Netrin-1 is a guidance cue that can trigger either attraction or repulsion effects on migrating neurons, depending on the repertoire of receptors available on the growth cone. How a single chemotropic molecule can act in such contradictory ways has long been a puzzle at the molecular level. Here we present the crystal structure of netrin-1 in complex with the Deleted in Colorectal Cancer (DCC) receptor. We show that one netrin-1 molecule can simultaneously bind to two DCC molecules through a DCC-specific site and through a unique generic receptor binding site, where sulfate ions staple together positively charged patches on both DCC and netrin-1. Furthermore, we demonstrate that UNC5A can replace DCC on the generic receptor binding site to switch the response from attraction to repulsion. We propose that the modularity of binding allows for the association of other netrin receptors at the generic binding site, eliciting alternative turning responses.

Abstract-Test suites play a key role in ensuring software quality. A good test suite may detect more faults than a poor-quality one. Mutation testing is a powerful methodology for evaluating the fault-detection ability of test suites. In mutation testing, a large number of mutants may be generated and need to be executed against the test suite under evaluation to check how many mutants the test suite is able to detect, as well as the kind of mutants that the current test suite fails to detect. Consequently, although highly effective, mutation testing is widely recognized to be also computationally expensive, inhibiting wider uptake. To alleviate this efficiency concern, we propose Predictive Mutation Testing (PMT): the first approach to predicting mutation testing results without executing mutants. In particular, PMT constructs a classification model, based on a series of features related to mutants and tests, and uses the model to predict whether a mutant would be killed or remain alive without executing it. PMT has been evaluated on 163 real-world projects under two application scenarios (cross-version and cross-project). The experimental results demonstrate that PMT improves the efficiency of mutation testing by up to 151.4X while incurring only a small accuracy loss. It achieves above 0.80 AUC values for the majority of projects, indicating a good tradeoff between the efficiency and effectiveness of predictive mutation testing. Also, PMT is shown to perform well on different tools and tests, be robust in the presence of imbalanced data, and have high predictability (over 60% confidence) when predicting the execution results of the majority of mutants.

Objective. We previously showed that Cyr61 acts to promote fibroblast-like synoviocyte (FLS) proliferation and Th17 cell differentiation, suggesting that Cyr61 plays an important role in mediating the joint inflammation and damage in rheumatoid arthritis (RA). The aim of this study was to investigate whether Cyr61 expression is regulated at the posttranscription level, and if so, how this regulation connects to other etiologic factors in RA.Methods. Expression of microRNA-22 (miR-22) in synovial tissue was detected by real-time polymerase chain reaction (PCR) using miRNA-specific TaqMan MGB probes. MicroRNA-22 promoter activity was analyzed using a Dual-Luciferase Reporter Assay. Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic joint inflammation and variable degrees of bone and cartilage erosion (1). Although the etiology and pathogenesis of RA are still poorly understood, accumulating evidence indicates that fibroblast-like synoviocytes (FLS) are important players in all aspects of the pathogenesis of RA (1-3). We previously demonstrated that the expression of Cyr61, a secreted extracellular matrix (ECM) protein produced by FLS, is stimulated by interleukin-17 (IL-17), and the overexpressed Cyr61 in turn acts to promote FLS proliferation in an autocrine/paracrine manner, thus contributing to the hyperplasia of synovial lining cells (4). Interestingly, Cyr61 can also stimulate FLS to produce IL-6, thus promoting Th17 cell differentiation (5). These results not only revealed for the first time that Cyr61 contributes to hyperplasia of synovial lining cells but also established a novel "feed-forward and malicious cycle" that leads to mutual stimulation of FLS and Th17

Psoriasis is a common chronic skin disease characterized by epidermal hyperplasia and inflammation. The pathogenesis of psoriasis is multifactorial and is not fully understood. Here we demonstrate that CCN1 (also called Cyr61, which is short for cysteine-rich 61), an extracellular matrix protein that is also considered a pro-inflammatory factor, is highly expressed in the lesional skin of psoriasis patients, as well as in that of imiquimod (IMQ)- and IL-23-treated psoriasis-like mice. Then we show that blocking CCN1 function in vivo attenuates epidermal hyperplasia and inflammation in psoriasis-like mice. Further, in primary cultured normal human keratinocytes and HaCaT (human keratinocyte cell line) cells, CCN1 promotes keratinocyte activation, including the proliferation and expression of immune-related molecules. Finally, we observe that integrin α6β1 is the receptor of CCN1 in keratinocytes, and CCN1 stimulation activates the downstream phosphoinositide-3 kinase/Akt/NF-κB signaling pathway. Taken together, our findings reveal that CCN1 has a critical role in psoriasis pathogenesis. Moreover, as CCN1 is a secreted extracellular matrix (ECM) protein, our study also provides evidence that ECM, which is involved in psoriatic pathogenesis, could be a potent target for psoriasis treatment.