SMN1 and proximal spinal muscular atrophy: Next, to validate the potential of HITI technology for gene correction in SMA, we employed SMA mice (SMN2+/+; SMNΔ7+/+; Smn1−/−) as a disease model, characterized by lacZ reporter gene insertion disrupting the endogenous Smn1 gene in exon 2 and harbor two transgenic alleles of human SMN219–21.