Essential role for Abi1 in embryonic survival and WAVE2 complex integrity

• Published in: Proceedings of the National Academy of Sciences - PNAS 2011-04, Vol.108 (17), p.7022-7027
• Main Authors: Dubielecka, Patrycja M., Ladwein, Kathrin I., Xiong, Xiaoling, Migeotte, Isabelle, Chorzalska, Anna, Anderson, Kathryn V., Sawicki, Janet A., Rottner, Klemens, Stradal, Theresia E., Kotula, Leszek, Koprowski, Hilary
• Format: Article
• Language: English
• Subjects: Actins; Adaptor Proteins, Signal Transducing - genetics; Adaptor Proteins, Signal Transducing - metabolism; Alleles; Animals; Biological Sciences; Brain - embryology; Cell Line; Cell lines; Cell motility; Cell Movement - physiology; Cells; Cytoskeletal Proteins - genetics; Cytoskeletal Proteins - metabolism; Cytoskeleton; Embryo, Mammalian - embryology; Embryos; Exons; Gene expression; Genotype & phenotype; Heart - embryology; Homeodomain Proteins - genetics; Homeodomain Proteins - metabolism; Membrane Proteins - genetics; Membrane Proteins - metabolism; Mice; Mice, Knockout; Microfilaments; Multiprotein Complexes - genetics; Multiprotein Complexes - metabolism; Proteins; Pseudopodia; Rodents; Ruffles; Wiskott-Aldrich Syndrome Protein Family - genetics; Wiskott-Aldrich Syndrome Protein Family - metabolism
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1016811108

AbI interactor 1 (Abi1) plays a critical function in actin cytoskeleton dynamics through participation in the WAVE2 complex. To gain a better understanding of the specific role of AbM, we generated a conditional Abi1-KO mouse model and MEFs lacking Abi1 expression. cells displayed defective regulation of the actin cytoskeleton, and this dysregulation was ascribed to altered activity of the WAVE2 complex. Changes in motility of Abi1-KO cells were manifested by a decreased migration rate and distance but increased directional persistence. Although these phenotypes did not correlate with peripheral ruffling, which was unaffected, Abi1-KO cells exhibited decreased dorsal ruffling. Western blotting analysis of Abi1-KO cell lysates indicated reduced levels of the WAVE complex components WAVE1 and WAVE2, Nap1, and Sra-1/PIR121. Although relative levels were more than doubled in Abi1-KO cells, the absolute expression in these cells amounted only to a fifth of Abi1 levels in the control cell line. This finding suggests that the presence of AbM is critical for the integrity and stability of WAVE complex and that levels are not sufficiently increased to compensate fully for the loss of AbM in KO cells and to restore the integrity and function of the WAVE complex. The essential function of AbM in WAVE complexes and their regulation might explain the observed embryonic lethality of Abi 1-deficient embryos, which survived until approximately embryonic day 11.5 and displayed malformations in the developing heart and brain. Cells lacking AbM and the conditional AbM-KO mouse will serve as critical models for defining Abi1 function.