CED-6/GULP and Components of the Clathrin-mediated Endocytosis Machinery Act Redundantly to Correctly Display CED-1 on the Cell Membrane in C. elegans.

CED-1 is a transmembrane receptor involved in the recognition of "eat-me" signals displayed on the surface of apoptotic cells and thus central for the subsequent engulfment of the cell corpse in C. elegans. The roles of CED-1 in engulfment are well established, as are its downstream effectors. The latter includes the adapter protein CED-6/GULP and the ABC family homolog CED-7. However, how CED-1 is maintained on the plasma membrane in the absence of engulfment is currently unknown. Here, we show that CED-6 and CED-7 have a novel role in maintaining CED-1 correctly on the plasma membrane. We propose that the underlying mechanism is via endocytosis as CED-6 and CED-7 act redundantly with clathrin and its adaptor, the AP2 complex, in ensuring correct CED-1 localization. In conclusion, CED-6 and CED-7 impact other cellular processes than engulfment of apoptotic cells.

Infanticide vs. inherited cardiac arrhythmias.

AIMS: In 2003, an Australian woman was convicted by a jury of smothering and killing her four children over a 10-year period. Each child died suddenly and unexpectedly during a sleep period, at ages ranging from 19 days to 18 months. In 2019 we were asked to investigate if a genetic cause could explain the children's deaths as part of an inquiry into the mother's convictions. METHODS AND RESULTS: Whole genomes or exomes of the mother and her four children were sequenced. Functional analysis of a novel CALM2 variant was performed by measuring Ca2+-binding affinity, interaction with calcium channels and channel function. We found two children had a novel calmodulin variant (CALM2 G114R) that was inherited maternally. Three genes (CALM1-3) encode identical calmodulin proteins. A variant in the corresponding residue of CALM3 (G114W) was recently reported in a child who died suddenly at age 4 and a sibling who suffered a cardiac arrest at age 5. We show that CALM2 G114R impairs calmodulin's ability to bind calcium and regulate two pivotal calcium channels (CaV1.2 and RyR2) involved in cardiac excitation contraction coupling. The deleterious effects of G114R are similar to those produced by G114W and N98S, which are considered arrhythmogenic and cause sudden cardiac death in children. CONCLUSION: A novel functional calmodulin variant (G114R) predicted to cause idiopathic ventricular fibrillation, catecholaminergic polymorphic ventricular tachycardia, or mild long QT syndrome was present in two children. A fatal arrhythmic event may have been triggered by their intercurrent infections. Thus, calmodulinopathy emerges as a reasonable explanation for a natural cause of their deaths.

Quantum dots-ßcyclodextrin-histidine labeled human adipose stem cells-laden chitosan hydrogel for bone tissue engineering.

Mesenchymal stem cells with differentiation ability to diverse cells play a crucial role in tissue engineering. Tracking the fate of these cells during the regeneration of tissue helps to obtain more information about their function. In this study, histidine conjugated ß-cyclodextrin as a cell-penetrating carrier with drug loading ability was attached to QDs nanoparticle (QD-ßCD-His) for stem cell labeling. Traceability of QD-ßCD-His labeled human adipose stem cells (hASCs) was monitored in 2D cell culture and 3D temperature-sensitive chitosan hydrogel scaffold. Dexamethasone (Dex) as an osteoinductive drug was loaded into QD-ßCD-His nano-carrier (QD-ßCD-His@Dex) to induce bone differentiation of labeled cells. Overall results indicated that QD-ßCD-His@Dex is a promising dual-purpose nano-carrier for stem cell labeling with osteoinductive potential in cell therapy as well as tissue engineering scaffolds.