Distinct expression of neuronal apoptosis inhibitory protein (NAIP) during murine development

The childhood spinal muscular atrophies (SMAs) are autosomal recessive neurodegenerative conditions characterized by progressive degeneration of lower motor neurons. The gene encoding NAIP (neuronal apoptosis inhibitory protein) has been proposed to be a modulator of the severity of SMA and is frequently deleted in type I SMA. In this study we have assessed NAIP (murine homologue of NAIP) transcript levels during mouse embryogenesis. NAIP mRNA is present in the developing brain and spinal cord of E9.5-E14.5 mouse embryos as detected by various in situ hybridization techniques. It is also found in the embryonic branchial arches, the nasal epithelium and in the future digits. At E16.5, NAIP mRNA transcripts were found in the marginal zone of the lateral ventricle, the follicles of the vibrissae, in the retina and in the intestinal villi. These results are the first report of NAIP gene transcript levels in embryogenesis. If motor neuron attrition occurs in the second and third trimester of gestation in SMA, the observation of NAIP transcription in the mouse spinal cord between E9.5 and E14.5 is consistent with a role for NAIP in modifying this disorder.