Abstract
ABSTRACTAstrocytes undergo intense morphological maturation during development, changing from individual sparsely branched cells to polarized and tremendously ramified cells. Connexin 30, an astroglial gap-junction channel-forming protein expressed postnatally, regulates in situ the extension and ramification of astroglial processes. However, the involvement of connexin 30 in astroglial polarization, which is known to control cell morphology, remains unexplored. We found that connexin 30, independently of gap-junction-mediated intercellular biochemical coupling, alters the orientation of astrocyte protrusion, centrosome and Golgi apparatus during polarized migration in an in vitro wound-healing assay. Connexin 30 sets the orientation of astroglial motile protrusions via modulation of the laminin/β1 integrin/Cdc42 polarity pathway. Connexin 30 indeed reduces laminin levels, inhibits the redistribution of the β1-integrin extracellular matrix receptors, and inhibits the recruitment and activation of the small Rho GTPase Cdc42 at the leading edge of migrating astrocytes. In vivo, connexin 30, the expression of which is developmentally regulated, also contributes to the establishment of hippocampal astrocyte polarity during postnatal maturation. This study thus reveals that connexin 30 controls astroglial polarity during development.
Highlights
During early postnatal stages, individual sparsely branched astrocytes mature into extremely ramified cells to form interconnected cellular networks
Cx30 regulates the polarization of migrating astrocytes To investigate a role for Cx30 in the polarization of migrating astrocytes, we first used the scratch-induced migration assay in cultured astrocytes (Etienne-Manneville, 2006) transfected with a construct encoding Cx30 fused to the Venus YFP mutant protein (Cx30-Venus) (Beltramello et al, 2003)
Cx30-mediated regulation of astrocyte polarization did not involve GJ-mediated intercellular biochemical coupling, as the defect in cell polarity still occurred in astrocytes expressing the Cx30T5M construct (% of polarized cells assessed by reorientation of the centrosome: 49.9±3.7%, n=418 cells; Golgi apparatus: 40.7±4.8%, n=503 cells, Fig. 1D-G), a mutated form of Cx30 in which the replacement of a threonine by a methionine at position 5 of Cx30 inhibits intercellular biochemical coupling mediated by Cx30 GJ channels (Grifa et al, 1999; Schütz et al, 2010) (Fig. S1)
Summary
Individual sparsely branched astrocytes mature into extremely ramified cells to form interconnected cellular networks. The two main astroglial Cxs, Cx43 and Cx30, show different developmental expression patterns: in mice, expression of Cx43 starts around embryonic day 12, whereas that of Cx30 is detectable from postnatal day 16 (P16) (Kunzelmann et al, 1999) Along with their well-known role in gap-junction (GJ)mediated intercellular coupling, the functions of Cxs include the formation of hemichannels (HCs) at the single cell level, which enables bidirectional exchanges with the extracellular space, as well as non-channel functions, which are mediated by Cx protein interactions or intracellular signaling. The non-channel functions of Cx43 and Cx26 are essential in vivo during embryonic neurodevelopment, notably by mediating intercellular adhesion between migrating cortical neurons and radial glia fibers (Elias et al, 2007) Such adhesion may rely on cross-junctional interactions between Cx-containing GJs and adhesion complexes (Xu et al, 2001, 2006)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
