Bestman JE and Cline HT (2008), The RNA binding protein CPEB regulates dendrite...

XB-ART-38669

Proc Natl Acad Sci U S A 2008 Dec 23;10551:20494-9. doi: 10.1073/pnas.0806296105.

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The RNA binding protein CPEB regulates dendrite morphogenesis and neuronal circuit assembly in vivo.

Bestman JE , Cline HT .

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Visual system development requires experience-dependent mechanisms that regulate neuronal structure and function, including dendritic arbor growth, synapse formation, and stabilization. Although RNA binding proteins have been shown to affect some forms of synaptic plasticity in adult animals, their role in the development of neuronal structure and functional circuitry is not clear. Using two-photon time-lapse in vivo imaging and electrophysiology combined with morpholino-mediated knockdown and expression of functional deletion mutants, we demonstrate that the mRNA binding protein, cytoplasmic polyadenylation element binding protein1 (CPEB1), affects experience-dependent neuronal development and circuit formation in the visual system of Xenopus laevis. These data indicate that sensory experience controls circuit development by regulating translational activity of mRNAs.

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Species referenced: Xenopus laevis
Genes referenced: cpeb1

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	Fig. 1. CPEB is required for dendritic arbor growth in vivo. (A–D) Time-lapse in vivo two-photon images of tectal neurons and their three-dimensional (3D) reconstructions, collected daily over 3 days. (E-G) Quantification of dendritic morphology showing total dendritic branch length (TDBL) (E), branch-tip number (F), and 3D Sholl analysis (G). (E) Compared to control cells, the dendritic growth of delCPEB-expressing neurons, but not CPEB or rbdCPEB-expressing neurons, is significantly impaired by day 2 and 3. (F) By day 3, only delCPEB-expressing neurons have significantly fewer branch tips compared to control neurons. (G) Sholl analysis of 3-day cells illustrating the radial distribution of the branches of the dendritic arbor. Shown are the average number of branch intersections at 10-μm intervals beyond the soma. Control, n = 11; CPEB, n = 12; delCPEB n = 10; rbdCPEB = 12; *, P ≤ 0.05. Values given in Table S2.
	Fig. 2. CPEB function is required for experience-dependent increased dendritic growth. (A-D) Time-lapse in vivo two photon images collected at 4-h intervals over 8 h, and 3D reconstructions showing terminal branches that are lost (pink), appeared transiently at the fourth hour (green), and are gained (blue) over the 4-h periods without or with visual stimulation (indicated with light-bulb icon) for tectal neurons. (E–H) Quantification of dendritic morphology. During the 4 h of light stimulation, control and CPEB-expressing neurons show a significant increase in TDBL (E) and branch-tip number (F). Individual cell's changes in TDBL (G) and branch-tip number (H) are plotted in gray, averages are plotted in black. Control and CPEB-expressing cells show significant changes in TDBL. Only CPEB-expressing cells show a significant change in branch-tip number. (I–L) Quantification of identified branch dynamics. Proportion of branches newly added (I) and lost (J) during each 4-h. (I) delCPEB-expressing cells add significantly fewer branches during the light-stimulation period compared to control neurons. There were no differences in the proportion of branches lost between groups (J). (K) The average increase in branch length of delCPEB cells is less than that of control cells in both the dark and during the light stimulus. CPEB cells also added significantly less average branch length during the visual stimulation period. (L) The average amount that delCPEB-retracting branches lost was less than control cells in both the dark and during the light stimulation. Control, n = 12; CPEB, n = 10; delCPEB, n = 14; rbdCPEB = 11; *, P < 0.05. Values given in Tables S3–S5.
	Fig. 3. Altering CPEB function reduces amplitude but not frequency of AMPA receptor mEPSCs. (A) Representative traces and examples of average mEPSCs. (B) Quantification of mEPSC amplitude (*, P < Control, n = 32; CPEB, n = 28; delCPEB n = 31.
	Fig. 4. Altering CPEB expression interferes with tectal cell performance in the visual circuit. (A–C) Whole-cell recordings of visual responses over the complete 2.5 s of the off responses. Each column shows recordings from the same cell for each 10-dB increase in intensity. Twenty responses are superimposed in gray with the average response in black. (D–F) Spontaneous activity recorded during the dark-adaptation period. Gray areas are expanded in the insets. Bursting activity is only seen in control cells. (G) Quantification of average charge transferred (Q) over 500 ms following light off for each stimulus intensity. Compared to control neurons, delCPEB-expressing cells showed significantly lower Q for each intensity tested. CPEB cells were significantly different at the stronger relative intensities. n = 6–10 cells for each intensity for control, CPEB and delCPEB groups. (H and I) Quantification of spontaneous synaptic activity recorded in the absence of TTX. Distribution and means (inset) for the single event amplitudes (H) and inter-event intervals (IEI) (I) were significantly shifted toward smaller values for both delCPEB and CPEB-expressing neurons compared to control cells. n = 1,190 events and 10 neurons per cell group. *, P < 0.05. Values given in Tables S6 and S7.

References [+] :

Aizenman, Enhanced visual activity in vivo forms nascent synapses in the developing retinotectal projection. 2007, Pubmed, Xenbase