Merkin Center Research Grant Recipients
The Merkin Peripheral Neuropathy and Nerve Regeneration Center is proud to announce its latest grants, awarded to nine researchers. Learn more about the recipients and their work below:
Ashley Kalinski, Ph.D.
Assistant Professor, Ball State University
Topic: Elucidating the cell-autonomy of SARM1 for injury induced axon regeneration, nerve inflammation, and Schwann cell reprogramming
Ashley Kalinski, Ph.D. is a neuroscientist with expertise in neural repair and axon regeneration. Dr. Kalinski earned her Ph.D. from Drexel University and completed a postdoctoral fellowship at The University of Michigan Medical School. She is currently an Assistant Professor at Ball State University.
Under the direction of Jeffery Twiss MD., Ph.D., her graduate work focused on intrinsic mechanisms that support axon regeneration. There she identified that central axons can upregulate a regeneration program if provided a permissive growth environment. Building from this work, she characterized the microenvironment of the injured sciatic nerve during her postdoctoral work with Dr. Roman Giger, Ph.D. She identified that efferocytosis is a key mechanism for nerve debridement after injury. Dr. Kalinski opened her lab at Ball State University in 2020. Her lab aims to understand the relationship between immune cells, Schwann cells, and neurons following sciatic nerve injury. Further, they are interested in how molecules like SARM1 and DLK are involved in the entire peripheral nerve injury signaling cascade.
Axons of the murine peripheral nervous system spontaneously regenerate after injury. This is due to a combination of the unique microenvironment of the nerve and the ability of the neurons to induce a transcriptional regeneration program. Following nerve injury, the proximal stump regenerates while the distal stump undergoes Wallerian degeneration. This degeneration program is important to remove the inhibitory debris and is mediated by immune cells and resident Schwann cells.
Activation of SARM1 in the distal stump is required for Wallerian degeneration. However, it is unknown whether this is solely due to neuronal SARM1, or if SARM1 expression in other cell types is also required. Currently, only a germline Sarm1 knockout mouse exists. As SARM1 inhibitors are a promising therapeutic target for neurodegenerative diseases and chemotherapy induced neuropathy, it is important to understand the full role of SARM1 in the degeneration process.
The objectives of this project are to generate Sarm1 conditional knockout mice and compare injury signaling processes to the germline Sarm1 knockout. We will generate 3 conditional knockout mice in neurons, Schwann cells, and macrophages, as all cell types play an integral role in the injury response. We will assess injury signaling after peripheral nerve injury by western blotting, immunostaining, and flow cytometry. Our study will reveal the cell-autonomy of SARM1 for injury induced axon degeneration, nerve inflammation, and Schwann cell reprogramming in the injured mammalian PNS in vivo.
Atul Rawat, Ph.D.
Post-Doctoral Research Fellow, Johns Hopkins University
Topic: Modulating macrophage phenotype in peripheral nerve injury to accelerate nerve regeneration and functional recovery
Atul Rawat, Ph.D., is a postdoc research fellow in Morrison Lab at Department of Neurology, School of Medicine, Johns Hopkins University. His research work focuses on modulating macrophage plasticity and their role in nerve repair in peripheral nerve injury models using lipid nanoparticles (LNP). He works on synthesis and characterization of LNPs and testing them in-vitro and in-vivo in control and transgenic animals.
He received his M.S. and Ph.D. from Babasaheb Bhimrao Ambedkar University, Lucknow, India in Biotechnology. His Ph.D. work was on identification and characterization of early diagnostics or discriminatory biomarker of disease like acute myocardial infraction, Takayasu arteritis, breast cancer, drug formulation and toxicity, using NMR based metabolomics. His first visiting research associate position at Indiana-Purdue University in Roy Lab provided the opportunity to train in lipid nanoparticles engineering and targeting to specific cells like macrophage.
In the pharmaceutical industry, LNPs have emerged as attractive carriers for various therapeutic agents. LNP are already being clinically used for many applications, such as cancer therapy and vaccine. Although there is a growing body of literature on tissue-specific liposomes, suitable formulations to target peripheral nervous system (PNS) cells are absent. LNPs offer great potential as neural cells are targets for drug delivery in multiple CNS disorders such as Alzheimer’s disease, Parkinson’s disease, ischemic stroke, peripheral nerve injuries, and neuropathic and inflammatory pain.
Recent work from Morrison lab highlights the imperative role of macrophage MCT1 in nerve regeneration in a sciatic nerve crush injury (SNCI) model. The proposed study involves developing and characterizing a novel lipid combination that permits the efficient and selective delivery of plasmid DNA (pDNA) to macrophages in the injured nerves. Using a combination of cationic and neutral cationic lipids, a polymer surfactant, and cholesterol, along with a targeting ligand to enhance uptake by targeted cells i.e., macrophages. Thus, macrophage targeted LNP with cargo pDNA (MCT1) provides a viable and non-invasive approach to exogenously upregulate MCT1 in macrophage at the injury site in the nerve. LNP’s and their targeted delivery to facilitate nerve regeneration represent an exciting new phase in medicine.
Baohan Pan, M.D., Ph.D.
Assistant Professor, Johns Hopkins University
Topic: Cutaneous Sensory Innervation in Human and Mouse and Its Implications in Neuropathic Pain
Dr. Baohan Pan is an Assistant Professor at the Department of Neurology, Johns Hopkins School of Medicine. His research interests include peripheral neuropathy, neuropathic pain and itch, mechanisms of peripheral nerve degeneration and regeneration.
Peripheral neuropathies and neuropathic pain are frequent debilitating disorders linked to degeneration of peripheral sensory nerves. To gain insight into mechanisms underlying human neuropathies, numerous mouse models, induced either by chemical compounds, physical injury, or genetic engineering, have been developed extensively. To enhance the translational value of the basic research knowledge carried out on mouse models into novel therapies for humans, we first need to better understand differences and similarities in skin nerves between the two species. Therefore, we will carry out a comprehensive comparative study of cutaneous somatosensory innervation in both hairy and glabrous skin between human and mouse which would provide critical insights in our understanding of the similarities and differences between the species and may help find new biomarkers.
Moreover, more than 25 % of diabetes patients suffer neuropathic pain. The mechanisms contributing to the development of neuropathic pain remain unclear. Therefore, we also will explore the potential differences in nerve fibers and their distributions between diabetic neuropathy patients with pain and those without pain. Findings from this study may provide new insight in the pathophysiological mechanisms of pain in diabetes and open the research towards new therapeutic targets.
Christopher Cashman, Ph.D.
Fellow, Mass General Brigham
Topic: Mitochondrial genome mutations and respiratory dysregulation as effectors of diabetic neuropathy
Dr. Christopher Cashman is excited to join the Merkin Peripheral Neuropathy and Nerve Regeneration Center community with his project investigating acquired mitochondrial mutations in diabetic neuropathy. Dr. Cashman received his B.A. in biochemistry from Bowdoin College in 2007, then completed his M.D. and Ph.D. in neuroscience at The Johns Hopkins School of Medicine. At Hopkins, Dr. Cashman worked in Dr. Ahmet Höke’s laboratory studying the ability of derived motor neurons to promote regeneration in chronically denervated nerves.
After his time at Johns Hopkins, Dr. Cashman completed a medicine internship at Brigham and Women’s Hospital and neurology residency at Mass General Brigham/Harvard Medical School. He is currently a neuromuscular fellow at Mass General Brigham and a postdoctoral researcher in the laboratory of Dr. Craig Blackstone investigating acquired mitochondrial dysfunction in neuropathies. Dr. Cashman will continue this work next year as he joins the faculty of Mass General Brigham as a staff physician scientist.
Diabetic neuropathy affects millions of Americans and is characterized as a length-dependent polyneuropathy. The mechanism of this length dependency remains unknown, but an increasing understanding of the mechanism of Wallerian degeneration suggests energetic collapse may be central to this process. If this is the case, then a length dependent neuropathy could develop if the distal axon is more susceptible to respiratory dysregulation. This susceptibility, we believe, is due to the mitochondria in the distal, versus the proximal, axon being older with a greater burden of damage to its DNA and proteins. Diabetes, for example, may exacerbate this aging phenomenon and thereby lead to a length dependent neuropathy. This aging is expected to manifest as DNA mutations and protein modifications. We hypothesize that in a rodent model of non-insulin dependent diabetic neuropathy, mitochondrial aging is increased, such that there will be a higher mitochondrial DNA mutation burden in the distal aspect of a nerve as compared to control animals, and the distal mitochondria will have decreased respiratory capacity than their more proximal counterparts. To this end, whole mitochondrial DNA will be sequenced in the proximal and distal aspect of sciatic and caudal nerves in diabetic and control rats, and the mitochondria will be isolated for measures of respiratory efficiency. Mitochondrial protein lysate will also be isolated for proteomics analysis to identify differences in protein modification and expression between the proximal and distal aspects of a nerve, with more heterogeneity predicted in the diabetic samples.
Hyun Sung, Ph.D.
Neurobiologist, Johns Hopkins University
Topic: Deciphering the role of autophagy in the pathogenesis of peripheral neuropathy
Dr. Hyun Sung is a cellular neurobiologist who has studied the in vivo organelle dynamics in nervous systems. He specializes in axonal transport, mitochondrial life cycle, endoplasmic reticulum dynamics and autophagy process in multiple neuronal types.
Dr. Sung earned his bachelor’s and master’s degree in Biological Sciences from the Hanyang University (Seoul, Korea) and his Ph.D. in Cellular Neurobiology from the Purdue University (West Lafayette, IN). At Purdue, he completed his dissertation with Dr. Peter Hollenbeck studying axonal transport of mitochondria and its impact on mitochondrial quality control in the Drosophila larval motor neurons.
He joined the Johns Hopkins University as a postdoctoral fellow in the laboratory of Dr. Thomas Lloyd in 2016. As a postdoctoral fellow, he has performed live imaging of axonal and synaptic organelles in Drosophila models of multiple neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD) and Charcot-Marie-Tooth (CMT) disease.
In 2022, he was promoted to a research associate in the Department of Neurology, and his current work is focused on understanding the mechanisms of autophagy disruption in Drosophila models of C9orf72-mediated ALS/FTD. He is particularly interested in organelle dynamics underlying innate cellular physiology, with a specific focus on neuronal pathologies.
Autophagy is a major pathway to remove dysfunctional organelles and protein aggregates, and increasing evidence suggests that defects in autophagy are associated with multiple peripheral neuropathies including Charcot-Marie-Tooth (CMT) disease. In this project, our goal is to better understand the mechanisms of autophagy in peripheral nerves, and how the autophagy process is altered in CMT disease.
By using Drosophila as a model system, we will test autophagy alterations in CMT disease including CMT2C and CMT4J, while we explore genetic targets in neuronal autophagy; 1) determining the cause and consequence of altered autophagy in Drosophila CMT models, 2) identifying genetic modifiers of autophagy in Drosophila motor neurons.
Our experimental activities will include Drosophila larval dissection for observing neuronal autophagosomes, Drosophila larval in vivo assay for monitoring organelle dynamics in autophagy processes, and Drosophila genetic screening for identifying novel genetic regulators of neuronal autophagy.
Our strategies include quantifying the number of autophagosomes in Drosophila larval motor and sensory neurons, and monitoring of multiple organelle dynamics, including autophagosomes, lysosomes and endoplasmic reticulum, to define underlying cellular mechanisms in autophagy. At the same time, we will perform a forward genetic screen by scoring autophagosomes in synaptic terminal boutons to find key genetic regulators of neuronal autophagy initiation.
We anticipate that our studies will define genetic and cellular mechanisms of axonal autophagy, and determine if autophagy disruptions are implicated in the pathogenesis of CMT disease.
Masnsen Cherief, Ph.D.
Post-Doctoral Research Fellow, Johns Hopkins University
Topic: Preventing diabetic bone disease using a neuroprotective agent
Throughout my academic training and research in Algeria and France, I had the chance to develop my scientific background in several disciplines including molecular biology, histology, microscopy, and radiography. My engineering training in Algeria was oriented toward food industry.
I moved to Baltimore in 2019, As a postdoctoral fellow at the James lab, my research interests include perivascular mesenchymal progenitor cells for osteoarthritis repair and the study of the peripheral nervous system and its importance in bone and tendon tissue repair.
We recently described two perivascular mesenchymal cells subtypes (Pdgfrα+ and Pdgfrβ+) that improved murine osteoarthritis. Pdgfrα+ and Pdgfrβ+ cell preparations improved metrics of cartilage degradation and reduced markers of chondrocyte hypertrophy in a mice osteoarthritis model (5).
One of my interests, is studying the role of peripheral nervous system in bone and tendon. I'm working on developing a better understanding to the link between diabetic neuropathy and diabetic bone disease using omnics, histology and µCT data.
Diabetic neuropathy afflicts skeletal nerves, which is hypothesized to contribute to diabetic bone disease. In this project, we will use the novel neuroprotectant EQ-6, to prevent diabetic neuropathy and diabetic bone disease.
We will study two diabetes models: Streptozotocin (STZ) induced Type 1 diabetes, and high fat diet (HFD) induced insulin resistance
We aim to determine to which extent EQ-6 can prevent skeletal neuropathy and improve bone fragility in diabetic models. ScRNA-Seq will examine to which extent EQ-6 modifies the skeletal cell transcriptome and neuro-skeletal interactome in diabetic conditions, with a focus on cellular proliferation and BMP signaling activity restorations.
Pabitra Sahoo, Ph.D.
Research Assistant Professor, University of South Carolina
Topic: Establishing the kinetics for failure of axonal protein synthesis in chronic nerve injury
Pabi Sahoo, Ph.D., is a molecular neurobiologist with expertise in neural repair mechanisms. He specializes in axonal protein synthesis, neuronal mRNA storage mechanisms, and nerve regeneration. Dr. Sahoo earned his Ph.D. from the National Centre for Cell Science, University of Pune, India. He then came to the University of South Carolina for his Postdoctoral fellowship under the mentorship of Prof. Jeff Twiss. Currently, Dr. Sahoo is appointed as a Research Assistant Professor at the University of South Carolina.
Dr. Sahoo’s research focuses on deciphering the functions of stress granules (SGs) formed under physiological conditions during neuronal development, nerve repair, and pathological conditions using a combination of genetic, molecular, and cell biological tools.
Peripheral nerves spontaneously regenerate after injury but the capacity for these decreases with increasing intervals after injury. Axonal protein synthesis has been consistently shown to promote peripheral nerve regeneration. My work has focused on understanding how axonal protein synthesis is regulated and I found that the core stress granule (SG) protein RasGAP SH3- domain Binding Protein 1 (G3BP1) undergoes liquid-liquid phase separation (LLPS) in axons to form granules and sequester specific axonal mRNAs away from translation.
Axonal SGs inhibit axon growth by decreasing availability of regeneration-associated gene mRNAs for translation. I designed a cell permeable peptide-based strategy using amino acids 190-208 of G3BP1 that triggers axonal SG disassembly, increases axonal protein synthesis, and increases axon growth. This peptide accelerates regeneration and target re-innervation after acute sciatic nerve injury (2 d after injury), but not in chronically injured nerves (i.e.,16 weeks post injury).
Based on these observations, I hypothesize that regeneration failure after chronic nerve injury results from decrease in protein synthetic capacity of the chronically injured axons (decreased transport, granules refractory to disassembly, &/or failed translational activation). In this proposal, I will test this hypothesis with the following specific aims: Aim 1: Does chronic injury inhibit axonal mRNA transport? Aim 2: Does chronic injury leads to formation of refractory G3BP1 aggregates? Aim 3: Does chronic injury inhibit axonal protein synthesis?
Qin Zheng, M.D., Ph.D.
Instructor, Johns Hopkins University
Topic: In-vivo characterization of chemotherapy-induced neuropathy using large scale calcium imaging
Qin Zheng, M.D., Ph.D., received her medical degree and Ph.D. degree in China. Now as an instructor in the Department of Anesthesiology and Critical Care Medicine at John Hopkins.
While in graduate school, using rat as a genetic model, she characterized the intrinsic electrophysiological properties and gene expression patterns of primary sensory neurons in bone cancer and identified KCNQ (Kv7) K+ channel as a critical factor in the development of bone cancer pain.
She obtained postdoctoral training with Dr. Xinzhong Dong at Johns Hopkins University. She made a complete change in her approach and developed a new imaging system to visualize large populations of primary sensory neurons activities in vivo in the dorsal root ganglions (DRGs) of live mice. Using this technology, she identified a novel gap-junction mediated neuronal coupling phenomenon following tissue injury, and observed a distinct form of abnormal spontaneous activity in neuropathic pain: clusters of adjacent DRG neurons firing synchronously due to ectopic sympathetic innervation of DRG following nerve injury.
Throughout her academic career, she has received rigorous training on a variety of neuroscientific techniques including rodent behavior, electrophysiology, dorsal root ganglion and spinal cord in vivo imaging and molecular biology. Her research aims to utilize high throughput in vivo imaging to elucidate the neuronal and non-neuronal mechanisms of neuropathy, and to develop new strategies for the treatment of neuropathy and chronic pain.
Chemotherapy-induced peripheral neuropathy (CIPN) is a common and debilitating side effect of cancer treatments that affects millions of patients each year. Chemotherapeutic agents such as paclitaxel can cause severe peripheral neural degeneration and severe chronic pain. Unfortunately, basic research using traditional cell culture systems and single unit electrophysiological methods have not been able to uncover the full pathological mechanisms of CIPN, and to date, there are no effective treatment for this painful disease.
In the proposed project, we aim to utilize a novel in vivo imaging technology developed in our lab to systematically probe the neurological defects induced by CIPN. Using genetically encoded calcium indicator GCamp6, we have been able to visualize the activity of over 1600 dorsal root ganglion (DRG) neurons simultaneously. We plan to 1) comprehensively characterize the excitability of all neurons in CIPN-affected DRGs, 2) identify the specific cell types that suffer degeneration, and 3) use unbiased transcriptomics to determine the molecular mechanisms underlying CIPN. Preliminary results show that medium-sized DRG sensory neurons are significantly over-activated in CIPN and might be causal to chronic pain. Successful completion of this project will provide fundamental knowledge about the pathology of CIPN and potentially open novel therapeutic avenues.
Simone Thomas, M.S.
Research Associate, Johns Hopkins University
Topic: Chemotherapy-Induced Peripheral Neuropathy (CIPN) Assessment
Simone Thomas received her MS degree in Animal Science from the University of Hohenheim, Stuttgart, Germany. She started her professional career working as a scientific collaborator at the German Aerospace Center in Cologne and later worked in the human life sciences programs at the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) before joining the Neurology department at Johns Hopkins.
Her research includes peripheral neuropathies caused by different underlying etiologies, including metabolic syndrome and neurotoxic chemotherapy agents. She is the Principal Investigator in several clinical natural history studies to better understand peripheral neuropathies. She is also involved in several efforts to develop better outcome measures to accurately assess efficacy of treatment in different neuromuscular conditions including polyneuropathies and myopathies. She is currently chairing the IMACS special interest group to develop better patient reported outcome measures for Inclusion Body Myositis (IBM).
International Chemotherapy-Induced Neurotoxicity (CIPN) Assessment and Validation Study (ICAVS)” is the first prospective study about CIPN that enrolls patients before they receive their first cycle of chemotherapy. The Merkin PNNR Center Grant will provide funding to expand the original ICAVS protocol and add full neurological examinations at all study visits and Nerve Conduction studies, blood collection and biobanking at selected visits, including PBMC’s. The data from this study will be used to develop biomarkers to predict who develops CIPN and examine genetic risk factors. Furthermore, PBMCs can be used to derive induced pluripotent stem cells (iPSCs) to develop in vitro models of CIPN using human cells to better understand mechanisms of CIPN and validate drug candidates to prevent it.
- Sarah Berth, M.D., Ph.D.
Topic: Genetic Screen for Axonal Degeneration Modifiers
- Aysel Fisgin, Ph.D.
Topic: MAP4K4 Inhibition to Prevent CIPN
- Sang-Min Jeon, Ph.D.
Topic: Sprouting Mediated Skin Reinnervation
- Ying Liu, M.D., Ph.D.
Topic: Evaluating the effect of SARM1 deficiency on peripheral neuropathy in db/db mouse model of type 2 diabetes.
- Brett McCray, M.D., Ph.D.
Topic: TRVP4 in Nerve Injury
- Kathryn Moss, Ph.D.
Topic: Development of a CMT1A/CIPN Mouse Model
- Bipasha Mukherjee-Clavin, M.D., Ph.D.
- Seong-Hyun Park, Ph.D.
Topic: CMT PNSorganoid Model
- Sami Tuffaha, M.D.
Topic: Gene Expression Changes with Schwann Cell Denervation
- Eric Villalón Landeros, Ph.D.
Topic: DRG Neuroproteasome Signaling Peptides