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Caldendrin is a novel calcium-binding protein confined to the somatodendritic compartment of neurons. Here we have studied the expression pattern of caldendrin in the rat retina. First we assessed the distribution of caldendrin transcripts in the adult and developing retina by in situ hybridization. In the adult retina, transcripts are expressed mainly in the inner half of the inner nuclear layer (INL) and to a lesser extent in the ganglion cell layer (GCL). During development labeling of the inner part of the cytoblast layer, where amacrine cells reside, is already present at postnatal day 1 (P1). The intensity of hybridization signal in this sublamina of the developing INL increases up to P8, whereas significant labeling in the GCL was first found at P14, coinciding with eye opening. Immunodetection with a polyclonal antibody revealed intensive staining of cells in the inner retina, which are presumably mainly amacrine and significantly fewer bipolar and ganglion cells. All parvalbumin-containing AII amacrines were immunopositive for caldendrin. Colocalization with calbindin was found in cone bipolar cells, the majority of AII amacrines, and calbindin-positive cells in the GCL. In the GCL, caldendrin was also colocalized with calretinin-immunopositive cells. Most caldendrin-positive amacrine cells in the adult rat retina were glycinergic and only a few were GABAergic. In retinal flat mounts, it was confirmed that less than 10% of retrogradely labeled retinal ganglion cells (RGC) are caldendrin-positive. Caldendrin immunoreactivity does not colocalize with tyrosine hydroxylase, VIP, substance P and somatostatin immunoreactivity. In summary, caldendrin expression is regulated differentially in retinal cell types during development and is restricted to a subpopulation of amacrine, bipolar, and ganglion cells, suggesting specific functions in the developing and mature retina. [ABSTRACT FROM AUTHOR]

· Background: Stiff-man syndrome is a rare neurological disorder characterised by rigidity and violent spasms of the body musculature. In the majority of patients, presence of antibodies against glutamic acid decarboxylase (GAD), the enzyme synthesizing γ-aminobutyric acid (GABA), suggests an autoimmune attack against GABA-ergic inhibitory neurons. We report a 32-year-old patient with stiff-man syndrome and anti-GAD antibodies who developed subacute progressive loss of vision in the right eye, and in the left eye 18 months thereafter. · Methods: Ophthalmological work-up included electro-retinogram (ERG), visual evoked potentials (VEP) and fluorescein angiography. Antiretinal antibodies were investigated using an indirect immunofluorescence technique on frozen sections of macaque retina with patient´s serum and FITC-conjugated goat antihuman immunoglobulin. Staining with monoclonal anti-GAD65 antibodies and with serum from three healthy normals served as controls. · Results: Visual acuity of both eyes decreased to 0.16 within a span of 6 weeks. Perimetry revealed a central scotoma in the visual field of both eyes. VEP and flash ERG were progressively disturbed on the right eye. On the left eye, initially only pattern ERG and photopic responses were abnormal. Follow-up recordings revealed widespread pathology of photopic single and flicker responses. Immunofluorescence revealed strong reactivity of the inner plexiform layer and to a lesser extent staining of the outer plexiform layer at dilutions of 1:1000 with patients serum. The same retinal staining pattern was obtained with monoclonal anti-GAD65 antibodies. · Conclusions: These findings suggest autoimmune retinopathy, mediated by anti-GAD65 autoantibodies as the underlying cause of visual loss. [ABSTRACT FROM AUTHOR]

The article presents an abstract of the research paper "Expression and Subcellular Localization of the Novel Neuronal Calcium-binding Protein Caldendrin." It will be presented in the joint meeting of the International Society for Neurochemistry and the European Society of Neurochemistry that will be held in Berlin, Germany from August 8-14, 1999. A novel EF-hand CaBP has been named as caldendrin.