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The Journal of Neuroscience, November 15, 2000, 20(22):8331-8343
Molecular and Functional Diversity of Neural Connexins in the
Retina
R.
Dermietzel1,
M.
Kremer1,
G.
Paputsoglu1,
A.
Stang1,
I. M.
Skerrett3,
D.
Gomès4,
M.
Srinivas5,
U.
Janssen-Bienhold2,
R.
Weiler2,
B. J
Nicholson3,
R.
Bruzzone4, and
D. C.
Spray5
1 Department of Neuroanatomy and Molecular Brain
Research, Ruhr Universität Bochum, DE-45801 Bochum, Germany,
2 Universität Oldenburg, Department of Biology, Carl
von Ossietzky Universität, DE-2611 Oldenburg Germany,
3 Department of Biological Sciences, State University of
New York Buffalo, Buffalo, New York 14260, 4 Institut
Pasteur, Unité de Neurovirologie et
Régénération du Système Nerveux, F-75724 Paris
Cedex 15, France, and 5 Department of Neuroscience, Albert
Einstein College of Medicine, Bronx, New York 10461
Electrical synapses (gap junctions) in neuronal circuits have
become a major focus in the study of network properties such as
synchronization and oscillation (Galarreta and Hestrin, 1999; Gibson et al., 1999). Despite the recent progress made in unraveling the contribution of gap junctions to network behavior, little is known
about the molecular composition of the junctional constituents. By
cloning gap junction proteins [connexins (Cxs)] from zebrafish retina and through functional expression, we demonstrate that the
retina possesses a high degree of connexin diversity, which may account
for differential functional properties of electrical synapses. Three
new Cxs, designated as zebrafish Cx27.5 (zfCx27.5), zfCx44.1, and
zfCx55.5, and the carp ortholog of mammalian Cx43 were cloned. By
in situ hybridization and in situ RT-PCR,
we demonstrate that the four fish connexin mRNAs show differential
localization in the retina. Transient functional expression in paired
Xenopus oocytes and in the neuroblastoma N2A cell line
indicate an extreme range of electrophysiological properties of these
connexins in terms of voltage dependence and unitary conductance. For
instance, the new zfCx44.1 exhibited high sensitivity to
voltage-induced closure with currents decaying rapidly for
transjunctional potentials >10 mV, whereas zfCx55.5 channels showed an
opposite voltage dependence in response to voltage steps of either
polarity. Moreover, although zfCx44.1 channels showed unitary
conductance as high as any previously reported for junctional channels
(nearly 300 pS), zfCx55.5 and zfCx27.5 exhibited much lower unitary
conductances (<60 pS).
Key words:
electrical synapses; gap junctions; retina; cloning; zebrafish connexins; functional diversity
Copyright © 2000 Society for Neuroscience 0270-6474/00/20228331-13$05.00/0
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