TMEM259 and proximal spinal muscular atrophy: Although the early disease onset in membralin KO mice is similar to that seen in an SMA mouse model (Hsieh-Li et al., 2000; Monani et al., 2000), the pattern of motor neuron injury in membralin KO mice is reminiscent of human distal HMN rather than proximal HMN, as observed in SMA.