The Journal of Neuroscience, July 15, 1998, 18(14):5191-5202
Alternative RNA Splicing of the NMDA Receptor NR1 mRNA in the
Neurons of the Teleost Electrosensory System
Daniele
Bottai1,
Leonard
Maler2, and
Robert
J.
Dunn1, 3, 4
1 Center for Research in Neuroscience, Montréal
General Hospital Research Institute, Montréal, Québec,
Canada H3G 1A4, 2 Department of Anatomy and Neurobiology,
University of Ottawa, Ottawa, Ontario, Canada K1H 8M5, and Departments
of 3 Biology and 4 Neurology, McGill
University, Montréal, Québec, Canada H3G 1A4
The sequence for cDNA encoding the NMDA receptor subunit 1 (aptNR1)
of the weakly electric fish Apteronotus leptorhynchus has been determined. The deduced amino acid sequence is ~88%
identical to other vertebrate NR1 proteins, with sequence homology
extending to the alternatively spliced cassettes N1 and C1. The fish
and mammalian N1 and C1 splice cassettes are identical at 20 of 21 and
30 of 37 amino acid positions, respectively. We did not detect a C2
splice cassette in aptNR1 mRNA, but we did find two novel C-terminal
alternative splice cassettes labeled C1' and C1".
The relative levels of NR1 transcripts containing the N1 and C1 splice
cassettes were determined by using RNase protection and in
situ hybridization analysis. N1-containing mRNAs are more abundant in caudal brain regions, similar to the patterns reported for
mammalian brain. In contrast, the relative levels of transcripts containing the C1 splice cassette are much lower in fish than in
mammals, averaging only 9% for the whole brain. The levels of C1
splicing increased in more rostral brain regions. In
situ hybridizations with N1- and C1-specific probes
demonstrated that N1 cassette splicing occurs in most neurons but that
C1 splicing is heterogeneous and is restricted to a subset of neuronal
types in the electrosensory system.
Key words:
NMDA receptor; electrosensory system; NR1 subunit; RNA
splicing; evolution; fish neurons
Copyright © 1998 Society for Neuroscience 0270-6474/98/18145191-12$05.00/0
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