In optic neuropathies, including glaucoma, retinal ganglion cells (RGCs) die. Cell transplantatio... more In optic neuropathies, including glaucoma, retinal ganglion cells (RGCs) die. Cell transplantation and endogenous regeneration offer strategies for retinal repair, however, developmental programs required for this to succeed are incompletely understood. To address this, we explored cellular reprogramming with transcription factor (TF) regulators of RGC development which were integrated into human pluripotent stem cells (PSCs) as inducible gene cassettes. When the pioneer factor NEUROG2 was combined with RGC-expressed TFs (ATOH7, ISL1, and POU4F2) some conversion was observed and when pre-patterned by BMP inhibition, RGC-like induced neurons (RGC-iNs) were generated with high efficiency in just under a week. These exhibited transcriptional profiles that were reminiscent of RGCs and exhibited electrophysiological properties, including AMPA-mediated synaptic transmission. Additionally, we demonstrated that small molecule inhibitors of DLK/LZK and GCK-IV can block neuronal death in two ...
This Early Release article has been peer reviewed and accepted, but has not been through the comp... more This Early Release article has been peer reviewed and accepted, but has not been through the composition and copyediting processes.The final version may differ slightly in style or formatting and will contain links to any extended data. Alerts: Sign up at www.eneuro.org/alerts to receive customized email alerts when the fully formatted version of this article is published.
Vision restoration strategies aim to reestablish vision by replacing the function of lost photore... more Vision restoration strategies aim to reestablish vision by replacing the function of lost photoreceptors with optoelectronic hardware or through gene therapy. One complication to these approaches is that retinal circuitry undergoes remodeling after photoreceptor loss. Circuit remodeling following perturbation is ubiquitous in the nervous system and understanding these changes is crucial for treating neurodegeneration. Spontaneous oscillations that arise during retinal degeneration have been well-studied, however, other changes in the spatiotemporal processing of evoked and spontaneous activity have received less attention. Here we use subretinal electrical stimulation to measure the spatial and temporal spread of both spontaneous and evoked activity during retinal degeneration. We found that electrical stimulation synchronizes spontaneous oscillatory activity, over space and through time, thus leading to increased correlations in ganglion cell activity. Intriguingly, we found that spatial selectivity was maintained in rd10 retina for evoked responses, with spatial receptive fields comparable to wt retina. These findings indicate that different biophysical mechanisms are involved in mediating feed forward excitation, and the lateral spread of spontaneous activity in the rd10 retina, lending support toward the possibility of high-resolution vision restoration.
Ambroxol reduces SBAC AI, but TTX or cadmium does not
<p>A, (top row) shows the average IV relation measured 1.2 ms after the command step to vol... more <p>A, (top row) shows the average IV relation measured 1.2 ms after the command step to voltages between −100 and 0 mV, under control conditions (closed squares) and drug (open circles). Error bars show standard error. The linear portion of the IV has been subtracted leaving the negative slope portion of the IV (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0012447#s2" target="_blank">Methods</a>). The solid lines indicate the best-fit line between −40 and 0 mV. A shows 300 µM ambroxol hydrochloride (n = 3), B shows 500 nM TTX (n = 6), and C shows 25 µM cadmium (n = 5). B and C, (second and third rows) show the average filtered (25 Hz cutoff Gaussian) current traces in response to centrifugal and centripetal stimulation, respectively in control conditions (black trace), and drug treatment (gray trace). Left column shows 300 µM ambroxol hydrochloride (n = 3). Middle column shows. 500 nM TTX (n = 5). Right column shows 25 µM cadmium (n = 6).</p
The On-Off direction-selective ganglion cell (DSGC) in mammalian retinas responds most strongly t... more The On-Off direction-selective ganglion cell (DSGC) in mammalian retinas responds most strongly to a stimulus moving in a specific direction. The DSGC initiates spikes in its dendritic tree, which are thought to propagate to the soma with high probability. Both dendritic and somatic spikes in the DSGC display strong directional tuning, whereas somatic PSPs (postsynaptic potentials) are only weakly directional, indicating that spike generation includes marked enhancement of the directional signal. We used a realistic computational model based on anatomical and physiological measurements to determine the source of the enhancement. Our results indicate that the DSGC dendritic tree is partitioned into separate electrotonic regions, each summing its local excitatory and inhibitory synaptic inputs to initiate spikes. Within each local region the local spike threshold nonlinearly amplifies the preferred response over the null response on the basis of PSP amplitude. Using inhibitory conductances previously measured in DSGCs, the simulation results showed that inhibition is only sufficient to prevent spike initiation and cannot affect spike propagation. Therefore, inhibition will only act locally within the dendritic arbor. We identified the role of three mechanisms that generate directional selectivity (DS) in the local dendritic regions. First, a mechanism for DS intrinsic to the dendritic structure of the DSGC enhances DS on the null side of the cell's dendritic tree and weakens it on the preferred side. Second, spatially offset postsynaptic inhibition generates robust DS in the isolated dendritic tips but weak DS near the soma. Third, presynaptic DS is apparently necessary because it is more robust across the dendritic tree. The pre-and postsynaptic mechanisms together can overcome the local intrinsic DS. These local dendritic mechanisms can perform independent nonlinear computations to make a decision, and there could be analogous mechanisms within cortical circuitry.
Organized and quality-controlled CalCOFI data for CTD casts and bottle measurements from CalCOFI stations between La Jolla, California to Point Conception between 1984-2019
In this dataset, we analyzed daytime casts (09:00-16:00) of both discrete bottle data and continu... more In this dataset, we analyzed daytime casts (09:00-16:00) of both discrete bottle data and continuous CTD casts from CalCOFI stations restricted to an area from La Jolla, California to Point Conception and 215 km maximum offshore. This dataset has combined bottle and CTD casts to represent the date range 1984-2019. We used the oxygen and irradiance measurements to determine the visual luminoxyscape for each of the larval species. This range was bounded by the oxygen (partial pressure) where the pO2 would permit 50% minimum retinal function (V50; 13, 7.2, 10.2, and 6.8 kPa for larvae of 'Doryteuthis opalescens', 'Octopus bimaculatus', 'Metacarcinus gracilis', and 'Pleuroncodes planipes', respectively), and where there is sufficient irradiance for a visual response (0.0311 µmol photons m-2 s-1) for each species. Additionally, oxygen limits for metabolism were used to determine the depth of occurrence of the Pcrit (the oxygen below which the animal cannot...
Maximum depths of the visual luminoxyscape for four species of marine invertebrate larvae from CalCOFI stations between La Jolla, California to Point Conception between 1984-2019
In this dataset, the maximum depths of the visual luminoxyscape for four species of marine invert... more In this dataset, the maximum depths of the visual luminoxyscape for four species of marine invertebrate larvae were recorded. Data in this study are from CalCOFI stations restricted to an area from La Jolla, California to Point Conception and 215 kilometers maximum offshore (Station 60). We analyzed daytime casts (09:00-16:00) of both discrete bottle data and continuous CTD casts to represent the date range of 1984-2019 and used the oxygen and irradiance measurements to determine the visual luminoxyscape for each of the larval species. This range was bounded by the oxygen (partial pressure) where the pO2 would permit 50% minimum retinal function (V50; 13, 7.2, 10.2, and 6.8 kPa for larvae of 'Doryteuthis opalescens', 'Octopus bimaculatus', 'Metacarcinus gracilis', and 'Pleuroncodes planipes', respectively), and where there is sufficient irradiance for a visual response (0.0311 µmol photons m-2 s-1) for each species. Additionally, oxygen limits for met...
Photobehavior for octopus ('Octopus bimaculatus') and squid ('Doryteuthis opalescens') paralarvae during exposure to 9 light irradiance levels and 4 oxygen conditions in trials conducted in April of 2019
This dataset gives the results of photobehavior experiments under different oxygen conditions in ... more This dataset gives the results of photobehavior experiments under different oxygen conditions in larvae of the market squid ('Doryteuthis opalescens') and two-spot octopus ('Octopus bimaculatus'). Photobehavior experiments were conducted to determine whether the impairment of visual physiology observed in marine invertebrate larvae (McCormick et al., 2019) is subsequently affecting visual behavior in marine larvae.
Investigative Opthalmology & Visual Science, 2018
PURPOSE. For more than 20 years, there has been an international, multidisciplinary effort to dev... more PURPOSE. For more than 20 years, there has been an international, multidisciplinary effort to develop retinal prostheses to restore functional vision to patients blinded by retinal degeneration. We developed a novel subretinal prosthesis with 1512 optically addressed silicon nanowire photodiodes, which transduce incident light into an electrical stimulation of the remaining retinal circuitry. This study was conducted to evaluate the efficacy of optically driving the subretinal prosthesis to produce visual cortex activation via electrical stimulation of the retina. METHODS. We measured electrically evoked potential responses (EEPs) in rabbit visual cortex in response to illumination of the subretinal nanowire prosthesis with pulsed 852-nm infrared (IR) light. We compared the EEP responses to visually evoked potential responses (VEPs) to pulsed 532-nm visible light (positive control) and pulsed 852-nm IR light (negative control). RESULTS. Activating the devices with IR light produced EEP responses with a significantly higher trough-to-peak amplitude (54.17 6 33.4 lV) than IR light alone (24.07 6 22.1 lV) or background cortical activity (23.22 6 17.2 lV). EEP latencies were significantly faster than focal VEP latencies. Focal VEPs produced significantly higher amplitudes (94.88 6 43.3 lV) than EEPs. We also demonstrated how an electrode placed on the cornea can be used as a noninvasive method to monitor the function of the implant. CONCLUSIONS. These results show that subretinal electrical stimulation with nanowire electrodes can elicit EEPs in the visual cortex, providing evidence for the viability of a subretinal nanowire prosthetic approach for vision restoration.
For many animals, evolution has selected for complex visual systems despite the high energetic de... more For many animals, evolution has selected for complex visual systems despite the high energetic demands associated with maintaining eyes and their processing structures. The metabolic demands of visual systems therefore make them highly sensitive to fluctuations in available oxygen. In the marine environment, oxygen changes over daily, seasonal, and inter-annual time scales and there are large gradients of oxygen with depth. Vision is linked to survival in many marine animals, particularly among the crustaceans, cephalopods, and fish, and early life stages of these groups rely on vision for prey capture, predator detection, and their distribution in the water column. Using in vivo electroretinogram recordings, we show that there is a decrease in retinal sensitivity to light in marine invertebrates when exposed to reduced oxygen availability. We found a 60-100% reduction in retinal responses in the larvae of cephalopods and crustaceans: the market squid (Doryteuthis opalescens), two-s...
Synaptic and dendritic mechanisms mediating direction-selective signaling in the retina
Understanding how information is integrated and processed in single neurons and small circuits is... more Understanding how information is integrated and processed in single neurons and small circuits is crucial for comprehending information processing in neural circuits, and will help elucidate the biophysical basis of cognition and cognitive dysfunction. The direction selective circuit of the retina has been an archetypical model for understanding how neural circuits process information in the brain since the direction selective ganglion cell (DSGC) was first discovered more than 40 years ago. Much progress has been made towards understanding how the direction selective circuits extracts information from moving stimuli on the retina and computes the direction of motion; however, several key questions have remained unanswered. While it had been shown that directional inhibitory inputs to the DSGC are crucial to forming directional responses, the mechanisms underlying the integration of synaptic inputs to produce directional spiking in the DSGC are unknown. Furthermore, the cell that mediates the crucial directional inhibition, the starburst amacrine cell (SBAC) has been identified, yet we do not have a complete understand how the SBAC generates this directional inhibitory signal. Using In-vitro patch-clamp recordings and two-photon calcium imaging, we show that DSGCs employ orthograde spikes originating in the dendrites to locally integrate excitatory and inhibitory synaptic inputs and signal the direction of motion, which enhances the directional selectivity of the circuit. This represents the first demonstration of how dendritic action potentials contribute to direction selectivity and more generally it is one of the first demonstrations of a
In optic neuropathies, including glaucoma, retinal ganglion cells (RGCs) die. Cell transplantatio... more In optic neuropathies, including glaucoma, retinal ganglion cells (RGCs) die. Cell transplantation and endogenous regeneration offer strategies for retinal repair, however, developmental programs required for this to succeed are incompletely understood. To address this, we explored cellular reprogramming with transcription factor (TF) regulators of RGC development which were integrated into human pluripotent stem cells (PSCs) as inducible gene cassettes. When the pioneer factor NEUROG2 was combined with RGC-expressed TFs (ATOH7, ISL1, and POU4F2) some conversion was observed and when pre-patterned by BMP inhibition, RGC-like induced neurons (RGC-iNs) were generated with high efficiency in just under a week. These exhibited transcriptional profiles that were reminiscent of RGCs and exhibited electrophysiological properties, including AMPA-mediated synaptic transmission. Additionally, we demonstrated that small molecule inhibitors of DLK/LZK and GCK-IV can block neuronal death in two ...
This Early Release article has been peer reviewed and accepted, but has not been through the comp... more This Early Release article has been peer reviewed and accepted, but has not been through the composition and copyediting processes.The final version may differ slightly in style or formatting and will contain links to any extended data. Alerts: Sign up at www.eneuro.org/alerts to receive customized email alerts when the fully formatted version of this article is published.
Vision restoration strategies aim to reestablish vision by replacing the function of lost photore... more Vision restoration strategies aim to reestablish vision by replacing the function of lost photoreceptors with optoelectronic hardware or through gene therapy. One complication to these approaches is that retinal circuitry undergoes remodeling after photoreceptor loss. Circuit remodeling following perturbation is ubiquitous in the nervous system and understanding these changes is crucial for treating neurodegeneration. Spontaneous oscillations that arise during retinal degeneration have been well-studied, however, other changes in the spatiotemporal processing of evoked and spontaneous activity have received less attention. Here we use subretinal electrical stimulation to measure the spatial and temporal spread of both spontaneous and evoked activity during retinal degeneration. We found that electrical stimulation synchronizes spontaneous oscillatory activity, over space and through time, thus leading to increased correlations in ganglion cell activity. Intriguingly, we found that spatial selectivity was maintained in rd10 retina for evoked responses, with spatial receptive fields comparable to wt retina. These findings indicate that different biophysical mechanisms are involved in mediating feed forward excitation, and the lateral spread of spontaneous activity in the rd10 retina, lending support toward the possibility of high-resolution vision restoration.
Ambroxol reduces SBAC AI, but TTX or cadmium does not
<p>A, (top row) shows the average IV relation measured 1.2 ms after the command step to vol... more <p>A, (top row) shows the average IV relation measured 1.2 ms after the command step to voltages between −100 and 0 mV, under control conditions (closed squares) and drug (open circles). Error bars show standard error. The linear portion of the IV has been subtracted leaving the negative slope portion of the IV (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0012447#s2" target="_blank">Methods</a>). The solid lines indicate the best-fit line between −40 and 0 mV. A shows 300 µM ambroxol hydrochloride (n = 3), B shows 500 nM TTX (n = 6), and C shows 25 µM cadmium (n = 5). B and C, (second and third rows) show the average filtered (25 Hz cutoff Gaussian) current traces in response to centrifugal and centripetal stimulation, respectively in control conditions (black trace), and drug treatment (gray trace). Left column shows 300 µM ambroxol hydrochloride (n = 3). Middle column shows. 500 nM TTX (n = 5). Right column shows 25 µM cadmium (n = 6).</p
The On-Off direction-selective ganglion cell (DSGC) in mammalian retinas responds most strongly t... more The On-Off direction-selective ganglion cell (DSGC) in mammalian retinas responds most strongly to a stimulus moving in a specific direction. The DSGC initiates spikes in its dendritic tree, which are thought to propagate to the soma with high probability. Both dendritic and somatic spikes in the DSGC display strong directional tuning, whereas somatic PSPs (postsynaptic potentials) are only weakly directional, indicating that spike generation includes marked enhancement of the directional signal. We used a realistic computational model based on anatomical and physiological measurements to determine the source of the enhancement. Our results indicate that the DSGC dendritic tree is partitioned into separate electrotonic regions, each summing its local excitatory and inhibitory synaptic inputs to initiate spikes. Within each local region the local spike threshold nonlinearly amplifies the preferred response over the null response on the basis of PSP amplitude. Using inhibitory conductances previously measured in DSGCs, the simulation results showed that inhibition is only sufficient to prevent spike initiation and cannot affect spike propagation. Therefore, inhibition will only act locally within the dendritic arbor. We identified the role of three mechanisms that generate directional selectivity (DS) in the local dendritic regions. First, a mechanism for DS intrinsic to the dendritic structure of the DSGC enhances DS on the null side of the cell's dendritic tree and weakens it on the preferred side. Second, spatially offset postsynaptic inhibition generates robust DS in the isolated dendritic tips but weak DS near the soma. Third, presynaptic DS is apparently necessary because it is more robust across the dendritic tree. The pre-and postsynaptic mechanisms together can overcome the local intrinsic DS. These local dendritic mechanisms can perform independent nonlinear computations to make a decision, and there could be analogous mechanisms within cortical circuitry.
Organized and quality-controlled CalCOFI data for CTD casts and bottle measurements from CalCOFI stations between La Jolla, California to Point Conception between 1984-2019
In this dataset, we analyzed daytime casts (09:00-16:00) of both discrete bottle data and continu... more In this dataset, we analyzed daytime casts (09:00-16:00) of both discrete bottle data and continuous CTD casts from CalCOFI stations restricted to an area from La Jolla, California to Point Conception and 215 km maximum offshore. This dataset has combined bottle and CTD casts to represent the date range 1984-2019. We used the oxygen and irradiance measurements to determine the visual luminoxyscape for each of the larval species. This range was bounded by the oxygen (partial pressure) where the pO2 would permit 50% minimum retinal function (V50; 13, 7.2, 10.2, and 6.8 kPa for larvae of 'Doryteuthis opalescens', 'Octopus bimaculatus', 'Metacarcinus gracilis', and 'Pleuroncodes planipes', respectively), and where there is sufficient irradiance for a visual response (0.0311 µmol photons m-2 s-1) for each species. Additionally, oxygen limits for metabolism were used to determine the depth of occurrence of the Pcrit (the oxygen below which the animal cannot...
Maximum depths of the visual luminoxyscape for four species of marine invertebrate larvae from CalCOFI stations between La Jolla, California to Point Conception between 1984-2019
In this dataset, the maximum depths of the visual luminoxyscape for four species of marine invert... more In this dataset, the maximum depths of the visual luminoxyscape for four species of marine invertebrate larvae were recorded. Data in this study are from CalCOFI stations restricted to an area from La Jolla, California to Point Conception and 215 kilometers maximum offshore (Station 60). We analyzed daytime casts (09:00-16:00) of both discrete bottle data and continuous CTD casts to represent the date range of 1984-2019 and used the oxygen and irradiance measurements to determine the visual luminoxyscape for each of the larval species. This range was bounded by the oxygen (partial pressure) where the pO2 would permit 50% minimum retinal function (V50; 13, 7.2, 10.2, and 6.8 kPa for larvae of 'Doryteuthis opalescens', 'Octopus bimaculatus', 'Metacarcinus gracilis', and 'Pleuroncodes planipes', respectively), and where there is sufficient irradiance for a visual response (0.0311 µmol photons m-2 s-1) for each species. Additionally, oxygen limits for met...
Photobehavior for octopus ('Octopus bimaculatus') and squid ('Doryteuthis opalescens') paralarvae during exposure to 9 light irradiance levels and 4 oxygen conditions in trials conducted in April of 2019
This dataset gives the results of photobehavior experiments under different oxygen conditions in ... more This dataset gives the results of photobehavior experiments under different oxygen conditions in larvae of the market squid ('Doryteuthis opalescens') and two-spot octopus ('Octopus bimaculatus'). Photobehavior experiments were conducted to determine whether the impairment of visual physiology observed in marine invertebrate larvae (McCormick et al., 2019) is subsequently affecting visual behavior in marine larvae.
Investigative Opthalmology & Visual Science, 2018
PURPOSE. For more than 20 years, there has been an international, multidisciplinary effort to dev... more PURPOSE. For more than 20 years, there has been an international, multidisciplinary effort to develop retinal prostheses to restore functional vision to patients blinded by retinal degeneration. We developed a novel subretinal prosthesis with 1512 optically addressed silicon nanowire photodiodes, which transduce incident light into an electrical stimulation of the remaining retinal circuitry. This study was conducted to evaluate the efficacy of optically driving the subretinal prosthesis to produce visual cortex activation via electrical stimulation of the retina. METHODS. We measured electrically evoked potential responses (EEPs) in rabbit visual cortex in response to illumination of the subretinal nanowire prosthesis with pulsed 852-nm infrared (IR) light. We compared the EEP responses to visually evoked potential responses (VEPs) to pulsed 532-nm visible light (positive control) and pulsed 852-nm IR light (negative control). RESULTS. Activating the devices with IR light produced EEP responses with a significantly higher trough-to-peak amplitude (54.17 6 33.4 lV) than IR light alone (24.07 6 22.1 lV) or background cortical activity (23.22 6 17.2 lV). EEP latencies were significantly faster than focal VEP latencies. Focal VEPs produced significantly higher amplitudes (94.88 6 43.3 lV) than EEPs. We also demonstrated how an electrode placed on the cornea can be used as a noninvasive method to monitor the function of the implant. CONCLUSIONS. These results show that subretinal electrical stimulation with nanowire electrodes can elicit EEPs in the visual cortex, providing evidence for the viability of a subretinal nanowire prosthetic approach for vision restoration.
For many animals, evolution has selected for complex visual systems despite the high energetic de... more For many animals, evolution has selected for complex visual systems despite the high energetic demands associated with maintaining eyes and their processing structures. The metabolic demands of visual systems therefore make them highly sensitive to fluctuations in available oxygen. In the marine environment, oxygen changes over daily, seasonal, and inter-annual time scales and there are large gradients of oxygen with depth. Vision is linked to survival in many marine animals, particularly among the crustaceans, cephalopods, and fish, and early life stages of these groups rely on vision for prey capture, predator detection, and their distribution in the water column. Using in vivo electroretinogram recordings, we show that there is a decrease in retinal sensitivity to light in marine invertebrates when exposed to reduced oxygen availability. We found a 60-100% reduction in retinal responses in the larvae of cephalopods and crustaceans: the market squid (Doryteuthis opalescens), two-s...
Synaptic and dendritic mechanisms mediating direction-selective signaling in the retina
Understanding how information is integrated and processed in single neurons and small circuits is... more Understanding how information is integrated and processed in single neurons and small circuits is crucial for comprehending information processing in neural circuits, and will help elucidate the biophysical basis of cognition and cognitive dysfunction. The direction selective circuit of the retina has been an archetypical model for understanding how neural circuits process information in the brain since the direction selective ganglion cell (DSGC) was first discovered more than 40 years ago. Much progress has been made towards understanding how the direction selective circuits extracts information from moving stimuli on the retina and computes the direction of motion; however, several key questions have remained unanswered. While it had been shown that directional inhibitory inputs to the DSGC are crucial to forming directional responses, the mechanisms underlying the integration of synaptic inputs to produce directional spiking in the DSGC are unknown. Furthermore, the cell that mediates the crucial directional inhibition, the starburst amacrine cell (SBAC) has been identified, yet we do not have a complete understand how the SBAC generates this directional inhibitory signal. Using In-vitro patch-clamp recordings and two-photon calcium imaging, we show that DSGCs employ orthograde spikes originating in the dendrites to locally integrate excitatory and inhibitory synaptic inputs and signal the direction of motion, which enhances the directional selectivity of the circuit. This represents the first demonstration of how dendritic action potentials contribute to direction selectivity and more generally it is one of the first demonstrations of a
Uploads
Papers by Nicholas Oesch