Related Experiment Video
Updated: Jun 10, 2026
10:17
An Allele-specific Gene Expression Assay to Test the Functional Basis of Genetic Associations
Published on: November 3, 2010
Nicotinic α5 receptor subunit mRNA expression is associated with distant 5' upstream polymorphisms.
Ryan M Smith1, Houda Alachkar, Audrey C Papp
1Neuroscience Graduate Studies Program, Department of Pharmacology, The Ohio State University, Columbus, OH 43210, USA.
European Journal of Human Genetics : EJHG
|August 12, 2010
Summary
Genetic variants upstream of the CHRNA5 gene significantly impact its expression in the brain, influencing nicotine addiction risk. These findings highlight tissue-specific gene regulation and the importance of considering enhancer variants in clinical associations.
Area of Science:
- Genetics
- Neuroscience
- Molecular Biology
Background:
- The CHRNA5 gene, encoding the nicotinic acetylcholine receptor α5 subunit, is linked to nicotine addiction and lung cancer.
- Previous research identified associations between CHRNA5 promoter polymorphisms and gene expression, but specific causal variants were unclear.
Purpose of the Study:
- To identify cis-regulatory variants affecting CHRNA5 mRNA expression.
- To investigate the tissue-specific regulation of CHRNA5.
Main Methods:
- Measured allele-specific CHRNA5 mRNA expression in human prefrontal cortex autopsy tissues.
- Scanned the CHRNA5 locus for regulatory single-nucleotide polymorphisms (SNPs).
- Assessed the impact of identified variants on CHRNA5 expression in peripheral blood lymphocytes.
Main Results:
- A cluster of six linked SNPs (rs1979905, rs1979906, rs1979907, rs880395, rs905740, rs7164030) located >13 kb upstream of CHRNA5 fully explained significant allelic expression differences and increased overall mRNA levels.
- These upstream variants demonstrated tissue-specific effects, altering CHRNA5 expression in the brain but not in lymphocytes.
- Identified three main haplotypes, formed by the enhancer region and rs16969968, associated with altered nicotine dependence risk.
Conclusions:
- A novel upstream enhancer region significantly regulates CHRNA5 expression in a tissue-specific manner in the brain.
- These findings are crucial for understanding the genetic basis of nicotine addiction and necessitate consideration of upstream variants in clinical association studies.
Related Concept Videos
01:11Pharmacogenetics of Drug Targets: β₂-Adrenergic Receptors, Apo E, Thymidylate Synthase
Genetic polymorphisms in drug targets have emerged as critical determinants of interindividual variability in drug response and toxicity. Pharmacogenomic investigations increasingly focus on identifying these variations to personalize and optimize therapeutic interventions. A drug target may be a receptor, enzyme, or signaling protein involved in pharmacologic responses or disease-related pathways. While early pharmacogenetic studies focused primarily on drug metabolism, current research...
01:29Pharmacogenetic Phenotypes: Alterations in Pharmacokinetics, Drug Targets and Biologic Milieu
Genetic variations significantly influence drug response through pharmacokinetics, receptor interactions, and biologic milieu modifications. Pharmacokinetic alterations impact drug metabolism and clearance, affecting efficacy and toxicity. Variants in drug-metabolizing enzymes, such as CYP2C9 and CYP2C19, alter drug activation and elimination. For example, CYP2C9 loss-of-function variants require lower warfarin doses to prevent excessive bleeding, while CYP2C19 variants reduce clopidogrel...
01:05Single Nucleotide Polymorphisms-SNPs
A single nucleotide polymorphism or SNP is a single nucleotide variation at a specific genomic position in a large population. It is the most prevalent type of sequence variation found in the human genome. Point mutations that occur in more than 1% of the population qualify as SNPs. These are present once every 1000 nucleotides on an average in the human genome. Replacement of a purine with another purine (A/G) or a pyrimidine with another pyrimidine (C/T) is known as a transition. In contrast,...
01:16Pharmacogenetics of Drug Transporters: P-Glycoprotein and Solute Carrier Transporters
The pharmacogenetics of drug transporters is increasingly recognized as a critical factor influencing interindividual variability in drug absorption, distribution, and elimination. These membrane-bound proteins regulate drugs' movement across cellular barriers by actively pumping them out (efflux) or facilitating their uptake (influx). Among the major transporter families, ATP-binding cassette (ABC) and solute carrier (SLC) transporters play particularly prominent roles. Genetic polymorphisms...
01:29Pharmacogenomics: Identification of New Drug Targets
Advances in genomics have profoundly influenced drug discovery by increasing both the speed and accuracy of pharmaceutical development. Pharmacogenomics, which examines how genetic variation influences drug response, facilitates the identification of novel therapeutic targets and enables patient stratification for personalized treatment. These strategies contribute to improved drug efficacy, minimized adverse effects, and more efficient clinical trial design.Mapping genetic differences...
01:15Cholinergic Receptors: Nicotinic
Nicotinic receptors are ligand-gated ion channels that are activated by acetylcholine and nicotine. Upon activation, they cause a rapid increase in the permeability of cells to K+, Na+, and Ca2+, followed by depolarization and excitation. They are in the autonomic ganglia, skeletal neuromuscular junction, CNS, and adrenal medulla.
There are two types of nicotinic receptors: neuromuscular (NM/NM/N1) and neuronal (NN/NN/N2). The two families differ based on their location and selectivity to...
There are two types of nicotinic receptors: neuromuscular (NM/NM/N1) and neuronal (NN/NN/N2). The two families differ based on their location and selectivity to...