DELETIONS IN THE SMN AND NAIP GENES IN PATIENTS WITH SPINAL MUSCULAR-ATROPHY IN CROATIA

Two genes, i.e. survival motor neuron (SMN) and neuronal apoptosis inh ibitory protein (NAIP) have been mapped to the SMA region of chromosom e 5q13. Both genes are frequently deleted or truncated in SMA patients . We have studied 26 patients with SMA types I-III, 29 first relatives , and 14 subjects with mild adult-onset type IV. DNA deletion genotype s were determined by PCR techniques amplifying exons 7 and 8 of SMN, a nd exon 5 of NAIP gene which distinguish SMN and NAIP telomeric copy f rom a nonpathogenic gene homologue as a centromeric copy. Results reve aled the homozygous deletions of exon 7 and 8 of the SMN gene and exon 5 of the NAIP gene in 3/3 infants with SMA I and in 1/20 with SMA typ e II. Exons 7 and 8 of the SMN gene were homozygously deleted in 10/20 and only exon 7 in 6/20 children with SMA type II. The overall percen tage of deletion cases observed was 77% in children with SMA types I-I II. Adult patients with type IV SMA showed no homozygous deletion of e xons 7, 8 and 5 of the SMN and NAIP genes. Also, all relatives had bot h a telomeric and centromeric SMN and NAIP copy. Deletion analysis of SMN and NAIP genes are a significant diagnostic tool, because there ar e clinical entities resembling SMA which most likely have another path ogenetic background.