A Cytophotometric analysis of the DNA in the nucleus of the giant cell, R-2, in Aplysia

Coggeshall, Richard E.; Yaksta, Barbara A.; Swartz, Frank J.

doi:10.1007/bf00286009

Cited by 30 publications

(22 citation statements)

References 6 publications

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“…Since the discovery of giant neurons in the brains of gastropods, most researchers have analyzed the extent of DNA endoreplication by cytophotometric methods (Kuhlmann, 1969;Coggeshall et al, 1970;Boer et al, 1977). These analyses, however, do not (Fig.…”

Section: Dna Synthesis During Body Growthmentioning

confidence: 99%

DNA Endoreplication in the Brain Neurons during Body Growth of an Adult Slug

Yamagishi¹,

Ito²,

Matsuo³

2011

J. Neurosci.

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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.

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Section: Dna Synthesis During Body Growthmentioning

confidence: 99%

DNA Endoreplication in the Brain Neurons during Body Growth of an Adult Slug

Yamagishi¹,

Ito²,

Matsuo³

2011

J. Neurosci.

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“…being directly introduced into the nucleus. Aplysia neurons are highly polyploid, containing up to 2 x 105 copies of the genome (12,34), while the injections presented in this report were usually of about 106 to 107 copies of DNA. Injection of an order of magnitude less DNA did not result in detectable expression.…”

Section: Discussionmentioning

confidence: 63%

“…Neuropeptides can travel some distance from their site of release, and the duration of their actions may be quite prolonged (4 messengers, and in some cells up to 10 to 25% of the mRNA encodes precursors for the biologically active peptide products (for a review, see reference 26). RNA blotting, in situ hybridization, and immunohistochemistry techniques all demonstrate that the various neuropeptides are expressed in cell-specific patterns ranging from as few as 12 cells in the case of the R14 peptide to as many as 100 or so cells in the case of the Lii peptide ( Fig. 1) (for example, see references 30, 39, and 47).…”

mentioning

confidence: 99%

Aplysia californica neurons express microinjected neuropeptide genes.

DesGroseillers¹,

Cowan²,

Miles³

et al. 1987

Mol. Cell. Biol.

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Neuropeptide genes are expressed in specific subsets of large polyploid neurons in Aplysia californica. We have defined the transcription initiation sites of three of these neuropeptide genes (the R14, Lll, and ELH genes) and determined the nucleotide sequence of the promoter regions. The genes contain the usual eucaryotic promoter signals as well as other structures of potential regulatory impoortance, including inverted and direct repeats. The Lll and ELH genes, which are otherwise unrelated, have homology in the promoter regions, while the R14 promoter was distinct. When cloned plasmids were microinjected into Aplysia neurons in organ culture, transitions between supercoiled, relaxed circular, and linear DNAs occurred along with ligation into high-molecular-weight species. About 20% of the microinjected neurons expressed the genes. The promoter region of the R14 gene functioned in expression of the microinjected DNA in all cells studied. When both additional 5' and 3' sequences were included, the gene was specifically expressed only in R14, suggesting that the specificity of expression is generated by a multicomponent repression system. Finally, the R14 peptide could be expressed in Lll, demonstrating that it is possible to alter the transmitter phenotype of these neurons by introduction of cloned genes.Control of gene expression in the central nervous system (CNS) may require novel and complex regulatory networks to generate the vast and intricate communication network between cells. The specificity of this network is determined by the expression of specific sets of genes, including those which determine neurotransmitter and receptor phenotype. In addition, the CNS can be considered to develop continuously throughout the life of an animal as experience shapes the fine structure of this communication network. The complexity, which affords the nervous system with remarkable properties, makes cellular and molecular studies, including those of gene expression, a difficult task. Neurons are generally postmitotic, and the vast number of unique cells makes the study of identified neurons with known functions very difficult in vertebrates.Many invertebrate species, including mollusks, have provided partial solutions to these problems due to the numerical simplicity of their CNSs and the large size of the component neurons.

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“…In addition to being few in number, neurons in Aplysia can be quite large, up to 1 mm in diameter. Most of these large cells are polyploid and contain as much as 2 #g of DNA, more than 105 times the content of the haploid genome (Coggeshall et al 1971;Lasek and Dower 1971). Furthermore, our data indicate that mRNA content is proportional to cell size such that the largest of cells contains up to 5 ng of mRNA.…”

mentioning

confidence: 59%