rs1045642

rs1045642 is a single nucleotide polymorphism (SNP) in the human ABCB1 gene, which encodes the P-glycoprotein (P-gp) efflux transporter. The variant involves a cytosine to thymine substitution at nucleotide 3435, commonly referred to as C3435T. It is a synonymous polymorphism, meaning it does not change the amino acid sequence of P-gp, though some studies have reported effects on gene expression and transporter activity.

The ABCB1 gene is located on chromosome 7q21.12 and encodes a membrane transporter that pumps a wide range of substrates out of cells. rs1045642 has been investigated extensively as a pharmacogenomic marker due to potential influences on drug absorption, distribution, and brain penetration. Research has produced mixed results; several studies suggest associations between rs1045642 and drug plasma levels, therapeutic response, or adverse effects for certain medications, while others find no reproducible effect.

In terms of population genetics, the T allele of rs1045642 is common but its frequency varies across ethnic groups, with reported minor allele frequencies typically ranging from about 0.3 to 0.6 in different populations. Despite substantial interest, there is no broad consensus that rs1045642 alone provides reliable predictive value for clinical decision-making. It is often studied as part of multi-variant haplotypes or pharmacogenomic panels rather than as a single clinical test.