A new polymorphism in human calmodulin III gene promoter is a potential modifier gene for familial hypertrophic cardiomyopathy.
OBJECTIVE
Familial hypertrophic cardiomyopathy (FHC) is caused by mutations in genes encoding sarcomeric proteins. Incomplete penetrance suggests the existence of modifier genes. Calmodulin (CaM) could be of importance given the key role of Ca(2+) for cardiac contractile function and growth. Any variant that affects CaM expression and/or function may impact on FHC clinical expression.


RESULTS
We screened the promoter region of human calmodulin III gene (CALM3) and identified a new -34T>A polymorphism with a T-allele frequency of 0.70. The distribution of CALM3 genotypes differed in 180 unrelated FHC patients carrying a known FHC mutation compared with 134 controls, with higher TT-genotype frequency (0.73 vs. 0.51) and lower frequencies of AT- (0.24 vs. 0.37) and AA genotypes (0.03 vs. 0.11; P = 0.0005). To study whether the -34T>A polymorphism could play a modifier role, patients' relatives including both affected and healthy carriers were added. Affected carriers had a 0.56 times higher odds of carrying a T allele than healthy carriers (P = 0.053). We then investigated whether the -34T>A polymorphism affects the promoter activity using luciferase reporter vectors containing either CALM3-T or CALM3-A promoters. The activity of CALM3-T was lower than CALM3-A in HEK293 cells (1.00 +/- 0.19 vs. 2.31 +/- 0.13, P = 0.00001) and in cardiomyocytes (0.96 +/- 0.10 vs. 1.33 +/- 0.08, P = 0.00727).


CONCLUSIONS
These data suggest that the -34T>A CALM3 polymorphism is a modifier gene for FHC, potentially by affecting expression level of CALM3 and therefore Ca(2+)-handling and development of hypertrophy.
Institute of Experimental and Clinical Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
Felix W
FW
Friedrich
Pedro
P
Bausero
Yuli
Y
Sun
Andras
A
Treszl
Elisabeth
E
Krämer
Denise
D
Juhr
Pascale
P
Richard
Karl
K
Wegscheider
Ketty
K
Schwartz
Dulce
D
Brito
Eloisa
E
Arbustini
Anders
A
Waldenström
Richard
R
Isnard
Michel
M
Komajda
Thomas
T
Eschenhagen
Lucie
L
Carrier
D000328:Adult; D017677:Age Distribution; D000368:Aged; D000818:Animals; D001483:Base Sequence; D002147:Calmodulin / Q000235:genetics* / Q000378:metabolism; D024741:Cardiomyopathy, Hypertrophic, Familial / Q000235:genetics* / Q000378:metabolism; D005260:Female; D005787:Gene Frequency; D005838:Genotype; D006579:Heterozygote; D006801:Humans; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D032383:Myocytes, Cardiac / Q000378:metabolism; D011110:Polymorphism, Genetic; D011401:Promoter Regions, Genetic / Q000235:genetics; D051381:Rats; D014162:Transfection
C082965:CALML3 protein, human; D002147:Calmodulin