Davis, E. M. | Search bioRxiv

bioRxiv2020

Epithelial cell biomarkers are predictive of response to biologic agents in Crohn's disease

ObjectiveTherapeutic efficacy of biologics has remained at about 50% for 2 decades. In Crohns disease (CD) patients, we examined the predictive value of an epithelial cell biomarker, ileal microvillar length (MVL), for clinical response to ustekinumab (UST) and vedolizumab (VDZ), and its relationship to another biomarker, intestinal epithelial cell (IEC) pyroptosis with respect to response to VDZ. DesignIleal biopsies from the UNITI-2 randomized controlled trial were analyzed for MVL as a predictor of clinical response to UST. In a 5-center academic retrospective cohort of CD patients, ileal MVL was analyzed to determine its predictive value for response to VDZ. Correlation between ileal MVL and IEC pyroptosis was determined, and the discriminant ability of the combination of two biomarkers to VDZ was examined. ResultsClinical response in UST was significantly higher than placebo (65% vs. 39%, p=0.03), with patients with normal MVL (>1.7 {micro}m) having the greatest therapeutic effect: 85% vs. 20% (p=0.02). For VDZ, clinical response with MVL of 1.35-1.55 {micro}m was 82% vs. 44% (<1.35 {micro}m) and 40% (>1.55 {micro}m) (p=0.038). There was no correlation between ileal MVL and IEC pyroptosis. The combination criteria of ileal pyroptosis < 14 positive cells/1000 IECs or MVL of 1.35-1.55 {micro}m could identify 84% of responders and 67% of non-responders (p=0.001). ConclusionsIleal MVL was predictive of response to UST and VDZ in prospective and retrospective CD cohorts. It was independent of ileal IEC pyroptosis, combination of the two biomarkers enhanced the discriminate ability of responders from non-responders to VDZ.

cell biology↗

bioRxiv2020

K-fiber bundles in the mitotic spindle are mechanically reinforced by Kif15

The mitotic spindle, a self-constructed microtubule-based machine, segregates chromosomes into two eventual daughter nuclei. In mammalian cells, microtubule bundles called kinetochore-fibers (k-fibers) anchor chromosomes within the spindle. Chromosome segregation thus depends on the mechanical integrity of k-fibers. Here, we investigate the physical and molecular basis of k-fiber bundle cohesion. We sever k-fibers using laser ablation, thereby detaching them from poles and testing the contribution of pole-localized force generation to k-fiber cohesion. We then measure the physical response of the remaining kinetochore-bound segments of the k-fibers. We observe that microtubules within ablated k-fibers often, but not always, splay apart from their minus-ends. Furthermore, we find that minus-end clustering forces induced in response to ablation seem at least partially responsible for k-fiber splaying. We also investigate the role of the putative k-fiber-binding kinesin-12 Kif15. We find that pharmacological inhibition of Kif15 microtubule binding reduces k-fiber mechanical integrity. In contrast, inhibition of its motor activity but not its microtubule binding does not greatly affect splaying. Altogether, the data suggest that forces holding k-fibers together are of similar magnitude to other spindle forces, and that Kif15, acting as a microtubule crosslinker, helps fortify and repair k-fibers. This feature of Kif15 may help support robust k-fiber function and prevent chromosome segregation errors.

cell biology↗