Gross observation of D156844-treated SMN7 SMA mice shows an improvement in engine activity when compared with vehicle-treated mice (Supplementary Material, Movie). the engine phenotype of SMN7 SMA mice. == Intro == Proximal spinal muscular atrophy (SMA) is an autosomal recessive neurodegenerative disease characterized by selective loss of engine neurons in the anterior horn of the spinal cord (1). This prospects to atrophy of limb and trunk muscle tissue. In humans, the survival engine neuron (SMN) gene is definitely duplicated and the two SMN genes (SMN1andSMN2) differ by a single nucleotide (C T) within an exon splice enhancer of exon 7 (2,3). SMN1 transcripts create full-length SMN (FL-SMN) protein. Most of the transcripts from SMN2 lacking exon 7 (SMN7) and therefore produce SMN7 protein; however, 1020% of SMN2 transcripts are correctly spliced and produce FL-SMN protein. BPTU SMA results from deletions or mutations of theSMN1gene; theSMN2gene remains undamaged (4). The severity of disease in SMA depends on the copy quantity BPTU ofSMN2and the levels of SMN protein (57). Mice carry only BPTU one SMN gene (mSmn) which is definitely orthologous toSMN1in humans (8,9). Loss ofmSmnresults in embryonic lethality (10). Conditional knockdown of mSmn in neurons, muscle mass and hepatocytes also prospects to death of those cells (1113). Antisense morpholino-mediated reduction of SMN protein levels in zebrafish causes truncation of axons followed by excessive branching before reaching their target (14). Loss of practical SMN in the fruit fly prospects to neuromuscular abnormalities and a progressive loss of RGS19 motility and coordinated movement before death in the late larval stage (1517). Deletion of the nematode orthologue of SMN (cSmn) prospects to reduced locomotor activity and premature death (18). These studies suggest that SMN is essential for cell function and survival. Transgenic insertion ofSMN2into a mSmn null background in mice rescues the embryonic lethal phenotype (19). mSmn null mice with lowSMN2copy figures (i.e. 2) develop severe (type I-like) SMA and die at 68 days (19,20). mSmn null mice with higher copy figures (i.e. 8), on the other hand, are normal when compared with non-transgenic littermates (19) demonstrating that theSMN2gene product can correct the SMA phenotype. Enhancing the inclusion of exon 7 in SMN2 transcripts with a bifunctional U7 snRNA markedly enhances the survival of severe SMA mice (SMN2+/+;mSmn/) (21). Severe SMA mice that also contain an exon 7-lacking SMN (SMN7) develop a less severe SMA phenotype and these mice pass away at 1415 days (22). These transgenic experiments show that modulatingSMN2as well as SMN7 levels can be beneficial to SMA mouse models. Over the years, a number of groups have recognized SMN-inducing compounds using cultured fibroblasts derived from SMA patients. Some of these compounds include aclarubicin (23), butyrate (24), 4-phenylbutyrate (25), valproic acid (2628), hydroxyurea (2830), indoprofen (31), interferons- and – (32), forskolin (33), ortho-vanadate (34), cantharidin (35), tautomycin (35), aminoglycosides (36,37), resveratrol (38), suberoylanilide hydroxamic acid (39) and M344 (40). Many of these compounds would not make good therapeutic brokers since high concentrations (micromolar and, in some cases, millimolar levels) are required to increase SMN expression, these compounds are rapidly metabolizedin vivoor are harmful and many are unable to cross the blood-brain barrier. A recently published study (41) explained a series of compounds that increased SMN promoter activity in a reporter gene cell collection. One such compound was a C5-quinazoline that increased SMN promoter activity with an EC50= 330 110 nm. This compound resulted in a 2.5-fold increase in the amount of FL-SMN mRNA, a 23-fold increase in SMN protein and a 5-fold increase in the number of gemsSMN-containing subnuclear foci (or bodies)in a fibroblast cell line derived from an SMA individual. Through a focused medicinal chemistry effort, a series of modified C5-quinazolines have been designed so as to more potently induce SMN2 promoter activity, increase SMN protein levels and more easily penetrate the blood-brain barrier [Fig.1and Table1; (42)]. One such compound, a piperidine 2,4-diaminoquinazoline known as D156844, was highly potent (EC50= 4 nm) at activating SMN2 promoter activity with a maximal response of 2.3-fold (42). D156844 also increased SMN protein levels in SMA patient fibroblast cultures and increased.