In the process of development of a multicellular organism, cells must make stable, binary fate decisions in response to intercellular signaling. A critical question is how weak or transient activation of signaling pathways achieves a robust and long-term switch in gene expression, and thus determines cell fate. I report that...
The Wnt signalling pathway is used multiple times throughout the development of an organism. Early in embryonic development this path is known to be involved in the induction of the ectodermally derived neural crest. The Wnt pathway is also thought to function in other ectodermal cell types. How the same...
Substrate-mediated delivery involves the immobilization of DNA, complexed with nonviral vectors, to a biomaterial or surface that supports cell adhesion. Cells cultured on the substrate are exposed to elevated DNA concentrations within the local microenvironment, which enhances transfection. As surface properties are critical to this delivery approach, self-assembled monolayers (SAMs)...
In mammalian development, cell specification and organogenesis are achieved by the regulated expression and repression of specific subsets of genes. The anterior pituitary gland, comprised of five cell types that arise from a common precursor, is an excellent model system for understanding these developmental processes. Examination of factors regulating transcription...
RNA interference (RNAi) is a newly discovered gene control pathway that silences gene expression in response to double-stranded RNA. This sequence-specific downregulation occurs at the level of mRNA stability, and is directed by the double-stranded RNA trigger itself. RNAi can be separated into two distinct steps; during the initiation phase,...
The detection of bio-molecules (e.g. nucleic acids and proteins) is the bedrock upon which research in the life sciences and diagnostic medicine rests. For nucleic acids, the polymerase chain reaction (PCR) is the ultimate in terms of target detection sensitivity (10s - 100s of copies/sample). For proteins, the enzyme-linked immunosorbent...
Hypoxia is a reduction in the normal level of oxygen tension and occurs during acute and chronic vascular disease, pulmonary disease, and cancer. The key transcription factor that regulates the cellular responses to hypoxia is hypoxia-inducible-factor-1 (HIF-1). Understanding how HIF-1 is regulated is fundamental for understanding the biology of tumor...
Chronic kidney disease (CKD) is the ninth leading cause of death in the United States. According to the National Kidney Foundation, more than 20 million people already have CKD, and another 20 million are at risk for developing CKD. The primary causes of kidney disease are diabetes followed closely by...
Activin, a member of the TGF-b superfamily, controls a variety of physiological events from the cell cycle to reproductive health. Activin activates the Smad signaling pathway through ActRII/B and ALK4 receptors. The regulation of activin signaling is carried out in part by the inhibitor protein follistatin. The mechanistic details of...
Packaging of DNA into nucleosomes and chromatin not only enables DNA to fit within the nucleus, but it also protects and organizes DNA. However, the wrapping of DNA around histones occludes DNA from binding proteins in solution. Proteins that regulate, express and repair DNA are able to function only when...
Epstein-Barr virus (EBV) is the cause of infectious mononucleosis and is associated with the etiology of several human cancers of lymphoid and epithelial cell origin, including Burkitt's lymphoma and nasopharyngeal carcinoma. It is an extremely prevalent virus in human populations worldwide. All herpesviruses, including EBV, infect cells by fusing the...
The neural crest is a population of multipotent precursors that are found only in vertebrate embryos. These cells migrate extensively throughout the body and give rise to diverse derivatives, including craniofacial bone and cartilage, melanocytes, and the enteric nervous system. There is a large network of factors involved in neural...
Receptor tyrosine kinases (RTKs) play a fundamental role in cell growth, metabolism and survival. Altered cell surface expression of RTKs has profound effects on organismal physiology and is associated with both metabolic disease and neoplasia. The insulin receptor (IR) is a prototypical RTK that regulates metabolism and lifespan and as...
Influenza virus assembly and budding is a complex process involving the organization of viral membrane proteins on the cell surface, incorporation of the segmented RNA genome, and formation of viral particles that must bud from the cell by pinching off from the plasma membrane. Interactions between the soluble influenza virus...
Lead poisoning is the most common environmentally-caused disease in the United States and is threat to human health worldwide. Although efforts to prevent lead exposure have increased throughout the years, lead poisoning still remains a common problem. Lead toxicity is more prevalent in children, who suffer from permanent neurodevelopment and...
Eukaryotic gene transcription is a coordinated process involving the participation of a large number of proteins. Sequence-specific DNA-binding transcription factors function as activators or repressors of transcription and frequently recruit transcriptional coregulators that lack specific DNA-binding activity. These multi-protein complexes with intrinsic chromatin-modifying and chromatin-remodeling activities have emerged as key...
Since its discovery, RNA interference (RNAi) has become a powerful tool used in laboratories to understand developmental processes, and it is now commonly used to investigate gene function. Using RNAi, scientists can routinely knock out specific genes to prevent their expression, observe its phenotypes, and then help determine the function...
A pyramidal neuron receives thousands of inputs spread throughout its dendritic tree, which it must integrate into a decision about whether or not to fire action-potential output. Since action potentials are the primary means by which these neurons communicate with their network partners, understanding this input-output relationship is critical for...
Polarized epithelial cells are divided by tight junctions into an apical membrane domain, which faces the lumen of an organ, and a basolateral domain, which is in contact with underlying connective tissues. To establish and maintain polarity, newly synthesized and recycling transmembrane proteins are sorted to either the apical or...
Assembly of the large and small subunits of the <em>E. coli</em> ribosome is a complicated process that involves transcription, processing, and modifying of the ribosomal RNA, the binding of ribosomal proteins, and the folding of the particles into complex structures. A number of ribosome assembly factors, including maturation factors, GTPases,...
Rsp5 is a ubiquitin ligase that controls a broad range of cellular processes in budding yeast and is part of a large family of proteins that controls analogous processes in mammalian cells. Although Rsp5 targets a number of different substrates for ubiquitination, the mechanisms that regulate Rsp5 catalytic activity are...
In male mammals, testosterone (T) is critical for sexual differentiation during development and reproductive success in adulthood. This thesis examines the cellular and molecular processes that mediate T's actions in the male brain and reproductive axis. Although T is clearly necessary for sexual behavior, the cellular mechanisms by which it...
To maintain polarity, epithelial cells continuously sort transmembrane proteins to the apical or basolateral membrane domains during biosynthetic delivery or after internalization. This thesis was designed to elucidate the molecular mechanism underlying protein trafficking. Our studies identified Rab13 as a critical GTPase regulator of biosynthetic cargos that are transported from...
The formation of a primary endocytic vesicle bud is a dynamic process involving the transient organization of adaptor and scaffold proteins at the plasma membrane. The proteins involved in early endocytosis have modular protein interaction motifs and domains that are predicted to contribute to scaffold formation. These motifs are found...
Short interfering RNAs (siRNAs) and microRNAs (miRNAs) are both processed from longer, double-stranded RNA (dsRNA) presursors by a member of the Dicer (Dcr) family of proteins. siRNAs generally arise from perfectly base-paired dsRNAs, whereas miRNAs are excised from 60-70 nt pre-miRNA hairpins containing multiple bulges and mismatches within the duplexed...