Five microRNAs Encoded on Chromosome 21

Abstract

Down’s syndrome, sometimes referred to as trisomy 21, is due to the triplication of all or some portion of chromosome 21. The Down’s syndrome phenotype is generally characterized by intellectual disabilities and cognitive deficits. Although the extent and severity of these abnormalities varies with each individual it affects, each abnormality results in cognitive disruption. Since the discovery of the extra copy of chromosome 21, it has been demonstrated that these disruptions are attributed to a naturally-occurring abnormality of the gene dosage. A recent discovery of a cluster of five microRNAs, microRNA let-7c, micrRNA-99a, microRNA-125b, microRNA-155, and microRNA-802, that are encoded and clustered on chromosome 21 have proved to be potential contributors to the remarkably diverse phenotype. Research has yet to find any effective treatment for this diversely complex neurological disorder. The continued study and understanding of this five-member cluster is likely to provide insight into potential beneficial therapeutic strategies to treat Down’s syndrome and many other diseases often associated with it.