Investigation into pathology of CAG repeat diseases and development of therapies

脊髓和延髓肌萎缩症(SBMA)是一种遗传性运动神经元病。SBMA的分子基础是雄激素受体(AR)基因中编码聚谷氨酰胺(PolyQ)链的三核苷酸CAG重复序列的扩展。我们建立了在巨细胞病毒增强子和鸡β-肌动蛋白启动子的控制下表达全长人AR的转基因小鼠模型(AR-97Q小鼠)。首先，我们去势雄性AR-97Q小鼠。去势的雄鼠在运动功能、体重、寿命和突变型AR的核积累方面都有显著的改善。另一方面，注射睾丸素后，雌性小鼠的症状显著加重，并增加了突变AR的核积聚。在大多数多聚Q疾病中，突变蛋白随着多聚Q区的扩张而积累的核很可能是导致神经细胞功能障碍和变性的重要因素。…前对男性的阉割更多地通过降低睾酮水平来排泄突变AR的核积聚，并改善他们的运动功能。类似地，使用LHRH类似物亮丙瑞林(Leuprorelin)进行睾酮阻断治疗，显示出显著的改善运动功能和突变AR的核积聚。在这些结果的基础上，我们开始了使用亮丙瑞林的双盲临床试验。接下来，我们将AR-97Q小鼠与过度表达人HSP70诱导形式的小鼠杂交。高表达HSP70可显著改善AR-97Q小鼠的运动功能。在双转基因小鼠中，核突变AR的积累显著减少，尤其是大的复合体。单体突变体AR的数量也因HSP70过表达而减少，表明突变体AR的降解作用增强。这些发现表明，HSP70的过表达通过减少核定位的突变AR来改善小鼠的SBMA表型，这可能是由于增强了突变AR的降解。较少

Spinal and bulbar muscular atrophy (SBMA) is an inherited motor neuron disease. The molecular basis of SBMA is the expansion of a trinucleotide CAG repeat, which encodes the polyglutamine (polyQ) tract, in the androgen receptor (AR) gene. We generated transgenic mouse model expressing the full-length human AR containing either 24 or 97 CAG repeats under the control of a cytomegalovirus enhancer and a chicken β-actin promoter (AR-97Q mice). First, we castrated male AR-97Q mice. Castrated males showed profound improvement of their motor function, body weight, lifespan and nuclear accumulation of the mutant AR. On the other hand, testosterone administration caused a significant aggravation of their symptoms and enhanced nuclear accumulation of the mutant AR in female mice. Nuclear accumulation of the mutant protein with an expended polyQ tract is likely to be important in inducing neuronal cell dysfunction and degeneration in the majority of the polyQ diseases. Castration of the males pre … More vented the nuclear accumulation of the mutant AR by reducing the testosterone level, and improved their motor function. Similarly, testosterone blockade therapy, using leuprorelin, a LHRH analogue which reduces testosterone release from the testis, showed a marked amelioration of motor function and nuclear accumulation of the mutant AR. On the basis of these results, we started the double-blind clinical trial using leuprorelin.Next, we cross-bred AR-97Q mice with mice over-expressing the inducible form of human HSP70. High expression of HSP70 markedly ameliorated motor function of AR-97Q mice. In double transgenic mice, nuclear mutant AR accumulation, particularly that of the large complex form, was significantly reduced. Monomeric mutant AR was also reduced in amount by HSP70 over-expression, suggesting the enhanced degradation of mutant AR. These findings suggest that HSP70 over-expression ameliorates SBMA phenotypes in mice by reducing nuclear-localized mutant AR, which probably due to enhanced mutant AR degradation. Less