Dr. Chang is the director of the Comparative Neuromechanics Laboratory in the School of Applied Physiology. His research program focuses on trying to understand how animals move through and interact with their environment. He integrates approaches and techniques from both biomechanics and neurophysiology to elucidate both passive mechanical and active neural mechanisms that control limbed locomotion in humans and other terrestrial vertebrates. This multidisciplinary approach allows him to test hypotheses about the basic design and function of the locomotor apparatus throughout a variety of conditions. His current goal is to understand the extent to which muscular reflexes can influence limb coordination during locomotion and how global limb control strategies may be affected by sensorimotor perturbations.
Bacteria and Archaea constitute the overwhelming majority of genetic and metabolic diversity on this planet. To understand these organisms in their native habitats, environmental microbiologists are tasked with two fundamental questions. First, how do ecological and evolutionary processes (e.g., symbiosis, competition, recombination, natural selection) create and structure genetic diversity? Second, how is this genetic diversity linked to the diverse biogeochemical functions of microorganisms in nature?
Our research explores these questions for marine microorganisms, using the tools of genomics and molecular biology. We are particularly interested in how microbial genome evolution and physiology are affected by symbiotic interactions with higher taxa. In tandem with this work, we study free-living microorganisms, as they provide important reference points for understanding symbiont biology and mediate key global biogeochemical cycles in the ocean’s water column and sediments. In particular, we are interested in how oxygen loss affects the diversity and metabolism of marine microbes. Our research integrates the broad fields of microbiology, molecular evolution, and marine biology. This work has both descriptive and experimental components, and involves a blend of field, molecular, and bioinformatic techniques, the latter focused in part on the analysis of high-throughput sequencing datasets. We welcome inquiries from potential students, post-docs, and collaborators who share these interests.
Major transitions in evolution (mainly multicellularity). Spatial dynamics of microbial social interactions. Bet hedging. Life cycle evolution. Origin of multicellular development.
The transition to multicellularity was critical for the evolution of of large, complex organisms. However, little is known about how early multicellular organisms arise from unicellular ancestors, or how these relatively simple clusters of cells evolve greater complexity. We address both of these issues using experimental evolution, creating new multicellular life in a test tube.
Using these model systems (and a good bit of mathematical / computational modeling), my lab explores the origin of multicellular development, cellular division of labor, and mechanisms to prevent cell-level evolution from eroding multicellular complexity.
Major transitions in evolution (e.g. multicellularity) are a special case of a more general phenomenon: social evolution. Through collaborations with Brian Hammer (GT Biology), Peter Yunker (GT Physics), and Joshua Weitz (GT Biology), our group examines the spatial dynamics of microbial ecology and evolution.
Dr. Jang’s lab uses multi-disciplinary approaches to study muscle stem cell biology and develops bioactive stem cell delivery vehicles for use in regenerative medicine. Dr. Jang’s lab studies both basic aspects of muscle stem cell biology, especially systemic/metabolic regulations of stem cell and stem cell niche, as well as more translational aspects of muscle stem cell and mesenchymal stem cell for use in therapeutic approaches for musculoskeletal aging, neuromuscular diseases, and traumatic injuries.
1. Metabolic regulation of stem cell function
2. Systemic regulation of muscle homeostasis
3. Engineering muscle stem cell niche for regenerative medicine
The fundamental question we are trying to answer is how the coordinated cell movements are regulated during animal development. Different groups of cells move to different locations in a growing embryo to give rise to specific tissue and structures. It is a very complex process since the “ground” cells travel on is also undergoing constant rearrangement and growth. We use neural crest as a model to study the mechanisms of cell migration during embryonic development. The neural crest is a vertebrate innovation, comprised of highly migratory stem-like cells that give rise to multiple tissue and structures, including craniofacial bones and cartilages, connective tissue in the heart, enteric nervous system in the gut, and pigment cells all over the skin. Defects in their proliferation, migration, differentiation, or survival lead to numerous diseases and birth defects, including craniofacial and heart malformations as well as different types of cancer. Ongoing studies aim to uncover how their migration is regulated and how do they achieve such extraordinary migratory abilities.
My research interests center on control of movement by sensorimotor integration in the mammalian spinal cord. Using predominantly electrophysiological methods applied in vivo, we study neural signaling by spinal motoneurons, somatosensory neurons, and their central synapses. Our primary analyses include electrical properties, synaptic function, and firing behavior of single neurons. We are actively examining how these neurons and synapses respond soon and long after peripheral nerve injury and regeneration. Our recent findings demonstrate that successful regeneration of damaged sensory axons does not prevent complex reorganization of their synaptic connections made within the spinal cord. In separate studies, we are examining novel mechanisms of sensory encoding and their impairment which recently discovered in rodents treated with anti-cancer drugs. Both nerve regeneration and chemotherapy projects are driven by the long-term goal of accurately identifying the neural mechanisms behind movement disorders. We also continue to explore fundamental operations of the normal adult nervous system. Our most recent studies focus on synaptic modulation of motoneuron firing and on interspecies comparisons of spinal circuits.
My lab studies human evolutionary genomics, population genetics, and health disparities. It’s an an exciting time for the field of population genetics, and our research group uses whole genome sequences and computer simulations to study how diverse human populations evolve. We are interested in questions like:
• How have human genomes evolved in response to modern environments?
• How difficult is it for alleles to move between divergent populations?
• Why do hereditary disease risks vary across populations?
• How to best estimate an individual’s predisposition to different genetic diseases?
• What will our genomes look like in the future?
Our lab explores major questions in evolution and quantitative genetics. We work with the nematode worm C. elegans and related Caenorhabditis species. Current projects include exploring how cryptic alleles in embryogenesis depend on genetic background, how development evolves over time, and the role of molecular mechanisms in trait determination and evolution. We are also interested in how the environment influences trait expression and imposes selection in natural populations, and are conducting field collection trips in the nearby Appalachian foothills.
Evolutionary microbiology, bacterial social life, virulence and drug resistance:
We study the multi-scale dynamics of infectious disease. Our goal is to improve the treatment and control of infectious diseases, through a multi-scale understanding of microbial interactions.
Our approach is highly interdisciplinary, combining theory and experiment, evolution, ecology and molecular microbiology in order to understand and control the multi-scale dynamics of bacteria pathogens.