David J. Schulz - US grants

DESCRIPTION (provided by applicant): The nervous system faces an extremely difficult task: it must be flexible, both during development and in adult life, so that it can respond to a variety of environmental demands and produce adaptive behavior. At the same time, it must be stable, so that the neural circuits that produce behavior function throughout the lifetime of the animal, and so that stable changes produced by learning endure. We are only beginning to understand how neural networks strike a balance between altering individual neurons and synapses in the name of plasticity, while maintaining long-term stability in neural system function. This homeostatic plasticity of neural networks could play a major role in functioning nervous systems. I propose to use the crustacean stomatogastric ganglion (STG), a central pattern generator which is one of the most well characterized neural networks, to investigate the mechanisms underlying homeostatic plasticity in neural networks. One possible outcome of this research is that different mechanisms will be discovered within a network that produces the same behavioral output. If this is the case, this will be one of the first demonstrations of multiple convergent mechanisms for vital behavior in a neural network of any kind. This study also proposed to begin molecular analyses of homeostatic plasticity in the STG by performing the first microarray experiments on crustacean neural function.

Intellectual Merit. How different are neurons of the same class across animals, or within a given animal? How precisely must neurons constrain the values of their many membrane conductances for them to function correctly in the networks in which they are found? Theoretical work using computer models has argued that similar activity patterns, both at the single neuron level and at the network level, can arise from different combinations of correlated and compensating membrane and synaptic currents. Recent work has added biological evidence for this novel idea: levels of both membrane conductance and the expression of genes responsible for the proteins which allow current to flow across the cell membrane (ion channels) vary considerably in the same cell in different animals. These results suggest that different solutions exist to carry out the same function in neurons from different animals. The first goal of this proposal is to investigate the functional relationships between different ion channel proteins that lead to these various solutions. This will be accomplished by studying the expression of multiple ion channel genes simultaneously in single identified neurons in the stomatogastric ganglion of the crab, Cancer borealis. A detailed analysis of these expression patterns will determine relationships of channel expression and membrane currents in single cells. The ability of these conductances to balance and compensate for one another then will be tested using a combination of computational (theoretical) and biological experiments that alter endogenous membrane conductances and look for compensation by other currents. The second goal of this proposal is to understand the mechanisms of how consistent network output is maintained in the face of radically altered inputs. The rhythmic activity of the stomatogastric ganglion is dependent on descending input from other centers of the nervous system. The activity of the stomatogastric ganglion activity stops completely soon after these inputs are removed, but if one waits 2-3 days the rhythm recovers. This recovery may at least in part be the result of changes in the expression of ion channels that re-tune these networks to regain functional output. Experiments will be performed to investigate the underlying changes in neuronal properties that lead to this recovery of rhythm.

Broader Implications. Previous work suggests that individual neurons use a combination of tuning rules to find combinations of conductance densities that allow them adequate performance in the networks in which they are found. Such homeostatic plasticity recently has become an area of increased attention because it has implications for the function of neural networks at all levels of the nervous system. Incorporation of undergraduate students into the conceptual and experimental activities has been and will continue to be an integral part of Dr. Schulz' professional efforts.

Life Science Biological (61). An interdisciplinary team of faculty from Colleges of Engineering and of Arts and Sciences are collaborating to develop and teach a new course in computational neuroscience. The intellectual merit is to introduce more quantitative experience to students from biological and behavioral science while exposing students from quantitative sciences to some interesting questions and experimental techniques from the biological sciences. By collaborating, the faculty from both colleges will extend their expertise and be able to involve students with investigations of emerging questions in computational neuroscience. The new course represents a first step for defining a minor in computational neuroscience. For broader impact, a summer workshop is providing opportunities for other faculty to learn about the course so they can increase their own capacity to apply more mathematics within the biology curriculum at other institutions.

DESCRIPTION (provided by applicant): Homeostatic processes are involved in the maintenance of unique neuronal phenotypes and circuit function in the face of plastic changes or injury. Neuronal homeostasis is a result of orchestrated activity of multiple gene products and, evidently, some of these can be neuron-specific. Here, we propose to use one of the best described "simple" neural circuits, the pyloric central pattern generator (CPG) in the stomatogastric ganglion of the crab (Cancer borealis), to address how gene expression patterns differ across different neuron types and how changes in gene expression maintain circuit function in response to changes in activity and modulatory state. We will start with two synaptically coupled, unambiguously identifiable neuron types that are known to be crucial for the production of rhythmic motor patterns controlling foregut movements. We propose 2 conceptually overlapping aims that will lead to the unbiased genome-wide view of neuron identity and function: Aim 1) Using sequencing-by-ligation &pyrosequencing platforms adapted to the single cell level, we will tag and quantify the majority of gene products expressed in both cholinergic (PD) and glutamatergic (LP) motoneurons, and identify which genes are differentially expressed between them, and which genes are relevant to neuronal excitability and rhythmic properties of the CPG circuit. Aim 2) We will determine which genes are involved in homeostatic regulation and functional recovery of the stereotypic rhythmic properties of the circuit. The decentralization of the stomatogastric ganglion by deprivation of descending modulatory inputs results in silencing of pyloric motor activity. However, the isolated circuit is able to restore its excitability and rhythmic properties within 2-3 days. This recovery requires changes in gene expression that can be both cell-specific and "universal". We will profile the gene expression patterns at different time points during circuit silencing and recovery of functional activity. As a result, we will identify candidate genes crucial for such functional rescue of the endogenous motor rhythms. We also hypothesize that there are evolutionarily conserved subsets of genes involved in these recovery/homeostatic mechanisms that can be shared between arthropods and mammals. PUBLIC HEALTH RELEVANCE: Here, we will characterize molecular mechanisms of how individual neurons maintain their specific properties and connections to meet the functional demands in a neural circuit controlling rhythmic foregut movements. Specifically we will describe homeostatic processes underlying functional recovery in a neural circuit following silencing and deprivation of modulatory inputs. Although we mainly develop these approaches in a model Cancer preparation where identifiable and experimentally accessible neurons allow such a proof of principle, the methods and related biological questions are of broad, general importance and their applicability to mammals will be tested as the project develops.

This Improving Undergraduate STEM Education (IUSE) project from the University of Missouri - Columbia addresses the need for professional development for biological sciences faculty in the area of computational neuroscience. Computational neuroscience is an emerging area that studies brain function in terms of the information processing properties of the structures that make up the nervous system. It is an interdisciplinary science that links the diverse fields of neuroscience, cognitive science, and psychology with electrical engineering, computer science, mathematics, and physics. While leading biology educators call for strong interdisciplinary curricula that include physical science, information technology, and mathematics, many biological and behavioral scientists lack adequate training in the quantitative sciences, limiting their understanding and use of tools from this area. Similarly, engineers and quantitative scientists lack the training in biological sciences and neuroscience necessary to understand the details of the diverse systems in biology, and facilitate improved interactions with biologists to develop relevant and advanced computational tools.

The PI team is building on the knowledge they have gained through their prior NSF-funded work in the development of a computational neuroscience course, as well as on their seven years of experience providing a professional development workshop entitled "Hardware and Software Experiments to Teach Undergraduate Neuroscience." The workshops offered through this project are enhancing the teaching expertise of faculty in neuroscience at both 2- and 4-year institutions. Faculty-student teams participate in one-week workshops that include instructional methodologies emphasizing computation via free software experiments. Bringing this expertise back to their home institutions, workshop participants are increasing the number and diversity of undergraduates studying computational neuroscience. In addition, an intensive two-week curriculum development course will be offered to four faculty-student teams. These rigorous workshops provide training in mathematics, software, teaching, and development of curricular modules in computational neuroscience and include a one-year long support program for faculty-student teams as they develop and implement software modules into their curriculum. In the course of the project, the PI team is also augmenting our knowledge of obstacles to the implementation of effective instructional practices by carrying out studies to identify barriers to student learning and to faculty professional development and implementation of effective teaching practices. Understanding these impediments will facilitate development of strategies to overcome them so that effective instructional practices can be more widely adopted in the nation's institution of higher education.

This REU Site award to University of Missouri (MU) located Columbia, MO, will support the training of 12 students for 9 weeks during the summers of 2014- 2016. MU is the largest institution of higher learning in Missouri and the flagship campus of the University of Missouri System. The program offers a wide range of very exciting interdisciplinary projects in neuroscience, with both wet-lab and computational components. The projects are drawn from all levels in neuroscience (i.e., intracellular/cellular, systems and behavioral levels), with participating faculty coming from the colleges of arts & science, engineering, and veterinary medicine. Students will attend a weekly class on computational neuroscience, conduct lab research, and participate in various seminars and professional development workshops on topics such as responsible conduct in research, communication skills, career opportunities in industry and academia, and the graduate school application process. Each student will have the opportunity to write reports, give presentations and design and present a scientific poster. They will also be part of a group of 100+ undergraduate researchers from all over U.S. who participate each summer in a vibrant summer research program (http://undergradresearch.missouri.edu/). All participants will be recruited from outside MU, and selection will be based on academic record, research performance, and potential for research in neuroscience. Participant support during the REU experience will include a stipend, lodging, food, travel to and from the university, and funding for the research project.

Diversity strengthens the experience for all students. Therefore, the program will emphasize recruitment from institutions without advanced research programs, and from historically black and traditional women's colleges. The team will follow-up with students to determine their continued interest in the chosen academic area and their career paths. Information about the program will be assessed by various means, including use of a BIO/REU common assessment tool.

Students are required to be tracked after the program and must respond to an automatic email sent via the NSF reporting system. More information is available by visiting http://engineering.missouri.edu/neuroreu/, or by contacting the PI (Dr. Satish S. Nair at nairs@missouri.edu) or co-PI (Dr. David J. Schulz at schulzd@missouri.edu).

Rhythmic movements, such as heartbeat and locomotion, must be flexible to allow animals to alter their behavior in response to changing conditions. Rhythmic movements are controlled by networks of nerve cells that interact with one another to produce patterns of nerve impulses that drive appropriate muscle movements. To alter movement patterns, these neural networks rely on the actions of chemical compounds called neuromodulators; these compounds alter (modulate) the properties and interactions of the cells in the network, thereby enabling them to alter the pattern of movements that are generated by the network. Such alterations include, for example, changes in the speed of the resulting behavior or the coordination of muscles that control different portions of the movement pattern. There is evidence, however, that the extent to which similar networks can be altered ("modulatory capacity") varies among species. This project addresses two fundamental questions related to this variability in modulatory capacity: first, on an evolutionary timescale, what variables determine the extent to which networks can be modulated, and second, what factors/mechanisms underlie differences in modulatory capacity. In addition to addressing these questions using as exemplars the stomatogastric network and the cardiac network in a crab that eats only kelp versus a crab that eats many different kinds of food, the current project also prepares the next generation of scientists by (1) training high school students and undergraduates in a variety of research techniques, as well as in designing experiments and in analyzing and presenting data, and (2) providing continuity and potential expansion of the neuroscience component of a program that engages 7th grade Native Americans in Maine in science to enhance their educational aspirations and success in high school and beyond.

This project uses the stomatogastric and cardiac networks of closely related majoid crab species with vastly different dietary diversity to test the hypothesis that modulatory capacity is an important evolutionary substrate for diversity within any given behavior, and to ask what mechanisms underlie differences in modulatory capacity. Current data suggest that the stomatogastric network in Pugettia producta, a species that eats only kelp, is not responsive to many modulators that alter the network in another majoid, Libinia emarginata, which has a highly diverse diet. This project expands the number of neuromodulators tested, as well as examines and compares modulation of the cardiac network in the same species. The investigators use transcriptomics and mass spectrometry to identify native isoforms of peptide modulators in these majoids, then use physiological recordings to compare the modulatory capacities of the Pugettia and Libinia stomatogastric and cardiac neuromuscular systems. The prediction is that modulatory capacity in the Pugettia stomatogastric system is less than that of the opportunistic feeder, but that modulation in systems that are presumably subject to similar demands for flexibility, e.g., the cardiac neuromuscular system, is not markedly different. To examine the mechanisms that underlie changes in modulatory capacity, the investigators use transcriptomics, testing the hypothesis that the mechanism underlying decreased modulatory capacity of the Pugettia stomatogastric system is an absence or decreased abundance of receptors to those modulators. Transcriptomics results are confirmed using qRT-PCR and through expression of the receptors of the two species to compare relative binding affinities.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.