Histone modifications and FMR role in Fragile X syndrome: A review

Abstract

Fragile X syndrome is the most common cause of genetically acquired mental disability and one of the most frequent single-gene disorders. FXS serves as an excellent model disorder for studies investigating disturbed molecular mechanisms and synapse function. FXS is an X-linked disorder that affects approximately 1 in 4000 males and females, with females experiencing milder cognitive deficits. It is caused due to expansion of trinucleotide CGG repeat above the normal range (>54 repeats) in the 5’ noncoding region of the fragile x mental retardation 1 (FMR1) gene located in the q27.3 loci of the X chromosome, which results in hypermethylation of CpG islands and eventually to transcriptional silencing of the gene hence suppressing the production of the Fragile X mental retardation protein (FMRP). The lack of FMRP, involved in multiple aspects of mRNA metabolism in the brain causing intellectual disability, autism spectrum disorder, and deregulation of multiple pathways, is thought to be the direct cause of the FXS phenotypes. The purpose of this review is to summarize the basic models used to study the aspects of fragile x syndrome, the relation of FMR1 gene and FMRP with the disease, histone modifications, and various targeted molecular therapy used for cure.