Steven FlieslerUniversity at Buffalo, The State University of New York | SUNY Buffalo · Department of Ophthalmology
Steven Fliesler
B.A., Ph.D.
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Publications (213)
Methylations of nucleic acids and histones are epigenetic modifications that are integral to normal development and function, as well as disease and dysfunction, of the nervous system, including the retina. One such disease is Smith-Lemli-Opitz syndrome (SLOS). 661W cells (a mouse cone photoreceptor-derived cell line) were incubated with cytotoxic...
Sterol homeostasis in mammalian cells and tissues involves balancing three fundamental processes: de novo sterol biosynthesis; sterol import (e.g., from blood-borne lipoproteins); and sterol export. In complex tissues, composed of multiple different cell types (such as the retina), import and export also may involve intratissue, intercellular stero...
Sterol homeostasis in mammalian cells and tissues involves balancing three fundamental processes: de novo sterol biosynthesis; sterol import (e.g., from blood-borne lipoproteins); and sterol export. In complex tissues, composed of multiple different cell types (such as the retina), import and export also may involve intra-tissue, inter-cellular ste...
Sterol homeostasis in mammalian cells and tissues involves balancing three fundamental processes: de novo sterol biosynthesis; sterol import (e.g., from blood-borne lipoproteins); and sterol export. In complex tissues, composed of multiple different cell types (such as the retina), import and export also may involve intra-tissue, inter-cellular ste...
Modern advances in disease genetics have uncovered numerous modifier genes that play a role in the severity of disease expression. One such class of genetic conditions is known as inherited retinal degenerations (IRDs), a collection of retinal degenerative disorders caused by mutations in over 300 genes. A single missense mutation (K42E) in the gen...
Introduction: Pulmonary hypertension (PH) is a fatal disease without a cure, in which endothelial dysfunction drives pathologic remodeling of the pulmonary vasculature. Individuals with Smith-Lemli-Opitz syndrome (SLOS) develop PH, but the underlying mechanisms remain undefined. SLOS is an autosomal recessive disorder of cholesterol synthesis, resu...
Although cell type-specific Cre recombinase-expressing mouse lines are commonly used to generate conditional knockout of genes of interest, germline recombination and ectopic "leakiness" in Cre recombinase expression in non-specific cell types has been observed in several neuronal and glial-specific Cre lines. This often leads to inadvertent loss o...
The recent success in the treatment of hereditary retinal disease caused by defects in the RPE65 gene and the FDA approval of this treatment has established the importance of the study of animal models and the translational impact of these research findings [...]
De novo synthesis of dolichol (Dol) and dolichyl phosphate (Dol-P) is essential for protein glycosylation. Herein, we provide a brief overview of Dol and Dol-P synthesis and the maintenance of their cellular content. Retinal Dol metabolism and the requirement of Dol-linked oligosaccharide synthesis in the neural retina also are discussed. There are...
Retinitis pigmentosa (RP) defines a group of hereditary progressive rod-cone degenerations that exhibit a common phenotype caused by variants in over 70 genes. While most variants in the dehydrodolichyl diphosphate synthase (DHDDS) gene result in syndromic abnormalities, some variants cause non-syndromic RP (RP59). DHDDS encodes one subunit of the...
Mammalian Müller glia (MG) possess limited regenerative capacities. However, the intrinsic capacity of mammalian MG to transdifferentiate to generate mature neurons without transgenic manipulations remains speculative. Here we show that MAP4K4, MAP4K6 and MAP4K7, which are conserved Misshapen subfamily of ste20 kinases homologs, repress YAP activit...
Traumatic brain injury (TBI) caused by acoustic blast overpressure (ABO) is frequently associated with chronic visual deficits in military personnel and civilians. In this study, we characterized retinal gliotic response in adult male rats following a single ABO exposure directed to one side of the head. Expression of gliosis markers and intermedia...
Retinitis pigmentosa-59 (RP59) is a rare, recessive form of RP, caused by mutations in the gene encoding DHDDS (dehydrodolichyl diphosphate synthase). DHDDS forms a heterotetrameric complex with Nogo-B receptor (NgBR; gene NUS1) to form a cis-prenyltransferase (CPT) enzyme complex, which is required for the synthesis of dolichol, which in turn is r...
Mammalian Müller glia (MG) possess limited regenerative capacities. However, the intrinsic capacity of mammalian MG to transdifferentiate to generate mature neurons without transgenic manipulations remains speculative. Here we show that MAP4K4, MAP4K6 and MAP4K7, which are conserved Misshapen subfamily of ste20 kinases homologs, repress YAP activit...
Congenital disorders of glycosylation (CDG) are a heterogenous group of primarily autosomal recessive mendelian diseases caused by disruptions in the synthesis of lipid-linked oligosaccharides and their transfer to proteins. CDGs usually affect multiple organ systems and vary in presentation, even within families. There is currently no cure, and tr...
Retinitis pigmentosa-59 (RP59) is a rare, recessive form of RP, caused by mutations in the gene encoding DHDDS (dehydrodolichyl diphosphate synthase). DHDDS forms a heterotetrameric complex with Nogo-B Receptor (NgBR; gene NUS1) to form a cis-prenyltransferase (CPT) enzyme complex, which is required for synthesis of dolichol, which in turn is requi...
Retinitis pigmentosa (RP) defines a group of hereditary progressive rod-cone degenerations that exhibit a common phenotype caused by mutations in over 70 genes. While most mutations in the dehydrodolichyl diphosphate synthase (DHDDS) gene result in syndromic abnormalities, some mutations cause non-syndromic RP (RP59). DHDDS encodes one subunit of t...
To effectively reduce vision loss due to age-related macular generation (AMD) on a global scale, knowledge of its genetic architecture in diverse populations is necessary. A critical element, AMD risk profiles in African and Hispanic/Latino ancestries, remains largely unknown due to lower lifetime prevalence. We combined genetic and clinical data i...
Congenital Disorders of Glycosylation (CDG) are a heterogenous group of primarily autosomal recessive mendelian diseases caused by disruptions in the synthesis of lipid linked oligosaccha-rides and their transfer to proteins. CDGs affect multiple organ systems and vary in presentation, even within families. Here we describe a chemically induced mou...
We describe the utility of a tandem-tagged autophagy reporter mouse model (CAG-RFP-EGFP-MAP1LC3B) in investigating basal macroautophagic/autophagic flux in the neural retina. Western blot, in situ hybridization, immunohistochemistry, and confocal microscopy showed that CAG promoter-driven expression of RFP-EGFP-MAP1LC3B increased “cytosolic” RFP-EG...
Blast-induced traumatic brain injury is the signature injury of modern military conflicts. To more fully understand the effects of blast exposure, we placed rats in different holder configurations, exposed them to blast overpressure, and assessed the degree of eye and brain injury.
Anesthetized Long-Evans rats received blast exposures directed at...
Traumatic brain injury (TBI) is the largest non-genetic, non-aging related risk factor for Alzheimer’s disease (AD). We report here that TBI induces tau acetylation (ac-tau) at sites acetylated also in human AD brain. This is mediated by S-nitrosylated-GAPDH, which simultaneously inactivates Sirtuin1 deacetylase and activates p300/CBP acetyltransfe...
The retinal pigment epithelium (RPE) provides vital metabolic support for retinal photoreceptor cells and also is an important player in numerous retinal diseases. Gene manipulation in mice using the Cre-LoxP system is an invaluable tool for studying the genetic basis of these retinal diseases. However, existing RPE-targeted Cre mouse lines have cr...
Smith–Lemli–Opitz Syndrome (SLOS) results from mutations in the gene encoding the enzyme DHCR7, which catalyzes conversion of 7-dehydrocholesterol (7DHC) to cholesterol (CHOL). Rats treated with a DHCR7 inhibitor serve as a SLOS animal model, and exhibit progressive photoreceptor-specific cell death, with accumulation of 7DHC and oxidized sterols....
In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this
topic has received increasing attention, and many scientists have entered the field. Our knowledge base
and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular
basis updated guidelines for monit...
In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this
topic has received increasing attention, and many scientists have entered the field. Our knowledge base
and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular
basis updated guidelines for monit...
the PDF can be download freely on pubmed.
https://pubmed.ncbi.nlm.nih.gov/33634751/
In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monit...
In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monit...
Smith-Lemli-Opitz Syndrome (SLOS) is a developmental disorder (OMIM #270400) caused by autosomal recessive mutations in the Dhcr7 gene, which encodes the enzyme 3β-hydroxysterol-Δ7 reductase. SLOS patients present clinically with dysmorphology and neurological, behavioral, and cognitive defects, with characteristically elevated levels of 7-dehydroc...
Cholesterol biosynthesis is a multi-step process involving several subcellular compartments, including peroxisomes. Cells adjust their sterol content by both transcriptional and post-transcriptional feedback regulation, for which sterol regulatory element-binding proteins (SREBPs) are essential; such homeostasis is dysregulated in peroxisome-defici...
Cholesterol is a quantitatively and biologically significant constituent of all mammalian cell membrane, including those that comprise the retina. Retinal cholesterol homeostasis entails the interplay between de novo synthesis, uptake, intra-retinal sterol transport, metabolism and efflux. Defects in these complex processes are associated with seve...
Dehydrodolichyl diphosphate synthase (DHDDS) catalyzes the committed step in dolichol synthesis. Recessive mutations in DHDDS cause retinitis pigmentosa (RP59), resulting in blindness. We hypothesized that rod photoreceptor-specific ablation of Dhdds would cause retinal degeneration due to diminished dolichol-dependent protein N-glycosylation. Dhdd...
Dehydrodolichyl diphosphate synthase (DHDDS) is required for protein N-glycosylation in eukaryotic cells. A K42E point mutation in the DHDDS gene causes an autosomal recessive form of retinitis pigmentosa (RP59), which has been classified as a congenital disease of glycosylation (CDG). We generated K42E Dhdds knock-in mice as a potential model for...
Patients with certain defects in the dehydrodolichyl diphosphate synthase (DHDDS) gene (RP59; OMIM #613861) exhibit classic symptoms of retinitis pigmentosa, as well as macular changes, suggestive of retinal pigment epithelium (RPE) involvement. The DHDDS enzyme is ubiquitously required for several pathways of protein glycosylation. We wish to unde...
Sterols represent one of the most ubiquitous and diverse classes of biological molecules derived from the common precursor mevalonic acid. While there are thematically similar modes by which various organisms synthesize sterols, there also are some unique twists in the pathways by which such organisms produce sterols as well as differences in the c...
Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive human disease caused by mutations in the gene encoding 7-dehydrocholesterol (7DHC) reductase (DHCR7), resulting in abnormal accumulation of 7DHC and reduced levels of cholesterol in bodily tissues and fluids. A rat model of the disease has been created by treating normal rats with the DHCR...
Oxidative modification of proteins can perturb their structure and function, often compromising cellular viability. Such modifications include lipid-derived adducts (e.g., 4-hydroxynonenal (HNE) and carboxyethylpyrrole (CEP)) as well as nitrotyrosine (NTyr). We compared the retinal proteome and levels of such modifications in the AY9944-treated rat...
Treatment of rats with the cholesterol pathway inhibitor AY9944 produces an animal model of Smith-Lemli-Opitz syndrome (SLOS), an autosomal recessive disease caused by defective cholesterol synthesis. This SLOS rat model undergoes progressive and irreversible degeneration of the neural retina, with associated pathological features of the retinal pi...
A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.
Acoustic blast overpressure (ABO) injury in military personnel and civilians is often accompanied by delayed visual deficits. However, most animal model studies dealing with blast-induced visual defects have focused on short-term (≤1 month) changes. Here, we evaluated long-term (≤8 months) retinal structure and function deficits in rats with ABO in...
Smith-Lemli-Opitz Syndrome (SLOS) is a recessive human disease caused by defective cholesterol (CHOL) synthesis at the level of DHCR7 (7-dehydrocholesterol reductase), which normally catalyzes the conversion of 7-dehydrocholesterol (7DHC) to CHOL. Formation and abnormal accumulation of 7DHC and 7DHC-derived oxysterols occur in SLOS patients and in...
The transient receptor potential cation channel mucolipin 1 (TRPML1) channel is a conduit for lysosomal calcium efflux, and channel activity may be affected by lysosomal contents. The lysosomes of retinal pigmented epithelial (RPE) cells are particularly susceptible to build-up of lysosomal waste products because they must degrade the outer segment...
Purpose: DHDDS (RP59) is required for the synthesis of functional dolichols that are essential for N-linked glycosylation of proteins. To assess the effects of selective ablation of DHDDS in RPE we generated and analyzed Dhdds conditional knockout mice.
Methods:A Cre conditional knockout construct (KOMP, UC Davis) was bred onto a C57Bl/6J backgrou...
Number: 265 B0318 Purpose:D HDDS catalyzes cisprenyl chain elongation to produce dolichylpyrophosphate, which is required for Nglycosylation of proteins (e.g., rhodopsin). Human mutations in DHDDS have been implicated in autosomal recessive Retinitis Pigmentosa (arRP). We examined the effects of rodspecific Dhdds ablation on the structural and...
A duplex fluorescence assay to assess the viability of cells cultured in multi-well plates is described, which can be carried out in the original culture plate using a plate reader, without exchanges of culture or assay medium, or transfer of cells or cell supernatant. The method uses freshly prepared reagents and does not rely on a proprietary, co...
Modification of proteins by 4-hydroxy-2-nonenal (HNE), a reactive by-product of ω6 polyunsaturated fatty acid oxidation, on specific amino acid residues is considered a biomarker for oxidative stress, as occurs in many metabolic, hereditary, and age-related diseases. HNE modification of amino acids can occur either via Michael addition or by format...
Tissue accumulation of 7-dehydrocholesterol (7DHC) is a hallmark of Smith-Lemli-Opitz Syndrome (SLOS), a human inborn error of the cholesterol (CHOL) synthesis pathway. Retinal 7DHC-derived oxysterol formation occurs in the AY9944-induced rat model of SLOS, which exhibits a retinal degeneration characterized by selective loss of photoreceptors and...
Rhodopsin, a G-protein coupled receptor, most abundant protein in retinal rod photoreceptors, is glycosylated at asparagines-2 and 15 on its N-terminus. To understand the role of rhodopsin's glycosylation in vivo, we generated and characterized a transgenic mouse model that expresses a non-glycosylated form of rhodopsin. We show that lack of glycos...
Smith-Lemli-Opitz syndrome is a recessive genetic disorder caused by mutations in the gene (. DHCR7) that encodes the enzyme sterol Delta7-reductase. Such mutations lead to inefficient conversion of 7-dehydrocholesterol to cholesterol. As a result, affected individuals exhibit abnormally low levels of cholesterol and excessive levels of 7-dehydroch...
Angiogenesis is a complex, step-wise process of new vessel formation that is involved in both normal embryonic development as well as postnatal pathological processes, such as cancer, cardiovascular disease, and diabetes. Aberrant blood vessel growth, also known as neovascularization, in the retina and the choroid is a major cause of vision loss in...
Significance
We show that the onecut transcription factors, Onecut1 and Onecut2, redundantly regulate the formation of all four early-born retinal cell types, namely horizontal cells, ganglion cells, cones, and amacrine cells, and prevent precocious formation of the late retinal cell type, rods. Expression profiling suggests these two factors regul...
The endoplasmic reticulum (ER) is the primary intracellular organelle responsible for protein and lipid biosynthesis, protein folding and trafficking, calcium homeostasis, and several other vital processes in cell physiology. Disturbance in ER function results in ER stress and subsequent activation of the unfolded protein response (UPR). The UPR up...
Mutations in the photoreceptor tetraspanin gene peripherin-2/retinal degeneration slow (PRPH2/RDS) cause both rod- and cone-dominant diseases. While rod-dominant diseases, such as autosomal dominant retinitis pigmentosa, are thought to arise due to haploinsufficiency caused by loss-of-function mutations, the mechanisms underlying PRPH2-associated c...
Purpose:
Age-related macular degeneration (AMD) is a leading cause of visual impairment worldwide. Genetics and diet contribute to the relative risk for developing AMD, but their interactions are poorly understood. Genetic variations in Complement Factor H (CFH), and dietary glycemic index (GI) are major risk factors for AMD. We explored the effec...
Blood-retinal barrier (BRB) breakdown and related vascular changes are implicated in several ocular diseases. The molecules and mechanisms regulating BRB integrity and pathophysiology are not fully elucidated. Caveolin-1 (Cav-1) ablation results in loss of caveolae and microvascular pathologies, but the role of Cav-1 in the retina is largely unknow...
Smith-Lemli-Opitz Syndrome (SLOS) is a recessive hereditary disease caused by an enzymatic defect in the biosynthesis of cholesterol. To date, the therapeutic standard of care for this disease has been cholesterol supplementation therapy. However, the efficacy of this treatment is extremely variable and, in many if not most cases, is poor. Results...
Smith-Lemli-Opitz syndrome (SLOS) is one of the most common recessive human disorders and is characterized by multiple congenital malformations as well as neurosensory and cognitive abnormalities. A rat model of SLOS has been developed, which exhibits progressive retinal degeneration and visual dysfunction; however, the molecular events underlying...
Horizontal cells are interneurons that synapse with photoreceptors in the outer retina. Their genesis during development is subject to regulation by transcription factors in a hierarchical manner. Previously, we showed that Onecut 1 (Oc1), an atypical homeodomain transcription factor, is expressed in developing horizontal cells (HCs) and retinal ga...
Age‐related macular degeneration (AMD) is a leading cause of visual impairment in aging Americans. Both genetics and diet contribute to the risk for developing AMD. For example, common variants in the Complement Factor H (Cfh) gene confer major susceptibility to‐ or protection from‐ developing AMD. Similarly, consuming diets with higher glycemic in...
Elevated (4 to 7-fold) levels of urinary dolichol and coenzyme Q and substantially longer chain lengths for urinary dolichols have been reported in Smith-Lemli-Opitz Syndrome (SLOS) patients, compared to normal subjects. We investigated the possibility of similar alterations in hepatic, nonsterol isoprenoids in a well-established rat model of SLOS....
In a report by Hadziahmetovic et al,1 oral administration of an iron chelator deferiprone (Ferriprox), which was recently approved by the Food and Drug Administration, showed substantial protection against retinal degeneration both in a chemically induced (NaIO3) mouse model as well as in a rd6 mouse, which exhibits a hereditary, slowly progressing...
Absence of TPST-1 or TPST-2 does not disrupt Müller glial cells. A–C: Müller cells in wt, Tpst1−/− and Tpst2−/− retina show normal morphology and express glutamine synthetase (GS) as appropriate. Labeling of blood vessels (bv) is non-specific. D–F: Müller cells in the wt, Tpst1−/− and Tpst2−/− retina are not reactive and show normal localization of...
Development of normal synaptic ultrastructure in Tpst1−/− and Tpst2−/− retinas. A–C: Rod terminals in (A) wt, (B) Tpst1−/−, and (C) Tpst2−/− retinas show normal ultrastructural organization. Post-synaptic triads comprised of horizontal cell processes (h) in the lateral position and a rod bipolar cell dendrite (b) in the central position are arrange...
Lack of TPST-1 or TPST-2 does not induce any large scale disruption of retinal horizontal, amacrine or ganglion cells. A–C: Horizontal cells labeled for calbindin in the wt, Tpst1−/− and Tpst2−/− retina show normal placement in the inner nuclear layer (INL) and project normally to the outer plexiform layer (OPL), although the extent of their plexus...
Elimination of TPST-1 or TPST-2 does not induce any large scale disruption of retinal bipolar cells. (A–D)
wt retina; (E–H)
Tpst1−/−; (I–L)
Tpst2−/− retina. The projections of rod bipolar cells (labeled for protein kinase C (PKC), green; panels A, E, I) and Type 2 and Type 6 Cone bipolar cells labeled for synaptotagmin 2 (blue; panels C, G, K) show...