Mutations in TRAPPC2 (Sedlin) block collagen II export from the ER and cause the skeletal dysplasia called SEDT (spondyloepiphyseal dysplasia tarda). Here, we present the first vertebrate model for SEDT by knocking out the medaka orthologue OlSedl. The KO fish show a downregulation of collagen expression and exhibit a skeletal phenotype (platyspondyly/reduced length) that is highly reminiscent of that observed in SEDT patients, confirming that Sedlin plays a major role in skeletal development. Extraskeletal defects were also observed that involved the eye and the gut. Our data suggest that Sedlin is required for vertebrate embryo development by regulating collagen production and secretion in different tissues.

We report that ESCRT-III protein IST1 and its binding partner CHMP1B contribute to scission of endosomal carriers and that IST1 is required to efficiently deliver select cargo from early/sorting endosomes to recycling endosomes. IST1 also interacts with SNX15, and together they localize to a subdomain of early/sorting endosomes distinct from those known to be involved in recycling or degradation. SNX15 and CHMP1B alternately control recruitment of IST1 to different sites on the endosome, suggesting that IST1 plays multiple roles on early/sorting endosomes.

“How do cells regulate their organelle populations in response to environmental changes?” is a major question in cell biology. We show that regulation of peroxisome populations in yeast requires integrity of phosphatidylinositol-4-phosphate (PI4P) signaling at the cell cortex. When PI4P conversion to phoshatidylinositol (PI) is disrupted, PI4P increases in amount at the cell cortex, peroxisomes (red) detach from their cortical anchors (green) and the numbers of peroxisomes and their motility increase.