Variations in the alpha2A-adrenergic receptor gene and their functional effects.
OBJECTIVE
The alpha2A-adrenergic receptor (ADRA2A) plays a central role in the regulation of systemic sympathetic activity and hence cardiovascular responses such as heart rate and blood pressure. The objectives of this study were to systematically search for variants in the ADRA2A gene, to define the gene's haplotype structure, and to examine potential functional effects of these variants.


METHODS
We examined 5957 base pairs of contiguous sequence of ADRA2A (promoter, exonic, and 3'-flanking region) using polymerase chain reaction to amplify the genomic target, followed by bidirectional sequencing, in 135 healthy subjects (85 white and 50 black subjects). Haplotypes were inferred by use of an expectation-maximization algorithm. Primary (plasma norepinephrine concentration) and secondary (resting heart rate and blood pressure) phenotypes were compared among subjects grouped by individual polymorphisms and haplotypes.


RESULTS
We identified 41 variants, including 24 novel variants. On the basis of 9 optimally selected markers, 11 haplotypes in 5 haplotype groups were inferred, representing approximately 99% of the cohort. Two uncommon variants in complete linkage disequilibrium (G>C at -1903 and C>G at -1607, identified in 3 black subjects) were associated with significantly increased plasma norepinephrine concentrations (376.7 +/- 6.1 pg/mL versus 218.4 +/- 95.0 pg/mL, P = .011). There was no other significant association between genetic variants or any of the haplotypes with phenotypes.


CONCLUSIONS
We describe novel variants and the haplotype structure of the ADRA2A gene. Common genetic ADRA2A variants are not important determinants of baseline cardiovascular measures (plasma norepinephrine, heart rate, and blood pressure) in healthy volunteers.
Kurnik
Daniel
D
Department of Medicine, Division of Clinical Pharmacology, Center for Human Genetics Research, Vanderbilt University School of Medicine, Nashville, TN 37232-6606, USA.
Muszkat
Mordechai
M
Li
Chun
C
Sofowora
Gbenga G
GG
Solus
Joseph
J
Xie
Hong-Guang
HG
Harris
Paul A
PA
Jiang
Lan
L
McMunn
Chara
C
Ihrie
Patrick
P
Dawson
Elliott P
EP
Williams
Scott M
SM
Wood
Alastair J J
AJ
Stein
C Michael
CM
D000328:Adult; D000483:Alleles; D044383:Black People; D001794:Blood Pressure / Q000235:genetics / Q000502:physiology; D017931:DNA Primers; D005260:Female; D005787:Gene Frequency; D014644:Genetic Variation; D006239:Haplotypes; D006339:Heart Rate / Q000235:genetics / Q000502:physiology; D006801:Humans; D015810:Linkage Disequilibrium; D008297:Male; D009638:Norepinephrine / Q000097:blood; D018341:Receptors, Adrenergic, alpha-2 / Q000235:genetics*; D013564:Sympathetic Nervous System / Q000502:physiology; D014481:United States; D044465:White People; D001741:Black or African American
C547768:ADRA2A protein, human; D017931:DNA Primers; D018341:Receptors, Adrenergic, alpha-2; D009638:Norepinephrine