The Journal of Neuroscience, September 1, 1999, 19(17):7317-7325
A Neuronal-specific Mammalian Homolog of the
Drosophila Retinal Degeneration B Gene with Expression
Restricted to the Retina and Dentate Gyrus
Changwan
Lu1,
Thomas S.
Vihtelic2,
David
R.
Hyde2, and
Tiansen
Li1
1 Berman-Gund Laboratory for the Study of Retinal
Degenerations, Harvard Medical School, Massachusetts Eye and Ear
Infirmary, Boston, Massachusetts 02114, and 2 Department of
Biological Sciences, University of Notre Dame, Notre Dame, Indiana
46556
Mutations in the Drosophila retinal degeneration B
(rdgB) gene cause a rapid loss of the
electrophysiological light response and subsequent light-enhanced
photoreceptor degeneration. The rdgB gene encodes a
protein with an N-terminal phosphatidylinositol transfer
protein domain, a large C-terminal segment, and several hydrophobic regions thought to multiply span the subrhabdomeric cisternal membrane. A mammalian rdgB homolog
(m-rdgB1) was previously identified and shown to exhibit
widespread tissue distribution and functionally rescue the
Drosophila rdgB mutant phenotypes. We describe a second
mammalian rdgB homolog (m-rdgB2) that
possesses 46% amino acid identity to Drosophila RdgB
and 56% identity to M-RdgB1. M-RdgB2 possesses a neuronal-specific
expression pattern, with high levels in the retina and the dentate
gyrus mossy fibers and dendritic field. Using M-RdgB2-specific
antibodies and subcellular fractionation, we demonstrate that M-RdgB2
is not an integral membrane protein but is stably associated with a
particulate fraction through protein-protein interactions. Although
transgenic expression of M-RdgB2 in rdgB2 null
mutant flies suppressed the retinal degeneration, it failed to fully
restore the electrophysiological light response. Because transgenic
expression of M-RdgB2 does not restore the wild-type phenotype to
rdgB2 mutant flies to the same extent as M-RdgB1,
functional differences likely exist between the two M-RdgB homologs.
Key words:
rdgB; retinal degeneration; PITP; dentate gyrus; hippocampus; autism
Copyright © 1999 Society for Neuroscience 0270-6474/99/19177317-09$05.00/0