In vitro gene manipulation of spinal muscular atrophy fibroblast cell line using gene-targeting fragment for restoration of SMN protein expression.

The reduced level of survival motor neuron (SMN) protein, caused by homozygous deletions in the SMN gene, led to a common neurodegenerative disorder known as spinal muscular atrophy (SMA). In spite of extensive efforts to find a cure for SMA, there is currently no effective treatment available for this devastating disease. In this study, restoration of SMN expression through 'gene-targeting' method in SMA fibroblast cells was attempted. We designed a 2697-bp gene-targeting cassette; it consisted of an SMN1 open reading frame expressing 38 kD SMN protein and the upstream and downstream regions of exon 1 of SMN1 gene at the ends as the homology arms. SMA fibroblast cells were transfected by gene-targeting cassette using Lipofectamine LTX-PLUS reagent. Occurrence of homologous recombination in selected cells was investigated by PCR analysis. Increased expression of SMN protein was shown by real-time PCR and western blotting analysis. The immunofluorescence analysis results demonstrated that the number of SMN nuclear structures, Gems, was the same as or greater than the number of Gems found in normal fibroblasts. The results of this study indicate that gene-targeting methods do, in fact, present as an alternative for restoration of SMN expression in SMA patients-derived cells in vitro.