School of Medicine Department of Genetics
The Kaestner lab is employing modern mouse genetic approaches (gene targeting, tissue-specific and inducible gene ablation) to understand the molecular mechanisms of organogenesis and physiology of the liver, pancreas and gastrointestinal tract.
- Transcriptional control of pancreatic development and glucose homeostasis by Foxa2
Recent evidence places the winged helix transcription factor Foxa2 on top of a transcription factor cascade that controls the development of the pancreas. Mutations in several of these transcription factor genes have been shown to cause non-insulin-dependent diabetes mellitus. The role of Foxa2 in pancreatic development and function has not yet been tested directly, as mice homozygous for a null mutation die at gastrulation, that is before the onset of pancreatic differentiation. Dr. Kaestner is employing the loxP/Cre recombinase system for tissue-specific gene ablation of Foxa2 in the pancreas to test its function in pancreatic differentiation and glucose homeostasis.
- Functional Genomics of the Endocrine Pancreas.
Diabetes mellitus is a highly significant health problem, affecting approximately 16 million people in the United States alone. Our understanding of the pathogenesis of diabetes has benefited immensely from the molecular genetic analysis of the disease both in human and in rodent models. Recent breakthroughs in microarray technology have enabled investigators in the fields of diabetes and endocrinology to simultaneously analyze the expression levels of thousands of genes, the only limitation being the high cost of the commercial microarrays. We have developed two important tools for functional genomics related to diabetes through our NIDDK funded project on “Functional Genomics of the Developing Endocrine Pancreas” (UO1-DK56947). These tools are: cDNA libraries and microarrays enriched for genes expressed in the endocrine pancreas containing more than 13,000 mouse and human cDNAs. We are currently using these arrays to determine the expression profile of the pancreas during fetal and postnatal development and during various metabolic and pathologic states.
- Control of hepatic transcription and glucose homeostasis by the Foxa proteins.
We are investigating the role of transcription factors in the organogenesis of the liver. The liver project focuses on the winged helix transcription factors Foxa1, 2 and 3, which have been shown to regulate many liver-specific genes in vitro. We have now generated null as well as loxP-flanked alleles for all three Foxa genes and are currently analyzing the phenotypic consequences of the mutations for liver development and physiology.
- Regulatory cascades in differentiation and proliferation of the gastrointestinal epithelium.
The mammalian gut epithelium is a highly organized and dynamic system which requires continuous controlled proliferation and differentiation throughout life. Proliferation, cell migration and cell adhesion all must be tightly controlled in order to prevent either inflammatory diseases or epithelial cancers. As with many other vertebrate organs, the digestive tract develops from heterogeneous embryonic origins. While the musculature and the connective tissue are derived from lateral plate mesoderm, the epithelium is derived from the endoderm. We have identified a novel member of the winged helix gene family termed Foxl1 which is expressed in the gut mesoderm and have begun its functional analysis in vivo through targeted mutagenesis in mice. Null mutations in the mesodermal transcription factor Foxl1 result in dramatic alterations in endoderm development, including epithelial hyperproliferation. We have now identified APC/Min and Klf4 as downstream targets of Foxl1 and have begun the analysis of these genes in gastrointestinal differentiation by tissue-specific gene ablation.