Human tyrosine hydroxylase natural genetic variation: delineation of functional transcriptional control motifs disrupted in the proximal promoter.
BACKGROUND
Tyrosine hydroxylase (TH) is the rate-limiting enzyme in catecholamine biosynthesis. Common genetic variation at the human TH promoter predicts alterations in autonomic activity and blood pressure, but how such variation influences human traits and, specifically, whether such variation affects transcription are not yet known.


RESULTS
Pairwise linkage disequilibrium across the TH locus indicated that common promoter variants (C-824T, G-801C, A-581G, and G-494A) were located in a single 5' linkage disequilibrium block in white, black, Hispanic, and Asian populations. Polymorphisms C-824T and A-581G were located in highly conserved regions and were predicted to disrupt known transcriptional control motifs myocyte enhancer factor-2 (MEF2), sex-determining region Y (SRY), and forkhead box D1 (FOXD1) at C-824T and G/C-rich binding factors specificity protein 1 (SP1), activating enhancer-binding protein 2 (AP2)], early growth response protein 1 (EGR1) at A-581G. At C-824T and A-581G, promoter and luciferase reporter plasmids indicated differential allele strength (T>C at C-824T; G>A at A-581G) under both basal circumstances and secretory stimulation. C-824T and A-581G displayed the most pronounced effects on both transcription in cella and catecholamine secretion in vivo. We further probed the functional significance of C-824T and A-581G by cotransfection of trans-activating factors in cella; MEF2, SRY, and FOXD1 differentially activated C-824T, whereas the G/C-rich binding factors SP1, AP2, and EGR1 differentially activated A-581G. At C-824T, factor MEF2 acted in a directionally coordinate fashion (at T>C) to explain the in vivo trait associations, whereas at A-581G, factors SP1, AP2, and EGR1 displayed similar differential actions (at G>A). Finally, chromatin immunoprecipitation demonstrated that the endogenous factors bound to the motifs in cella.


CONCLUSIONS
We conclude that common genetic variants in the proximal TH promoter, especially at C-824T and A-581G, are functional in cella and alter transcription so as to explain promoter marker-on-trait associations in vivo. MEF2, FOXD1, and SRY contribute to functional differences in C-824T expression, whereas SP1, AP2, and EGR1 mediate those of A-581G. The SRY effect on TH transcription suggests a mechanism whereby male and female sex may differ in sympathetic activity and hence blood pressure. These results point to new strategies for diagnostic and therapeutic intervention into disorders of human autonomic function and their cardiovascular consequences.
Zhang
Kuixing
K
Department of Medicine and Pharmacology, Center for Human Genetics and Genomics, University of California at San Diego, USA.
Zhang
Lian
L
Rao
Fangwen
F
Brar
Bhawanjit
B
Rodriguez-Flores
Juan L
JL
Taupenot
Laurent
L
O'Connor
Daniel T
DT
D000483:Alleles; D000818:Animals; D001483:Base Sequence; D002395:Catecholamines / Q000096:biosynthesis / Q000378:metabolism; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D051766:Early Growth Response Protein 1 / Q000235:genetics / Q000378:metabolism; D050556:Fatty Acid-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005260:Female; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism; D020022:Genetic Predisposition to Disease; D006801:Humans; D015810:Linkage Disequilibrium; D008297:Male; D008969:Molecular Sequence Data; D018006:Myogenic Regulatory Factors / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D011401:Promoter Regions, Genetic; D051381:Rats; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D014446:Tyrosine 3-Monooxygenase / Q000235:genetics*
D002395:Catecholamines; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; C493410:FABP4 protein, human; C500800:FOXD1 protein, human; D050556:Fatty Acid-Binding Proteins; D051858:Forkhead Transcription Factors; D018006:Myogenic Regulatory Factors; D016329:Sp1 Transcription Factor; D014446:Tyrosine 3-Monooxygenase