Deletion of Gas2l3 in mice leads to specific defects in cardiomyocyte cytokinesis during development.

GAS2L3 is a recently identified cytoskeleton-associated protein that interacts with actin filaments and tubulin. The in vivo function of GAS2L3 in mammals remains unknown. Here, we show that mice deficient in GAS2L3 die shortly after birth because of heart failure. Mammalian cardiomyocytes lose the ability to proliferate shortly after birth, and further increase in cardiac mass is achieved by hypertrophy. The proliferation arrest of cardiomyocytes is accompanied by binucleation through incomplete cytokinesis. We observed that GAS2L3 deficiency leads to inhibition of cardiomyocyte proliferation and to cardiomyocyte hypertrophy during embryonic development. Cardiomyocyte-specific deletion of GAS2L3 confirmed that the phenotype results from the loss of GAS2L3 in cardiomyocytes. Cardiomyocytes from Gas2l3-deficient mice exhibit increased expression of a p53-transcriptional program including the cell cycle inhibitor p21. Furthermore, loss of GAS2L3 results in premature binucleation of cardiomyocytes accompanied by unresolved midbody structures. Together these results suggest that GAS2L3 plays a specific role in cardiomyocyte cytokinesis and proliferation during heart development.

The GAR domain of GAS2L3 mediates binding to the chromosomal passenger complex and is required for localization of GAS2L3 to the constriction zone during abscission.

GAS2L3 is a recently identified tubulin- and actin-binding protein that regulates cytokinesis and abscission. In this study we show that GAS2L3 interacts with the chromosomal passenger complex (CPC), which plays key roles in mitosis and cytokinesis. Biochemical assays show that GAS2L3 directly interacts with the C-terminus of borealin and the N-terminus of survivin. We find that the interaction between these two CPC subunits and GAS2L3 is mediated by the conserved GAR domain of GAS2L3. We further show that the GAR domain of GAS2L3 is required for localization of GAS2L3 to the constriction zone. Taken together these data suggest that GAS2L3 is a downstream effector of the CPC during cytokinetic abscission.

GAS2L3, a target gene of the DREAM complex, is required for proper cytokinesis and genomic stability.

The mammalian DREAM complex is a key regulator of cell-cycle-regulated gene transcription and drives the expression of many gene products required for mitosis and cytokinesis. In this study, we characterized GAS2L3, which belongs to the GAS2 family of proteins with putative actin- and microtubule-binding domains as a target gene of DREAM. We found that GAS2L3 localizes to the spindle midzone and the midbody during anaphase and cytokinesis, respectively. Biochemical studies show that GAS2L3 binds to and bundles microtubules as well as F-actin in vitro. Strikingly, the RNAi-mediated knockdown of GAS2L3 results in chromosome segregation defects in multinucleated cells and in cells with multi-lobed nuclei. Likewise, chronic downregulation of GAS2L3 causes chromosome loss and aneuploidy. Time-lapse videomicroscopy experiments in GAS2L3-knockdown cells reveal abnormal oscillation of chromatin and the spindle during cytokinesis. Taken together, our data reveal novel, important roles of GAS2L3 for faithful cell division. Our work thus contributes to the understanding of how DREAM regulates cytokinesis.

Characterization of a novel interaction between vasodilator-stimulated phosphoprotein and Abelson interactor 1 in human platelets: a concerted computational and experimental approach.

OBJECTIVE: The goal of this study was systematic profiling of vasodilator-stimulated phosphoprotein (VASP)-Ena/VASP homology 1 (EVH1) interactors in human platelets using a combined in silico and in vitro approach. METHODS AND RESULTS: Exploiting the information of the comprehensive proteome catalogue in the PlateletWeb database (http://plateletweb.bioapps.biozentrum.uni-wuerzburg.de/PlateletWeb.php), we performed a motif search of all sequences and identified potential target sites of class I EVH1 domains in human platelet proteins. Performing affinity purification with VASP-EVH1 domain and the lysates of platelets, we examined complex partners by mass spectrometry. Combining the results of both analyses, we identified Abelson interactor 1 (Abi-1) as a novel EVH1 domain-specific interaction partner of VASP in human platelets and investigated this interaction by yeast 2-hybrid mutational studies and immunoprecipitation. Immunofluorescence microscopy indicated colocalization of both proteins at the lamellipodia of spread human platelets, suggesting a role in reorganizing the cytoskeleton during spreading. CONCLUSIONS: The combination of experimental and computational interactome research has emerged as a valuable tool for the analysis of protein-protein interaction networks and facilitates the discovery and characterization of novel interactions as detailed here for Abi-1 and VASP in human platelets. System biological approaches can be expected to play an important role in basic and clinical platelet research, as they offer the potential to analyze signal transduction beyond the scope of established pathways.