Personal History1983: B.Sc. in Biology, Department of Biology, Shandong University, China
1986: M.Sc in Cell Biology, Institute of Oceanography, Chinese Academy of Sciences
1993: Ph.D. in Biochemistry, Department of Biochemistry, University of Toronto, Canada
1993-1997: Post-Doctoral Fellow, Department of Pharmacology and Howard Hughes Medical Institute, University of Washington
1997- 2003: Assistant Professor, Center of Marine Biotechnology, University of Maryland Biotechnology Institute
2003-2010: Associate Professor, Center of Marine Biotechnology, University of Maryland Biotechnology Institute
2010-present: Associate Professor, Department of Biochemistry & Molecular Biology, University of Maryland School of Medicine
The process by which a fertilized egg gives rise to a fully-formed multicellular individual is part of the broad field known as developmental biology. Development is concerned with the life history of cells in general----including the complex ways that genetic information is translated into organismal structure and function. This includes the molecular mechanisms by which cells specialize and become different from one another, and the ways that shape, form and pattern arise in each generation.
The fundamental question that drives my research is: " How a single cell, the fertilized egg, develops into an animal with thousands of distinct type of cells - muscle cells, neurons, epidermal cells, blood cells, and so on?" We are particularly interested in the cellular and molecular mechanisms that control the differentiation of muscle and skeletal cells during embryogenesis. Specifically, we use zebrafish as a model system to investigate the role of growth factors and their downstream transcriptional factors in the formation and differentiation of vertebrate skeletal and muscle cells during embryogenesis.
Zebrafish as a Model Organism
Model organisms, also known as model systems, are animals or plants that are well characterized and amenable to laboratory study. Zebrafish provides unprecedented opportunities for the study of vertebrate development for several reasons: the genome of this organism is well characterized, the animal can be easily reared in laboratory settings, and techniques have been developed for genetic manipulations involving introduction of modified genes and manipulation of the expression of specific genes of interest. Also of great importance, the embryo remains translucent throughout much of its development, so that it can be studied in detail under the microscope. Such study includes ingenious methods that have been developed for tagging the protein products of specific genes with fluorescent markers.
Our laboratory is focused on the genetic regulation of muscle and bone development. Skeletal muscle and bone are specialized tissues that make up the muscle/skeletal system that confers multiple mechanical and biological functions, such as providing physical support for our body, protecting vital organs (e.g., brain, lung). The important function of muscle/skeletal system can be easily recognized in day-to-day life, where millions of people suffer from muscular and skeletal diseases such as muscular dystrophy, or osteoporosis. The better understanding of the regulation of muscle and bone formation during embryogenesis will provide new insights into the molecular mechanisms of muscle/skeletal diseases and give rise to novel strategies for new drug design as well as alternative therapeutic approach using embryonic stem cells.
Many important insights into muscle and bone formation have come from studies of animal models, such as mice, chick, and fish. These studies have provided fundamental information about genes that regulate the development of bone and muscle cells. It is apparent that most of the genes or genetic pathways that control muscle or skeleton formation are highly conserved in vertebrates, and signaling molecules required for embryonic muscle/skeletal development are also important in adulthood.
Therefore, in recent years there has been an increasing interest in the search for new genes involved in bone and muscle development in animal model systems. Zebrafish have become an important model for developmental studies, having several advantages compared with other model systems. In particular are the easy accessibility of zebrafish embryos for direct observation of their development and their suitability for systematic mutagenesis studies to identify genes regulating the development of various tissues and organs, including the muscle/skeletal system.
The research objective of my laboratory is to use zebrafish as a model system to identify the genetic program involved in muscle and skeleton formation. Our research focuses on the role of growth factors and their downstream transcription factors in the formation of vertebrate muscle and skeleton during embryogenesis. We discovered that the differentiation of muscle fibers is regulated by signals from their neighboring tissues. We found that growth factor Hedgehog protein, secreted by notochord cells, played an important positive role in specifying slow muscles. Overexpression of Hedgehog protein in zebrafish embryos (using transgenic technology) induced the formation of extra slow muscle cells, and at the same time blocked the formation of fast muscle cells. Mutation of Hedgehog protein or its downstream gene, named Gli2, blocked the development of slow muscle cells.
In addition, we demonstrated that the development of muscles is controlled by both positive and negative regulators. BMP (bone morphogenetic protein), another type of growth factor, acts as the negative regulator in slow muscle formation. Our recent studies are focused on the genetic regulation of muscle fiber maturation, the assembly of sarcomeres. We demonstrated that Smyd1, a member of the Smyd family and Hsp90a1 play vital roles in sarcomeres assembly. Knockdown of Smyd1 or Hsp90a1 resulted in defective thick and thin filament organization in skeletal and cardiac muscles.
Results from these studies have potential application in clinical research, because knowledge gained from these studies may lead to the design of new genetic screenings for muscle diseases, and development of new drugs that could regulate the activities of these factors for treatment of muscular and skeletal diseases, and new strategies to instruct differentiation of ES cells specifically into muscle or bone cells for cell-based therapy.
Lab Techniques and EquipmentZebrafish model; whole mount in situ hybridization; gene knockdown; transgenic fish technology
Haga Y., Dominique V., and Du S. J. (2009). Analyzing notochord segmentation and intervertebral disc formation using the twhh:gfp transgenic zebrafish model. Transgenic Research. 18, 669-683.
Li, H, Randall, W. and Du, S. J. (2009). skNAC (skeletal Naca), a muscle-specific isoform of Naca (nascent polypeptide-associated complex alpha), is required for myofibril organization. FASEB J. 23 (6): 1988-2000.
Rotllant J., Liu D., Yan Y. L., Postlethwait J. H., Westerfield, M. and S. J. Du (2008). Sparc (Osteonectin) functions in morphogenesis of the pharyngeal skeleton and inner ear. Matrix Biology. 27(6):561-72.
Du, S. J., Li, H., Bian Y. H. and Zhong, Y. (2008). Heat shock protein 90a1 is required for organized myofibril assembly in skeletal muscles of zebrafish embryos. Proc. Natl. Academy. Sci. USA. 105(2):554-559.
Tan, X. G., Rotllant, J., Li, H., DeDeyne, P. and Du, S. J. (2006). SmyD1, a histone methyltransferase, is required for myofibril organization and muscle contraction in zebrafish embryos. Proc. Natl. Academy. Sci. USA. 103, 2713-2718.
Du, S. J., Rotllant, J., and Tan, X. G. (2006). The zebrafish smyd1 promoter directs muscle-specific GFP expression in transgenic zebrafish embryos. Developmental Dynamic. 235:3306-3315.
Xu, C., Wu, G., Zohar Y. and Du, S. J. (2003) Analysis of myostatin gene structure, expression and function in zebrafish. J. Exp. Biol. 206, 4067-4080
Gothilf, Y., Toyama, R., Coon, S., Du, S. J., Dawid, I and Klein, D.C. (2002). Pineal-specific expression of green fluorescent protein, under the control of the serotonin-n-acetyltransferase gene regulatory regions in transgenic zebrafish. Developmental Dynamics, 225, 241-249.
Du, S. J., Frenkel, V., Kindschi, G. and Zohar Y. (2001). Visualizing normal and defective bone development in zebrafish embryos using the fluorescent chromophore calcein. Developmental Biology. 238, 239-246.
Du, S. J. Devoto, S., Westerfield M. and Moon, R. T. (1997). Positive and negative regulation of muscle cell identity by members of the hedgehog and TGFï?ï¢ï? gene families. J. Cell Biol. 139, 145-156.
Du, S. J., Purcell, S. M., Christian, J. L., McGrew, L. L. and Moon, R. T. (1995). Identification of distinct classes and functional domains of Wnts through expression of wild-type and chimeric proteins in Xenopus embryos. Molecular and Cellular Biology 15, 2625-2634.
Devlin, R. H., Yesaki, T. Y., Donaldson, E. M., Du, S. J. and Hew, C. L. (1995). Production of germline transgenic Pacific salmonids with dramatically increased growth performance. Canadian Journal of Fisheries and Aquatic Sciences 52, 1376-1384.
Du, S. J., Devlin, R. H. and Hew, C. L. (1993). Genomic structure of growth hormone genes in chinook salmon (Oncorhynchus tshawytscha): presence of two functional genes, GH-I and GH-II, and a male-specific pseudogene, GH-psi. DNA and Cell Biology 12, 739-751.
Du, S. J., Gong, Z., Fletcher, G., Shears, M. A., King, M. J., Idler, D. R. and Hew, C. L. (1992). Growth enhancement in transgenic Atlantic salmon by the use of an "all fish" chimeric growth hormone gene construct. Bio/Technology 10, 176-181.