Naip (the murine homologue of NAIP) expression during mouse embryogenesis.

Abstract

The childhood spinal muscular atrophies (SMAs) are autosomal recessive neurodegenerative conditions characterized by degeneration of lower motor neurons classified based on the age of onset and clinical severity. Type I is the most common and severe form of SMA with clinical presentation either in utero or immediately after birth. 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 I 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 to E14.5 mouse embryos as detected by various in situ hybridization techniques. It is also found in the embryonic liver, the branchial arches, the nasal epithelium and in the future digits. At E16.5 Naip 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. One model of SMA pathogenesis involves motor neuron attrition in the second and possibly third trimester of gestation. Our observation of Naip transcripts in the spinal cord between E9.5 and E14.5 (equivalent to the second trimester) is consistent with a role for Naip in modifying SMA severity.