August 2016 | Volume 214, No. 3
People & Ideas
- Novel role for the midbody in primary ciliogenesis by polarized epithelial cells
Polarized epithelial cells assemble a primary cilium by an unknown mechanism. After cytokinesis, the central part of the intercellular bridge, which is referred to as the midbody, is inherited as a remnant by one of the daughter cells. Here, Bernabé-Rubio et al. show that the midbody remnant meets the centrosome at the cell apex, enabling primary ciliogenesis.
- Syntaxin-17 delivers PINK1/parkin-dependent mitochondrial vesicles to the endolysosomal system
Vesicular transport from mitochondria to lysosomes is an emerging mitochondrial quality control mechanism. Here, McLelland et al. identify how mitochondrial vesicles are targeted for degradation, showing that syntaxin-17 is recruited to these structures to govern their SNARE-dependent fusion with endolysosomes.
- BLOC-1 and BLOC-3 regulate VAMP7 cycling to and from melanosomes via distinct tubular transport carriers
Dennis et al. analyze cycling of the v-SNARE VAMP7 during melanosome biogenesis in melanocytes. VAMP7 is targeted to and retrieved from maturing melanosomes in separate tubular carriers whose formation requires distinct BLOCs, each defective in variants of Hermansky–Pudlak syndrome.
- Assembly and activation of dynein–dynactin by the cargo adaptor protein Hook3
Metazoan dynein moves processively with the aid of dynactin and the endosomal cargo adaptor Hook3. A structure–function study of Hook3 reveals how it assembles dynein with dynactin and suggests that an additional step of allosteric activation is required beyond complex assembly.
- Tissue homogeneity requires inhibition of unequal gene silencing during development
Homogenous populations of cells make up individual tissues, yet how organisms achieve such homogeneity is unknown. Le et al. use the C. elegans intestine to reveal that an initiator of RNA silencing is segregated unequally between cells. Suppression of this inequality during early development achieves tissue homogeneity.
- mito-QC illuminates mitophagy and mitochondrial architecture in vivo
Whether mitophagy occurs within specific cellular subtypes in vivo is unclear. McWilliams et al. present “mito-QC,” a transgenic mouse containing a pH-sensitive fluorescent mitochondrial signal, allowing in vivo detection of mitophagy and mitochondrial morphology at single-cell resolution.
- Deciphering dynamics of clathrin-mediated endocytosis in a living organism
Ferguson et al. demonstrate that clathrin coat growth rates can be utilized as quantitative reporters of clathrin-mediated endocytic dynamics in cellular contexts where errors associated with single-particle tracking are significant. They validate the tool within tissues of Drosophila embryos.