Department of Laboratory Sciences, Gunma University Graduate School of Health Sciences, 3-39-22, Showa-Machi, Maebashi, Gunma, 371-8511, Japan.
Department of Orthopedic Surgery, Gunma University Graduate School of Medicine, 3-39-22, Showa-Machi, Maebashi, Gunma, 371-8511, Japan.
Sci Rep. 2022 Nov 4;12(1):18718. doi: 10.1038/s41598-022-23571-5.
Repeat-associated non-AUG translation (RAN translation) is observed in transcripts that are causative for polyglutamine (polyQ) diseases and generates proteins with mono amino acid tracts such as polyalanine (polyA), polyleucine (polyL) and polyserine (polyS) in neurons, astrocytes and microglia. We have previously shown that microglia with aggregated polyQ led to defective differentiation and degeneration of neuron-like cells. However, it has not been determined whether only microglia containing a specific RAN product, but not other RAN products, is harmful in vitro and in vivo. Here we show that polyL-incorporating microglia specifically led to altered startle response in mice. Aggregated polyA, polyS and polyL induced aberrant differentiation of microglia-like BV2 cells. Differentiated PC12 cells treated with conditioned medium (CM) of polyS- and polyL- but not polyA-incorporating microglia-like BV2 cells showed retraction of neurites and loss of branch of neurites. Injection of the polyL-CM, but not polyA-CM and polyS-CM, into the lateral ventricle lowered startle response in mice. Consistently, polyL induced the highest expression of CD68 in BV2 cells. The lowered startle response was replicated in mice given the polyL-CM in the caudal pontine reticular nucleus (PnC), the key region of startle response. Thus, endogenous RAN proteins having polyL derived from polyQ diseases-causative genes in microglia might specifically impair startle response.
重复相关的非 AUG 翻译（RAN 翻译）在引起多聚谷氨酰胺（polyQ）疾病的转录本中观察到，并在神经元、星形胶质细胞和小胶质细胞中生成具有单氨基酸序列的蛋白质，如多丙氨酸（polyA）、多亮氨酸（polyL）和多丝氨酸（polyS）。我们之前已经表明，含有聚集的 polyQ 的小胶质细胞导致神经元样细胞的分化缺陷和退化。然而，尚未确定仅含有特定 RAN 产物而不是其他 RAN 产物的小胶质细胞在体外和体内是否有害。在这里，我们表明，含有多亮氨酸的小胶质细胞特异性地导致了小鼠的惊跳反应改变。聚集的 polyA、polyS 和 polyL 诱导小胶质细胞样 BV2 细胞的异常分化。用含有 polyS 和 polyL 的小胶质细胞样 BV2 细胞的条件培养基（CM）处理分化的 PC12 细胞，表现出神经突回缩和分支丢失。将含有 polyS 和 polyL 的但不含有 polyA 的小胶质细胞样 BV2 细胞的 CM 注射到侧脑室中，会降低小鼠的惊跳反应。一致地，polyL 在 BV2 细胞中诱导了 CD68 的最高表达。在尾状桥脑网状核（PnC）中给予 polyL-CM 的小鼠中，惊跳反应降低得到了复制，PnC 是惊跳反应的关键区域。因此，源自 polyQ 疾病致病基因的小胶质细胞中的内源性 RAN 蛋白可能特异性地损害惊跳反应。
