Figure 3: BAF53a repression is essential for activity-dependent dendritic outgrowth in neurons.

a, Normal downregulation of BAF53a in post-mitotic neurons in transgenic embryos with wild type BAF53a BAC. The rightmost panel shows the lower-right quadrant of the neural tube. b, Persistent expression of BAF53a in neurons seen with BAF53a BAC containing point mutations in the miRNA-binding sites. c, Normal expression of BAF53b (red) in -tubulin-III-positive (green) neurons in transgenic embryos with wild-type BAF53a BAC. d, Reduced BAF53b expression with persistent expression of BAF53a in neurons. e, Quantification of BAF53b expression: ratio of BAF53b level (arbitrary units) and -tubulin-III-positive neurons. Average values are from eight sections of the neural tube. Error bars, s.e. *P < 0.005, Student's t-test. f, Constructs to overexpress BAF53a in cultured hippocampal neurons and quantification of dendritic outgrowth of GFP-positive neurons upon stimulation using KCl. The average values are from five individual coverslips from two independent experiments, with each coverslip containing 50–100 scored neurons. Error bars, s.e. *P < 0.005, Student's t-test. p, promoter; IRES, internal ribosome entry site. g, Schematic diagrams of BAF53a expression constructs using different 3' UTRs and quantification of dendritic outgrowth of transfected neurons upon stimulation using KCl. In independent experiments, we found that the 4-kb upstream region of BAF53a (illustrated) was sufficient to drive expression of GFP reporters that could be repressed by endogenous miR-9* and miR-124. Error bars, s.e. *P < 0.001, Student's t-test.

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