Abstract
Gap junctions are direct intercellular channels that permit the passage of ions and small signaling molecules. The temporal and spatial regulation of gap junctional communication is, thus, one mechanism by which cell interactions, and hence cell properties and cell fate, may be regulated during development. The nervous system of the leech, Hirudo medicinalis, is a particularly advantageous system in which to study developmental mechanisms involving gap junctions because interactions between identified cells may be studied in vivo in both the embryo and the adult. As in most invertebrates, gap junctions in the leech are composed of innexin proteins, which are distantly related to the vertebrate pannexins and are encoded by a multi-gene family. We have cloned ten novel leech innexins and describe the expression of these, plus two other previously reported members of this gene family, in the leech embryo between embryonic days 6 and 12, a period during which the main features of the central nervous system are established. Four innexins are expressed in neurons and two in glia, while several innexins are expressed in the excretory, circulatory, and reproductive organs. Of particular interest is Hm-inx6, whose expression appears to be restricted to the characterized S cell and two other neurons putatively identified as presynaptic to this cell. Two other innexins also show highly restricted expressions in neurons and may be developmentally regulated.
Similar content being viewed by others
References
Alexopoulos H, Bottger A, Fischer S, Levin A, Wolf A, Fujisawa T, Hayakawa S, Gojobori T, Davies JA, David CN, Bacon JP (2004) Evolution of gap junctions: the missing link? Curr Biol 14:R879–R880
Altevogt BM, Paul DL (2004) Four classes of intercellular channels between glial cells in the CNS. J Neurosci 24:4313–4323
Bauer R, Lehmann C, Fuss B, Eckardt F, Hoch M (2002) The Drosophila gap junction channel gene innexin 2 controls foregut development in response to wingless signalling. J Cell Sci 115:1859–1867
Contreras JE, Sanchez HA, Veliz LP, Bukauskas FF, Bennett MV, Saez JC (2004) Role of connexin-based gap junction channels and hemichannels in ischemia-induced cell death in nervous tissue. Brain Res Brain Res Rev 47:290–303
Crompton D, Todman M, Wilkin M, Ji S, Davies J (1995) Essential and neural transcripts from the Drosophila shaking-B locus are differentially expressed in the embryonic mesoderm and pupal nervous system. Dev Biol 170:142–158
Curtin KD, Zhang Z, Wyman RJ (2002) Gap junction proteins expressed during development are required for adult neural function in the Drosophila optic lamina. J Neurosci 22:7088–7096
Davies TC, Barr KJ, Jones DH, Zhu D, Kidder GM (1996) Multiple members of the connexin gene family participate in preimplantation development of the mouse. Dev Genet 18:234–243
Dykes IM, Freeman FM, Bacon JP, Davies JA (2004) Molecular basis of gap junctional communication in the CNS of the leech Hirudo medicinalis. J Neurosci 24:886–894
Fernandez J, Stent GS (1982) Embryonic development of the hirudinid leech Hirudo medicinalis: structure, development and segmentation of the germinal plate. J Embryol Exp Morphol 72:71–96
Gan WB, Wong VY, Phillips A, Ma C, Gershon TR, Macagno ER (1999) Cellular expression of a leech netrin suggests roles in the formation of longitudinal nerve tracts and in regional innervation of peripheral targets. J Neurobiol 40:103–115
Gao WQ, Macagno ER (1987a) Extension and retraction of axonal projections by some developing neurons in the leech depends upon the existence of neighboring homologues. I. The HA cells. J Neurobiol 18:43–59
Gao WQ, Macagno ER (1987b) Extension and retraction of axonal projections by some developing neurons in the leech depends upon the existence of neighboring homologues. II. The AP and AE neurons. J Neurobiol 18:295–313
Goodman CS, Spitzer NC (1979) Embryonic development of identified neurones: differentiation from neuroblast to neurone. Nature 280:208–214
Harris AL (2001) Emerging issues of connexin channels: biophysics fills the gap. Q Rev Biophys 34:325–472
Jungbluth S, Willecke K, Champagnat J (2002) Segment-specific expression of connexin31 in the embryonic hindbrain is regulated by Krox20. Dev Dyn 223:544–551
Kuwada JY, Kramer AP (1983) Embryonic development of the leech nervous system: primary axon outgrowth of identified neurons. J Neurosci 3:2098–2111
Lipshitz HD, Kankel DR (1985) Specificity of gene action during central nervous system development in Drosophila melanogaster: analysis of the lethal (1) optic ganglion reduced locus. Dev Biol 108:56–77
Lopresti V, Macagno ER, Levinthal C (1974). Structure and development of neuronal connections in isogenic organisms: transient gap junctions between growing optic axons and lamina neuroblasts. Proc Natl Acad Sci USA 71:1098–1102
Maranto R, Calabrese RL (1984) Neural control of the hearts in the leech, Hirudo medicinalis. I. Anatomy, electrical coupling and innervation of the hearts. J Comp Physiol A 154:367–380
Martinez S, Geijo E, Sanchez Vives MV, Puelles L, Gallego R (1992) Reduced junctional permeability at interrhombomeric boundaries. Development 116:1069–1076
Martinez-Arias A, Lawrence PA (1985) Parasegments and compartments in the Drosophila embryo. Nature 313:639–642
Maschhoff KL, Baldwin HS (2000) Molecular determinants of neural crest migration. Am J Med Genet 97:280–288
Muller KJ, Scott SA (1981) Transmission at a ‘direct’ electrical connexion mediated by an interneurone in the leech. J Physiol 311:565–583
Panchin YV (2005) Evolution of gap junction proteins — the pannexin alternative. J Exp Biol 208:1415–1419
Phelan P (2005) Innexins: members of an evolutionarily conserved family of gap-junction proteins. Biochim Biophys Acta 1711:225–245
Phelan P, Bacon JP, Davies JA, Stebbings LA, Todman MG, Avery L, Baines RA, Barnes TM, Ford C, Hekimi S, Lee R, Shaw JE, Starich TA, Curtin KD, Sun YA, Wyman RJ (1998) Innexins: a family of invertebrate gap-junction proteins. Trends Genet 14:348–349
Sahley CL, Modney BK, Boulis NM, Muller KJ (1994) The S cell: an interneuron essential for sensitization and full dishabituation of leech shortening. J Neurosci 14:6715–6721
Simon AM, McWhorter AR, Dones JA, Jackson CL, Chen H (2004) Heart and head defects in mice lacking pairs of connexins. Dev Biol 265:369–383
Sohl G, Maxeiner S, Willecke K (2005) Expression and functions of neuronal gap junctions. Nat Rev Neurosci 6:191–200
Starich T, Sheehan M, Jadrich J, Shaw J (2001) Innexins in C. elegans. Cell Adhes Commun 8:311–314
Starich TA, Miller A, Nguyen RL, Hall DH, Shaw JE (2003) The Caenorhabditis elegans innexin INX-3 is localized to gap junctions and is essential for embryonic development. Dev Biol 256:403–417
Stebbings LA, Todman MG, Phillips R, Greer CE, Tam J, Phelan P, Jacobs K, Bacon JP, Davies JA (2002) Gap junctions in Drosophila: developmental expression of the entire innexin gene family. Mech Dev 113:197–205
Szabo TM, Faber DS, Zoran MJ (2004) Transient electrical coupling delays the onset of chemical neurotransmission at developing synapses. J Neurosci 24:112–120
Taghert PH, Bastiani MJ, Ho RK, Goodman CS (1982) Guidance of pioneer growth cones: filopodial contacts and coupling revealed with an antibody to Lucifer Yellow. Dev Biol 94:391–399
Tazuke SI, Schulz C, Gilboa L, Fogarty M, Mahowald AP, Guichet A, Ephrussi A, Wood CG, Lehmann R, Fuller MT (2002) A germline-specific gap junction protein required for survival of differentiating early germ cells. Development 129:2529–2539
Warner AE, Lawrence PA (1982) Permeability of gap junctions at the segmental border in insect epidermis. Cell 28:243–252
Watanabe T, Kankel DR (1992) The l(1)ogre gene of Drosophila melanogaster is expressed in postembryonic neuroblasts. Dev Biol 152:172–183
Wenning A, Cahill MA, Greisinger U, Kaltenhauser U (1993) Organogenesis in the leech: development of nephridia, bladders and their innervation. Roux’s Arch Dev Biol 202:329–340
White TW, Wang H, Mui R, Litteral J, Brink PR (2004) Cloning and functional expression of invertebrate connexins from Halocynthia pyriformis. FEBS Lett 577:42–48
Wolszon LR, Gao WQ, Passani MB, Macagno ER (1994) Growth cone “collapse” in vivo: are inhibitory interactions mediated by gap junctions? J Neurosci 14:999–1010
Zerbst-Boroffka I, Bazin B, Wenning A (1997) Chloride secretion drives urine formation in leech nephridia. J Exp Biol 200:2217–2227
Zhang Z, Curtin KD, Sun YA, Wyman RJ (1999) Nested transcripts of gap junction gene have distinct expression patterns. J Neurobiol 40:288–301
Acknowledgements
This work was supported in part by National Institute of Health Grant NS043546 and by the University of California, San Diego funds. We thank Dr. Alejandro Sanchez for his help with the sense in situ hybridization control experiments.
Author information
Authors and Affiliations
Corresponding author
Additional information
Communicated by DA Weisblat
Electronic supplementary material
Supplementary Fig. 1
Figa
Multiple sequence alignment to show the translated protein sequence of the leech Innexin genes discussed in the text. Identical residues are shaded. Note that Hm-inx7, Hm-inx8 and Hm-inx10 are partial sequences and only the C-terminal portion of the sequence is known. Accession numbers of the corresponding cDNA sequences are as follows: Hm-inx1 = AJ512833; Hm-inx2 = AJ512834; Hm-inx3 = DQ228700; Hm-inx4 = DQ228701; Hm-inx5 = DQ228702; Hm-inx6 = DQ228703; Hm-inx7 = DQ228704; Hm-inx8 = DQ228705; Hm-inx9 = DQ228706; Hm-inx10 = DQ228707; Hm-inx11 = DQ228708; Hm-inx12 = DQ228709
Rights and permissions
About this article
Cite this article
Dykes, I.M., Macagno, E.R. Molecular characterization and embryonic expression of innexins in the leech Hirudo medicinalis . Dev Genes Evol 216, 185–197 (2006). https://doi.org/10.1007/s00427-005-0048-1
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00427-005-0048-1