Strategies for inducing expression of scFv in PV cells or in CSF.

<p><b>A)</b> Co-staining for Myc and PV in layers II-IV of the binocular zone of the visual cortex (V1b) of P30 <i>PV</i>::<i>Cre</i>, <i>PV</i>::<i>Cre;scFvPax6</i>^<i>tg/o</i> and <i>PV</i>::<i>Cre;scFvOtx2</i>^<i>tg/o</i> mice (scale bar: 100μm). The enlarged view shows the immunofluorescence overlap. <b>B)</b> Western blot of cerebrospinal fluid (CSF) protein extracts from <i>scFvOtx2</i>^<i>tg/o</i> and <i>scFvPax6</i>^<i>tg/o</i> adult mice injected (+Cre) or not (ctrl) with Cre-TAT protein in lateral ventricles. Anti-Otx2 and anti-Pax6 scFvs (revealed with anti-Myc antibody) are secreted in the CSF upon choroid plexus recombination.</p

Anti-Otx2 scFv in adult CSF restores ocular dominance plasticity.

<p><b>A)</b><i>scFvOtx2</i>^<i>tg/o</i> adult (P90) mice were injected with NaCl or Cre-TAT and, after 15 d, the left eye was sutured for 4 d. Intrinsic optical imaging was then performed in the right visual cortex to measure visual acuity for each eye. <b>B)</b> Intrinsic signals recorded for the ipsilateral eye stimulation in <i>scFvOtx2</i>^<i>tg/o</i> adult mice injected with NaCl (top) or Cre-TAT (bottom). Ten spatial frequencies (SFs) ranging from 0.03 to 1 cycle/degree were tested. The binocular zone is delineated in white (A, Anterior; M, Medial; Scale bar, 1 mm). <b>C)</b> Estimation of the ipsilateral eye visual acuity for the two mice shown in (B). Each point corresponds to the average magnitude in the binocular zone. For each animal, data were normalized by the maximal amplitude among SFs and visual acuity was defined as the intersection of a fitted line segment with the X-axis. Representative stimuli are shown below. <b>D)</b> Visual acuity of the ipsilateral eye in adult <i>scFvOtx2</i>^<i>tg/o</i> injected with NaCl or Cre-TAT. <b>E)</b> Same as (D) for the contralateral eye. <b>F)</b> Ocular dominance index at different SF thresholds in adult <i>scFvOtx2</i>^<i>tg/o</i> mice injected with NaCl or Cre-TAT. Positive values indicate a preference for the contralateral eye. (t-tests; *p<0.05; error bars indicate SEM)</p

Anti-Otx2 scFv in adult CSF activates plasticity genes.

<p><b>A)</b> Immunostaining for Otx2, PV, WFA, CR and GABA in V1b layers II-IV of adult <i>scFvPax6</i>^<i>tg/o</i> and <i>scFvOtx2</i>^<i>tg/o</i> mice, 15 days after intracerebroventricular (icv) injection of Cre-TAT protein (scale bar: 100μm). <b>B)</b> Quantification of number of Otx2-, PV-, WFA, CR- and GABA-positive cells in V1b layers II-IV of adult <i>scFvOtx2</i>^<i>tg/o</i> and <i>scFvPax6</i>^<i>tg/o</i> mice, 15 days after icv injection of Cre-TAT (in percentage of <i>scFvPax6</i>^<i>tg/o</i> mice, dashed line indicates <i>scFvPax6</i>^<i>tg/o</i> levels). Absolute numbers are provided in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1006035#pgen.1006035.s002" target="_blank">S2 Fig</a>. <b>C)</b> Quantification of <i>Arc</i>, <i>Fos</i>, <i>Nr4a1</i>, <i>Egr4</i> and <i>HPRT</i> mRNA content (relative to <i>GAPDH</i>) in V1 layer IV extracts from adult <i>scFvOtx2</i>^<i>tg/o</i> and <i>scFvPax6</i>^<i>tg/o</i> mice, 15 d after icv injection of Cre-TAT. (t-tests; 3–12 mice per group; *p<0.05, **p<0.01, ***p<0.001; error bars indicate SEM)</p

Input-specific control of interneuron numbers in nascent striatal networks

The assembly of functional neuronal circuits requires appropriate numbers of distinct classes of neurons, but the mechanisms through which their relative proportions are established remain poorly defined. Investigating the mouse striatum, we found that the two most prominent subtypes of striatal interneurons, parvalbumin-expressing (PV+) GABAergic and cholinergic (ChAT+) interneurons, undergo extensive programmed cell death between the first and second postnatal weeks. Remarkably, the survival of PV+ and ChAT+ interneurons is regulated by distinct mechanisms mediated by their specific afferent connectivity. While long-range cortical inputs control PV+ interneuron survival, ChAT+ interneuron survival is regulated by local input from the medium spiny neurons. Our results identify input-specific circuit mechanisms that operate during the period of programmed cell death to establish the final number of interneurons in nascent striatal networks.</p