In the latest edition of JCB, Ladouceur et al. investigate what dictates the size of chromosomes in early C. elegans embryos. Chromosomes get increasingly smaller during the early stages of C. elegans development, and, as explained in this week’s In Focus, Ladouceur et al. reveal that this is a response to the decrease in size of both the embryonic cells and their nuclei.
Jiang et al. reveal that migrating neurons generate traction forces at three different regions of the cell. In cerebellar granule cells, these regions – known as contraction centers – localize just behind the tip of the cell’s forward projection, at the base of this projection, and in the cell’s trailing projection. As described here, the relative strength of the forces produced at each of these contraction centers is altered by attractive and repulsive cues that direct the cell’s migration.
Rana et al. demonstrate that alternative splicing transforms a protein that stimulates calcium uptake into one that inhibits it. When calcium levels in the endoplasmic reticulum are low, STIM1 and STIM2 proteins induce Orai channels in the plasma membrane to open up and allow more calcium into the cell. Rana et al. identify a splice variant of STIM2, called STIM2beta, that blocks calcium influx through the Orai1 channel, and which may therefore allow cells to fine tune their calcium dynamics. More here.
And Holtz et al. show that cells secrete an inhibitor of Hedgehog signaling. As summarized here, HHIP1 binds to heparan sulfate molecules in the extracellular matrix, causing the protein to accumulate in basement membranes, where it can control the distribution and activity of Hedgehog ligands.
This month’s biosights video podcast is also out today, highlighting the recent paper by Dennis et al. Senior author Michael Marks describes how the BLOC-2 complex, whose subunits are encoded by genes mutated in Hermansky-Pudlak syndrome, promotes the delivery of melanosomal cargoes by targeting recycling endosomal tubules to maturing melanosomes.
That’s all for today, but, of course, you should visit the JCB’s table of contents page to see all of our latest papers.
Cover image of HHIP1(green) accumulating in the basement membrane underlying the lung epithelium in an E14.5 mouse embryo © 2015 Holtz et al.