Stine O C, Li S H, Pleasant N, Wagster M V, Hedreen J C, Ross C A
Department of Psychiatry, Johns Hopkins School of Medicine, Baltimore, MD 21287, USA.
Hum Mol Genet. 1995 Jan;4(1):15-8. doi: 10.1093/hmg/4.1.15.
Huntington's disease (HD) is an inherited neurodegenerative disorder expressed when a trinucleotide repeat in the gene IT-15 is expanded. The mechanism by which the expanded repeat causes the expression of the disease is unknown. Possible mechanisms include alterations in the amount of the mRNA, potentially resulting from changes in gene transcription or abnormal mRNA stability. In order to determine whether the expanded IT-15 allele is present in mRNA, we isolated total RNA from the cortex and striatum of patients and controls. To distinguish the two alleles of the IT-15 transcript in HD patients, we amplified across a region containing a dimorphic single triplet deletion observed on some chromosomes and found that the relative intensity of the two PCR bands amplified from genomic DNA and those amplified from first strand cDNA from brain tissue were essentially equal. In order to determine whether the exon containing the expanded CAG repeat is present in IT-15 mRNA from HD patients, we amplified across this region and demonstrated the presence of the expanded repeat in cDNA from both striatum and cortex. Based on this evidence, we suggest that the mechanism of disease expression does not occur during transcription or in the stability of the RNA, but rather occurs during translation or postranslationally.
亨廷顿舞蹈症（HD）是一种遗传性神经退行性疾病，当IT-15基因中的三核苷酸重复序列扩增时就会表现出来。扩增的重复序列导致疾病表达的机制尚不清楚。可能的机制包括mRNA数量的改变，这可能是由基因转录变化或异常的mRNA稳定性引起的。为了确定HD患者的mRNA中是否存在扩增的IT-15等位基因，我们从患者和对照的皮质和纹状体中分离出总RNA。为了区分HD患者中IT-15转录本的两个等位基因，我们在一个包含在某些染色体上观察到的双态单三联体缺失的区域进行扩增，发现从基因组DNA扩增的两条PCR条带与从脑组织第一链cDNA扩增的条带的相对强度基本相等。为了确定含有扩增的CAG重复序列的外显子是否存在于HD患者的IT-15 mRNA中，我们在该区域进行扩增，并证明在纹状体和皮质的cDNA中都存在扩增的重复序列。基于这些证据，我们认为疾病表达的机制不是发生在转录过程中或RNA的稳定性方面，而是发生在翻译过程中或翻译后。
