Human-Induced Pluripotent Stem Cell-Derived Models for the Study of Spinal Muscular Atrophy

Spinal muscular Atrophy (SMA) is an autosomal recessive neurodegenerative disease caused by mutations in the Survival of Motor Neuron 1 gene (SMN1), which result in dramatic decreases in the levels of SMN protein. Low levels of SMN lead to degeneration of alpha motor neurons (MNs) in the anterior horn of the spinal cord. Since human MNs cannot be obtained from living individuals, most human research has been performed with surrogate cells of limited relevance to SMA. However, the recent development of iPS (induced pluripotent stem) cell technology, has made it possible to derive ES (embryonic stem)-like cells from somatic cells. For this a combination of transcription factor-encoding trans-genes are introduced into cells. Subsequently, iPS cells can be induced to differentiation into many cell types, including MNs. We are keen to generate iPS cell models from a cohort of Spanish SMA patients, with three major aims: (i) to improve our understanding of SMA; (ii) to test potentially therapeutic vectors; and (iii) to produce clinically applicable patient-specific iPS cells. For the latter case, it would be crucial to avoid stable integration of the iPS-inducing transgenes, which we hope to achieve with the use of integration-deficient lentiviral vectors (IDLVs). We have demonstrated efficient transduction of human fibroblasts with IDLVs expressing eGFP. We have then compared expression levels of iPS cell-inducing transgenes from IDLVs or standard integrating lentivectors driven by the EF1alpha, CMV or CAG promoters. Optimum combinations of vectors have thus been defined and used in preliminary attempts of iPS cell generation.