Acetylated microtubules let the ER slide

submitted by: JCB
The endoplasmic reticulum is highly dynamic, although little is known about why and how its membrane tubules move. Friedman et al. reveal that ER membranes slide along stable, acetylated microtubules, which might help them contact other organelles such as mitochondria. This biosights episode presents the paper by Friedman et al. from the August 9, 2010 issue of The Journal of Cell Biology, and includes an interview with senior author Gia Voeltz. Produced by Caitlin Sedwick and Ben Short....

Long Asters Rock The Spindle

submitted by: JCB
Astral microtubules help position the cytokinetic furrow by confining actomyosin contractility to the cell equator. Rankin and Wordeman reveal that if astral microtubules grow too long, they expand membrane blebs at the mitotic cell poles that squeeze the mitotic spindle back and forth between the two daughter cells. This biosights episode presents the paper by Rankin and Wordeman from the July 12, 2010 issue of The Journal of Cell Biology, and includes an interview with senior author Linda...

Laminin Adhesions Help Microtubules Reach Base

submitted by: JCB
Microtubules align along the apical-basal axis of epithelial cells with their plus ends pointing to the basal side. Hotta et al. reveal how signals from the extracellular matrix establish this arrangement by recruiting the microtubule-anchoring factors LL5s to the basal cell cortex. This biosights episode presents the paper by Hotta et al. from the May 31, 2010 issue of The Journal of Cell Biology, and includes an interview with senior author Yuko Mimori-Kiyosue. Produced by Caitlin...

A Turning Point for Macrophages

submitted by: JCB
Drosophila macrophages disperse themselves around the body during embryogenesis, ready to mount an immune response at the site of a wound. Stramer et al. image the cells in vivo, revealing that they form microtubule "arms" to point them in the right direction and push themselves away from their fellow leukocytes. This biosights episode presents the paper by Stramer et al. from the May 17th, 2010 issue of The Journal of Cell Biology, and includes an interview with lead author Brian Stramer....

CyclinB1-Cdk1 Makes Its Move

submitted by: JCB
Cells drastically alter their structure at the onset of mitosis. Gavet and Pines reveal that the mitotic kinase CyclinB1-Cdk1 triggers its own nuclear import in prophase to ensure reorganization of the nucleus and cytoplasm is synchronized. This biosights episode presents the paper by Gavet and Pines from the April 19, 2010 issue of The Journal of Cell Biology, and includes an interview with senior author Jonathon Pines. Produced by Justin Paul and Ben Short. See the full article online...

Integrating the forces that fold tissues

submitted by: JCB
During gastrulation, pulsed contractions of the actomyosin cytoskeleton apically constrict a strip of cells on the ventral surface of Drosophila embryos. Martin et al. examine how these contractile forces are integrated across the tissue so that it invaginates to form the embryonic mesoderm. This biosights episode presents the paper by Martin et al. from the March 8, 2010 issue of The Journal of Cell Biology, and includes an interview with lead author Adam Martin. Produced by Eun Choi and...

Probing the spindle matrix

submitted by: JCB
A microtubule-independent network of proteins called the spindle matrix is involved in assembling mitotic and meiotic spindles, but whether the matrix makes a mechanical contribution to spindle shape is unclear. Gatlin et al. manipulate spindles with microneedles to directly probe the mechanical properties of the spindle matrix. This biosights episode presents the paper by Gatlin et al. from the February 22, 2010 issue of The Journal of Cell Biology, and includes an interview with lead...

Systems biology of the mitotic spindle

submitted by: JCB
A novel high-throughput screening approach that combines yeast mutant arrays with high-content imaging provides fresh insights into mitotic spindle disassembly. This biosights episode presents the paper by Vizeacoumar et al. from the January 11, 2010 issue of The Journal of Cell Biology, and includes interviews with authors Brenda Andrews and Charles Boone, and JCB editorial board member John Aitchison. Produced by Eun Choi. Read the complete paper at:...

AP-1 and KIF13A coordinate endosomal sorting and positioning during melanosome biogenesis

submitted by: JCB
Specialized cell types exploit endosomal trafficking to deliver protein cargoes to cell type–specific lysosome-related organelles (LROs), but how endosomes are specified for this function is not known. In this study, we show that the clathrin adaptor AP-1 and the kinesin motor KIF13A together create peripheral recycling endosomal subdomains in melanocytes required for cargo delivery to maturing melanosomes. In cells depleted of AP-1 or KIF13A, a subpopulation of recycling endosomes...
Authors: Cédric Delevoye, Ilse Hurbain, Danièle Tenza, Jean-baptist Sibarita, Stéphanie Uzan-gafsou, Hiroshi Ohno, Willie Geerts, Arie Verkleij, Jean Salamero, Graça Raposo

DNA replication times the cell cycle and contributes to the mid-blastula transition in Drosophila embryos

submitted by: JCB
We examined the contribution of S phase in timing cell cycle progression during Drosophila embryogenesis using an approach that deletes S phase rather than arresting its progress. Injection of Drosophila Geminin, an inhibitor of replication licensing, prevented subsequent replication so that the following mitosis occurred with uninemic chromosomes, which failed to align. The effect of S phase deletion on interphase length changed with development. During the maternally regulated syncytial...
Authors: Ml Mccleland, Aw Shermoen, Ph O'farrell