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Spatial codes in dendritic BC1 RNA.

Muslimov IA, Iacoangeli A, Brosius J, Tiedge H - J. Cell Biol. (2006)

Bottom Line: This element features a GA kink-turn (KT) motif that is indispensable for distal targeting.It specifically interacts with heterogeneous nuclear ribonucleoprotein A2, a trans-acting targeting factor that has previously been implicated in the transport of MBP mRNA in oligodendrocytes and neurons.Our work suggests that a BC1 KT motif encodes distal targeting via the A2 pathway and that architectural RNA elements, such as KT motifs, may function as spatial codes in neural cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology and Pharmacology, The Robert F. Furchgott Center for Neural and Behavioral Science, State University of New York Health Science Center at Brooklyn, Brooklyn, NY 11203, USA.

ABSTRACT
BC1 RNA is a dendritic untranslated RNA that has been implicated in local translational control mechanisms in neurons. Prerequisite for a functional role of the RNA in synaptodendritic domains is its targeted delivery along the dendritic extent. We report here that the targeting-competent 5' BC1 domain carries two dendritic targeting codes. One code, specifying somatic export, is located in the medial-basal region of the 5' BC1 stem-loop structure. It is defined by an export-determinant stem-bulge motif. The second code, specifying long-range dendritic delivery, is located in the apical part of the 5' stem-loop domain. This element features a GA kink-turn (KT) motif that is indispensable for distal targeting. It specifically interacts with heterogeneous nuclear ribonucleoprotein A2, a trans-acting targeting factor that has previously been implicated in the transport of MBP mRNA in oligodendrocytes and neurons. Our work suggests that a BC1 KT motif encodes distal targeting via the A2 pathway and that architectural RNA elements, such as KT motifs, may function as spatial codes in neural cells.

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Long-range dendritic targeting codes: the GA apical internal loop (IL-A) motif. (A) Introduction of standard WC base pairs (IL-A:WC). (B) Conversion sense–antisense (IL-A:AUC). Both mutations resulted in reduced long-range dendritic targeting; somatic export remained unaffected, but dendritic transport was now restricted to proximal-medial segments. The photomicrographs show dark-field (DF; left) and phase-contrast (PC; right) images of injected neurons. Arrows in phase-contrast images demarcate the distal-most extent of dendritic labeling signal. Extended incubation times did not result in changes of the observed distribution patterns. Statistical analyses performed (comparison of both BC1 derivatives with wild-type BC1 RNA; Fig. 2) were one-way ANOVA for interval point 50 μm (measured from base of dendrite) (P > 0.5); one-way ANOVA for interval points 100, 150, and 200 μm (P < 0.001 in each case); and Scheffe's multiple comparison post hoc analysis for both derivatives at interval points 100, 150, and 200 μm (P < 0.001 in each case). Quantitative data are presented as the mean ± the SEM of relative signal intensities along the dendritic extent. Bar, 50 μm.
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fig4: Long-range dendritic targeting codes: the GA apical internal loop (IL-A) motif. (A) Introduction of standard WC base pairs (IL-A:WC). (B) Conversion sense–antisense (IL-A:AUC). Both mutations resulted in reduced long-range dendritic targeting; somatic export remained unaffected, but dendritic transport was now restricted to proximal-medial segments. The photomicrographs show dark-field (DF; left) and phase-contrast (PC; right) images of injected neurons. Arrows in phase-contrast images demarcate the distal-most extent of dendritic labeling signal. Extended incubation times did not result in changes of the observed distribution patterns. Statistical analyses performed (comparison of both BC1 derivatives with wild-type BC1 RNA; Fig. 2) were one-way ANOVA for interval point 50 μm (measured from base of dendrite) (P > 0.5); one-way ANOVA for interval points 100, 150, and 200 μm (P < 0.001 in each case); and Scheffe's multiple comparison post hoc analysis for both derivatives at interval points 100, 150, and 200 μm (P < 0.001 in each case). Quantitative data are presented as the mean ± the SEM of relative signal intensities along the dendritic extent. Bar, 50 μm.

Mentions: To address this question, we first converted the GA apical internal loop into an A-form helical stem. Standard WC base pairs were introduced by exchanging three nucleotides in the 3′ strand of the loop (to generate mutant IL-A:WC; Fig. 4 A). This substitution resulted in a substantially reduced range in dendritic transport; IL-A:WC mutant full-length BC1 RNA advanced, on average, to only about half of the dendritic distance that was covered by wild-type BC1 RNA (Fig. 4 A). Thus, BC1 RNA with the GA apical internal loop replaced by a helical stem was still delivered to proximal dendrites, but it now failed to reach distal dendritic segments at 200 μm and beyond. Signal intensities in proximal-most dendritic segments (≤50 μm) did not differ substantially between apical internal loop mutant and wild-type BC1 RNA. Thus, it appears that IL-A:WC mutant BC1 RNA is exported normally from the soma, but is deficient in long-range transport along the dendritic extent.


Spatial codes in dendritic BC1 RNA.

Muslimov IA, Iacoangeli A, Brosius J, Tiedge H - J. Cell Biol. (2006)

Long-range dendritic targeting codes: the GA apical internal loop (IL-A) motif. (A) Introduction of standard WC base pairs (IL-A:WC). (B) Conversion sense–antisense (IL-A:AUC). Both mutations resulted in reduced long-range dendritic targeting; somatic export remained unaffected, but dendritic transport was now restricted to proximal-medial segments. The photomicrographs show dark-field (DF; left) and phase-contrast (PC; right) images of injected neurons. Arrows in phase-contrast images demarcate the distal-most extent of dendritic labeling signal. Extended incubation times did not result in changes of the observed distribution patterns. Statistical analyses performed (comparison of both BC1 derivatives with wild-type BC1 RNA; Fig. 2) were one-way ANOVA for interval point 50 μm (measured from base of dendrite) (P > 0.5); one-way ANOVA for interval points 100, 150, and 200 μm (P < 0.001 in each case); and Scheffe's multiple comparison post hoc analysis for both derivatives at interval points 100, 150, and 200 μm (P < 0.001 in each case). Quantitative data are presented as the mean ± the SEM of relative signal intensities along the dendritic extent. Bar, 50 μm.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC1808587&req=5

fig4: Long-range dendritic targeting codes: the GA apical internal loop (IL-A) motif. (A) Introduction of standard WC base pairs (IL-A:WC). (B) Conversion sense–antisense (IL-A:AUC). Both mutations resulted in reduced long-range dendritic targeting; somatic export remained unaffected, but dendritic transport was now restricted to proximal-medial segments. The photomicrographs show dark-field (DF; left) and phase-contrast (PC; right) images of injected neurons. Arrows in phase-contrast images demarcate the distal-most extent of dendritic labeling signal. Extended incubation times did not result in changes of the observed distribution patterns. Statistical analyses performed (comparison of both BC1 derivatives with wild-type BC1 RNA; Fig. 2) were one-way ANOVA for interval point 50 μm (measured from base of dendrite) (P > 0.5); one-way ANOVA for interval points 100, 150, and 200 μm (P < 0.001 in each case); and Scheffe's multiple comparison post hoc analysis for both derivatives at interval points 100, 150, and 200 μm (P < 0.001 in each case). Quantitative data are presented as the mean ± the SEM of relative signal intensities along the dendritic extent. Bar, 50 μm.
Mentions: To address this question, we first converted the GA apical internal loop into an A-form helical stem. Standard WC base pairs were introduced by exchanging three nucleotides in the 3′ strand of the loop (to generate mutant IL-A:WC; Fig. 4 A). This substitution resulted in a substantially reduced range in dendritic transport; IL-A:WC mutant full-length BC1 RNA advanced, on average, to only about half of the dendritic distance that was covered by wild-type BC1 RNA (Fig. 4 A). Thus, BC1 RNA with the GA apical internal loop replaced by a helical stem was still delivered to proximal dendrites, but it now failed to reach distal dendritic segments at 200 μm and beyond. Signal intensities in proximal-most dendritic segments (≤50 μm) did not differ substantially between apical internal loop mutant and wild-type BC1 RNA. Thus, it appears that IL-A:WC mutant BC1 RNA is exported normally from the soma, but is deficient in long-range transport along the dendritic extent.

Bottom Line: This element features a GA kink-turn (KT) motif that is indispensable for distal targeting.It specifically interacts with heterogeneous nuclear ribonucleoprotein A2, a trans-acting targeting factor that has previously been implicated in the transport of MBP mRNA in oligodendrocytes and neurons.Our work suggests that a BC1 KT motif encodes distal targeting via the A2 pathway and that architectural RNA elements, such as KT motifs, may function as spatial codes in neural cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology and Pharmacology, The Robert F. Furchgott Center for Neural and Behavioral Science, State University of New York Health Science Center at Brooklyn, Brooklyn, NY 11203, USA.

ABSTRACT
BC1 RNA is a dendritic untranslated RNA that has been implicated in local translational control mechanisms in neurons. Prerequisite for a functional role of the RNA in synaptodendritic domains is its targeted delivery along the dendritic extent. We report here that the targeting-competent 5' BC1 domain carries two dendritic targeting codes. One code, specifying somatic export, is located in the medial-basal region of the 5' BC1 stem-loop structure. It is defined by an export-determinant stem-bulge motif. The second code, specifying long-range dendritic delivery, is located in the apical part of the 5' stem-loop domain. This element features a GA kink-turn (KT) motif that is indispensable for distal targeting. It specifically interacts with heterogeneous nuclear ribonucleoprotein A2, a trans-acting targeting factor that has previously been implicated in the transport of MBP mRNA in oligodendrocytes and neurons. Our work suggests that a BC1 KT motif encodes distal targeting via the A2 pathway and that architectural RNA elements, such as KT motifs, may function as spatial codes in neural cells.

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