Whole-Genome Sequencing Uncovers Two Loci for Coronary Artery Calcification and Identifies Arse as a Regulator of Vascular Calcification

Coronary artery calcification (CAC) is a measure of atherosclerosis and a well-established predictor of coronary artery disease (CAD) events. Here we describe a genome-wide association study (GWAS) of CAC in 22,400 participants from multiple ancestral groups. We confirmed associations with four known loci and identified two additional loci associated with CAC (ARSE and MMP16), with evidence of significant associations in replication analyses for both novel loci. Functional assays of ARSE and MMP16 in human vascular smooth muscle cells (VSMCs) demonstrate that ARSE is a promoter of VSMC calcification and VSMC phenotype switching from a contractile to a calcifying or osteogenic phenotype. Furthermore, we show that the association of variants near ARSE with reduced CAC is likely explained by reduced ARSE expression with the G allele of enhancer variant rs5982944. Our study highlights ARSE as an important contributor to atherosclerotic vascular calcification, and a potential drug target for vascular calcific disease

Kinesin Kip2 enhances microtubule growth in vitro through length-dependent feedback on polymerization and catastrophe.

The size and position of mitotic spindles is determined by the lengths of their constituent microtubules. Regulation of microtubule length requires feedback to set the balance between growth and shrinkage. Whereas negative feedback mechanisms for microtubule length control, based on depolymerizing kinesins and severing proteins, have been studied extensively, positive feedback mechanisms are not known. Here we report that the budding yeast kinesin Kip2 is a microtubule polymerase and catastrophe inhibitor in vitro that uses its processive motor activity as part of a feedback loop to further promote microtubule growth. Positive feedback arises because longer microtubules bind more motors, which walk to the ends where they further reinforce growth and inhibit catastrophe. We propose that positive feedback, common in biochemical pathways to switch between signaling states, can also be used in a mechanical signaling pathway to switch between structural states, in this case between short and long polymers

Camera-based three-dimensional real-time particle tracking at kHz rates and Ångström accuracy

Optical and magnetic tweezers are widely employed to probe the mechanics and activity of individual biomolecular complexes. They rely on micrometer-sized particles to detect molecular conformational changes from the particle position. Real-time particle tracking with Ångström accuracy has so far been only achieved using laser detection through photodiodes. Here we demonstrate that camera-based imaging can provide a similar performance for all three dimensions. Particle imaging at kHz rates is combined with real-time data processing being accelerated by a graphics processing unit. For particles that are fixed in the sample cell we can detect 3 Å sized steps that are introduced by cell translations at rates of 10 Hz, while for DNA-tethered particles 5 Å steps at 1 Hz can be resolved. Moreover, 20 particles can be tracked in parallel with comparable accuracy. Our approach provides a simple and robust way for high-resolution tweezers experiments using multiple particles at a time

Effects of surface passivation on gliding motility assays

In this study, we report differences in the observed gliding speed of microtubules
dependent on the choice of bovine casein used as a surface passivator. We observed
differences in both speed and support of microtubules in each of the assays. Whole
casein, comprised of [alpha]~s1~, [alpha]~s2~, [beta], and [kappa] casein, supported motility and averaged speeds of
966 ± 7 nm/s. Alpha casein can be purchased as a combination of s1 and s2 and
supported gliding motility and average speeds of 949 ± 4 nm/s. Beta casein did not
support motility very well and averaged speeds of 870 ± 30 nm/s. Kappa casein
supported motility very poorly and we were unable to obtain an average speed. Finally,
we observed that mixing alpha, beta, and kappa casein with the proportions found in
bovine whole casein supported motility and averaged speeds of 966 ± 7 nm/s