Urine microRNA Profiling Displays miR-125a Dysregulation in Children with Fragile X Syndrome

Abstract

A triplet repeat expansion leading to transcriptional silencing of the FMR1 gene results in fragile X syndrome (FXS), which is a common cause of inherited intellectual disability and autism. Phenotypic variation requires personalized treatment approaches and hampers clinical trials in FXS. We searched for microRNA (miRNA) biomarkers for FXS using deep sequencing of urine and identified 28 differentially regulated miRNAs when 219 reliably identified miRNAs were compared in dizygotic twin boys who shared the same environment, but one had an FXS full mutation, and the other carried a premutation allele. The largest increase was found in miR-125a in the FXS sample, and the miR-125a levels were increased in two independent sets of urine samples from a total of 19 FXS children. Urine miR-125a levels appeared to increase with age in control subjects, but varied widely in FXS subjects. Should the results be generalized, it could suggest that two FXS subgroups existed. Predicted gene targets of the differentially regulated miRNAs are involved in molecular pathways that regulate developmental processes, homeostasis, and neuronal function. Regulation of miR-125a has been associated with type I metabotropic glutamate receptor signaling (mGluR), which has been explored as a treatment target for FXS, reinforcing the possibility that urine miR-125a may provide a novel biomarker for FXS.

Identification of microRNAs Associated With Human Fragile X Syndrome Using Next Generation Sequencing

“…There are twelve brain miRNAs identi ed to interact with FMRP in mouse brain including, miR-125a, miR-125b, and miR-132 [30]. To the best of our knowledge, there is only one published study on miRNA expression pro ling in FXS patients using deep sequencing [7]. In a most recent study Putkonen et al [7] showed upregulation of miR-125a in urine from children with FXS.…”

“…To the best of our knowledge, there is only one published study on miRNA expression pro ling in FXS patients using deep sequencing [7]. In a most recent study Putkonen et al [7] showed upregulation of miR-125a in urine from children with FXS. The investigators did not examine differential miRNA expression changes in FXS blood samples or the correlations of miR-125a levels in urine with those of in the cell-free circulation (i.e., in serum and plasma) and other body uids [7].…”

“…The intuition behind this selection was that we expected these miRNAs present more powerful signals with lower noises as opposed to miRNAs with lower level of expressions. miR-125, though was not in 30 highly dysregulated candidate miRNAs in this study, was also analyzed due to its importance in urine in Putkonen et al [7] study and the existence of small number of NGS studies about FXS. As seen in Table 3, all members of miR-125 family were found to be downregulated in patients with FXS.…”

“…Using next-generation sequencing, the investigators found twenty-eight miRNAs with different levels between the two twins. In the brother with fragile X, eight miRNAs had higher levels, the greatest increase (i.e., a 1.6-fold increase) was found in the levels of miR-125a compared to his twin brother [7]. This increase in miR-125a levels was also shown in two other sets of urine samples; ten Spanish FXS children aged 2-7 years and nine Finnish FXS children aged 4-17 years, as compared to healthy subjects but with a wide variation in urine miR-125a levels among young fragile X patients [7].…”

“…Many miRNAs have been shown to be engaged in neurodevelopmental disorders and disruption of miRNA, by impairing the communication between nerve cells, seems to contribute in the development of FXS as the primary cause of inherited intellectual disability [6]. In a twin study for identifying miRNA biomarkers of this disorder, the levels of miRNAs in the urine of a boy with FXS and his twin brother, who was a premutation carrier and had no clinical signs of fragile X, were compared [7]. Using next-generation sequencing, the investigators found twenty-eight miRNAs with different levels between the two twins.…”