Graduate Program in Neuroscience, The University of British Columbia, Vancouver, Canada.
Department of Psychiatry and Djavad Mowafaghian Centre for Brain Health, The University of British Columbia, Vancouver, Canada.
J Huntingtons Dis. 2020;9(2):149-161. doi: 10.3233/JHD-200400.
Huntington's disease (HD) is an inherited neurodegenerative disorder caused by expansion of CAG repeats in the Huntingtin gene (HTT). Studies suggest cortical to striatal (C-S) projections, which regulate movement and provide cell survival signals to SPNs, are altered in the pre-manifest and early symptomatic stages of HD. But whether and how presynaptic cortical terminals are affected in HD is not well explored.
Test size and replenishment of readily releasable pool (RRP), and assess glutamate refill of C-S synapses in HD models.
Immunocytochemistry was applied in C-S co-cultures generated from FVB/N (WT: wildtype) mice and YAC128, an HD mouse model expressing human HTT with 128 CAG repeats on the FVB/N background; Whole-cell patch clamp recordings from striatal neurons were performed both in cultures, with or without osmotic stimuli, and in acute brain slices from 6-month-old early symptomatic YAC128 mice and WT following prolonged trains of electrical stimuli in corpus callosum.
We found no change in the average size or vesicle replenishment rate of RRP in C-S synapses of YAC128, compared with WT, cultures at day in vitro 21, a time when immunocytochemistry showed comparable neuronal survival between the two genotypes. However, YAC128 C-S synapses showed a slowed rate of recovery of glutamate release in co-cultures as well as in acute brain slices.
Mutant HTT expression impairs glutamate refill but not RRP size or replenishment in C-S synapses. This work provides a foundation for examining the contribution of deficits in presynaptic cortical terminals on HD progression.
亨廷顿病（HD）是一种遗传性神经退行性疾病，由亨廷顿基因（HTT）中的 CAG 重复扩展引起。研究表明，调节运动并向 SPN 提供细胞存活信号的皮质纹状体（C-S）投射在 HD 的前表现和早期症状阶段发生改变。但是，HD 中皮质前突是否以及如何受到影响尚不清楚。
测试易释放池（RRP）的大小和补充情况，并评估 C-S 突触中的谷氨酸再填充。
免疫细胞化学应用于从 FVB/N（WT：野生型）小鼠和 YAC128（一种在 FVB/N 背景下表达人类 HTT 且具有 128 个 CAG 重复的 HD 小鼠模型）中生成的 C-S 共培养物；使用全细胞膜片钳记录从纹状体神经元中进行记录，无论是在培养物中还是在没有渗透刺激的情况下，还是在经过延长的胼胝体电刺激后从 6 个月大的早期症状性 YAC128 小鼠和 WT 急性脑片中进行记录。
我们发现，与 WT 相比，YAC128 中的 C-S 突触的 RRP 平均大小或囊泡补充率在第 21 天的体外培养物中没有变化，此时免疫细胞化学显示两种基因型之间的神经元存活情况相当。然而，YAC128 C-S 突触在共培养物以及急性脑片中显示出谷氨酸释放恢复速度较慢。
突变 HTT 表达会损害 C-S 突触中的谷氨酸再填充，但不会影响 RRP 大小或补充。这项工作为研究皮质前突缺陷对 HD 进展的贡献提供了基础。
