T-cell Intracellular Antigen (TIA)-Proteins Deficiency in Murine Embryonic Fibroblasts Alters Cell Cycle Progression and Induces Autophagy

Mice lacking either T-cell intracellular antigen 1 (TIA1) or TIA1 related/like protein (TIAR/TIAL1) show high rates of embryonic lethality, suggesting a relevant role for these proteins during embryonic development. However, intrinsic molecular and cellular consequences of either TIA1 or TIAR deficiency remain poorly defined. By using genome-wide expression profiling approach, we demonstrate that either TIA1 or TIAR inactivation broadly alter normal development-associated signalling pathways in murine embryonic fibroblasts (MEF). Indeed, these analyses highlighted alterations of cytokine-cytokine and ECM-receptor interactions and Wnt, MAPK, TGF-beta dependent signalling pathways. Consistent with these results, TIA1 and TIAR knockout (KO) MEF show reduced rates of cell proliferation, cell cycle progression delay and increased cell size. Furthermore, TIA-proteins deficiency also caused metabolic deficiencies, increased ROS levels and DNA damage, promoting a gentle rise of cell death. Concomitantly, high rates of autophagy were detected in both TIA1 and TIAR KO MEF with induction of the formation of autophagosomes, as evidenced by the up-regulation of the LC3B protein, and autolysosomes, measured by colocalization of LC3B and LAMP1, as a survival mechanism attempt. Taken together, these observations support that TIA proteins orchestrate a transcriptome programme to activate specific developmental decisions. This program is likely to contribute to mouse physiology starting at early stages of the embryonic development. TIA1/TIAR might function as cell sensors to maintain homeostasis and promote adaptation/survival responses to developmental stress.