KLF15 and proximal spinal muscular atrophy: However, seeing as the toxicity of AAV8-Klf15 was dose-dependent in both compromised SMA mice and healthy littermates and not observed in parallel experiments with AAV8-GFP, it is most likely that the adverse effects were directly linked to the supraphysiological levels of Klf15 in several key metabolic tissues such as muscle, heart and liver.