Connexin29 is uniquely distributed within myelinating glial cells of the central and peripheral nervous systems.
Although both Schwann cells and oligodendrocytes express connexin32 (Cx32), the loss of this connexin causes demyelination only in the PNS. To determine whether oligodendrocytes might express another connexin that can function in place of Cx32, we searched for novel CNS-specific connexins using reverse transcriptase-PCR and degenerate primers. We identified Cx29, whose transcript was restricted to brain, spinal cord, and sciatic nerve. Developmental expression of Cx29 mRNA in the CNS paralleled that of other myelin-related mRNAs, including Cx32. In the CNS, Cx29 antibodies labeled the internodal and juxtaparanodal regions of small myelin sheaths, whereas Cx32 staining was restricted to large myelinated fibers. In the PNS, Cx29 expression preceded that of Cx32 and declined to lower levels than Cx32 in adulthood. In adult sciatic nerve, Cx29 was primarily localized to the innermost aspects of the myelin sheath, the paranode, the juxtaparanode, and the inner mesaxon. Cx29 displayed a striking coincidence with Kv1.2 K(+) channels, which are localized in the axonal membrane. Both Cx29 and Cx32 were found in the incisures. Cx29 expressed in N2A cells did not induce intercellular conductances but did participate in the formation of active channels when coexpressed with Cx32. Together, these data show that Cx29 and Cx32 are expressed by myelinating glial cells with distinct distributions.
Altevogt
Bruce M
BM
Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Kleopa
Kleopas A
KA
Postma
Friso R
FR
Scherer
Steven S
SS
Paul
David L
DL
D000818:Animals; D000918:Antibody Specificity; D001921:Brain / Q000378:metabolism; D002490:Central Nervous System / Q000166:cytology / Q000378:metabolism*; D017630:Connexins / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D051379:Mice; D008969:Molecular Sequence Data; D009186:Myelin Sheath / Q000378:metabolism*; D009419:Nerve Tissue Proteins; D009457:Neuroglia / Q000166:cytology / Q000378:metabolism*; D009836:Oligodendroglia / Q000166:cytology / Q000378:metabolism; D009865:Oocytes / Q000378:metabolism; D009928:Organ Specificity; D018408:Patch-Clamp Techniques; D017933:Peripheral Nervous System / Q000166:cytology / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012583:Schwann Cells / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure; D012584:Sciatic Nerve / Q000378:metabolism / Q000502:physiology; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013116:Spinal Cord / Q000378:metabolism; D014981:Xenopus; D000097002:Gap Junction beta-1 Protein
D017630:Connexins; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D000097002:Gap Junction beta-1 Protein; C464674:GJC3 protein, human; C464673:Gje1 protein, mouse