Stella Finkelstein - Academia.edu (original) (raw)

Papers by Stella Finkelstein

˜The œjournal of neuroscience/˜The œJournal of neuroscience, Apr 19, 2024

Investigative Ophthalmology & Visual Science, 2013

Investigative Ophthalmology & Visual Science, 2017

Investigative Ophthalmology & Visual Science, 2009

Cells, 2020

Phosphoinositides are known to play multiple roles in eukaryotic cells. Although dysregulation of... more Phosphoinositides are known to play multiple roles in eukaryotic cells. Although dysregulation of phosphoinositide metabolism in the retina has been reported to cause visual dysfunction in animal models and human patients, our understanding of the phosphoinositide composition of the retina is limited. Here, we report a characterization of the phosphoinositide profile of the mouse retina and an analysis of the subcellular localization of major phosphorylated phosphoinositide forms in light-sensitive photoreceptor neurons. Using chromatography of deacylated phosphatidylinositol headgroups, we established PI(4,5)P2 and PI(4)P as two major phosphorylated phosphoinositides in the retina. Using high-resolution mass spectrometry, we revealed 18:0/20:4 and 16:0/20:4 as major fatty-acyl chains of retinal phosphoinositides. Finally, analysis of fluorescent phosphoinositide sensors in rod photoreceptors demonstrated distinct subcellular distribution patterns of major phosphoinositides. The PI(...

eneuro, 2018

The heterotrimeric G-protein transducin mediates visual signaling in vertebrate photoreceptor cel... more The heterotrimeric G-protein transducin mediates visual signaling in vertebrate photoreceptor cells. Many aspects of the function of transducin were learned from knock-out mice lacking its individual subunits. Of particular interest is the knockout of its rod-specific γ-subunit (Gγ1). Two studies using independently generated mice documented that this knockout results in a considerable >60-fold reduction in the light sensitivity of affected rods, but provided different interpretations of how the remaining α-subunit (Gαt) mediates phototransduction without its cognate Gβ1γ1-subunit partner. One study found that the light sensitivity reduction matched a corresponding reduction in Gαtcontent in the light-sensing rod outer segments and proposed that Gαtactivation is supported by remaining Gβ1associating with other Gγ subunits naturally expressed in photoreceptors. In contrast, the second study reported the same light sensitivity loss but a much lower, only approximately sixfold, redu...

Nature communications, Apr 30, 2018

Inherited retinal degenerations, affecting more than 2 million people worldwide, are caused by mu... more Inherited retinal degenerations, affecting more than 2 million people worldwide, are caused by mutations in over 200 genes. This suggests that the most efficient therapeutic strategies would be mutation independent, i.e., targeting common pathological conditions arising from many disease-causing mutations. Previous studies revealed that one such condition is an insufficiency of the ubiquitin-proteasome system to process misfolded or mistargeted proteins in affected photoreceptor cells. We now report that retinal degeneration in mice can be significantly delayed by increasing photoreceptor proteasomal activity. The largest effect is observed upon overexpression of the 11S proteasome cap subunit, PA28α, which enhanced ubiquitin-independent protein degradation in photoreceptors. Applying this strategy to mice bearing one copy of the P23H rhodopsin mutant, a mutation frequently encountered in human patients, quadruples the number of surviving photoreceptors in the inferior retina of 6-m...

The Journal of Neuroscience, 2008

Transducin is a prototypic heterotrimeric G-protein mediating visual signaling in vertebrate phot... more Transducin is a prototypic heterotrimeric G-protein mediating visual signaling in vertebrate photoreceptor cells. Despite its central role in phototransduction, little is known about the mechanisms that regulate its expression and maintain approximately stoichiometric levels of the α- and βγ-subunits. Here we demonstrate that the knock-out of transducin γ-subunit leads to a major downregulation of both α- and β-subunit proteins, despite nearly normal levels of the corresponding transcripts, and fairly rapid photoreceptor degeneration. Significant fractions of the remaining α- and β-subunits were mislocalized from the light-sensitive outer segment compartment of the rod. Yet, the tiny amount of the α-subunit present in the outer segments of knock-out rods was sufficient to support light signaling, although with a markedly reduced sensitivity. These data indicate that the γ-subunit controls the expression level of the entire transducin heterotrimer and that heterotrimer formation is e...

The Journal of Neuroscience, 2010

The remarkable ability of our vision to function under ever-changing conditions of ambient illumi... more The remarkable ability of our vision to function under ever-changing conditions of ambient illumination is mediated by multiple molecular mechanisms regulating the light sensitivity of rods and cones. One such mechanism involves massive translocation of signaling proteins, including the G-protein transducin, into and out of the light-sensitive photoreceptor outer segment compartment. Transducin translocation extends the operating range of rods, but in cones transducin never translocates, which is puzzling because cones typically function in much brighter light than rods. Using genetically manipulated mice in which the rates of transducin activation and inactivation were altered, we demonstrate that, like in rods, transducin translocation in cones can be triggered when transducin activation exceeds a critical level, essentially saturating the photoresponse. However, this level is never achieved in wild-type cones: their superior ability to tightly control the rates of transducin acti...

Investigative Ophthalmology & Visual Science, 2007

We present results from depth-resolved light scattering measurements of triple transgenic mouse r... more We present results from depth-resolved light scattering measurements of triple transgenic mouse retinas for Alzheimer’s Disease (AD) using a multimodal coherent imaging system. Use of a co-registered angle-resolved low-coherence interferometry (a/LCI) and optical coherence tomography (OCT) system allows unique analysis that is otherwise unavailable using a single modality to provide complementary information on tissue structural changes associated with AD. This abstract summarizes the light scattering parameters drawn using this system at selective retinal layers guided by OCT image segmentation. Future developments of this combined system for human retinal imaging, which involve a low-cost OCT engine, are also discussed.

Scientific Reports, May 13, 2020

We acquired depth-resolved light scattering measurements from the retinas of triple transgenic Al... more We acquired depth-resolved light scattering measurements from the retinas of triple transgenic Alzheimer's Disease (3xTg-AD) mice and wild type (WT) age-matched controls using co-registered angle-resolved low-coherence interferometry (a/LCI) and optical coherence tomography (OCT). Angleresolved light scattering measurements were acquired from the nerve fiber layer, outer plexiform layer, and retinal pigmented epithelium using image guidance and segmented thicknesses provided by coregistered OCT B-scans. Analysis of the OCT images showed a statistically significant thinning of the nerve fiber layer in AD mouse retinas compared to WT controls. The a/LCI scattering measurements provided complementary information that distinguishes AD mice by quantitatively characterizing tissue heterogeneity. The AD mouse retinas demonstrated higher mean and variance in nerve fiber layer light scattering intensity compared to WT controls. Further, the difference in tissue heterogeneity was observed through short-range spatial correlations that show greater slopes at all layers of interest for AD mouse retinas compared to Wt controls. A greater slope indicates a faster loss of spatial correlation, suggesting a loss of tissue self-similarity characteristic of heterogeneity consistent with AD pathology. Use of this combined modality introduces unique tissue texture characterization to complement development of future AD biomarker analysis.

ENeuro, Dec 11, 2019

Inherited retinal degenerations originate from mutations in Ͼ300 genes, many of which cause the p... more Inherited retinal degenerations originate from mutations in Ͼ300 genes, many of which cause the production of misfolded mutant photoreceptor proteins that are ultimately degraded by the ubiquitin-proteasome system (UPS). It was previously shown that rod photoreceptors in multiple mouse models of retinal degeneration suffer from proteostatic stress consisting of an insufficient cellular capacity for degrading UPS substrates. In this study, we focused on a specific UPS component required for the degradation of a subset of proteasome targets: the substrate-processing complex formed by the AAAϩ ATPase P97/VCP and associated cofactors. To assess whether P97 capacity may be insufficient in degenerating rods, we employed two complementary in vivo proteasomal activity reporters whose degradation is either P97-dependent or P97-independent. Retinal accumulation of each reporter was measured in two models of retinal degeneration: the transducin ␥-subunit knockout (G␥ 1-/-) and P23H rhodopsin knock-in (P23H) mice. Strikingly, the patterns of reporter accumulation differed between these models, indicating that the proteostatic stress observed in G␥ 1-/and P23H rods likely originates from different pathobiological mechanisms, in which UPS substrate degradation may or may not be limited by P97-dependent substrate processing. Further, we assessed whether P97 overexpression could ameliorate pathology in G␥ 1-/mice, in which proteostatic stress appears to result from P97 insufficiency. However, despite P97 overexpression being aphenotypic in other tissues, the ϳ2.4-fold increase in retinal P97 content was toxic to rods, which complicated the interpretation of the observed phenotype. Our results highlight the complexity of pathophysiological mechanisms related to degrading misfolded proteins in mutant photoreceptors.

The Journal of Neuroscience, Nov 1, 2019

Retinal photoreceptor cells contain the highest concentration of docosahexaenoic acid (DHA) in ou... more Retinal photoreceptor cells contain the highest concentration of docosahexaenoic acid (DHA) in our bodies, and it has been long assumed that this is critical for supporting normal vision. Indeed, early studies using DHA dietary restriction documented reduced light sensitivity by DHA-deprived retinas. Recently, it has been demonstrated that a major route of DHA entry in the retina is the delivery across the blood-retina barrier by the sodium-dependent lipid transporter, Mfsd2a. This discovery opened a unique opportunity to analyze photoreceptor health and function in DHA-deprived retinas using the Mfsd2a knockout mouse as animal model. Our lipidome analyses of Mfsd2a ؊/؊ retinas and outer segment membranes corroborated the previously reported decrease in the fraction of DHA-containing phospholipids and a compensatory increase in phospholipids containing arachidonic acid. We also revealed an increase in the retinal content of monounsaturated fatty acids and a reduction in very long chain fatty acids. These changes could be explained by a combination of reduced DHA supply to the retina and a concomitant upregulation of several fatty acid desaturases controlled by sterol regulatory element-binding transcription factors, which are upregulated in Mfsd2a ؊/؊ retinas. Mfsd2a ؊/؊ retinas undergo slow progressive degeneration, with ϳ30% of photoreceptor cells lost by the age of 6 months. Despite this pathology, the ultrastructure Mfsd2a ؊/؊ photoreceptors and their ability to produce light responses were essentially normal. These data demonstrate that, whereas maintaining the lysophosphatidylcholine route of DHA supply to the retina is essential for long-term photoreceptor survival, it is not important for supporting normal phototransduction.

Investigative Ophthalmology & Visual Science, 2009

We present results from depth-resolved light scattering measurements of triple transgenic mouse r... more We present results from depth-resolved light scattering measurements of triple transgenic mouse retinas for Alzheimer’s Disease (AD) using a multimodal coherent imaging system. Use of a co-registered angle-resolved low-coherence interferometry (a/LCI) and optical coherence tomography (OCT) system allows unique analysis that is otherwise unavailable using a single modality to provide complementary information on tissue structural changes associated with AD. This abstract summarizes the light scattering parameters drawn using this system at selective retinal layers guided by OCT image segmentation. Future developments of this combined system for human retinal imaging, which involve a low-cost OCT engine, are also discussed.

The Journal of Neuroscience, 2007

Light causes massive translocation of G-protein transducin from the light-sensitive outer segment... more Light causes massive translocation of G-protein transducin from the light-sensitive outer segment compartment of the rod photoreceptor cell. Remarkably, significant translocation is observed only when the light intensity exceeds a critical threshold level. We addressed the nature of this threshold using a series of mutant mice and found that the threshold can be shifted to either a lower or higher light intensity, dependent on whether the ability of the GTPase-activating complex to inactivate GTP-bound transducin is decreased or increased. We also demonstrated that the threshold is not dependent on cellular signaling downstream from transducin. Finally, we showed that the extent of transducin α subunit translocation is affected by the hydrophobicity of its acyl modification. This implies that interactions with membranes impose a limitation on transducin translocation. Our data suggest that transducin translocation is triggered when the cell exhausts its capacity to activate transduc...

Proceedings of the National Academy of Sciences, 2013

Inherited retinal degenerations, caused by mutations in over 100 individual genes, affect approxi... more Inherited retinal degenerations, caused by mutations in over 100 individual genes, affect approximately 2 million people worldwide. Many of the underlying mutations cause protein misfolding or mistargeting in affected photoreceptors. This places an increased burden on the protein folding and degradation machinery, which may trigger cell death. We analyzed how these cellular functions are affected in degenerating rods of the transducin γ-subunit (Gγ 1 ) knockout mouse. These rods produce large amounts of transducin β-subunit (Gβ 1 ), which cannot fold without Gγ 1 and undergoes intracellular proteolysis instead of forming a transducin βγ-subunit complex. Our data revealed that the most critical pathobiological factor leading to photoreceptor cell death in these animals is insufficient capacity of proteasomes to process abnormally large amounts of misfolded protein. A decrease in the Gβ 1 production in Gγ 1 knockout rods resulted in a significant reduction in proteasomal overload and ...

The Journal of Immunology, 2002

The CCR3 binds at least seven different CC chemokines and is expressed on eosinophils, mast cells... more The CCR3 binds at least seven different CC chemokines and is expressed on eosinophils, mast cells (MC), and a subset of Th cells (Th2) that generate cytokines implicated in mucosal immune responses. Using mice with a targeted disruption of CCR3 (CCR3 ؊/؊) and their ؉/؉ littermates, we investigated the role of CCR3 in the amplification of tissue eosinophilia and MC hyperplasia in the mouse after infection with Trichinella spiralis. In CCR3 ؊/؊ mice, eosinophils are not recruited to the jejunal mucosa after infection and are not present in the skeletal muscle adjacent to encysting larvae. In addition, the number of cysts in the skeletal muscle is increased and the frequency of encysted larvae exhibiting necrosis is reduced. The CCR3 ؊/؊ mice exhibit the expected MC hyperplasia in the jejunum and caecum and reject the adult worms from the small intestine at a normal rate. This study is consistent with distinct functions for MC (adult worm expulsion) and eosinophils (toxicity to larvae) in immunity to a helminth, T. spiralis, and defines the essential requirement for CCR3 in eosinophil, but not MC recruitment to tissues.

Proceedings of the National Academy of Sciences, 2013

Inherited retinal degenerations, caused by mutations in over 100 individual genes, affect approxi... more Inherited retinal degenerations, caused by mutations in over 100 individual genes, affect approximately 2 million people worldwide. Many of the underlying mutations cause protein misfolding or mistargeting in affected photoreceptors. This places an increased burden on the protein folding and degradation machinery, which may trigger cell death. We analyzed how these cellular functions are affected in degenerating rods of the transducin γ-subunit (Gγ1) knockout mouse. These rods produce large amounts of transducin β-subunit (Gβ1), which cannot fold without Gγ1 and undergoes intracellular proteolysis instead of forming a transducin βγ-subunit complex. Our data revealed that the most critical pathobiological factor leading to photoreceptor cell death in these animals is insufficient capacity of proteasomes to process abnormally large amounts of misfolded protein. A decrease in the Gβ1 production in Gγ1 knockout rods resulted in a significant reduction in proteasomal overload and caused a striking reversal of photoreceptor degeneration. We further demonstrated that a similar proteasomal overload takes place in photoreceptors of other mutant mice where retinal degeneration has been ascribed to protein mistargeting or misfolding, but not in mice whose photoreceptor degenerate as a result of abnormal phototransduction. These results establish the prominence of proteasomal insufficiency across multiple degenerative diseases of the retina, thereby positioning proteasomes as a promising therapeutic target for treating these debilitating conditions.

˜The œjournal of neuroscience/˜The œJournal of neuroscience, Apr 19, 2024

Investigative Ophthalmology & Visual Science, 2013

Investigative Ophthalmology & Visual Science, 2017

Investigative Ophthalmology & Visual Science, 2009

Cells, 2020

Phosphoinositides are known to play multiple roles in eukaryotic cells. Although dysregulation of... more Phosphoinositides are known to play multiple roles in eukaryotic cells. Although dysregulation of phosphoinositide metabolism in the retina has been reported to cause visual dysfunction in animal models and human patients, our understanding of the phosphoinositide composition of the retina is limited. Here, we report a characterization of the phosphoinositide profile of the mouse retina and an analysis of the subcellular localization of major phosphorylated phosphoinositide forms in light-sensitive photoreceptor neurons. Using chromatography of deacylated phosphatidylinositol headgroups, we established PI(4,5)P2 and PI(4)P as two major phosphorylated phosphoinositides in the retina. Using high-resolution mass spectrometry, we revealed 18:0/20:4 and 16:0/20:4 as major fatty-acyl chains of retinal phosphoinositides. Finally, analysis of fluorescent phosphoinositide sensors in rod photoreceptors demonstrated distinct subcellular distribution patterns of major phosphoinositides. The PI(...

eneuro, 2018

The heterotrimeric G-protein transducin mediates visual signaling in vertebrate photoreceptor cel... more The heterotrimeric G-protein transducin mediates visual signaling in vertebrate photoreceptor cells. Many aspects of the function of transducin were learned from knock-out mice lacking its individual subunits. Of particular interest is the knockout of its rod-specific γ-subunit (Gγ1). Two studies using independently generated mice documented that this knockout results in a considerable >60-fold reduction in the light sensitivity of affected rods, but provided different interpretations of how the remaining α-subunit (Gαt) mediates phototransduction without its cognate Gβ1γ1-subunit partner. One study found that the light sensitivity reduction matched a corresponding reduction in Gαtcontent in the light-sensing rod outer segments and proposed that Gαtactivation is supported by remaining Gβ1associating with other Gγ subunits naturally expressed in photoreceptors. In contrast, the second study reported the same light sensitivity loss but a much lower, only approximately sixfold, redu...

Nature communications, Apr 30, 2018

Inherited retinal degenerations, affecting more than 2 million people worldwide, are caused by mu... more Inherited retinal degenerations, affecting more than 2 million people worldwide, are caused by mutations in over 200 genes. This suggests that the most efficient therapeutic strategies would be mutation independent, i.e., targeting common pathological conditions arising from many disease-causing mutations. Previous studies revealed that one such condition is an insufficiency of the ubiquitin-proteasome system to process misfolded or mistargeted proteins in affected photoreceptor cells. We now report that retinal degeneration in mice can be significantly delayed by increasing photoreceptor proteasomal activity. The largest effect is observed upon overexpression of the 11S proteasome cap subunit, PA28α, which enhanced ubiquitin-independent protein degradation in photoreceptors. Applying this strategy to mice bearing one copy of the P23H rhodopsin mutant, a mutation frequently encountered in human patients, quadruples the number of surviving photoreceptors in the inferior retina of 6-m...

The Journal of Neuroscience, 2008

Transducin is a prototypic heterotrimeric G-protein mediating visual signaling in vertebrate phot... more Transducin is a prototypic heterotrimeric G-protein mediating visual signaling in vertebrate photoreceptor cells. Despite its central role in phototransduction, little is known about the mechanisms that regulate its expression and maintain approximately stoichiometric levels of the α- and βγ-subunits. Here we demonstrate that the knock-out of transducin γ-subunit leads to a major downregulation of both α- and β-subunit proteins, despite nearly normal levels of the corresponding transcripts, and fairly rapid photoreceptor degeneration. Significant fractions of the remaining α- and β-subunits were mislocalized from the light-sensitive outer segment compartment of the rod. Yet, the tiny amount of the α-subunit present in the outer segments of knock-out rods was sufficient to support light signaling, although with a markedly reduced sensitivity. These data indicate that the γ-subunit controls the expression level of the entire transducin heterotrimer and that heterotrimer formation is e...

The Journal of Neuroscience, 2010

The remarkable ability of our vision to function under ever-changing conditions of ambient illumi... more The remarkable ability of our vision to function under ever-changing conditions of ambient illumination is mediated by multiple molecular mechanisms regulating the light sensitivity of rods and cones. One such mechanism involves massive translocation of signaling proteins, including the G-protein transducin, into and out of the light-sensitive photoreceptor outer segment compartment. Transducin translocation extends the operating range of rods, but in cones transducin never translocates, which is puzzling because cones typically function in much brighter light than rods. Using genetically manipulated mice in which the rates of transducin activation and inactivation were altered, we demonstrate that, like in rods, transducin translocation in cones can be triggered when transducin activation exceeds a critical level, essentially saturating the photoresponse. However, this level is never achieved in wild-type cones: their superior ability to tightly control the rates of transducin acti...

Investigative Ophthalmology & Visual Science, 2007

We present results from depth-resolved light scattering measurements of triple transgenic mouse r... more We present results from depth-resolved light scattering measurements of triple transgenic mouse retinas for Alzheimer’s Disease (AD) using a multimodal coherent imaging system. Use of a co-registered angle-resolved low-coherence interferometry (a/LCI) and optical coherence tomography (OCT) system allows unique analysis that is otherwise unavailable using a single modality to provide complementary information on tissue structural changes associated with AD. This abstract summarizes the light scattering parameters drawn using this system at selective retinal layers guided by OCT image segmentation. Future developments of this combined system for human retinal imaging, which involve a low-cost OCT engine, are also discussed.

Scientific Reports, May 13, 2020

We acquired depth-resolved light scattering measurements from the retinas of triple transgenic Al... more We acquired depth-resolved light scattering measurements from the retinas of triple transgenic Alzheimer's Disease (3xTg-AD) mice and wild type (WT) age-matched controls using co-registered angle-resolved low-coherence interferometry (a/LCI) and optical coherence tomography (OCT). Angleresolved light scattering measurements were acquired from the nerve fiber layer, outer plexiform layer, and retinal pigmented epithelium using image guidance and segmented thicknesses provided by coregistered OCT B-scans. Analysis of the OCT images showed a statistically significant thinning of the nerve fiber layer in AD mouse retinas compared to WT controls. The a/LCI scattering measurements provided complementary information that distinguishes AD mice by quantitatively characterizing tissue heterogeneity. The AD mouse retinas demonstrated higher mean and variance in nerve fiber layer light scattering intensity compared to WT controls. Further, the difference in tissue heterogeneity was observed through short-range spatial correlations that show greater slopes at all layers of interest for AD mouse retinas compared to Wt controls. A greater slope indicates a faster loss of spatial correlation, suggesting a loss of tissue self-similarity characteristic of heterogeneity consistent with AD pathology. Use of this combined modality introduces unique tissue texture characterization to complement development of future AD biomarker analysis.

ENeuro, Dec 11, 2019

Inherited retinal degenerations originate from mutations in Ͼ300 genes, many of which cause the p... more Inherited retinal degenerations originate from mutations in Ͼ300 genes, many of which cause the production of misfolded mutant photoreceptor proteins that are ultimately degraded by the ubiquitin-proteasome system (UPS). It was previously shown that rod photoreceptors in multiple mouse models of retinal degeneration suffer from proteostatic stress consisting of an insufficient cellular capacity for degrading UPS substrates. In this study, we focused on a specific UPS component required for the degradation of a subset of proteasome targets: the substrate-processing complex formed by the AAAϩ ATPase P97/VCP and associated cofactors. To assess whether P97 capacity may be insufficient in degenerating rods, we employed two complementary in vivo proteasomal activity reporters whose degradation is either P97-dependent or P97-independent. Retinal accumulation of each reporter was measured in two models of retinal degeneration: the transducin ␥-subunit knockout (G␥ 1-/-) and P23H rhodopsin knock-in (P23H) mice. Strikingly, the patterns of reporter accumulation differed between these models, indicating that the proteostatic stress observed in G␥ 1-/and P23H rods likely originates from different pathobiological mechanisms, in which UPS substrate degradation may or may not be limited by P97-dependent substrate processing. Further, we assessed whether P97 overexpression could ameliorate pathology in G␥ 1-/mice, in which proteostatic stress appears to result from P97 insufficiency. However, despite P97 overexpression being aphenotypic in other tissues, the ϳ2.4-fold increase in retinal P97 content was toxic to rods, which complicated the interpretation of the observed phenotype. Our results highlight the complexity of pathophysiological mechanisms related to degrading misfolded proteins in mutant photoreceptors.

The Journal of Neuroscience, Nov 1, 2019

Retinal photoreceptor cells contain the highest concentration of docosahexaenoic acid (DHA) in ou... more Retinal photoreceptor cells contain the highest concentration of docosahexaenoic acid (DHA) in our bodies, and it has been long assumed that this is critical for supporting normal vision. Indeed, early studies using DHA dietary restriction documented reduced light sensitivity by DHA-deprived retinas. Recently, it has been demonstrated that a major route of DHA entry in the retina is the delivery across the blood-retina barrier by the sodium-dependent lipid transporter, Mfsd2a. This discovery opened a unique opportunity to analyze photoreceptor health and function in DHA-deprived retinas using the Mfsd2a knockout mouse as animal model. Our lipidome analyses of Mfsd2a ؊/؊ retinas and outer segment membranes corroborated the previously reported decrease in the fraction of DHA-containing phospholipids and a compensatory increase in phospholipids containing arachidonic acid. We also revealed an increase in the retinal content of monounsaturated fatty acids and a reduction in very long chain fatty acids. These changes could be explained by a combination of reduced DHA supply to the retina and a concomitant upregulation of several fatty acid desaturases controlled by sterol regulatory element-binding transcription factors, which are upregulated in Mfsd2a ؊/؊ retinas. Mfsd2a ؊/؊ retinas undergo slow progressive degeneration, with ϳ30% of photoreceptor cells lost by the age of 6 months. Despite this pathology, the ultrastructure Mfsd2a ؊/؊ photoreceptors and their ability to produce light responses were essentially normal. These data demonstrate that, whereas maintaining the lysophosphatidylcholine route of DHA supply to the retina is essential for long-term photoreceptor survival, it is not important for supporting normal phototransduction.

Investigative Ophthalmology & Visual Science, 2009

We present results from depth-resolved light scattering measurements of triple transgenic mouse r... more We present results from depth-resolved light scattering measurements of triple transgenic mouse retinas for Alzheimer’s Disease (AD) using a multimodal coherent imaging system. Use of a co-registered angle-resolved low-coherence interferometry (a/LCI) and optical coherence tomography (OCT) system allows unique analysis that is otherwise unavailable using a single modality to provide complementary information on tissue structural changes associated with AD. This abstract summarizes the light scattering parameters drawn using this system at selective retinal layers guided by OCT image segmentation. Future developments of this combined system for human retinal imaging, which involve a low-cost OCT engine, are also discussed.

The Journal of Neuroscience, 2007

Light causes massive translocation of G-protein transducin from the light-sensitive outer segment... more Light causes massive translocation of G-protein transducin from the light-sensitive outer segment compartment of the rod photoreceptor cell. Remarkably, significant translocation is observed only when the light intensity exceeds a critical threshold level. We addressed the nature of this threshold using a series of mutant mice and found that the threshold can be shifted to either a lower or higher light intensity, dependent on whether the ability of the GTPase-activating complex to inactivate GTP-bound transducin is decreased or increased. We also demonstrated that the threshold is not dependent on cellular signaling downstream from transducin. Finally, we showed that the extent of transducin α subunit translocation is affected by the hydrophobicity of its acyl modification. This implies that interactions with membranes impose a limitation on transducin translocation. Our data suggest that transducin translocation is triggered when the cell exhausts its capacity to activate transduc...

Proceedings of the National Academy of Sciences, 2013

Inherited retinal degenerations, caused by mutations in over 100 individual genes, affect approxi... more Inherited retinal degenerations, caused by mutations in over 100 individual genes, affect approximately 2 million people worldwide. Many of the underlying mutations cause protein misfolding or mistargeting in affected photoreceptors. This places an increased burden on the protein folding and degradation machinery, which may trigger cell death. We analyzed how these cellular functions are affected in degenerating rods of the transducin γ-subunit (Gγ 1 ) knockout mouse. These rods produce large amounts of transducin β-subunit (Gβ 1 ), which cannot fold without Gγ 1 and undergoes intracellular proteolysis instead of forming a transducin βγ-subunit complex. Our data revealed that the most critical pathobiological factor leading to photoreceptor cell death in these animals is insufficient capacity of proteasomes to process abnormally large amounts of misfolded protein. A decrease in the Gβ 1 production in Gγ 1 knockout rods resulted in a significant reduction in proteasomal overload and ...

The Journal of Immunology, 2002

The CCR3 binds at least seven different CC chemokines and is expressed on eosinophils, mast cells... more The CCR3 binds at least seven different CC chemokines and is expressed on eosinophils, mast cells (MC), and a subset of Th cells (Th2) that generate cytokines implicated in mucosal immune responses. Using mice with a targeted disruption of CCR3 (CCR3 ؊/؊) and their ؉/؉ littermates, we investigated the role of CCR3 in the amplification of tissue eosinophilia and MC hyperplasia in the mouse after infection with Trichinella spiralis. In CCR3 ؊/؊ mice, eosinophils are not recruited to the jejunal mucosa after infection and are not present in the skeletal muscle adjacent to encysting larvae. In addition, the number of cysts in the skeletal muscle is increased and the frequency of encysted larvae exhibiting necrosis is reduced. The CCR3 ؊/؊ mice exhibit the expected MC hyperplasia in the jejunum and caecum and reject the adult worms from the small intestine at a normal rate. This study is consistent with distinct functions for MC (adult worm expulsion) and eosinophils (toxicity to larvae) in immunity to a helminth, T. spiralis, and defines the essential requirement for CCR3 in eosinophil, but not MC recruitment to tissues.

Proceedings of the National Academy of Sciences, 2013

Inherited retinal degenerations, caused by mutations in over 100 individual genes, affect approxi... more Inherited retinal degenerations, caused by mutations in over 100 individual genes, affect approximately 2 million people worldwide. Many of the underlying mutations cause protein misfolding or mistargeting in affected photoreceptors. This places an increased burden on the protein folding and degradation machinery, which may trigger cell death. We analyzed how these cellular functions are affected in degenerating rods of the transducin γ-subunit (Gγ1) knockout mouse. These rods produce large amounts of transducin β-subunit (Gβ1), which cannot fold without Gγ1 and undergoes intracellular proteolysis instead of forming a transducin βγ-subunit complex. Our data revealed that the most critical pathobiological factor leading to photoreceptor cell death in these animals is insufficient capacity of proteasomes to process abnormally large amounts of misfolded protein. A decrease in the Gβ1 production in Gγ1 knockout rods resulted in a significant reduction in proteasomal overload and caused a striking reversal of photoreceptor degeneration. We further demonstrated that a similar proteasomal overload takes place in photoreceptors of other mutant mice where retinal degeneration has been ascribed to protein mistargeting or misfolding, but not in mice whose photoreceptor degenerate as a result of abnormal phototransduction. These results establish the prominence of proteasomal insufficiency across multiple degenerative diseases of the retina, thereby positioning proteasomes as a promising therapeutic target for treating these debilitating conditions.