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Introduction to Multivariate Genetic Analysis

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Presentation on theme: "Introduction to Multivariate Genetic Analysis"— Presentation transcript:

1 Introduction to Multivariate Genetic Analysis
Meike Bartels, Hermine Maes, Elizabeth Prom-Wormley and Michel Nivard

2 Aim and Rationale Aim: to examine the source of factors that make
traits correlate or co-vary Rationale: Traits may be correlated due to shared genetic factors (A) or shared environmental factors (C or E) Can use information on multiple traits from twin pairs to partition covariation into genetic and environmental components

3 Example 1 Why do traits correlate/covary?
How can we explain the association? Additive genetic factors (rG) Shared environment (rC) Non-shared environment (rE) rG rC 1 1 1 1 A1 C1 A2 C2 A112 C112 A222 C222 ADHD IQ E112 E222 1 1 E1 E2 rE

4 Adolescent depression
Example 2 Associations between phenotypes over time Does anxiety in childhood lead to depression in adolescence? How can we explain the association? Additive genetic factors (a21) Shared environment (c21) Non-shared environment (e21) How much is not explained by prior anxiety? 1 1 1 1 A1 C1 A2 C2 c21 a11 c11 a21 a22 c22 Childhood anxiety Adolescent depression e11 e21 e22 1 1 E1 E2

5 Sources of Information
For example: two traits measured in twin pairs Interested in: Cross-trait covariance within individuals Cross-trait covariance between twins MZ:DZ ratio of cross-trait covariance between twins

6 Observed Covariance Matrix
Twin 1 Twin 2 Phenotype 1 Phenotype 2 Variance P1 Covariance P1-P2 P2 Within-trait Cross-trait Twin 1 Twin 2

7 Observed Covariance Matrix
Twin 1 Twin 2 Phenotype 1 Phenotype 2 Variance P1 Covariance P1-P2 P2 Within-trait Cross-trait Within-twin covariance Twin 1 Within-twin covariance Twin 2

8 Observed Covariance Matrix
Twin 1 Twin 2 Phenotype 1 Phenotype 2 Variance P1 Covariance P1-P2 P2 Within-trait Cross-trait Within-twin covariance Twin 1 Cross-twin covariance Within-twin covariance Twin 2

9 SEM: Cholesky Decomposition
1 1 1 1 A1 C1 A2 C2 a11 c11 a22 c22 Twin 1 Phenotype 1 Twin 1 Phenotype 2 e11 e22 1 1 E1 E2

10 SEM: Cholesky Decomposition
1 1 1 1 A1 C1 A2 C2 c21 a11 c11 a21 a22 c22 Twin 1 Phenotype 1 Twin 1 Phenotype 2 e11 e21 e22 1 1 E1 E2

11 SEM: Cholesky Decomposition
1/0.5 1/0.5 1 1 1 1 1 1 1 1 1 1 A1 C1 A2 C2 A1 C1 A2 C2 c21 c21 a11 c11 a21 a22 c22 a11 c11 a21 a22 c22 Twin 1 Phenotype 1 Twin 1 Phenotype 2 Twin 2 Phenotype 1 Twin 2 Phenotype 2 e11 e21 e22 e11 e21 e22 1 1 1 1 E1 E2 E1 E2

12 Cholesky Decomposition
Path Tracing

13 Within-Twin Covariances (A)
1 1 A1 A2 a11 a21 a22 Twin 1 Phenotype 1 Twin 1 Phenotype 2 Twin 1 Phenotype 1 Phenotype 2 a112+c112+e112 a11a21+c11c21+e11e21 a222+a212+c222+c212+e222+e212 Twin 1

14 Within-Twin Covariances (A)
1 1 A1 A2 a11 a21 a22 Twin 1 Phenotype 1 Twin 1 Phenotype 2 Twin 1 Phenotype 1 Phenotype 2 a112+c112+e112 a11a21+c11c21+e11e21 a222+a212+c222+c212+e222+e212 Twin 1

15 Within-Twin Covariances (A)
1 1 A1 A2 a11 a21 a22 Twin 1 Phenotype 1 Twin 1 Phenotype 2 Twin 1 Phenotype 1 Phenotype 2 a112+c112+e112 a11a21+c11c21+e11e21 a222+a212+c222+c212+e222+e212 Twin 1

16 Within-Twin Covariances (A)
1 1 A1 A2 a11 a21 a22 Twin 1 Phenotype 1 Twin 1 Phenotype 2 Twin 1 Phenotype 1 Phenotype 2 a112+c112+e112 a11a21+c11c21+e11e21 a222+a212+c222+c212+e222+e212 Twin 1

17 Within-Twin Covariances (C)
1 1 C1 C2 c11 c21 c22 Twin 1 Phenotype 1 Twin 1 Phenotype 2 Twin 1 Phenotype 1 Phenotype 2 a112+c112+e112 a11a21+c11c21+e11e21 a222+a212+c222+c212+e222+e212 Twin 1

18 Within-Twin Covariances (E)
Phenotype 1 Twin 1 Phenotype 2 e11 e21 e22 1 1 E1 E2 Twin 1 Phenotype 1 Phenotype 2 a112+c112+e112 a11a21+c11c21+e11e21 a222+a212+c222+c212+e222+e212 Twin 1

19 Cross-Twin Covariances (A)
1/0.5 1/0.5 1 1 1 1 A1 A2 A1 A2 a11 a21 a22 a11 a21 a22 Twin 1 Phenotype 1 Twin 1 Phenotype 2 Twin 2 Phenotype 1 Twin 2 Phenotype 2 Twin 1 Phenotype 1 Phenotype 2 +c11c21 +c222+c212 Twin 2

20 Cross-Twin Covariances (A)
1/0.5 1/0.5 1 1 1 1 A1 A2 A1 A2 a11 a21 a22 a11 a21 a22 Twin 1 Phenotype 1 Twin 1 Phenotype 2 Twin 2 Phenotype 1 Twin 2 Phenotype 2 Twin 1 Phenotype 1 Phenotype 2 1/0.5a112+ +c11c21 +c222+c212 Twin 2

21 Cross-Twin Covariances (A)
1/0.5 1/0.5 1 1 1 1 A1 A2 A1 A2 a11 a21 a22 a11 a21 a22 Twin 1 Phenotype 1 Twin 1 Phenotype 2 Twin 2 Phenotype 1 Twin 2 Phenotype 2 Twin 1 Phenotype 1 Phenotype 2 1/0.5a112+c112 1/0.5a11a21+c11c21 +c222+c212 Twin 2

22 Cross-Twin Covariances (A)
1/0.5 1/0.5 1 1 1 1 A1 A2 A1 A2 a11 a21 a22 a11 a21 a22 Twin 1 Phenotype 1 Twin 1 Phenotype 2 Twin 2 Phenotype 1 Twin 2 Phenotype 2 Twin 1 Phenotype 1 Phenotype 2 1/0.5a112+c112 1/0.5a11a21+c11c21 1/0.5a222+1/0.5a212+c222+c212 Twin 2

23 Cross-Twin Covariances (C)
1 1 1 1 1 1 C1 C2 C1 C2 c21 c21 c11 c22 c11 c22 Twin 1 Phenotype 1 Twin 1 Phenotype 2 Twin 2 Phenotype 1 Twin 2 Phenotype 2 Twin 1 Phenotype 1 Phenotype 2 1/0.5a112+c112 1/0.5a11a21+c11c21 1/0.5a222+1/0.5a212+c222+c212 Twin 2

24 Predicted Model Twin 1 Twin 2 Twin 1 Twin 2 Within-twin covariance
Phenotype 1 Phenotype 2 a112+c112+e112 a11a21+c11c21+e11e21 a222+a212+c222+c212+e222+e212 1/.5a112+c112 1/.5a11a21+ c11c21 1/.5a222+1/.5 a212+c222+c212 Within-twin covariance Twin 1 Cross-twin covariance Within-twin covariance Twin 2

25 Predicted Model Twin 1 Twin 2 Twin 1 Twin 2 Within-twin covariance
Phenotype 1 Phenotype 2 Variance P1 Covariance P1-P2 P2 Within-trait Cross-trait Within-twin covariance Twin 1 Cross-twin covariance Within-twin covariance Twin 2

26 Predicted Model Twin 1 Twin 2 Twin 1 Twin 2 Within-twin covariance
Phenotype 1 Phenotype 2 Variance P1 Covariance P1-P2 P2 Within-trait Cross-trait Within-twin covariance Variance of P1 and P2 the same across twins and zygosity groups Twin 1 Cross-twin covariance Within-twin covariance Twin 2

27 Predicted Model Twin 1 Twin 2 Twin 1 Twin 2 Within-twin covariance
Phenotype 1 Phenotype 2 Variance P1 Covariance P1-P2 P2 Within-trait Cross-trait Within-twin covariance Covariance of P1 and P2 the same across twins and zygosity groups Twin 1 Cross-twin covariance Within-twin covariance Twin 2

28 Predicted Model Twin 1 Twin 2 Twin 1 Twin 2 Within-twin covariance
Phenotype 1 Phenotype 2 Variance P1 Covariance P1-P2 P2 Within-trait Cross-trait Within-twin covariance Cross-twin covariance within each trait differs by zygosity Twin 1 Cross-twin covariance Within-twin covariance Twin 2

29 Predicted Model Twin 1 Twin 2 Twin 1 Twin 2 Within-twin covariance
Phenotype 1 Phenotype 2 Variance P1 Covariance P1-P2 P2 Within-trait Cross-trait Within-twin covariance Cross-twin cross-trait covariance differs by zygosity Twin 1 Cross-twin covariance Within-twin covariance Twin 2

30 Example Covariance Matrix
MZ Twin 1 Twin 2 P1 P2 1 .30 0.79 0.49 0.50 0.59 0.29 Within-twin covariance Twin 1 Cross-twin covariance Within-twin covariance Twin 2 Twin 1 Twin 2 DZ P1 P2 1 0.30 0.39 0.25 0.24 0.43 0.31 Within-twin covariance Twin 1 Cross-twin covariance Within-twin covariance Twin 2

31 Example Covariance Matrix
MZ Twin 1 Twin 2 P1 P2 1 .30 0.79 0.49 0.50 0.59 0.29 Within-twin covariance Twin 1 Cross-twin covariance Within-twin covariance Twin 2 Twin 1 Twin 2 DZ P1 P2 1 0.30 0.39 0.25 0.24 0.43 0.31 Within-twin covariance Twin 1 Cross-twin covariance Within-twin covariance Twin 2

32 Example Covariance Matrix
MZ Twin 1 Twin 2 P1 P2 1 .30 0.79 0.49 0.50 0.59 0.29 Within-twin covariance Twin 1 Cross-twin covariance Within-twin covariance Twin 2 Twin 1 Twin 2 DZ P1 P2 1 0.30 0.39 0.25 0.24 0.43 0.31 Within-twin covariance Twin 1 Cross-twin covariance Within-twin covariance Twin 2

33 Summary Within-individual cross-trait covariance implies common aetiological influences Cross-twin cross-trait covariance implies common aetiological influences are familial Whether familial influences genetic or environmental shown by MZ:DZ ratio of cross-twin cross-trait covariances

34 Cholesky Decomposition Bivariate Genetic analyses
Specification in OpenMx

35 Within-Twin Covariance
1 1 Path Tracing: A1 A2 a11 a21 a22 P1 P2

36 Within-Twin Covariance
1 1 Path Tracing: A1 A2 a11 a21 a22 a Lower 2 x 2: a1 a2 P1 P2 P1 P2

37 Starting values and labels

38 Within-Twin Covariance
1 1 Path Tracing: A1 A2 a11 a11 a21 a21 a22 a22 a Lower 2 x 2: a1 a2 P1 P2 P1 P2

39 Within-Twin Covariance

40 Total Within-Twin Covar.
Using matrix addition, the total within-twin covariance for the phenotypes is defined as:

41 OpenMx Matrices & Algebra

42 Additive Genetic Cross-Twin Covariance (DZ)
0.5 0.5 Path Tracing: Within-traits P11-P12 = 0.5a112 P21-P22 = 0.5a a212 Cross-traits P11-P22 = 0.5a11a21 P21-P12 = 0.5a21a11 1 1 1 1 A1 A2 A1 A2 a11 a21 a22 a11 a21 a22 P11 P21 P12 P22 Twin 1 Twin 2

43 Additive Genetic Cross-Twin Covariance (MZ)
1 1 1 1 1 1 A1 A2 A1 A2 a11 a21 a22 a11 a21 a22 P11 P21 P12 P22 Twin 1 Twin 2

44 Common Environment Cross-Twin Covariance
1 1 1 1 1 1 C1 C2 C1 C2 c11 c21 c22 c11 c21 c22 P11 P21 P12 P22 Twin 1 Twin 2

45 Covariance Model for Twin Pairs

46 Obtaining Standardized Estimates

47 Three Important Results
Variance Decomposition -> Heritability, (Shared) environmental influences Covariance Decomposition -> The influences of genes and environment on the covariance between the two variables “how much of the phenotypic correlation is accounted for by genetic and environmental influences” Genetic and Environmental correlations -> the overlap in genes and environmental effects “is there a large overlap in gene/ environmental sets”

48 OpenMx Output Variance Decomposition -> Heritability, (Shared) environmental influences Covariance Decomposition -> The influences of genes and environment on the covariance between the two variables A A C C E E SA SA SC SC SE SE VC VC

49 Genetic correlation 1/.5 A1 A2 a11 P11 P21 a22 a21 P12 P22 Twin 1

50 OpenMx Output fitACE$rA [,1] [,2] [1,] 1.00000000 0.69847252
[,1] [,2] [1,] [2,] fitACE$rC [,1] [,2] [1,] [2,] fitACE$rE [,1] [,2] [1,] [2,]

51 Genetic correlation & contribution to observed correlation
rg If the rg = 1, the two sets of genes overlap completely A1 A2 If however a11 and a22 are near to zero, genes do not contribute to the observed correlation a11 a22 P11 P21 Twin 1

52 Interpreting Results High genetic correlation = large overlap in genetic effects on the two phenotypes Does it mean that the phenotypic correlation between the traits is largely due to genetic effects? No: the substantive importance of a particular rG depends the value of the correlation and the value of the A2 paths i.e. importance is also determined by the heritability of each phenotype

53 More Variables… a32 a33 c33 c21 c22 a21 c31 a31 c32 a11 c11 a22 e21
Twin 1 Phenotype 1 Twin 1 Phenotype 2 Twin 1 Phenotype 3 e21 e11 e31 e32 e22 e33 1 1 1 E1 E2 E3

54 More Variables… 1/0.5 1/0.5 1/0.5 1 1 1 a32 a33 c33 a32 a33 c33 c21
Twin 1 Phenotype 1 Twin 1 Phenotype 2 Twin 1 Phenotype 3 Twin 2 Phenotype 1 Twin 2 Phenotype 2 Twin 2 Phenotype 3 e21 e21 e11 e31 e32 e11 e31 e32 e22 e33 e22 e33 1 1 1 1 1 1 E1 E2 E3 E1 E2 E3

55 Expanded Matrices a Lower 3 x 3 c Lower 3 x 3 e Lower 3 x 3

56 OpenMx Parameter Matrices
vars <- c(’varx', ’vary’, ‘varz’) nv <- 3 OpenMx

57 Practical SCRIPT: DATA: F:\meike\2016\Multivariate\Bivariate
DHBQ_bs.dat

58 DATA - General Family Functioning, Subjective Happiness
- T1, T2, brother, sister - missing -999 58

59 Observed Cross-twin Cross-trait Correlations
colMeans(mzData,na.rm=TRUE) colMeans(dzData,na.rm=TRUE) cov(mzData,use="complete") cov(dzData,use="complete") cor(mzData,use="complete") cor(dzData,use="complete”) 59

60 Observed Cross-twin Cross-trait Correlations
> cor(mzData,use="complete") family1 happy1 family2 happy2 family happy family happy > cor(dzData,use="complete") family1 happy1 family2 happy2 family happy family happy 60

61 PRAC I. The ACE model and its estimates
1. Run the ACE model 2. What is the heritability of FAM and HAP? 3. What is the genetic influence on the covariance? 4. What is the genetic correlation? 61

62 OpenMx Output Variance Decomposition -> Heritability, (Shared) environmental influences Covariance Decomposition -> The influences of genes and environment on the covariance between the two variables A A C C E E SA SA SC SC SE SE VC VC

63 OpenMx Output fitACE$rA [,1] [,2] [1,] 1.00000000 0.69847252
[,1] [,2] [1,] [2,] fitACE$rC [,1] [,2] [1,] [2,] fitACE$rE [,1] [,2] [1,] [2,]

64 PRAC II. Trivariate Model
Add a third variable (Satisfaction with Life) to the model Run model What are the parameter estimates? What is the genetic correlation? 64

65 Changes that had to be made
# Select Variables for Analysis Vars <- c('family','happy', 'life') nv < # number of variables ntv <- nv*2 # number of total variables selVars <- paste(Vars,c(rep(1,nv),rep(2,nv)),sep="") svMe <- c(7,5,5) 65

66 Genetic and Environmental Influences
[1] "Matrix A/V" stCovA1 stCovA2 stCovA3 family happy life [1] "Matrix C/V" stCovC1 stCovC2 stCovC3 Family happy life [1] "Matrix E/V" stCovE1 stCovE2 stCovE3 Family happy life 66

67 Genetic and Environmental Correlations
[1] "Matrix solve(sqrt(I*A)) %&% A" Family Happy Life Family Happy life [1] "Matrix solve(sqrt(I*C)) %&% C" Family happy life [1] "Matrix solve(sqrt(I*E)) %&% E" Family happy life 67

68 Genetic Models Common Pathway Model Independent Pathway Model
Genetic and environmental factor analysis examples Common Pathway Model Independent Pathway Model 68

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