The Lack of ADAM17 Activity during Embryonic Development Causes Hemorrhage and Impairs Vessel Formation

Background: ADAM17/TACE activity is important during embryonic development. We wished to investigate possible roles of this metalloprotease, focusing on vascular development. Methodology/Principal Findings: Mice mutant in the enzymatic activity of ADAM17 were examined at various stages of embryonic development for vascular pattern and integrity using markers for vessel wall cells. We observed hemorrhage and edema starting at embryonic day E14.5 and becoming more severe as development proceeded; prior to embryonic day E14.5, embryos appeared normal. Staining for PECAM-1/CD31 revealed abnormalities in the patterns of branching of the embryonic vasculature at E14.5. Conclusions/Significance: These abnormalities preceded association of pericytes or monocyte/macrophage cells with the affected vessels and, therefore, presumably arise from defects in endothelial function consequent upon failure of ADAM17 to cleave one or more substrates involved in vascular development, such as Notch, Delta, VEGFR2 or JAM-A. Our study demonstrates a role for ADAM17 in modulating embryonic vessel development and function

Generation and characterization of new alleles of <i>quiver</i> (<i>qvr</i>) that encodes an extracellular modulator of the <i>Shaker</i> potassium channel

<p>Our earlier genetic screen uncovered a paraquat-sensitive leg-shaking mutant <i>quiver¹</i> (<i>qvr¹</i>), whose gene product interacts with the <i>Shaker</i> (<i>Sh</i>) K⁺ channel. We also mapped the <i>qvr</i> locus to EY04063 and noticed altered day–night activity patterns in these mutants. Such circadian behavioral defects were independently reported by another group, who employed the <i>qvr¹</i> allele we supplied them, and attributed the extreme restless phenotype of EY04063 to the <i>qvr</i> gene. However, their report adopted a new noncanonical gene name <i>sleepless</i> (<i>sss</i>) for <i>qvr</i>. In addition to <i>qvr¹ </i>and <i>qvr^EY</i>, our continuous effort since the early 2000s generated a number of novel recessive <i>qvr</i> alleles, including ethyl methanesulfonate (EMS)-induced mutations <i>qvr²</i> and <i>qvr³</i>, and P-element excision lines <i>qvr^ip6</i> (imprecise jumpout), <i>qvr^rv7</i>, and <i>qvr^rv9</i> (revertants) derived from <i>qvr^EY</i>. Distinct from the original intron-located <i>qvr¹ </i>allele that generates abnormal-sized mRNAs, <i>qvr²</i>, and <i>qvr³</i> had their lesion sites in exons 6 and 7, respectively, producing nearly normal-sized mRNA products. A set of RNA-editing sites are nearby the lesion sites of <i>qvr³</i> and <i>qvr^EY</i> on exon 7. Except for the revertants, all <i>qvr</i> alleles display a clear ether-induced leg-shaking phenotype just like <i>Sh</i>, and weakened climbing abilities to varying degrees. Unlike <i>Sh</i>, all shaking <i>qvr</i> alleles (except for <i>qvr^f01257</i>) displayed a unique activity-dependent enhancement in excitatory junction potentials (EJPs) at larval neuromuscular junctions (NMJs) at very low stimulus frequencies, with <i>qvr^EY</i> displaying the largest EJP and more significant NMJ overgrowth than other alleles. Our detailed characterization of a collection of <i>qvr</i> alleles helps to establish links between novel molecular lesions and different behavioral and physiological consequences, revealing how modifications of the <i>qvr</i> gene lead to a wide spectrum of phenotypes, including neuromuscular hyperexcitability, defective motor ability and activity-rest cycles.</p