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Colonization of Euprymna scolopes Squid by Vibrio fischeri
Published on: March 1, 2012
DNA in Squid Synaptosomes
Carolina Cefaliello1,2, Marina Prisco1, Marianna Crispino1
1Department of Biology, University of Naples Federico II, Via Cinthia, 80126, Naples, Italy.
Abstract:
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.
Insights
Brain metabolic DNA (BMD) synthesis occurs in synaptosomes, not for cell division. This newly discovered synaptic DNA may play a role in neuronal function, distinct from mitochondrial DNA.
Area of Science:
- Neuroscience
- Molecular Biology
- Biochemistry
Background:
- Brain metabolic DNA (BMD) synthesis is influenced by learning and circadian rhythms.
- BMD is distinct from mitochondrial DNA (mtDNA) and not involved in DNA repair or cell division.
- Previous studies suggested BMD's association with mitochondrial fractions, hinting at potential localization in synaptosomes.
Purpose of the Study:
- To investigate the localization of newly synthesized brain metabolic DNA (BMD) within synaptosomes.
- To confirm the presence and synthesis of DNA within synaptosomes.
Main Methods:
- Immunochemical analysis of large synaptosomes isolated from squid optic lobes.
- Incubation of optic lobe slices with 5-bromo-2-deoxyuridine (BrdU) to label newly synthesized DNA.
- Detection of BrdU-labeled BMD using anti-BrdU antibodies and Hoechst 33258 staining for dsDNA.
Main Results:
- Newly synthesized BrdU-labeled BMD was detected in a significant percentage of large synaptosomes from retinal photoreceptor neurons and smaller synaptosomal bodies.
- Synaptosomal BMD synthesis was significantly inhibited by actinomycin D, indicating a transcriptional process.
- Native double-stranded DNA (dsDNA) was confirmed to be present in all examined synaptosomes.
Conclusions:
- Brain metabolic DNA (BMD) is synthesized within synaptosomes, particularly in nerve terminals.
- This finding suggests a novel role for synaptic DNA in neuronal function, separate from its role in cell division or repair.
- Further research is warranted to elucidate the specific functions of synaptic BMD.
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