The molecular genetic basis of spinal muscular atrophy (SMA), an autosomal 
recessive neuromuscular disorder, is the loss of function of the survival motor 
neuron gene (SMN1). The SMN2 gene, a nearly identical copy of SMN1, has been 
detected as a promising target for SMA therapy. Both genes are ubiquitously 
expressed and encode identical proteins, but markedly differ in their splicing 
patterns: While SMN1 produces full-length (FL)-SMN transcripts only, the 
majority of SMN2 transcripts lacks exon 7. Transcriptional SMN2 activation or 
modulation of its splicing pattern to increase FL-SMN levels is believed to be 
clinically beneficial and therefore a crucial challenge in SMA research. Drugs 
such as valproic acid, phenylbutyrate, sodium butyrate, M344 and SAHA that 
mainly act as histone deacetylase inhibitors can mediate both: they stimulate 
the SMN2 gene transcription and/or restore the splicing pattern, thereby 
elevating the levels of FL-SMN2 protein. Preliminary phase II clinical trials 
and individual experimental curative approaches SMA patients show promising 
results. However, phase III double-blind placebo controlled clinical trials have 
to finally prove the efficacy of these drugs.