Remembering Immunity, Central regulation of peripheral immune processes
Thoughts and emotions can impact physiology. This connection is evident by the emergence of disease following stress, psychosomatic disorders, or recovery in response to placebo treatment. Nevertheless, this fundamental aspect of physiology remains largely unexplored. In this talk, I will focus on the brain’s involvement in regulating the peripheral immune response and explore the question of how the brain evaluates and represents the state of the immune system it regulates.
Roles of microglia in the pathogenesis of neurodegeneration
Microglia are implicated in a variety of functions in the central nervous system, ranging from shaping neural circuits during early brain development, to surveying the brain parenchyma, and providing trophic support to neurons across the entire lifespan. In neurodegeneration, microglia have been considered for long time mere bystanders, accompanying and worsening neuronal damage. However, recent evidence indicates that microglia can causally contribute to neurodegenerative diseases, and that their dysfunction can even be at the origin of the pathology. In fact, the broad range of physiological roles microglia play in the healthy brain suggest that faulty microglia can initiate neurodegeneration through several possible mechanisms. In particular, in this seminar, we will discuss how dysfunctional microglia can affect synaptic function leading to pathological synapse loss, thus putting microglia center stage in the pathogenesis of brain disorders.
STDP and the transfer of rhythmic signals in the brain
Rhythmic activity in the brain has been reported in relation to a wide range of cognitive processes. Changes in the rhythmic activity have been related to pathological states. These observations raise the question of the origin of these rhythms: can the mechanisms responsible for generation of these rhythms and that allow the propagation of the rhythmic signal be acquired via a process of learning? In my talk I will focus on spike timing dependent plasticity (STDP) and examine under what conditions this unsupervised learning rule can facilitate the propagation of rhythmic activity downstream in the central nervous system. Next, the I will apply the theory of STDP to the whisker system and demonstrate how STDP can shape the distribution of preferred phases of firing in a downstream population. Interestingly, in both these cases STDP dynamics does not relax to a fixed-point solution, rather the synaptic weights remain dynamic. Nevertheless, STDP allows for the system to retain its functionality in the face of continuous remodeling of the entire synaptic population.
Beyond energy - an unconventional role of mitochondria in cone photoreceptors
The long-term goal of my research is to study the mammalian retina as a model for the central nervous system (CNS) -- to understand how it functions in physiological conditions, how it is formed, how it breaks down in pathological conditions, and how it can be repaired. I have focused on two research themes: 1) Photoreceptor structure, synapse, circuits, and development, 2) Hibernation and metabolic adaptations in the retina and beyond. As the first neuron of the visual system, photoreceptors are vital for photoreception and transmission of visual signals. I am particularly interested in cone photoreceptors, as they mediate our daylight vision with high resolution color information. Diseases affecting cone photoreceptors compromise visual functions in the central macular area of the human retina and are thus most detrimental to our vision. However, because cones are much less abundant compared to rods in most mammals, they are less well studied. We have used the ground squirrel (GS) as a model system to study cone vision, taking advantage of their unique cone-dominant retina. In particular, we have focused on short-wavelength sensitive cones (S-cones), which are not only essential for color vision, but are also an important origin of signals for biological rhythm, mood and cognitive functions, and the growth of the eye during development. We are studying critical cone synaptic structures – synaptic ribbons, the synaptic connections of S-cones, and the development of S-cones with regard to their specific connections. These works will provide knowledge of normal retinal development and function, which can also be extended to the rest of CNS; for example, the mechanisms of synaptic targeting during development. In addition, such knowledge will benefit the development of optimal therapeutic strategies for regeneration and repair in cases of retinal degenerative disease. Many neurodegenerative diseases, including retinal diseases, are rooted in metabolic stress in neurons and/or glial cells. Using the same GS model, we aim to learn from this hibernating mammal, which possesses an amazing capability to adapt to the extreme metabolic conditions during hibernation. By exploring the mechanisms of such adaptation, we hope to discover novel therapeutic tactics for neurodegenerative diseases.
Microenvironment role in axonal regeneration- looking beyond the neurons
After an injury in the adult mammalian central nervous system, lesioned axons fail to regenerate. This failure to regenerate contrasts with the remarkable potential of axons to grow during embryonic development and after an injury in the peripheral nervous system. Peripheral sensory neurons with cell soma in dorsal root ganglia (DRG) switch to a regenerative state after nerve injury to enable axon regeneration and functional recovery. Decades of research have focused on the signaling pathways elicited by injury in sensory neurons and in Schwann cells that insulate axons as central mechanisms regulating nerve repair. However, neuronal microenvironment is far more complex and is composed of multiple cell types including endothelial, immune and glial cells. Whether the microenvironment surrounding neuronal soma contribute to the poor regenerative outcomes following central injuries remains largely unexplored. To answer this question, we performed a single cell transcriptional profiling of the DRG neuronal microenvironment response to peripheral and central injuries. In dissecting the roles of the microenvironment contribution, we have focused on a poorly studied population of Satellite Glial Cells (SGC) surrounding the neuronal cell soma. This study has uncovered a previously unknown role for SGC in nerve regeneration and defined SGC as transcriptionally distinct from Schwann cells while sharing similarities with astrocytes. Upon a peripheral injury, SGC contribute to axon regeneration via Fatty acid synthase (Fasn)-PPARα signaling pathway. Through repurposing fenofibrate, an FDA- approved PPARα agonist used for dyslipidemia treatment, we were able to rescue the impaired regeneration in mice lacking Fasn in SGC. Our analysis reveals that in response to central injuries, SGC do not activate the PPAR signaling pathway. However, induction of this pathway with fenofibrate treatment, rescued axon regeneration following an injury to the central nerves. Collectively, our results uncovered a previously unappreciated role of the neuronal microenvironment differential response in central and peripheral injuries.
Treating neurodevelopmental disorders: challenges, issues, problems, concerns, difficulties, harms, worries, doubts, but we need to start from somewhere
Neurodevelopmental disorders are a group of very heterogeneous diseases in which the development of the central nervous system is defective. In neurodevelopmental disorders defective brain development translates into aberrant brain function, which can manifest for example as impaired learning, motor function, or social interaction. Despites years of investigation in animal models and clinical research on neurodevelopmental disorders, there are currently no approved pharmacological treatments for core symptoms of the vast majority of them. Here, I will share some recent work (but also some apprehensions) of our laboratory on the development of strategies for the treatment of neurodevelopmental disorders, with a focus on Down syndrome.
Electrophysiology application for optic nerve and the central nervous system diseases
Electrophysiology of eye and visual pathway is useful tool in ophthalmology and neurology. It covers a few examinations to find out if defect of vision is peripheral or central. Visual evoked potentials (VEP) are most frequently used in neurology and neuroophthalmology. VEP are evoked by flash or pattern stimulations. The combination of these both examinations gives more information about the visual pathway. It is very important to remember that VEP originate in the retina and reflect its function as well. In many cases not only VEP but also electroretinography (ERG) is essential for diagnosis. The seminar presents basic electrophysiological procedures used for diagnosis and follow-up of optic neuropathies and some of central nervous system diseases which affect vision (mostly multiple sclerosis, CNS tumors, stroke, traumas, intracranial hypertension).
Cell Fate Determination in the Retina
The Cepko lab investigates the mechanisms that direct development of the central nervous system (CNS) of vertebrates, with a focus on the retina. These studies have revealed that the retina has distinct types of progenitor cells that are biased, or committed, to produce distinct types of daughter cells in terminal divisions. The gene regulatory networks that underlie these cell fate choices are being studied by analysis of both gene function and cis-regulatory networks. New methods that enable these studies have been developed, including high throughput enhancer assays and quantitative, inexpensive and sensitive multiplex in situ hybridization methods.