Identification of two distinct transcripts for the neuronal apoptosis inhibitory protein gene

The spinal muscular atrophies (SMA), characterized by motor neuron loss and progressive paralysis, are among the most common autosomal recessive disorders. Recently, two SMA candidate genes, NAIP (neuronal apoptosis inhibitory protein) and survival motor neuron (SMN), were reported and a 131-kb genomic sequence of 5q13.1 encompassing these two genes was determined. Based upon this genomic sequence, the original NAIP cDNA sequence published in 1995 was shown to contain foreign fragments. We therefore conducted an extensive cDNA cloning of NAIP from a human fetal brain library. Our studies confirmed that the cDNA sequence deduced from the 131-kb genomic sequence was the major transcript in the human fetal brain. In addition, a shorter and minor transcript was also newly identified. We thus designated the longer and shorter transcripts as NAIPl and NAIPs, respectively. The cDNA clones for NAIPl and NAIPs should facilitate the functional analysis of the NAIP gene and its association with neuronal apoptosis and SMA.