biostudies-literaturePretto DNICHD NIH HHSNCATS NIH HHS318https://www.ebi.ac.uk/biostudies/studies/S-EPMC4166380biostudies-literatureUnknown5Expansions of more than 200 CGG repeats (full mutation) in the FMR1 gene give rise to fragile X syndrome (FXS) through a process that generally involves hypermethylation of the FMR1 promoter region and gene silencing, resulting in absence of expression of the encoded protein, FMRP. However, mosaicism with alleles differing in size and extent of methylation often exist within or between tissues of individuals with FXS. In the current work, CGG-repeat lengths and methylation status were assessed for eighteen individuals with FXS, including 13 mosaics, for which peripheral blood cells (PBMCs) and primary fibroblast cells were available. Our results show that for both PBMCs and fibroblasts, FMR1 mRNA and FMRP expression are directly correlated with the percent of methylation of the FMR1 alleleFrontiers in geneticsClinical and molecular implications of mosaicism in FMR1 full mutations.PMC4166380R01 HD040661UL1 TR000002P30 HD002274Espinal GPretto DIwahashi CKTang HTYrigollen CMHagerman RJWilliamson JHagerman PJDurbin-Johnson BTassone FfalseClinical and molecular implications of mosaicism in FMR1 full mutations.Expansions of more than 200 CGG repeats (full mutation) in the FMR1 gene give rise to fragile X syndrome (FXS) through a process that generally involves hypermethylation of the FMR1 promoter region and gene silencing, resulting in absence of expression of the encoded protein, FMRP. However, mosaicism with alleles differing in size and extent of methylation often exist within or between tissues of individuals with FXS. In the current work, CGG-repeat lengths and methylation status were assessed for eighteen individuals with FXS, including 13 mosaics, for which peripheral blood cells (PBMCs) and primary fibroblast cells were available. Our results show that for both PBMCs and fibroblasts, FMR1 mRNA and FMRP expression are directly correlated with the percent of methylation of the FMR1 allele2014-01-01T00:00:00Z20142025-04-03T22:55:28.004Z2019-03-27T01:35:49ZS-EPMC41663802527895710.3389/fgene.2014.00318