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At least nine human genetic diseases, including myotonic dystrophy (DM) and fragile X syndrome have been associated with the expansion of CTG or CGG trinucleotide repeats within the disease loci. Little is known about the molecular mechanisms or the genetic control of the expansion of triplet repeats. Mutations in human mismatch repair genes are associated with the increased polymorphism of many microsatellites, including dinucleotide repeats. The effect of mutations in two mismatch repair genes on the size of trinucleotide repeats in the DM and FRAXA loci has been analyzed. PCR and Southern analysis of the triplet repeat regions of the DM and fragile X mental retardation (FRAXA) loci in cell lines HTC116 and LoVo, which contain mutations in both alleles of the hMLH1 and hMSH2 genes, respectively, indicated that the size of the endogenous (CTG)n and (CGG)n tracts fall within the range observed in the normal population. This suggests that mutations in hMLH1 or hMSH2 do not result in the instability of CTG or CGG tracts to the levels observed in individuals with myotonic dystrophy or fragile X syndrome.

BackgroundEstrogen is known to play role in temporomandibular joint (TMJ) disorders and estrogen effects can be mediated by estrogen receptor (ER) alpha present in the TMJ. Cells expressing the estrogen receptor ERalpha are present in the temporomandibular joint (TMJ) but changes in expression due to estrogen and inflammation have not been characterized. In this study, ERalpha protein content and the number of cells expressing ERalpha was measured in 17 beta-estradiol-treated rats after inflammation was induced in the TMJ.MethodsSixteen ovariectomized female rats were divided into two groups such that one group received 17 beta estradiol (E2) and the other was given vehicle (VEH). Groups were then subdivided further, one received injections of saline and the other received Complete Freund's adjuvant (CFA) within the superior joint space of the TMJ. Thus the four groups include no E2/saline, E2/saline, no E2/CFA and E2/CFA. After treatment, the rats were sacrificed, and the TMJ anterior, disc, retrodiscal and synovial tissues were analyzed by western blot and immunocytochemistry. Positive stained cells were counted using a Nikon epifluorescent microscope.ResultsThe western blot showed that ERalpha protein significantly decreased with inflammation. The number of ERalpha-positive cells in the TMJ was not affected by inflammation or 17 beta-estradiol with exception of the retrodiscal tissue. In the retrodiscal tissue 17 beta-estradiol significantly decreased the number of ERalpha-positive cells but only in a non-inflamed joint.ConclusionsIn conclusion, inflammation and 17 beta-estradiol can modulate ERalpha expression in the TMJ but the effects are tissue specific.