Abstracts

RATIONALE: This study was undertaken in order to attempt to replicate the findings of Sander et al. (2000). The human gene encoding the ?-opioid receptor (OPRM) has been mapped to chromosomal region 6q24-25 (Wang et al., 1993). Mutation screening identified a single-nucleotide polymorphism at position 118 (A118G) resulting in substitution of asparagine to aspartic acid (Asn40Asp) at an N-glycosylation site in the extracellular N-terminal region of the protein (Bergen et al., 1997; Bond et al., 1998). METHODS: To date, genotyping has been carried out on 122 caucasian patients, unselected for IGE subtype, and 183 caucasian controls. Allele-specific PCR was performed using one common forward primer and either of 2 reverse primers for each of A118 and G118 alleles, using the PCR conditions of Sander et al., (1998). The resulting 206bp product was electrophoresed on 2% agarose gel and visualised by ethidium bromide staining. RESULTS: The frequency of the Asp40 allele was found to be significantly higher in the IGE patients (0.27 for patients and 0.16 for controls, ?2 = 11.98, p = 0.00054). CONCLUSIONS: This result confirms that of Sander et al., (2000) who found a positive association using a sample consisting of 72 German idiopathic absence epilepsy (IAE) patients. However, we have found a stronger association using a larger IGE sample, unselected for subtype. This may reflect an association with several subtypes of IGE rather than a specific association with any particular subtype. This work is continuing, with genotyping of higher numbers of patients and controls, as well as within family studies currently being carried out.