Ph.D. University of California at Los Angeles
Developmental Biology/ Gene Regulation During Embryonic Development
The development of a fertilized egg into a complex organism has been the focus of Developmental Biology since the 19th century. The need to identify genes responsible for embryonic development is particularly important to those working in the area of human birth defects. It was from this perspective that Dr. Strecker began work in this field at the Central Lab for Human Embryology, University of Washington (Seattle). The complex phenotypes associated with human birth defects underscore the need for basic research in simple animal systems amenable to direct manipulation. In this setting, Dr. Strecker used the chick as a model system for the study of vertebrate limb development. With Dr. Trent Stephens, she identified the tissue source of the vertebrate limb inducer as the intermediate mesoderm and its time and spatial level of action during limb development. Later, other labs would extend this discovery by identifying FGF-8 as the endogenous inducer of chick limb formation in this tissue. Drs. Stephens and Strecker also investigated the effects of thalidomide on vertebrate skeletal development.
Later, other labs would extend this discovery by identifying FGF-8 as the endogenous inducer of chick limb formation in this tissue. Drs. Stephens and Strecker also investigated the effects of thalidomide on vertebrate skeletal development. Their findings demonstrated that the proper development of limb skeletal pattern is independent of specific neural crest and peripheral nerve innervation.
The first reports of segmentation patterning genes in Drosophila melanogaster drew Dr. Strecker away from the chick to the fruit fly. In the labs of John Merriam and the late Judith Lengyel at UCLA, Dr. Strecker carried out a genetic, cytological and phenotypic characterizations of the gap gene, tailless. This work led directly to the cloning and molecular characterization of tailless (tll), which is an orphan nuclear receptor that acts as a transcription factor in the terminal system of segmentation patterning genes. In the absence of tll, homozygous mutant embryos fail to develop a brain (in particular the optic lobe) and a tail (eighth abdominal segment, telson, and posterior gut). Later, the mouse homolog of tailless was found also to be expressed in the developing vertebrate forebrain.
In the lab of Howard Lipshitz, Dr. Strecker continued her study of tailless and its relationship to the maternal terminal gene, torso. Using a hypermorphic allele of torso, mutations in tll were observed to suppress the effects of the overexpression of the maternal terminal gene, torso. This genetic evidence placed tailless directly downstream of torso in the terminal system.
In her own laboratory, Dr. Strecker has used the Drosophila embryo to identify genetic pathways affected by exposure to known human teratogens. While others had tested the effects of teratogens in Drosophila cell culture, this is one of the first demonstrations that a human teratogen could affect the overall pattern of the embryo. The glucocorticoid, dexamethasone, is commonly used as an anti-inflammatory agent. High doses of dexamethasone in the first trimester of pregnancy have been linked to an increased incident of craniofacial clefting in humans and in mice. The process of craniofacial development in mammals is dependent upon epithelial cell shape changes and movement. Drosophila embryos exposed to dexamethasone consistently exhibited a disruption in a process also controlled by epithelial cell shape change and movement, namely germband retraction and dorsal closure. Mutations in several Drosophila genes, such as u-shaped, serpent, tail-up and hindsight, also disrupt germband retraction and dorsal closure. The elucidation of the genetic basis of dexamethasone’s effect on Drosophila development may improve our understanding of the molecular basis for craniofacial clefting in mammalian embryos.
Dr. Strecker has turned to study the role of bioethics in reproductive medicine and genetics. With the emerging importance of genetic testing and its direct application to human medicine, bioethics is rapidly influencing the scope of basic research and medicine alike. Issues under consideration include the role genetic testing plays in the exercise of an individual's free will and choice. Given the growing importance of bioethics, students in Dr. Strecker's courses at SMU are asked to engage in research and debate on these issues as they relate to medical research and treatment in the 21st century.
Stephens, T.D., and T. R. McNulty, Evidence for a Metameric Pattern in the Development of the Chick Humerus. J. Embryol. exp. Morph. 61, 191-205, (1981)
Strecker, T.R., and T.D. Stephens, Peripheral Nerves Do Not Play a Trophic Role in Limb Skeletal Morphogenesis. Teratology 27, 159-167, (1983).
Stephens, T.D., and T.R. Strecker, A Critical Review of the McCredie - McBride Hypothesis of Neural Crest Influence on Limb Morphogenesis. Teratology 28, 287-292, (1983).
Stephens, T.D., and T.R. Strecker, Radial Condensation in the Axis of the Evolving Limb. Evolution 39(5): 1159-1163, (1985).
Strecker, T., K. Kongsuwan, J. Lengyel and J. Merriam, The Zygotic Mutant tailless Affects the Anterior and Posterior of the Drosophila embryo. Developmental Biology 113, 64-76, (1986).
Strecker, T.R., J.R. Merriam, and J.A. Lengyel, Graded requirement for the zygotic terminal gene, tailless, in the brain and tail region of the Drosophila embryo. Development 102(4), 721-734, (1988).
Strecker, T.R. and J.A. Lengyel, Anterior-Posterior Pattern Formation: An Evolutionary Perspective on Genes Specifying Terminal Domains. Bioessays 9(1), 3-7, (1988).
Strecker, T.R., S.R. Halsell, W.W. Fisher, and H.D. Lipshitz, Reciprocal Effects of Hyper- and Hypoactivity Mutations in the Drosophila Pattern Gene torso. Science 243, 1062-1066, (1989).
Strecker, T.R., M.L.R. Yip, and H.D. Lipshitz, Zygotic Genes that Mediate torso Receptor Tyrosine Kinase Functions in the Drosophila Embryo. Proc. Nat'l Acad. Sci. USA 88, 5824-5828, (1991).
Strecker, T. R., M.L.R. Yip and H. D. Lipshitz, Genetic Control of Cell Fate in the Termini of the Drosophila Embryo. Developmental Biology 150, 422-426, (1992).
Strecker, T. R., S. McGhee, S. Shih and D. Ham. Permeabilization, Staining, and Culture of Living Drosophila Embryos. Biotechnic and Histochemistry 69: 25-30, (1994).
Strecker, T. R., S. McGhee, S. Shih and D. Ham. A Modified Protocol for Permeabilization and Culture of Living Drosophila Embryos. Dros Info Serv 75: 38-39, (1994).
Strecker, T. R., P. Li, S. McGhee, D. Ham, S. Smith, J. Schreck, S. Youn, and P. Kon. The Effects of the Glucocorticoid, Dexamethasone, on the Development of the Drosophila Embryo. Roux Arch Devel Biol 204, 359-368, (1995).
Strecker, T. Alzheimer's: Making Sense of Suffering. 1997. Vital Issues Press, Lafayette, LA.
Strecker, T. UCLA Bulletin on Law and Technology, April 1997. "Mammalian Cloning: An Exciting Technical Advance with Practical and Ethical Considerations." Web Site: http://www.lawtechjournal.com/archives/blt/i3-trs.html
Strecker, T. Dallas Morning News, 5/17/97. "Alzheimer's challenges us to learn, love more deeply" was guest column in Saturday's Religion Section.
Strecker, T. Dallas Morning News, 6/27/98. Letter to editor responding to "God on Trial" article's reference to Alzheimer's disease.
Service to SMU and Greater Dallas Community
- Instructor in Texas Regional Science Collaborative for High School Science teachers in North Texas (2011).
- Organizer, Collegium da Vinci: "Texas: Leading the Way in Curative Therapies using Stem Cells", Dedman College, SMU (September 2005).
- Judge, Dallas Regional Science & Engineering Fair.
- Invited speaker for the Greater Dallas Chapter of the Alzheimer's Association, Dallas, TX (1997 - present).
- Weekend Coordinator, Advocacy and Pregnancy Center for Women, Lewisville, TX (1996 - 2008).
- Meal distribution at Salvation Army (2012)
- University of Washington, Seattle (1976 - 1980), B.S. in Biology, Magna Cum Laude, Phi Beta Kappa.
- University of California at Los Angeles, (1982 - 1987), Ph.D. in Biology, awarded Graduate Woman of the Year and the Scherbaum Award for distinguished graduate research.
- California Institute of Technology, Pasadena (1987 – 1990), Postdoctoral research fellow with Dr. Howard Lipshitz, Division of Biology; Postdoctoral Fellow of the American Cancer Society (1988 - 1990).
- Perkins School of Theology, SMU (1995 – 1998), Postgraduate studies in Bioethics.
Current Teaching Assignments
BIOL 1303 Essentials of BiologyAn introduction to the major concepts of Biology for the non-science major. The course includes the scientific method, cell biology, genetics, human reproduction, cancer prevention and treatment, stem cell research and regenerative medicine, forensic DNA science, metabolism, photosynthesis, natural selection and genetic diversity, and environmental sustainability.
BIOL 4331 Developmental BiologyThis junior-senior level lecture course shows students how molecular genetics has revolutionized the precision with which developmental systems can be studied. Emphasis is placed on the common mechanisms that regulate pattern formation across the animal kingdom, and how Development Biology is shaping the direction of medical research in the 21st century.
BIOL 3222 Molecular Genetics LaboratoryThis lecture/lab course instructs students in techniques commonly used by molecular biologists which include: restriction digestion and electrophoresis, PCR, bacterial transformation and plasmid purification, in vitro mutagenesis, and genetic testing of their own DNA as well as DNA isolated from Drosophila melanogaster.
BIOL 5305 Genomics and BioinformaticsThis lecture course instructs students in the technology that has revolutionized our ability to learn the function and structure of gene products from their genomic sequence as well as the relationship between genes of different species. Students carry out interactive gene annotation, DNA barcoding, and utilize several bioinformatics programs to explore the application of genomics to medicine and pharmacogenetics.
CFB 3313 Genetic Determinism and Free WillThis lecture course, which fulfills the cultural formations requirement in the General Education Curriculum, addresses the role molecular genetics impacts the choices and free will of an individual in the areas of medicine, reproduction, and behavior. This writing intensive course addresses whether genetic determinism is compatible with free will from historical, philosophical and scientific perspectives.