The neuronal apoptosis inhibitory protein (NAIP) was identified as a candidate gene for the inherited neurodegenerative disorder spinal muscular atrophy. NAIP is the founding member of a human protein family that is characterized by highly conserved N-terminal motifs called baculovirus inhibitor of apoptosis repeats (BIR). Five members of the human family of inhibitor of apoptosis proteins including NAIP have been shown to be antiapoptotic in various systems. To date, a mechanism for the antiapoptotic effect of NAIP has not been elucidated.Baculoviral IAP repeat-containing protein 1 is part of a 500 kb inverted duplication on chromosome 5q13. This duplicated region contains at least four genes and repetitive elements which make it prone to rearrangements and deletions.