Characterization of innexin gene expression and functional roles of gap-junctional communication in planarian regeneration.
Planaria possess remarkable powers of regeneration. After bisection, one blastema regenerates a head, while the other forms a tail. The ability of previously-adjacent cells to adopt radically different fates could be due to long-range signaling allowing determination of position relative to, and the identity of, remaining tissue. However, this process is not understood at the molecular level. Following the hypothesis that gap-junctional communication (GJC) may underlie this signaling, we cloned and characterized the expression of the Innexin gene family during planarian regeneration. Planarian innexins fall into 3 groups according to both sequence and expression. The concordance between expression-based and phylogenetic grouping suggests diversification of 3 ancestral innexin genes into the large family of planarian innexins. Innexin expression was detected throughout the animal, as well as specifically in regeneration blastemas, consistent with a role in long-range signaling relevant to specification of blastema positional identity. Exposure to a GJC-blocking reagent which does not distinguish among gap junctions composed of different Innexin proteins (is not subject to compensation or redundancy) often resulted in bipolar (2-headed) animals. Taken together, the expression data and the respecification of the posterior blastema to an anteriorized fate by GJC loss-of-function suggest that innexin-based GJC mediates instructive signaling during regeneration.
Nogi
Taisaku
T
Department of Cytokine Biology, The Forsyth Institute, 140 The Fenway, Boston, MA 02115, USA.
Levin
Michael
M
D000595:Amino Acid Sequence; D000818:Animals; D019521:Body Patterning / Q000502:physiology; D017630:Connexins / Q000235:genetics / Q000378:metabolism*; D017629:Gap Junctions / Q000502:physiology*; D017403:In Situ Hybridization; D007422:Intestines / Q000502:physiology; D008969:Molecular Sequence Data; D009424:Nervous System Physiological Phenomena; D017956:Photoreceptor Cells, Invertebrate / Q000502:physiology; D010802:Phylogeny; D010932:Planarians / Q000502:physiology*; D012038:Regeneration / Q000502:physiology; D015398:Signal Transduction
D017630:Connexins