Our results also identify HBL-1 as a molecular mediator of activity’s effects on DD plasticity. HBL-1 expression is restricted to a specific set of neuronal cell types, and thus could confer activity dependence in a cell and circuit specific manner. By contrast, it is unclear how the general activity-induced genes that are implicated in ocular dominance plasticity (e.g., CREB and BDNF) could mediate refinement in a cell and temporally specified manner. This result also demonstrates that the effect of hbl-1 on developmental

timing is regulated by the nervous system. It will be interesting to see Stem Cells inhibitor if the nervous system also controls other heterochronic pathways. In summary, we show that patterning of DD plasticity is achieved by the convergence of multiple regulatory pathways on hbl-1. Convergent regulation of hbl-1 defines a cell intrinsic pathway that confers cell and temporal specificity and activity-dependence

on this form of circuit refinement. Strains were maintained at 20°C using standard protocols, on lawns of OP50 for imaging and behavior, and on HB101 for electrophysiology. Strains are listed in the Supplemental Information. Whole worm lysates of synchronized L3 animals were prepared by Trizol extraction (Invitrogen). Three biological replicates of wild-type and unc-55(e1170) samples were collected on different days. cDNA library construction, primer validation, and quantitative RT-PCR were carried out according to standard protocols. Changes in hbl-1 mRNA levels, were Etoposide concentration normalized relative to rpl-32 levels. The hbl-1 reporters are similar to those used previously ( Fay et al., 1999). These constructs contain 7.7 kb, including 6.4 kb upstream and 1.3 kb of exons 1–4. These constructs encode a protein containing the first 133 amino acids of hbl-1 fused to GFP-PEST, along with 1 kb of the hbl-1 3′UTR (HgfpH) or the control unc-54 3′UTR (HgfpC). In HmutgfpC, the four 6 bp UNC-55 binding sites in the hbl-1 promoter were replaced with BamHI Histone demethylase sites. Images were collected on a laser-scanning

Olympus FV1000 confocal microscope. To quantify GFP fluorescence, areas of interest were drawn around DD or VD neuron cell bodies (identified by the unc-25 GAD mCherry signal) in a single plane through the center of the cell bodies, and median GFP fluorescence was determined for that plane. DD neurons were distinguished from VD neurons based on anterior-posterior position in the ventral nerve cord, cell body size, and morphology ( White et al., 1986). The ratio of GFP signal in DD5 to VD10 was determined in each animal, log2 transformed, then averaged for all animals of a genotype. To enhance our ability to detect increases in hbl-1 expression in mir-84 and tom-1 mutants, we used an HgfpH transgene (nuIs427) that has a low baseline expression level. Electrophysiology was done on ventral and dorsal body muscles of dissected C.