title: DNA endoreplication in the brain neurons during body growth of an adult slug.
abstract: Endoreplication is DNA synthesis without cell division. Giant neurons observed in the brains of mollusks are thought to be generated as a result of DNA endoreplication. It has been hypothesized that neuronal size becomes larger in parallel with an increase in body size and that DNA endoreplication is involved in this process to meet the increasing demand for macromolecules in neurons. There is, however, no experimental evidence for this hypothesis to date. In the present study, we investigated the following quantitatively: (1) the size of the brain and each ganglion, (2) the size of identified neurons, (3) the total number of neurons undergoing DNA endoreplication, (4) the total number of the neurons containing a cardioexcitatory peptide, and (5) the gene expression level per neuron, using terrestrial slugs whose body growth was regulated through the amount of food supplied in the laboratory. The body growth was accompanied by increases in the sizes of both neurons and ganglia and triggered more frequent DNA endoreplication events in each ganglion of the growth-promoted slugs, without increasing the total number of neurons. Increase in the neuronal size also involved the increase in the amount of transcripts expressed in a single neuron. This is the first quantitative evidence showing that the DNA endoreplication, neuronal size, and gene expression are increased concomitantly with body growth in adult mollusks.
authors.affiliation: Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, Sanuki, Kagawa 769-2193, Japan.
authors.forename: Miki
authors.initials: M
authors.lastname: Yamagishi
authors.forename: Etsuro
authors.initials: E
authors.lastname: Ito
authors.forename: Ryota
authors.initials: R
authors.lastname: Matsuo
mesh_terms: D000818:Animals; D000963:Antimetabolites; D001835:Body Weight / Q000502:physiology; D001921:Brain / Q000166:cytology; D001923:Brain Chemistry / Q000502:physiology*; D001973:Bromodeoxyuridine; D002452:Cell Count; D048429:Cell Size; D004261:DNA Replication / Q000502:physiology*; D004032:Diet; D017952:Ganglia, Invertebrate / Q000166:cytology / Q000254:growth & development; D049851:Gastropoda / Q000502:physiology*; D006128:Growth / Q000502:physiology*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D009474:Neurons / Q000378:metabolism* / Q000648:ultrastructure; D009479:Neuropeptides / Q000096:biosynthesis / Q000235:genetics; D009842:Oligopeptides / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014048:Tolonium Chloride
chemical_list: D000963:Antimetabolites; D009479:Neuropeptides; D009842:Oligopeptides; D012333:RNA, Messenger; C109335:asparaginyl-tryptophyl-phenylalaninamide; D014048:Tolonium Chloride; D001973:Bromodeoxyuridine