No abstract

Coordination of microtubules and the actin cytoskeleton is important in several types of cell movement. mDia1 is a member of the formin-homology family of proteins and an effector of the small GTPase Rho. It contains the Rho-binding domain in its amino terminus and two distinct regions of formin homology, FH1 in the middle and FH2 in the carboxy terminus. Here we show that expression of mDia1(DeltaN3), an active mDia1 mutant containing the FH1 and FH2 regions without the Rho-binding domain, induces bipolar elongation of HeLa cells and aligns microtubules in parallel to F-actin bundles along the long axis of the cell. The cell elongation and microtubule alignment caused by this mutant is abolished by co-expression of an FH2-region fragment, and expression of mDia1(DeltaN3) containing point mutations in the FH2 region causes an increase in the amount of disorganized F-actin without cell elongation and microtubule alignment. These results indicate that mDia1 may coordinate microtubules and F-actin through its FH2 and FH1 regions, respectively.

Human altruism shaped our evolutionary history and pervades social and political life. There are, however, enormous individual differences in altruism. Some people are almost completely selfish, while others display strong altruism, and the factors behind this heterogeneity are only poorly understood. We examine the neuroanatomical basis of these differences with voxel-based morphometry and show that gray matter (GM) volume in the right temporoparietal junction (TPJ) is strongly associated with both individuals' altruism and the individual-specific conditions under which this brain region is recruited during altruistic decision making. Thus, individual differences in GM volume in TPJ not only translate into individual differences in the general propensity to behave altruistically, but they also create a link between brain structure and brain function by indicating the conditions under which individuals are likely to recruit this region when they face a conflict between altruistic and selfish acts.