Ultrastructural localization of retinal guanylate cyclase in human and monkey retinas
ABSTRACT Immuno-imaging with confocal and electron microscopy revealed the localization of retinal guanylate cyclase (RetGC) in human and monkey retinas. Using an antibody against a peptide derived from human RetGC, RetGC was found predominantly in the photoreceptor layer in these retinas, although a small amount of RetGC was detected in various other retinal cells. In particular, the cone outer segments were more densely labeled with the antibody than the rod outer segments. The RetGC in outer segments was localized exclusively in the membrane-rich domains, and appeared to be associated with the marginal region of the disk membrane and/or the plasma membrane. The connecting cilium and its cytoplasmic extension never showed immunoreactivity with the antibody. The localization of RetGC in photoreceptor cells is discussed from the viewpoint of mechanisms for the recovery of photoreceptors to the dark level.
SourceAvailable from: Jason Edward Coleman
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ABSTRACT: One-fifth of all cases of Leber Congenital Amaurosis (LCA) are Type 1, a severe form of retinal dystrophy caused by loss-of-function mutations in guanylate cyclase1 (GC1), a key member of the phototransduction cascade involved in modulating the photocurrents. Although GC1 has been studied for some time, the mechanisms responsible for its regulation and membrane targeting are not fully understood. We reported earlier that retinal degeneration 3 (RD3) protein interacts with GC1 and promotes its targeting to the photoreceptor outer segments (POS). Here we extend our studies to show direct association between RD3 and guanylate cyclase activating protein1 (GCAP1) and that this functional interaction is important for GC1 targeting to POS. We also show that most LCA1-causing mutations in GC1 result in loss of its interaction with RD3 or being targeted to the plasma membrane. Our data suggest that GC1, GCAP1, and RD3 form a complex in the endoplasmic reticulum that target GC1 to POS. Interruption of this assembly is likely the underlying mechanism for a subset of LCA1. This study offers insights for the development of therapeutic strategies to treat this severe form of blindness. Copyright © 2014, The American Society for Biochemistry and Molecular Biology.Journal of Biological Chemistry 12/2014; 290(6). DOI:10.1074/jbc.M114.616656 · 4.60 Impact Factor
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ABSTRACT: Purpose: The Israeli population has a unique genetic make-up, with a high prevalence of consanguineous marriages and autosomal recessive diseases. In rod-dominated phenotypes, disease-causing genes and mutations that differ from those identified in other populations are often incurred. Here we use whole exome sequencing (WES) to identify genetic defects in Israeli families with cone-dominated retinal phenotypes. Methods: Clinical analysis included family history, detailed ocular examination, visual function testing and retinal imaging. WES, followed by segregation analysis, was performed in 6 cone-dominated retinopathy families in which prior mutation analysis did not reveal the causative gene. Based on the WES findings, we screened 106 additional families with cone-dominated phenotypes. Results: WES analysis revealed mutations in known retinopathy genes in five out of the six families: two pathogenic mutations in the GUCY2D gene in three families, and one each in CDHR1 and C8orf37. Targeted screening of additional cone-dominated families led to identification of GUCY2D mutations in four other families, which included two highly probable novel disease-causing variants. Conclusions: Our study suggest that GUCY2D is a major cause of autosomal dominant cone- and cone-rod dystrophies in Israel; this is similar to other Caucasian populations and is in contrast to retinitis pigmentosa (primary rod disease) where the genetic make-up of the Israeli population is distinct from other ethnic groups. We also conclude that WES permits more comprehensive and rapid analyses that can be followed by targeted screens of larger samples to delineate the genetic structure of retinal disease in unique population cohorts. Copyright © 2014 by Association for Research in Vision and Ophthalmology.Investigative Ophthalmology & Visual Science 12/2014; 56(1). DOI:10.1167/iovs.14-15647 · 3.66 Impact Factor