressure, etc.
- Sports--Preselection and training of individuals
- Taller: basketball, volleyball
- Shorter: jockey, ice skater, gymnastics
- Thinner: runner, dancer

## Genetics of Skin Color

## Genetics of Skin Color

*golden *gene (SLC24A5 in humans) encodes a cation exchanger that localizes to the melanosome or its precursor.
- Protein product affects pigmentation in both zebrafish and humans
- Melanophores of golden mutations are smaller, more pale, more transparent, and contain fewer melanosomes

*Lamason et al., (2005) Science 310:1782-1786*

- wt

- wt

***gol***

***gol***

## Region of decreased heterozygosity in Europeans at  SLC24A5 gene

***Region of decreased heterozygosity in Europeans at  SLC24A5 gene***

- Conservation of ancestral allele predominates
- in African and East Asian populations.
- Variant allele is nearly fixed in European populations correlating with lighter skin..
**Study suggest that **_**SLC24A5 explains 25-38%**_** of the European-African difference in skin melanin index. **

***Lamason et al., (2005) Science  310, 1782 -1786***

## Mapping Variation in the Canine System

***Mapping Variation in the Canine System***
- Each breed fixed for specific traits
- Creation of breeds recent and rapid
- Small number of genes responsible for many complex traits

*Sutter et al., (2007) Science 316:112-5*

## Strong Statistical Association With Skeletal Size In Portuguese Water Dogs 

## Identical Selective Sweep Across IGF1 in 14 Small Dog Breeds

*Identical Selective Sweep Across IGF1 in 14 Small Dog Breeds*

## Mapping Breed-Fixed Morphology

**Achondroplasia**

**Force vs. speed axis**
**of variation**

**Body size**

*Mapping Breed-Fixed Morphology*

**Brachycephaly**

**Herding behavior**

## Performance Enhancing Polymorphisms: 

***Genes Controlling Racing Speed In Dogs***

- Mosher et al., (2007) PLoS Genetics (in press)

## “Bully” whippets appear similar to other species with “double muscle” phenotype. 

**Belgian Blue Cattle**

- “Bully” whippets appear similar to other species with “double muscle” phenotype.
- Phenotype caused by two copies of a 2 bp deletion in exon 3 removes the latter 17% of the protein disrupts structure

**Bully Whippet**

***Muscle Mass Controlled in Part by Levels of Myostatin***

**Notes:**
Describe belgian blue cattle, breed developed for their meatiness, lean meet etc.; 

## Dogs Heterozygous for the MSTN Deletion Show an Intermediate Phenotype

***Dogs Heterozygous for the MSTN Deletion Show an Intermediate Phenotype***

## Mh mutation explains 60% of the variation in measurements

**P ≈ 7.43 x 10****-6**** ; Kruskal-Wallis Test**

**P = 0.0015; Kruskal-Wallis test**

**P = 3.47 x 10****-5****; Kruskal-Wallis test**

**Mh mutation explains 60% of the variation in measurements**

**Notes:**
Withers = shoulder!! Shown are P values for females. 60% for first 2 graphs and 31% for chest. Least-squared regression analysis found allelic distribution and dominance effects to be significantly different than zero- suggests that the mutation is semi dominant with heterozygotes (mh/+) having musculature closer to, but significantly different from, that of wild types (+/+) No samples collected from male mutants due to a lack of dogs, not many available because they are rehomed or euthanized

## Could this increased musculature affect a dog’s speed?

**Notes:**
Highest grade ever achieved in life

## MSTN Deletion is Overrepresented in Grade A Racers

***MSTN Deletion is Overrepresented in Grade A Racers***

**Notes:**
Only one mutant races and she is an A though not self reported bully

## MSTN in Athletics

- Are similar mutations found in other competitive or high performing groups?
- What other *performance-enhancing polymorphisms* remain to be found?  Many?
- Vital area of research for both humans and animals
- Little is known about risks and side effects

- Vogel. Science (2004)
- Sweeney. Sci. Am. (2004)

**Notes:**
What people will do with these results or other later findings is unknown and can only be speculated but health risks should be considered.

## Genetics of Behavior

- Dozens of putative loci identified for behavioral disorders and many others
- Bipolar disorder, Schizophrenia
- Autism
- ADD and ADHD
- Etc.
- Ongoing canine studies for:
- “Rage” in English Spring Spaniels
- Obsessive Compulsive Disorder in Bull Terriers
- Naturally occurring behaviors such as prey drive, herding, learning, etc.

- ?

- ?

- ?

* *

## Summary

*Summary*

- The question of Nature versus Nurture remains, except now we know a great deal more about the “nature” part.
- Will this knowledge affect our collective behaviors?
- Will we as a society and as individuals continue to view ourselves as full of potential?
- Or will our genetic profiles make us self-limiting?
*Next inroads must be into genetic loci affect our ability to rise above our “genetic mandates”*