부산대학교 도서관

Spinal muscular atrophy (SMA) is an autosomal recessive disease characterized by degeneration of the anterior horn cells of the spinal cord. The survival motor neuron ( SMN) gene has been identified as an SMA-determining gene. SMN exists as two copies in 5q13, and deletions in exons 7 and 8 of the telomeric copy (SMNT) occur in 95% of patients, regardless of disease severity. In a minority of patients, exon 7 but not exon 8 of SMNT appears deleted. We now report a patient with typical features of SMA type II who carried homozygous deletions of SMNT exon 7 and centromeric SMN (SMNC) exon 8 but retained SMNT exon 8 and SMNC exon 7. Sequence analysis demonstrated that SMNC exon 7 was adjacent to SMNT exon 8 on both SMN copies, indicating a double conversion. We confirm that sequence conversion is a common event in SMA and is associated with the milder form of the disease. The severity, however, can be modified in either positive or negative direction by other factors. [ABSTRACT FROM AUTHOR]