SMN1 and proximal spinal muscular atrophy: Given the link between the components of the SMN complex and microRNA (miRNA), as well as the increasingly recognized role of miRNAs in the pathophysiology of SMA [43,44], this review aims to provide insights into the current state of research and bridge the gap due to the absence of biomarkers, which are needed to improve patient classification, track SMA progression, and monitor the response to treatment.