Parvalbumin expression changes with retinal ganglion cell degeneration

BackgroundGlaucoma is one of the main causes of irreversible visual field loss and blindness worldwide. Vision loss in this multifactorial neurodegenerative disease results from progressive degeneration of retinal ganglion cells (RGCs) and their axons. Identifying molecular markers that can be measured objectively and quantitatively may provide essential insights into glaucoma diagnosis and enhance pathophysiology understanding.MethodsThe chronic, progressive DBA/2J glaucomatous mouse model of glaucoma and C57BL6/J optic nerve crush (ONC) mouse model were used in this study. Changes in PVALB expression with RGC and optic nerve degeneration were assessed via gene expression microarray analysis, quantitative real-time polymerase chain reaction (qRT-PCR), Western blot and immunohistochemistry.ResultsMicroarray analysis of the retinal gene expression in the DBA/2J mice at different ages showed that the expression of PVALB was downregulated as the mice aged and developed glaucoma with retinal ganglion cell loss. Analysis of qRT-PCR results demonstrated PVALB at the mRNA level was reduced in the retinas and optic nerves of old DBA/2J mice and in those after ONC compared to baseline young DBA2/J mice. PVALB protein expression measured by Western blot was also significantly reduced signal in the retinas and optic nerves of old DBA/2J mice and those eyes with crushed nerves. Immunohistochemical staining results demonstrated that there were fewer PVALB-positive cells in the ganglion cell layer (GCL) of the retina and staining pattern changed in the optic nerve from old DBA/2J mice as well as in mice eyes following ONC.ConclusionPVALB is abundantly expressed both by RGCs’ soma in the retinas and RGCs’ axons in the optic nerves of C57BL/6J. Furthermore, the expression level of PVALB decreases with RGC degeneration in the glaucomatous DBA/2J mice and after ONC injury of C57BL6/6J, indicating that PVALB is a reliable RGC molecular marker that can be used to study retinal and optic nerve degeneration

Vesicular Glutamate Transporter 3 in age-dependent optic neuropathy

To determine retinal vesicular glutamate transporter 3 (VGLUT3) expression alterations in a mouse model of progressive optic neuropathy (glaucoma). Tissue specimens were obtained from age-matched DBA/2J and control C57BL/6J mice for western blot analysis. Enucleated globes from DBA/2J, C57BL/6J, and BALB/cJ mice were fixed in formalin, paraffin-embedded, and sectioned for VGLUT3 protein localization. western blot analysis of the control retinas revealed the expression of a ~55 kDa immunoreactive VGLUT3 protein that is to be expected in tissues such as retina, brain, liver, heart, and kidney tissue, but not in intestinal or lung tissue. Furthermore, a strong ~130 kDa immunoreactive VGLUT3 isoform that is restricted to the central nervous system (the brain and retinas) was also identified in the controls, but was not detected in the DBA/2J retinas. Immunofluorescence microscopy showed a lack of VGLUT3 expression in the synapses between amacrine and retinal ganglion cells in DBA/2J retinas, in contrast to its strong expression in the C57BL/6J and BALB/cJ controls. Our results implicate the dysregulated expression of a central nervous system-specific VGLUT3 isoform as a predisposing factor in the development of optic neuropathy in DBA/2J mice, a spontaneous mouse model of glaucoma. In striking parallel to the visual system defects of glaucomatous DBA/2J mice, the inner ear of VGLUT3 knockout mice displays a progressive loss of inner hair cell to spiral-ganglion neuron synapses. A significant reduction in the number of spiral-ganglion neurons leads to age-associated deafness. Thus, we propose that the absence of this biochemically uncharacterized 130 kDa VGLUT3 isoform in the DBA/2J retina is a predisposing factor in synaptic instability, and a contributing factor in the age-dependent and progressive loss of ganglion cells projecting to the brain

Sphingolipids and ceramides in human aqueous humor

To determine the differential profiles of sphingomyelin, sphingoid base, sphingoid base-1-phosphate and ceramide lipid species and their quantitative differences between control and glaucomatous aqueous humor (AQH) derived from human donors. AQH from control and primary open-angle glaucoma donors was collected and subjected to lipid extraction using suitable modifications of the Bligh and Dyer method. Proteins were estimated using Bradford's method. Lipids were identified and ratiometrically quantified in a two-step process using precursor ion scan or neutral loss scan (NLS) with appropriate class-specific lipid standards on a TSQ Quantum Access Max mass spectrometer following established procedures. Primary human trabecular meshwork cells and video microscopic imaging were used to assess changes in cell shape and motility upon exposure to 20 pmol of Cer(d18:0/18:1(9Z)) in 10% dimethyl sulfoxide (vehicle). We identified several species of sphingomyelin, sphingoid base, sphingoid base-1-phosphate, and ceramides that were common between control and glaucomatous AQH. Some unique lipid species in these classes were also identified in controls but not in glaucoma and vice versa. We found exposure to 20 pmol of Cer(d18:0/18:1(9Z)) resulted in changes in the trabecular meshwork cell shape and observed motility changes compared to vehicle-only control. Most lipids belonging to the sphingomyelin, sphingoid base, sphingoid base-1-phosphate, and ceramide species were common between control and primary open-angle glaucoma donors. However, some sphingolipids and ceramides were found to be uniquely present in control but absent in the glaucomatous AQH and vice versa. Identification of unique lipid species present or absent in the pathophysiological context may contribute further insight into glaucoma pathology

Corepressor CtBP and Nuclear Speckle Protein Pnn/DRS Differentially Modulate Transcription and Splicing of the E-Cadherin Gene▿

CtBP is a transcriptional corepressor with tumorigenic potential that targets the promoter of the tumor suppressor gene E-cadherin. Pnn/DRS (Pnn) is a “nuclear speckle”-associated protein involved in mRNA processing as well as transcriptional regulation of E-cadherin via its binding to CtBP. Here, we show that CtBP can recruit Pnn to CtBP-associated complexes, resulting in Pnn-dependent chromatin remodeling at the E-cadherin promoter. In addition, CtBP and Pnn can differentially modulate E-cadherin mRNA splicing, with polymerase II serving as an interface in this event. Therefore, the Pnn/CtBP functional interplay represents a novel mechanism linking the corepressor CtBP and Pnn to the transcription-coupled mRNA splicing of a major tumor suppressor gene. Our findings implicate the existence of the molecular switches involved in tumorigenesis, which coordinate promoter-specific events and mRNA processing, by serving as bridging elements between the regulatory complexes both at gene promoters and within the mRNA splicing machineries