**9. Tumour-suppressing microRNA: neural differentiation and proliferation**

### **9.1. MiR-124**

There are three genes that codify for miR-124 and are located in different regions; thus, we have miR-124-1 located in chromosome 8p23.1, miR-124-2 located in 8q12.3 and miR-124-3 in 20q13.33. It is the most profuse brain-specific miRNA; during neural differentiation, it expresses itself mainly in neurons [49]. It is considered a tumour suppressor weakly expressed in anaplastic astrocytomas and GBM, in relation with the non-neoplastic brain tissue. In this regard, Silber et al. studied the expression of several miRNAs during the differentiation of adult neural stem cells, and it was observed that miR-124 increased its expression eight times, instead of what happens in high-grade tumours, where their expression is less. In this same study, they also determined that miR-124 may induce differentiation and inhibit the proliferation of glioblastoma stem cells when inhibiting CDK6 (cyclin 6, dependent on kinases) which, as a goal, promotes the progress of the cell cycle (**Figure 8**) [45, 54].
