MEGF8 is a modifier of BMP signaling in trigeminal sensory neurons.

Bone morphogenetic protein (BMP) signaling has emerged as an important regulator of sensory neuron development. Using a three-generation forward genetic screen in mice we have identified Megf8 as a novel modifier of BMP4 signaling in trigeminal ganglion (TG) neurons. Loss of Megf8 disrupts axon guidance in the peripheral nervous system and leads to defects in development of the limb, heart, and left-right patterning, defects that resemble those observed in Bmp4 loss-of-function mice. Bmp4 is expressed in a pattern that defines the permissive field for the peripheral projections of TG axons and mice lacking BMP signaling in sensory neurons exhibit TG axon defects that resemble those observed in Megf8 (-/-) embryos. Furthermore, TG axon growth is robustly inhibited by BMP4 and this inhibition is dependent on Megf8. Thus, our data suggest that Megf8 is involved in mediating BMP4 signaling and guidance of developing TG axons. DOI:http://dx.doi.org/10.7554/eLife.01160.001.

Perioperative metoprolol and risk of stroke after noncardiac surgery.

BACKGROUND: Numerous risk factors have been identified for perioperative stroke, but there are conflicting data regarding the role of ß adrenergic receptor blockade in general and metoprolol in particular. METHODS: The authors retrospectively screened 57,218 consecutive patients for radiologic evidence of stroke within 30 days after noncardiac procedures at a tertiary care university hospital. Incidence of perioperative stroke within 30 days of surgery and associated risk factors were assessed. Patients taking either metoprolol or atenolol were matched based on a number of risk factors for stroke. Parsimonious logistic regression was used to generate a preoperative risk model for perioperative stroke in the unmatched cohort. RESULTS: The incidence of perioperative stroke was 55 of 57,218 (0.09%). Preoperative metoprolol was associated with an approximately 4.2-fold increase in perioperative stroke (P < 0.001; 95% CI, 2.2-8.1). Analysis of matched cohorts revealed a significantly higher incidence of stroke in patients taking preoperative metoprolol compared with atenolol (P = 0.016). However, preoperative metoprolol was not an independent predictor of stroke in the entire cohort, which included patients who were not taking ß blockers. The use of intraoperative metoprolol was associated with a 3.3-fold increase in perioperative stroke (P = 0.003; 95% CI, 1.4-7.8); no association was found for intraoperative esmolol or labetalol. CONCLUSIONS: Routine use of preoperative metoprolol, but not atenolol, is associated with stroke after noncardiac surgery, even after adjusting for comorbidities. Intraoperative metoprolol but not esmolol or labetalol, is associated with increased risk of perioperative stroke. Drugs other than metoprolol should be considered during the perioperative period if ß blockade is required.

A forward genetic screen in mice identifies Sema3A(K108N), which binds to neuropilin-1 but cannot signal.

We have performed a three-generation, forward genetic screen to identify recessive mutations that affect the patterning of the peripheral nervous system. Using this assay, we identified Sema3A(K108N), a novel loss-of-function allele of Sema3A. Class 3 semaphorins, which include Sema3A, are structurally conserved secreted proteins that play critical roles in the development and function of the nervous system. Sema3A(K108N) mutant mice phenocopy Sema3A-null mice, and Sema3A(K108N) protein fails to repel or collapse DRG axons in vitro. K108 is conserved among semaphorins, yet the loss-of-function effects associated with K108N are not the result of impaired expression, secretion, or binding of Sema3A to its high-affinity receptor Neuropilin-1 (Npn-1). Using in silico modeling and mutagenesis of other semaphorin family members, we predict that Sema3A(K108N) interacts poorly with the Npn-1/PlexA holoreceptor and, thus, interferes with its ability to signal at the growth cone. Therefore, through the use of a forward-genetic screen we have identified a novel allele of Sema3A that provides structural insight into the mechanism of Sema3A/Npn-1/PlexinA signaling.

Sec24b selectively sorts Vangl2 to regulate planar cell polarity during neural tube closure.

Craniorachischisis is a rare but severe birth defect that results in a completely open neural tube. Mouse mutants in planar cell polarity (PCP) signalling components have deficits in the morphological movements of convergent extension that result in craniorachischisis. Using a forward genetic screen in mice, we identified Sec24b, a cargo-sorting member of the core complex of the endoplasmic reticulum (ER)-to-Golgi transport vesicle COPII, as critical for neural tube closure. Sec24bY613 mutant mice exhibit craniorachischisis, deficiencies in convergent extension and other PCP-related phenotypes. Vangl2, a key component of the PCP-signalling pathway critical for convergent extension, is selectively sorted into COPII vesicles by Sec24b. Moreover, Sec24bY613 genetically interacts with a loss-of-function Vangl2 allele (Vangl2LP), causing a marked increase in the prevalence of spina bifida. Interestingly, the Vangl2 looptail point mutants Vangl2D255E and Vangl2S464N, known to cause defects in convergent extension, fail to sort into COPII vesicles and are trapped in the ER. Thus, during COPII vesicle formation, Sec24b shows cargo specificity for a core PCP component, Vangl2, of which proper ER-to-Golgi transport is essential for the establishment of PCP, convergent extension and closure of the neural tube.

Semaphorin 3E and plexin-D1 control vascular pattern independently of neuropilins.

The development of a patterned vasculature is essential for normal organogenesis. We found that signaling by semaphorin 3E (Sema3E) and its receptor plexin-D1 controls endothelial cell positioning and the patterning of the developing vasculature in the mouse. Sema3E is highly expressed in developing somites, where it acts as a repulsive cue for plexin-D1-expressing endothelial cells of adjacent intersomitic vessels. Sema3E-plexin-D1 signaling did not require neuropilins, which were previously presumed to be obligate Sema3 coreceptors. Moreover, genetic ablation of Sema3E or plexin-D1 but not neuropilin-mediated Sema3 signaling disrupted vascular patterning. These findings reveal an unexpected semaphorin signaling pathway and define a mechanism for controlling vascular patterning.

Drosophila melanogaster flatline encodes a myotropin orthologue to Manduca sexta allatostatin.

We identified a Drosophila melanogaster gene encoding a peptide that dramatically decreases spontaneous muscle contractions and, correspondingly, named the peptide flatline (FLT). This gene consisted of 4 exons and was cytologically localized to 32D2-3. Processing of a predicted 122 amino acid precursor would release pEVRYRQCYFNPISCF that differs from Manduca sexta allatostatin (Mas-AST) by one amino acid, Y4-->F4. FLT does not act as an allatostatin. In situ tissue hybridization further suggests FLT is a novel brain-gut peptide and specifically, the measured activity indicates that it is a potent myotropin. Despite its profound myotropic effect, pupae injected with FLT eclosed.

Drosophila melanogaster FMRFamide-containing peptides: redundant or diverse functions?

FMRFamide-related peptides (FaRPs) are expressed throughout the animal kingdom and regulate a multitude of physiological activities. FaRPs have an RFamide C-terminal consensus structure that is important for interaction with the receptor. The ease of genetic manipulation and availability of genomic sequences makes Drosophila melanogaster an important experimental organism. Multiple classes of FaRPs encoded by different genes have been identified within this species. Here, we review FMRFamide-containing peptides encoded by the D. melanogaster FMRFamide gene in order to review the data on the expression, regulation, and activity of these peptides as well as acknowledge further endeavors required to elucidate FaRP signaling.