Autocatalytic processing mediated by the carboxyterminal domain of the hedgehog (hh) protein precursor (Hh) generates an amino-terminal product that accounts for all known signaling activity. The role of autoprocessing biogenesis of the hh signal has been unclear, since a truncated unprocessed protein lacking all carboxy-terminal domain sequences retains signaling activity. Here, we present evidence that the autoprocessing reaction proceeds via an internal thioester intermediate and results in a covalent modification that increases the hydrophobic character of the signaling domain and influences its spatial and subcellular distribution. We demonstrate that truncated unprocessed amino-terminal protein causes embryonic mispatterning, even when expression is localized to cells that normally express Hh, thus suggesting a role for autoprocessing in spatial regulation of hh signaling. This type of processing also appears to operate in the biogenesis of other novel secreted proteins.

The dispatched (disp) gene is required for long-range Hedgehog (Hh) signaling in Drosophila. Here, we demonstrate that one of two murine homologs, mDispA, can rescue disp function in Drosophila and is essential for all Hh patterning activities examined in the early mouse embryo. Embryonic fibroblasts lacking mDispA respond normally to exogenously provided Sonic hedgehog (Shh) signal, but are impaired in stimulation of other responding cells when expressing Shh. We have developed a biochemical assay that directly measures the activity of Disp proteins in release of soluble Hh proteins. This activity is disrupted by alteration of residues functionally conserved in Patched and in a related family of bacterial transmembrane transporters, thus suggesting similar mechanisms of action for all of these proteins.

No abstract

RNA interference (RNAi) in both plants and animals is mediated by small RNAs of approximately 21-23 nucleotides in length for regulation of target gene expression at multiple levels through partial sequence complementarities. Combined with widespread genome sequencing, experimental use of RNAi has the potential to interrogate systematically all genes in a given organism with respect to a particular function. However, owing to a tolerance for mismatches and gaps in base-pairing with targets, small RNAs could have up to hundreds of potential target sequences in a genome, and some small RNAs in mammalian systems have been shown to affect the levels of many messenger RNAs besides their intended targets. The use of long double-stranded RNAs (dsRNAs) in Drosophila, where Dicer-mediated processing produces small RNAs inside cells, has been thought to reduce the probability of such 'off-target effects' (OTEs). Here we show, however, that OTEs mediated by short homology stretches within long dsRNAs are prevalent in Drosophila. We have performed a genome-wide RNAi screen for novel components of Wingless (Wg) signal transduction in Drosophila S2R + cells, and found few, if any, legitimate candidates. Rather, many of the top candidates exert their effects on Wg response through OTEs on known pathway components or through promiscuous OTEs produced by tandem trinucleotide repeats present in many dsRNAs and genes. Genes containing such repeats are over-represented in candidate lists from published screens, suggesting that they represent a common class of false positives. Our results suggest simple measures to improve the reliability of genome-wide RNAi screens in Drosophila and other organisms.

Transcriptional activation of Hedgehog (Hh) target genes requires Cubitus interruptus, a 155 kDa cytoplasmic zinc finger protein (Ci155), which in the absence of Hh signaling is processed to form a nuclear repressor (Ci75). We show that Hh signaling reduces phosphorylation of Ci155, and this reduction in turn appears to decrease processing. Blocking processing with proteasome inhibitors or altered Ci proteins, however, is insufficient for activation of Hh targets. We find that Hh signaling increases the rate of Ci155 nuclear import, resulting in significant nuclear accumulation. Even in the absence of signaling, nuclear accumulation of Ci155 suffices for significant induction of Hh targets, and active nuclear export of Ci155 is an essential mechanism for maintenance of the unstimulated state.

Recently, VIB-group layered transition metal dichalcogenides (TMDs), MX 2 (M = Mo, W; X = S, Se, Te), attracted extensive attention due to rich physiochemical properties, ranging from catalysis, [1][2][3] topological states, [4][5][6][7][8][9][10][11][12][13][14][15][16] valley polarization, [17][18][19][20][21][22] even to superconductivity. [23][24][25][26][27][28] These multiple electronic properties essentially originate from varied crystal structures of TMD materials. The typical crystal structure in TMD materials is the 2H-type structure with [X-M-X] atoms in ABA stacking in each monolayer (Figure S1a, Supporting Information). Usually, 2H MX 2 materials are semiconducting, such as, 2H MoS 2 , where the valley polarization was widely studied. [17][18][19] Also, Ising superconductivity was observed when the TMD materials are reduced down to a few or even oneRecently the metastable 1T′-type VIB-group transition metal dichalcogenides (TMDs) have attracted extensive attention due to their rich and intriguing physical properties, including superconductivity, valleytronics physics, and topological physics. Here, a new layered WS 2 dubbed "2M" WS 2 , is constructed from 1T′ WS 2 monolayers, is synthesized. Its phase is defined as 2M based on the number of layers in each unit cell and the subordinate crystallographic system. Intrinsic superconductivity is observed in 2M WS 2 with a transition temperature T c of 8.8 K, which is the highest among TMDs not subject to any fine-tuning process. Furthermore, the electronic structure of 2M WS 2 is found by Shubnikov-de Haas oscillations and first-principles calculations to have a strong anisotropy. In addition, topological surface states with a single Dirac cone, protected by topological invariant Z 2 , are predicted through first-principles calculations. These findings reveal that the new 2M WS 2 might be an interesting topological superconductor candidate from the VIB-group transition metal dichalcogenides.

No abstract

Defective function of the Sonic Hedgehog (SHH) signaling pathway is the most frequent alteration underlying holoprosencephaly (HPE) or its various clinical microforms. We performed an extensive mutational analysis of the entire human DISP1 gene, required for secretion of all hedgehog ligand (s) and which maps to the HPE 10 locus of human chromosome 1q41, as a HPE candidate gene. Here, we describe two independent families with truncating mutations in human DISP1 that resemble the cardinal craniofacial and neuro-developmental features of a recently described microdeletion syndrome that includes this gene; therefore, we suggest that DISP1 function contributes substantially to both of these signs in humans. While these clinical features are consistent with common HPE microforms, especially those linked to defective signaling by Sonic Hedgehog, we have insufficient evidence so far that functionally abnormal DISP1 alleles will commonly contribute to the more severe features of typical HPE.