[A study of survival motor neuron and neuronal apoptosis inhibitory protein gene in spinal muscular atrophy].

OBJECTIVE

To study the absence of survival motor neuron(SMN) gene exon 7,8 and neuronal apoptosis inhibitory protein(NAIP) gene exon 5,6 in Chinese patients with type I - IV spinal muscular atrophy (SMA) and to confirm the relationship between the deletions of SMN, NAIP and SMA phenotype.

METHODS

PCR and PCR-enzyme methods were used to detect the deletions of NAIP gene exon 5,6 and SMN gene exon 7,8 in 45 SMA (I - IV) patients and 30 healthy relatives of the patients and 30 normal controls.

RESULTS

Deletions of exon 7 and 8 of the telomeric SMN gene were 4/4, 2/3, 1/8 and 0/30 in type I, II, III and IV SMA patients, respectively. One patient with type II lacked the exon 7 but retained exon 8. No deletions was found in the relatives and controls(0/60). No deletions of exon 5 and 6 of the NAIP gene was detected in all the patients, healthy relatives and controls.

CONCLUSIONS

Deletions of SMN gene exon 7 and 8 exa mined by PCR-enzyme digestion could be recommended as an accurate gene diagnostic method for SMA with type I and II. However, the method was not as useful in type III as in I and II for making a diagnosis of SMA. Type IV SMA, a heterogeneous disease with phenotypical similarities to type I - III SMA, may be caused by deletion of other genes. The frequency of NAIP deletion was lower in Chinese SMA patients.