Department of Biology, University of Naples Federico II, Via Cinthia, 80126, Naples, Italy.
Department of Neurology, University of Massachusetts Medical School, Albert Sherman Center 6-1008, 368 Plantation St., Worcester, MA, 01605, USA.
Mol Neurobiol. 2019 Jan;56(1):56-60. doi: 10.1007/s12035-018-1071-3. Epub 2018 Apr 19.
The synthesis of brain metabolic DNA (BMD) is modulated by learning and circadian oscillations and is not involved in cell division or DNA repair. Data from rats have highlighted its prevalent association with the mitochondrial fraction and its lack of identity with mtDNA. These features suggested that BMD could be localized in synaptosomes that are the major contaminants of brain mitochondrial fractions. The hypothesis has been examined by immunochemical analyses of the large synaptosomes of squid optic lobes that are readily prepared and identified. Optic lobe slices were incubated with 5-bromo-2-deoxyuridine (BrdU) and the isolated synaptosomal fraction was exposed to the green fluorescent anti-BrdU antibody. This procedure revealed that newly synthesized BrdU-labeled BMD is present in a significant percent of the large synaptosomes derived from the nerve terminals of retinal photoreceptor neurons and in synaptosomal bodies of smaller size. Synaptosomal BMD synthesis was strongly inhibited by actinomycin D. In addition, treatment of the synaptosomal fraction with Hoechst 33258, a blue fluorescent dye specific for dsDNA, indicated that native DNA was present in all synaptosomes. The possible role of synaptic BMD is briefly discussed.
脑代谢 DNA（BMD）的合成受到学习和昼夜节律的调节，不参与细胞分裂或 DNA 修复。来自大鼠的数据突出了其与线粒体部分的普遍相关性，以及与 mtDNA 缺乏同一性。这些特征表明，BMD 可能定位于突触体中，突触体是脑线粒体部分的主要污染物。这一假设通过对鱿鱼视神经叶大突触体的免疫化学分析进行了检验，这些突触体很容易制备和鉴定。视神经叶切片用 5-溴-2-脱氧尿苷（BrdU）孵育，分离的突触体部分暴露于绿色荧光抗 BrdU 抗体。该程序表明，新合成的 BrdU 标记的 BMD 存在于源自视网膜光感受器神经元神经末梢的大突触体和较小大小的突触体体中。 actinomycin D 强烈抑制突触体 BMD 的合成。此外，用 Hoechst 33258（一种专门针对双链 DNA 的蓝色荧光染料）处理突触体部分表明，天然 DNA 存在于所有突触体中。简要讨论了突触 BMD 的可能作用。
