A dual role for ErbB2 signaling in cardiac trabeculation.

Cardiac trabeculation is a crucial morphogenetic process by which clusters of ventricular cardiomyocytes extrude and expand into the cardiac jelly to form sheet-like projections. Although it has been suggested that cardiac trabeculae enhance cardiac contractility and intra-ventricular conduction, their exact function in heart development has not been directly addressed. We found that in zebrafish erbb2 mutants, which we show completely lack cardiac trabeculae, cardiac function is significantly compromised, with mutant hearts exhibiting decreased fractional shortening and an immature conduction pattern. To begin to elucidate the cellular mechanisms of ErbB2 function in cardiac trabeculation, we analyzed erbb2 mutant hearts more closely and found that loss of ErbB2 activity resulted in a complete absence of cardiomyocyte proliferation during trabeculation stages. In addition, based on data obtained from proliferation, lineage tracing and transplantation studies, we propose that cardiac trabeculation is initiated by directional cardiomyocyte migration rather than oriented cell division, and that ErbB2 cell-autonomously regulates this process.

Do the Messages Matter? An Investigation of Classroom Messages and College Students’ Personal Theories about Education

Students hold a number of personal theories about education that influence motivation and achievement in the classroom: theories about their own abilities, knowledge, and the learning process. Therefore, college instructors have a great interest in helping to develop adaptive personal theories in their students. The current studies investigated whether specific messages that instructors send in college classroom might serve as a mechanism of personal theory development. Across 2 studies, 17 college instructors and 401 students completed surveys assessing their personal theories about education at the beginning and end of college courses. Students and instructors reported hearing and sending many messages in the classroom, including instructor help messages, conciliatory messages, uncertainty in the field messages, differential ability messages and generalized positive and negative feedback. Between-class and within-class differences in message reports were associated with students’ personal theories at the end of their courses, controlling for initial personal theories. Students’ initial personal theories were also related to the messages students reported hearing. The findings demonstrate the utility of assessing non-content messages in college classrooms as potential mechanisms for changing students’ personal theories in college. Implications for research and practice are discussed.