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Activity-dependent regulation of dendritic BC1 RNA in hippocampal neurons in culture.

Muslimov IA, Banker G, Brosius J, Tiedge H - J. Cell Biol. (1998)

Bottom Line: Inhibition of neuronal activity in hippocampal neurons resulted in a substantial but reversible reduction of somatodendritic BC1 expression.We conclude that expression of BC1 RNA in somatic and dendritic domains of hippocampal neurons is regulated in development, and is dependent upon neuronal activity.These results establish (for the first time to our knowledge) that an RNA polymerase III transcript can be subject to control through physiological activity in nerve cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology, State University of New York, Health Science Center at Brooklyn, Brooklyn, New York 11203, USA.

ABSTRACT
Several neuronal RNAs have been identified in dendrites, and it has been suggested that the dendritic location of these RNAs may be relevant to the spatiotemporal regulation of mosaic postsynaptic protein repertoires through transsynaptic activity. Such regulation would require that dendritic RNAs themselves, or at least some of them, be subject to physiological control. We have therefore examined the functional regulation of somatodendritic expression levels of dendritic BC1 RNA in hippocampal neurons in culture. BC1 RNA, an RNA polymerase III transcript that is a component of a ribonucleoprotein particle, became first detectable in somatodendritic domains of developing hippocampal neurons at times of initial synapse formation. BC1 RNA was identified only in such neurons that had established synapses on cell bodies and/or developing dendritic arbors. When synaptic contact formation was initiated later in low-density cultures, BC1 expression was coordinately delayed. Inhibition of neuronal activity in hippocampal neurons resulted in a substantial but reversible reduction of somatodendritic BC1 expression. We conclude that expression of BC1 RNA in somatic and dendritic domains of hippocampal neurons is regulated in development, and is dependent upon neuronal activity. These results establish (for the first time to our knowledge) that an RNA polymerase III transcript can be subject to control through physiological activity in nerve cells.

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Expression of BC1 RNA in cultured hippocampal neurons developing at different cell densities. Hippocampal neurons were  grown for 7 d in culture and were double-labeled for BC1 RNA (in situ hybridization; green) and synaptophysin (immunocytochemistry;  red). A green filter was used for visualizing autoradiographic silver grains in double-exposure photomicrographs in order to differentiate them from the red immunofluorescence signal. (A and B) 1,000 cells per cm2; (C) 4,000 cells per cm2; (D) 16,000 cells per cm2. At low  density, beginning BC1 expression can be observed in a few cells (B) while the majority shows no labeling (A). At medium density (C),  BC1 labeling was often observed over proximal segments of dendrites that were lined with synaptophysin puncta. At high density (D),  BC1 labeling was frequently observed over dendrites at considerable distances from somata. Bar, 25 μm.
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Figure 4: Expression of BC1 RNA in cultured hippocampal neurons developing at different cell densities. Hippocampal neurons were grown for 7 d in culture and were double-labeled for BC1 RNA (in situ hybridization; green) and synaptophysin (immunocytochemistry; red). A green filter was used for visualizing autoradiographic silver grains in double-exposure photomicrographs in order to differentiate them from the red immunofluorescence signal. (A and B) 1,000 cells per cm2; (C) 4,000 cells per cm2; (D) 16,000 cells per cm2. At low density, beginning BC1 expression can be observed in a few cells (B) while the majority shows no labeling (A). At medium density (C), BC1 labeling was often observed over proximal segments of dendrites that were lined with synaptophysin puncta. At high density (D), BC1 labeling was frequently observed over dendrites at considerable distances from somata. Bar, 25 μm.

Mentions: We consistently observed substantial differences in somatic and dendritic levels of BC1 RNA as a function of cell and synapse density. In Fig. 4, this is exemplified with hippocampal neurons that had been maintained in culture for 7 d. In low-density cultures at this stage, we observed only a small number of synaptophysin puncta per neuron (Fig. 4, A and B). This number was typically below 20. Often, very few puncta or none at all were seen associated with a particular neuron; this was usually the case with cells that developed in relative spatial isolation. A BC1 signal was observed at low levels in the somata of most of those cells that exhibited synaptophysin puncta on cell bodies and/or dendrites (Fig. 4 B). No significant levels of BC1 RNA were detected in cells that were devoid of synaptophysin puncta. In some cases, however, BC1 RNA was also undetectable in cells that clearly exhibited at least several synaptophysin puncta (Fig. 4 A). These data suggest that the onset of BC1 expression is concurrent with, or immediately subsequent to, initial synapse formation.


Activity-dependent regulation of dendritic BC1 RNA in hippocampal neurons in culture.

Muslimov IA, Banker G, Brosius J, Tiedge H - J. Cell Biol. (1998)

Expression of BC1 RNA in cultured hippocampal neurons developing at different cell densities. Hippocampal neurons were  grown for 7 d in culture and were double-labeled for BC1 RNA (in situ hybridization; green) and synaptophysin (immunocytochemistry;  red). A green filter was used for visualizing autoradiographic silver grains in double-exposure photomicrographs in order to differentiate them from the red immunofluorescence signal. (A and B) 1,000 cells per cm2; (C) 4,000 cells per cm2; (D) 16,000 cells per cm2. At low  density, beginning BC1 expression can be observed in a few cells (B) while the majority shows no labeling (A). At medium density (C),  BC1 labeling was often observed over proximal segments of dendrites that were lined with synaptophysin puncta. At high density (D),  BC1 labeling was frequently observed over dendrites at considerable distances from somata. Bar, 25 μm.
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Figure 4: Expression of BC1 RNA in cultured hippocampal neurons developing at different cell densities. Hippocampal neurons were grown for 7 d in culture and were double-labeled for BC1 RNA (in situ hybridization; green) and synaptophysin (immunocytochemistry; red). A green filter was used for visualizing autoradiographic silver grains in double-exposure photomicrographs in order to differentiate them from the red immunofluorescence signal. (A and B) 1,000 cells per cm2; (C) 4,000 cells per cm2; (D) 16,000 cells per cm2. At low density, beginning BC1 expression can be observed in a few cells (B) while the majority shows no labeling (A). At medium density (C), BC1 labeling was often observed over proximal segments of dendrites that were lined with synaptophysin puncta. At high density (D), BC1 labeling was frequently observed over dendrites at considerable distances from somata. Bar, 25 μm.
Mentions: We consistently observed substantial differences in somatic and dendritic levels of BC1 RNA as a function of cell and synapse density. In Fig. 4, this is exemplified with hippocampal neurons that had been maintained in culture for 7 d. In low-density cultures at this stage, we observed only a small number of synaptophysin puncta per neuron (Fig. 4, A and B). This number was typically below 20. Often, very few puncta or none at all were seen associated with a particular neuron; this was usually the case with cells that developed in relative spatial isolation. A BC1 signal was observed at low levels in the somata of most of those cells that exhibited synaptophysin puncta on cell bodies and/or dendrites (Fig. 4 B). No significant levels of BC1 RNA were detected in cells that were devoid of synaptophysin puncta. In some cases, however, BC1 RNA was also undetectable in cells that clearly exhibited at least several synaptophysin puncta (Fig. 4 A). These data suggest that the onset of BC1 expression is concurrent with, or immediately subsequent to, initial synapse formation.

Bottom Line: Inhibition of neuronal activity in hippocampal neurons resulted in a substantial but reversible reduction of somatodendritic BC1 expression.We conclude that expression of BC1 RNA in somatic and dendritic domains of hippocampal neurons is regulated in development, and is dependent upon neuronal activity.These results establish (for the first time to our knowledge) that an RNA polymerase III transcript can be subject to control through physiological activity in nerve cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology, State University of New York, Health Science Center at Brooklyn, Brooklyn, New York 11203, USA.

ABSTRACT
Several neuronal RNAs have been identified in dendrites, and it has been suggested that the dendritic location of these RNAs may be relevant to the spatiotemporal regulation of mosaic postsynaptic protein repertoires through transsynaptic activity. Such regulation would require that dendritic RNAs themselves, or at least some of them, be subject to physiological control. We have therefore examined the functional regulation of somatodendritic expression levels of dendritic BC1 RNA in hippocampal neurons in culture. BC1 RNA, an RNA polymerase III transcript that is a component of a ribonucleoprotein particle, became first detectable in somatodendritic domains of developing hippocampal neurons at times of initial synapse formation. BC1 RNA was identified only in such neurons that had established synapses on cell bodies and/or developing dendritic arbors. When synaptic contact formation was initiated later in low-density cultures, BC1 expression was coordinately delayed. Inhibition of neuronal activity in hippocampal neurons resulted in a substantial but reversible reduction of somatodendritic BC1 expression. We conclude that expression of BC1 RNA in somatic and dendritic domains of hippocampal neurons is regulated in development, and is dependent upon neuronal activity. These results establish (for the first time to our knowledge) that an RNA polymerase III transcript can be subject to control through physiological activity in nerve cells.

Show MeSH