McAndrew P E, Parsons D W, Simard L R, Rochette C, Ray P N, Mendell J R, Prior T W, Burghes A H
Department of Pathology, Ohio State University, Columbus 43210, USA.
Am J Hum Genet. 1997 Jun;60(6):1411-22. doi: 10.1086/515465.
The survival motor neuron (SMN) transcript is encoded by two genes, SMNT and SMNC. The autosomal recessive proximal spinal muscular atrophy that maps to 5q12 is caused by mutations in the SMNT gene. The SMNT gene can be distinguished from the SMNC gene by base-pair changes in exons 7 and 8. SMNT exon 7 is not detected in approximately 95% of SMA cases due to either deletion or sequence-conversion events. Small mutations in SMNT now have been identified in some of the remaining nondeletion patients. However, there is no reliable quantitative assay for SMNT, to distinguish SMA compound heterozygotes from non-5q SMA-like cases (phenocopies) and to accurately determine carrier status. We have developed a quantitative PCR assay for the determination of SMNT and SMNC gene-copy number. This report demonstrates how risk estimates for the diagnosis and detection of SMA carriers can be modified by the accurate determination of SMNT copy number.
存活运动神经元（SMN）转录本由两个基因SMNT和SMNC编码。定位于5q12的常染色体隐性近端脊髓性肌萎缩症是由SMNT基因突变引起的。SMNT基因可通过外显子7和8中的碱基对变化与SMNC基因区分开来。由于缺失或序列转换事件，约95%的脊髓性肌萎缩症病例中检测不到SMNT外显子7。现在在一些剩余的非缺失患者中已鉴定出SMNT中的小突变。然而，目前尚无可靠的定量检测方法来区分SMNT，以鉴别脊髓性肌萎缩症复合杂合子与非5q脊髓性肌萎缩症样病例（表型模拟），并准确确定携带者状态。我们开发了一种定量PCR检测方法来测定SMNT和SMNC基因的拷贝数。本报告展示了如何通过准确测定SMNT拷贝数来修改脊髓性肌萎缩症携带者诊断和检测的风险估计。
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