Human microsomal epoxide hydrolase: 5'-flanking region genetic polymorphisms

Area of Science:

• Biochemistry
• Genetics
• Toxicology

Background:

• Microsomal epoxide hydrolase (mEH) metabolizes harmful epoxides from environmental toxins.
• Enzymatic activity of mEH varies significantly across individuals and cell types.
• Genetic polymorphisms in the mEH gene are known to influence its functional expression.

Purpose of the Study:

• To identify and characterize novel polymorphic sites in the upstream regulatory region of the human mEH gene.
• To investigate the functional impact of these polymorphisms on mEH gene transcription and activity.

Main Methods:

• Single strand conformational polymorphism (SSCP) analysis and direct DNA sequencing were employed to identify polymorphisms.
• Allelic frequencies and linkage disequilibrium were assessed in a cohort of 51 individuals.
• Reporter gene assays in HepG2 cells were used to evaluate the functional significance of identified nucleotide substitutions.

Main Results:

• Seven novel polymorphic sites were identified in the 5' flanking region of the mEH gene (-743 to +185 bp).
• Certain identified polymorphisms demonstrated the ability to differentially regulate mEH gene transcription.
• Individual nucleotide substitutions could alter reporter gene activity by up to approximately 30%.

Conclusions:

• Genetic variations within the 5' flanking sequence of the mEH gene contribute to population-level differences in mEH functional expression.
• These findings enhance our understanding of the genetic basis for inter-individual variability in xenobiotic metabolism.
• The identified polymorphisms may have implications for susceptibility to diseases associated with exposure to polyaromatic hydrocarbons.