title: X-chromosome inactivation in monozygotic twins with systemic lupus erythematosus.
abstract: The hypothesis that a low concordance rate in monozygotic (MZ) twins with systemic lupus erythematosus (SLE) may be accounted for by differences in X-chromosome inactivation was examined. Five MZ twin pairs, four discordant and one concordant, were recruited, zygosity confirmed by DNA fingerprinting, and their pattern of X-chromosome inactivation in DNA samples prepared from peripheral blood and buccal cells were examined. X-chromosome inactivation was assessed by the methylation status of the CpG region near trinucleotide repeats in exon 1 of the androgen receptor gene on X-chromosome after digestion with the methylation-sensitive enzyme HpaII or HhaI and PCR amplification. X-chromosome inactivation patterns were found to be the same between affected and non-affected twins in all four discordant twin pairs, with random patterns in two pairs and skewed patterns in the others. The concordant twins demonstrated the same random patterns. X-chromosome inactivation was also examined from buccal smear DNA and shown to have the same pattern as that noted from peripheral blood DNA in one informative twin pair. Differences in X-chromosome inactivation patterns were not observed in these five MZ twin pairs. The results could not support the hypothesis that differences in X-chromosome inactivation is the mechanism accounting for the low concordance rate noted in MZ twins with SLE.
authors.affiliation: Department of Rheumatology, Royal North Shore Hospital St. Leonards, NSW, Australia.
authors.forename: Q
authors.initials: Q
authors.lastname: Huang
authors.forename: A
authors.initials: A
authors.lastname: Parfitt
authors.forename: D M
authors.initials: DM
authors.lastname: Grennan
authors.forename: N
authors.initials: N
authors.lastname: Manolios
mesh_terms: D000328:Adult; D000368:Aged; D000974:Antibodies, Antinuclear / Q000032:analysis; D002610:Cheek; D004247:DNA / Q000032:analysis; D016172:DNA Fingerprinting; D015257:DNA-Cytosine Methylases; D004200:Diseases in Twins / Q000235:genetics*; D004303:Dosage Compensation, Genetic; D004587:Electrophoresis, Agar Gel; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D008040:Genetic Linkage; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000235:genetics*; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics; D008875:Middle Aged; D018598:Minisatellite Repeats / Q000235:genetics; D016133:Polymerase Chain Reaction; D014430:Twins, Monozygotic / Q000235:genetics*; D014960:X Chromosome / Q000235:genetics* / Q000502:physiology
chemical_list: D000974:Antibodies, Antinuclear; D004247:DNA; D015257:DNA-Cytosine Methylases