Basic Life Science Research Scientist, Molecular & Cellular Physiology
Honors & Awards
Pediatric Research Award, Lucile Packard Foundation for Children's Health (2011)
Developmental Neuroscience, Weston Havens Foundation (2012)
Ph.D., Semmelweis Medical University, Clinical Neurosciences (2010)
M.S., Budapest University of Technology and Economics, Bioengineering (2007)
Current Research and Scholarly Interests
My research is focusing on correlating physiological changes of brain micro-circuits with resulting anatomical changes. Currently I am studying how the induction of synaptic plasticity results in a change in the number of synapses made between a pair of neurons, and whether sub-synaptic receptor localization can account for the mechanisms of certain synaptic states. I am testing two competing hypotheses: whether 1) certain subtypes of glutamate receptors are sorted based on interactions with the unique amino acid sequence of each subunit's C-terminal tail (tail-sorting model); or 2) long term potentiation/ depression results from changes in postsynaptic density and/or the volume of the postsynaptic spine (indiscriminate model). Understanding these processes will help address a variety of issues in normal and pathological brain functions, including the basic molecular and cellular mechanisms of learning and memory formation.
In another ongoing project, I am characterizing the myelination of inhibitory neurons and explore its functional significance. Only some neuron types form myelinated axons, for example cortical pyramidal cells, cerebellar Purkinje cells, and parvalbumin-expressing subclass of basket interneurons. Surprisingly little is known about the structural and molecular organization of myelin on different neuron types. Our preliminary data reveal that there are significant differences between the myelin of inhibitory and excitatory axons in cortex. My future studies will further compare molecular and structural features of myelinated axons of PV basket cells and excitatory neurons in cortical gray matter, as well as their involvement in cortical plasticity and pathology (multiple sclerosis model).
Array tomography of physiologically-characterized CNS synapses
JOURNAL OF NEUROSCIENCE METHODS
2016; 268: 43-52
The ability to correlate plastic changes in synaptic physiology with changes in synaptic anatomy has been very limited in the central nervous system because of shortcomings in existing methods for recording the activity of specific CNS synapses and then identifying and studying the same individual synapses on an anatomical level.We introduce here a novel approach that combines two existing methods: paired neuron electrophysiological recording and array tomography, allowing for the detailed molecular and anatomical study of synapses with known physiological properties.The complete mapping of a neuronal pair allows determining the exact number of synapses in the pair and their location. We have found that the majority of close appositions between the presynaptic axon and the postsynaptic dendrite in the pair contain synaptic specializations. The average release probability of the synapses between the two neurons in the pair is low, below 0.2, consistent with previous studies of these connections. Other questions, such as receptor distribution within synapses, can be addressed more efficiently by identifying only a subset of synapses using targeted partial reconstructions. In addition, time sensitive events can be captured with fast chemical fixation.Compared to existing methods, the present approach is the only one that can provide detailed molecular and anatomical information of electrophysiologically-characterized individual synapses.This method will allow for addressing specific questions about the properties of identified CNS synapses, even when they are buried within a cloud of millions of other brain circuit elements.
View details for DOI 10.1016/j.jneumeth.2016.04.017
View details for Web of Science ID 000379104400006
View details for PubMedID 27141856
Paired Whole Cell Recordings in Organotypic Hippocampal Slices
JOVE-JOURNAL OF VISUALIZED EXPERIMENTS
Pair recordings involve simultaneous whole cell patch clamp recordings from two synaptically connected neurons, enabling not only direct electrophysiological characterization of the synaptic connections between individual neurons, but also pharmacological manipulation of either the presynaptic or the postsynaptic neuron. When carried out in organotypic hippocampal slice cultures, the probability that two neurons are synaptically connected is significantly increased. This preparation readily enables identification of cell types, and the neurons maintain their morphology and properties of synaptic function similar to that in native brain tissue. A major advantage of paired whole cell recordings is the highly precise information it can provide on the properties of synaptic transmission and plasticity that are not possible with other more crude techniques utilizing extracellular axonal stimulation. Paired whole cell recordings are often perceived as too challenging to perform. While there are challenging aspects to this technique, paired recordings can be performed by anyone trained in whole cell patch clamping provided specific hardware and methodological criteria are followed. The probability of attaining synaptically connected paired recordings significantly increases with healthy organotypic slices and stable micromanipulation allowing independent attainment of pre- and postsynaptic whole cell recordings. While CA3-CA3 pyramidal cell pairs are most widely used in the organotypic slice hippocampal preparation, this technique has also been successful in CA3-CA1 pairs and can be adapted to any neurons that are synaptically connected in the same slice preparation. In this manuscript we provide the detailed methodology and requirements for establishing this technique in any laboratory equipped for electrophysiology.
View details for DOI 10.3791/51958
View details for Web of Science ID 000349301100073
View details for PubMedID 25285945
PLACENTAL HORMONE CONTRIBUTION TO FETAL BRAIN DAMAGE
Joint Meeting of the International-Federation-of-Placenta-Associations (IFPA) and European-Placenta-Group (EPG)
W B SAUNDERS CO LTD. 2014: A52–A52
View details for Web of Science ID 000342961400184
Integration of neuronally predifferentiated human dental pulp stem cells into rat brain in vivo
2011; 59 (3): 371-381
Pluripotency and their neural crest origin make dental pulp stem cells (DPSCs) an attractive donor source for neuronal cell replacement. Despite recent encouraging results in this field, little is known about the integration of transplanted DPSC derived neuronal pecursors into the central nervous system. To address this issue, neuronally predifferentiated DPSCs, labeled with a vital cell dye Vybrant DiD were introduced into postnatal rat brain. DPSCs were transplanted into the cerebrospinal fluid of 3-day-old male Wistar rats. Cortical lesion was induced by touching a cold (-60°C) metal stamp to the calvaria over the forelimb motor cortex. Four weeks later cell localization was detected by fluorescent microscopy and neuronal cell markers were studied by immunohistochemistry. To investigate electrophysiological properties of engrafted, fluorescently labeled DPSCs, 300 μm-thick horizontal brain slices were prepared and the presence of voltage-dependent sodium and potassium channels were recorded by patch clamping. Predifferentiated donor DPSCs injected into the cerebrospinal fluid of newborn rats migrated as single cells into a variety of brain regions. Most of the cells were localized in the normal neural progenitor zones of the brain, the subventricular zone (SVZ), subgranular zone (SGZ) and subcallosal zone (SCZ). Immunohistochemical analysis revealed that transplanted DPSCs expressed the early neuronal marker N-tubulin, the neuronal specific intermediate filament protein NF-M, the postmitotic neuronal marker NeuN, and glial GFAP. Moreover, the cells displayed TTX sensitive voltage dependent (VD) sodium currents (I(Na)) and TEA sensitive delayed rectifier potassium currents (K(DR)). Four weeks after injury, fluorescently labeled cells were detected in the lesioned cortex. Neurospecific marker expression was increased in DPSCs found in the area of the cortical lesions compared to that in fluorescent cells of uninjured brain. TTX sensitive VD sodium currents and TEA sensitive K(DR) significantly increased in labeled cells of the cortically injured area. In conclusion, our data demonstrate that engrafted DPSC-derived cells integrate into the host brain and show neuronal properties not only by expressing neuron-specific markers but also by exhibiting voltage dependent sodium and potassium channels. This proof of concept study reveals that predifferentiated hDPSCs may serve as useful sources of neuro- and gliogenesis in vivo, especially when the brain is injured.
View details for DOI 10.1016/j.neuint.2011.01.006
View details for Web of Science ID 000295182800008
View details for PubMedID 21219952
New Therapeutic Targets in Ulcerative Colitis: The Importance of Ion Transporters in the Human Colon
INFLAMMATORY BOWEL DISEASES
2011; 17 (4): 884-898
The absorption of water and ions (especially Na(+) and Cl(-)) is an important function of colonic epithelial cells in both physiological and pathophysiological conditions. Despite the comprehensive animal studies, there are only scarce available data on the ion transporter activities of the normal and inflamed human colon.In this study, 128 healthy controls and 69 patients suffering from ulcerative colitis (UC) were involved. We investigated the expressional and functional characteristics of the Na(+)/H(+) exchangers (NHE) 1-3, the epithelial sodium channel (ENaC), and the SLC26A3 Cl(-)/HCO 3- exchanger downregulated in adenoma (DRA) in primary colonic crypts isolated from human biopsy and surgical samples using microfluorometry, patch clamp, and real-time reverse-transcription polymerase chain reaction (RT-PCR) techniques.Data collected from colonic crypts showed that the activities of electroneutral (via NHE3) and the electrogenic Na(+) absorption (via ENaC) are in inverse ratio to each other in the proximal and distal colon. We found no significant differences in the activity of NHE2 in different segments of the colon. Surface cell Cl(-)/HCO 3- exchange is more active in the distal part of the colon. Importantly, both sodium and chloride absorptions are damaged in UC, whereas NHE1, which has been shown to promote immune response, is upregulated by 6-fold.These results open up new therapeutic targets in UC.
View details for DOI 10.1002/ibd.21432
View details for Web of Science ID 000288173500002
View details for PubMedID 20722063
Simultaneous PKC and cAMP activation induces differentiation of human dental pulp stem cells into functionally active neurons
2009; 55 (5): 323-332
The plasticity of dental pulp stem cells (DPSCs) has been demonstrated by several studies showing that they appear to self-maintain through several passages, giving rise to a variety of cells. The aim of the present study was to differentiate DPSCs to mature neuronal cells showing functional evidence of voltage gated ion channel activities in vitro. First, DPSC cultures were seeded on poly-l-lysine coated surfaces and pretreated for 48h with a medium containing basic fibroblast growth factor and the demethylating agent 5-azacytidine. Then neural induction was performed by the simultaneous activation of protein kinase C and the cyclic adenosine monophosphate pathway. Finally, maturation of the induced cells was achieved by continuous treatment with neurotrophin-3, dibutyryl cyclic AMP, and other supplementary components. Non-induced DPSCs already expressed vimentin, nestin, N-tubulin, neurogenin-2 and neurofilament-M. The inductive treatment resulted in decreased vimentin, nestin, N-tubulin and increased neurogenin-2, neuron-specific enolase, neurofilament-M and glial fibrillary acidic protein expression. By the end of the maturation period, all investigated genes were expressed at higher levels than in undifferentiated controls except vimentin and nestin. Patch clamp analysis revealed the functional activity of both voltage-dependent sodium and potassium channels in the differentiated cells. Our results demonstrate that although most surviving cells show neuronal morphology and express neuronal markers, there is a functional heterogeneity among the differentiated cells obtained by the in vitro differentiation protocol described herein. Nevertheless, this study clearly indicates that the dental pulp contains a cell population that is capable of neural commitment by our three step neuroinductive protocol.
View details for DOI 10.1016/j.neuint.2009.03.017
View details for Web of Science ID 000268372000009
View details for PubMedID 19576521