Isolation and Characterization of Drosophila retinal degeneration B Suppressors (original) (raw)
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Mammalian Homolog of Drosophila retinal degeneration B Rescues the Mutant Fly Phenotype
1997
Mutations in the Drosophila rdgB gene, which encodes a trans- membrane phosphatidylinositol transfer protein (PITP), cause a light-enhanced retinal degeneration. Cloning of mammalian rdgB orthologs (mrdgB) reveal predicted proteins that are 39% identical to rdgB, with highest homology in the N-terminal PITP domain (62%) and in a region near the C terminus (65%). The human mrdgB gene spans ;12 kb
rdgE: A Novel Retinal Degeneration Mutation in Drosophila melanogaster
Genetics, 1996
We report isolating the Drosophila retinal degeneration E (rdgh') mutation. The hypomorphic rdgE' allele causes rapid photoreceptor degeneration in light and a slower rate of degeneration when the flies are raised in constant darkness. The rdgE' flies exhibited an electrophysiological light response that decreased with age, coinciding with the degeneration. This suggests that degeneration caused the loss of the light response. We determined that the ninaE (rhodopsin) mutation, but not n q A [phospholipase C (PLC)], slowed the rdgmependent degeneration. This was consistent with the light-enhanced degeneration, but revealed that the degeneration is independent of the PLGmediated phototransduction cascade. Transmission electron microscopy revealed that rdgE' photoreceptors exhibited a number of vesicular transport defects including unpacking/vesiculation of rhabdomeres, endocytosis of novel vesicles by photoreceptors, a buildup of very large multivesicular bodies, and an increased amount of rough endoplasmic reticulum. We determined that the rdgE null phenotype is a late embryonic lethality. Therefore, rdgp is required in cells outside of the retina, quite possibly in a large number of neurons. Thus, rdgE may define a mutational class that exhibits both light-enhanced retinal degeneration and a recessive null lethality by perturbing neuronal membrane biosynthesis and/or recycling.
Genes and Function, 1997
Correspondence Sandro Banfi evolution of complex physiological processes. The Drosophila retinal degeneration B (rdgB) gene encodes a protein involved in phototransduction in the fly. We have isolated a human gene, DRES9, and its murine homologue (Dres9), which show a high degree of similarity to the Drosophila rdgB gene. RNA in situ hybridization studies performed on mouse-embryo tissue sections at various developmental stages revealed that Dres9 is expressed at very high levels in the neural retina and in the central nervous system (CNS), similar to its Drosophila counterpart. The high level of sequence conservation and similarities in the expression patterns of rdgB and DRES9 during development in Drosophila and mammals indicate that Dres9 is the orthologue of RdgB, and strongly suggest a possible functional conservation of these proteins during evolution. DRES9 encodes a phosphatidylinositol-transfer protein, suggesting that phosphatidylinositol may have a role as an intracellular messenger in vertebrate phototransduction. The identification of this gene and the study of its expression pattern in mammals will help shed new light on the evolution of vision mechanisms and suggest DRES9 as a candidate gene for human retinopathies.
Identification of a Suppressor of Retinal Degeneration in Drosophila Photoreceptors
During sensory transduction, Drosophila photoreceptors experience substantial increases in intracellular Ca 2 ϩ levels ([Ca 2 ϩ ] i ). Nevertheless in a number of mutants associated with excessive Ca 2 ϩ infl ux through transient receptor potential (TRP) channels, Drosophila photoreceptors undergo loss of normal cellular structure manifest as a retinal degeneration. However, the molecular mechanisms that underpin this degeneration process remain unclear. The authors previously isolated a mutant, su , that is able to suppress the retinal degeneration seen in photoreceptors from loss-of-function alleles of rdgA that are known to have constitutively active TRP channels. Here the authors report the genetic mapping of su(40) as well the isolation of additional alleles of su(40) . Studies of su(40) as well as these new alleles should facilitate the understanding of the mechanisms by which excessive Ca 2 ϩ infl ux results in retinal degeneration.
Isolation and Characterization of the Drosophila Retinal Degeneration B (RdgB) Gene
Genetics, 1991
retinal degeneration-B (rdgB) mutants of Drosophila melanogaster undergo rapid light-induced retinal degeneration. We conducted a molecular characterization of the rdgB gene to examine the nature of the gene product. Through the isolation and analysis of X-ray-induced rdgB alleles, the cytogenetic position of the gene was determined to be the 12C 1 salivary region. Genomic DNA corresponding to this region was isolated by a chromosomal walk. The chromosomal aberrations associated with the three X-ray-induced rdgB alleles were shown to be within a 5-kb genomic region. A single transcription unit was affected by the alleles, identifying it as the rdgB gene. RNA-RNA Northern hybridization indicated the rdgB gene transcribed five mRNAs ranging in size from 3.9 to 9.5 kb. These mRNAs were expressed in adult heads, but not detected in bodies. Analysis of RNA isolated from wild-type and eyes absent heads indicated that rdgB mRNA expression was not restricted to the retina. DNA sequence analysis of the transcription unit revealed an open reading frame capable of encoding a 1 16-kD transmembrane protein. The deduced protein shows no overall homology to previously described proteins, but has sequences in common with proposed functional domains of Ca*+-ATPase.
The Journal of Neuroscience, 1999
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.
Visual Neuroscience, 1989
Quantitative light and electron microscopy was used to monitor the extent of retinal degeneration as a function of age and temperature in the white-eyedrdgBKS222mutant ofDrosophila melanogaster. Parallel measurements of the electroretinogram (ERG) of the degenerating retina reveal a new phenomenon – the appearance of spike potentials following illumination with bright light. These spikes, which do not appear in the normal fly retina, have a relatively long duration (20–50 ms), regenerative properties, and a rate of occurrence which increases with increasing light intensity. The spikes differed from the light response in being more susceptible to CO2and to cuts in the eye. The spikes completely disappeared at low extracellular Ca2+levels which did not reduce the amplitude of the light response. The spike potentials become triphasic when the recording electrode is advanced to the level of the basement membrane. This suggests that the spike potentials originate from the photoreceptor a...
The Journal of neuroscience : the official journal of the Society for Neuroscience, 1999
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 bu...