Connexin 43-mediated modulation of polarized cell movement and the directional migration of cardiac neural crest cells

Abstract

Connexin 43 knockout (Cx43␣1KO) mice have conotruncal heart defects that are associated with a reduction in the abundance of cardiac neural crest cells (CNCs) targeted to the heart. In this study, we show CNCs can respond to changing fibronectin matrix density by adjusting their migratory behavior, with directionality increasing and speed decreasing with increasing fibronectin density. However, compared with wild-type CNCs, Cx43␣1KO CNCs show reduced directionality and speed, while CNCs overexpressing Cx43␣1 from the CMV43 transgenic mice show increased directionality and speed. Altered integrin signaling was indicated by changes in the distribution of vinculin containing focal contacts, and altered temporal response of Cx43␣1KO and CMV43 CNCs to ␤1 integrin function blocking antibody treatment. High resolution motion analysis showed Cx43␣1KO CNCs have increased cell protrusive activity accompanied by the loss of polarized cell movement. They exhibited an unusual polygonal arrangement of actin stress fibers that indicated a profound change in cytoskeletal organization. Semaphorin 3A, a chemorepellent known to inhibit integrin activation, was found to inhibit CNC motility, but in the Cx43␣1KO and CMV43 CNCs, cell processes failed to retract with semaphorin 3A treatment. Immunohistochemical and biochemical analyses suggested close interactions between Cx43␣1, vinculin and other actin-binding proteins. However, dye coupling analysis showed no correlation between gap junction communication level and fibronectin plating density. Overall, these findings indicate Cx43␣1 may have a novel function in mediating crosstalk with cell signaling pathways that regulate polarized cell movement essential for the directional migration of CNCs.

Connexins, cell motility, and the cytoskeleton

“…In some systems both effects, regulation of the cytoskeleton and migration, have been observed [Iacobas et al, 2003;Xu et al, 2006;Elias et al, 2007]. This strengthens the notion of a functional relationship of Cxs and the cytoskeleton and we will peruse this further in the following chapter.…”

“…Association of Cx43 and drebrin was confirmed by an independent study, where regions of co-localization were abundantly found at areas of cell-cell contact and along cell processes [Xu et al, 2006]. These data suggest that drebrin is a strong candidate for interaction with Cx43 and might prevent Cx degradation thereby playing an important for maintaining Cx43 plaques in situ at the plasma membrane.…”

“…Moreover, a-actinin was found to co-immunoprecipitate with Cx43 [Xu et al, 2006]. Current knowledge about aactinin includes multiple important roles in cell biology.…”

“…Wildtype CNCs mostly have two major stress fiber bundles along the axis of the cell body, while KO CNCs show three or four intersecting bundles encircling the cell cortex. Additionally, Cx43 KO CNCs exhibit reduced cell migration and directionality [Xu et al, 2006].…”

Cell biology of embryonic migration

“…Increased cell protrusive activity, loss of polarized cell movement, rearrangement of actin stress fibers (Xu et al, 2006) Total Die at birth from severe pulmonary outflow tract obstruction (Reaume et al, 1995) PECAM-1 Cell-cell adhesion In vitro studies of cells froom knockout mice…”