A functional single-nucleotide polymorphism in the TRPC6 gene promoter associated with idiopathic pulmonary arterial hypertension.
BACKGROUND
Excessive proliferation of pulmonary artery smooth muscle cells (PASMCs) plays an important role in the development of idiopathic pulmonary arterial hypertension (IPAH), whereas a rise in cytosolic Ca2+ concentration triggers PASMC contraction and stimulates PASMC proliferation. Recently, we demonstrated that upregulation of the TRPC6 channel contributes to proliferation of PASMCs isolated from IPAH patients. This study sought to identify single-nucleotide polymorphisms (SNPs) in the TRPC6 gene promoter that are associated with IPAH and have functional significance in regulating TRPC6 activity in PASMCs.


RESULTS
Genomic DNA was isolated from blood samples of 237 normal subjects and 268 IPAH patients. Three biallelic SNPs, -361 (A/T), -254(C/G), and -218 (C/T), were identified in the 2000-bp sequence upstream of the transcriptional start site of TRPC6. Although the allele frequencies of the -361 and -218 SNPs were not different between the groups, the allele frequency of the -254(C-->G) SNP in IPAH patients (12%) was significantly higher than in normal subjects (6%; P<0.01). Genotype data showed that the percentage of -254G/G homozygotes in IPAH patients was 2.85 times that of normal subjects. Moreover, the -254(C-->G) SNP creates a binding sequence for nuclear factor-kappaB. Functional analyses revealed that the -254(C-->G) SNP enhanced nuclear factor-kappaB-mediated promoter activity and stimulated TRPC6 expression in PASMCs. Inhibition of nuclear factor-kappaB activity attenuated TRPC6 expression and decreased agonist-activated Ca2+ influx in PASMCs of IPAH patients harboring the -254G allele.


CONCLUSIONS
These results suggest that the -254(C-->G) SNP may predispose individuals to an increased risk of IPAH by linking abnormal TRPC6 transcription to nuclear factor-kappaB, an inflammatory transcription factor.
Yu
Ying
Y
Department of Medicine, University of California, San Diego, La Jolla, CA 92093-0725, USA. Ying.Yu@AlconLabs.com
Keller
Steve H
SH
Remillard
Carmelle V
CV
Safrina
Olga
O
Nicholson
Ann
A
Zhang
Shenyuan L
SL
Jiang
Weihua
W
Vangala
Nivruthi
N
Landsberg
Judd W
JW
Wang
Jian-Ying
JY
Thistlethwaite
Patricia A
PA
Channick
Richard N
RN
Robbins
Ivan M
IM
Loyd
James E
JE
Ghofrani
Hossein A
HA
Grimminger
Friedrich
F
Schermuly
Ralph T
RT
Cahalan
Michael D
MD
Rubin
Lewis J
LJ
Yuan
Jason X-J
JX
D001665:Binding Sites / Q000235:genetics; D016022:Case-Control Studies; D049109:Cell Proliferation; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006801:Humans; D006973:Hypertension / Q000209:etiology* / Q000235:genetics; D009131:Muscle, Smooth, Vascular; D032389:Myocytes, Smooth Muscle; D016328:NF-kappa B / Q000235:genetics* / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide; D011401:Promoter Regions, Genetic; D011651:Pulmonary Artery / Q000503:physiopathology*; D050052:TRPC Cation Channels / Q000235:genetics*; D000074287:TRPC6 Cation Channel
D016328:NF-kappa B; D050052:TRPC Cation Channels; D000074287:TRPC6 Cation Channel; C117032:TRPC6 protein, human