ALS Research Could Shed Light on What Drives SMA, Study Reports
According to scientists, new research on ALS may shed light on the mechanisms underlying spinal muscular atrophy. Two RNA binding proteins, TDP-43 and hnRNP A1, are abnormal in certain cases of ALS. This leads to their accumulation in ALS patients' nerve cells associated with movement. As the name suggests, RNA binding proteins have the capacity to bind with RNA molecules, limiting their ability to become proteins. University of Montreal researchers wanted to understand what happened to movement nerve cells when they removed TDP-43 from the cells' nucleus. Depleting the binding protein TDP-43 led to changes in the processing, or splicing, of messenger RNA in the cell. Because TDP-43 binds with RNA, and can change how it is spliced, depleting it in the cell nucleus led to alterations to another RNA binding protein, hnRNP A1. This protein can get spliced into two variations, both regulated by TDP-43. Changes in hnRNP A1 messenger RNA also resulted in protein aggregation and were toxic to cells. Importantly, hnRNP A1 controls splicing of the SMN gene, the underlying cause of SMA. Researchers don’t know how the hnRNP A1-triggered SMN splice variation affects the function of the SMN gene. But they noted that Spinraza, a therapy recently approved for SMA, targets the hnRNP A1 protein's splicing of the gene. Spinraza was derived from this same type of research.
