Cell growth, differentiation and development; Molecular Basis of Disease; Proteins and metalloenzymes; Gene Expression; Inherited Metabolic Disorders; Protein Function and Structure; Cell Cycle
Protein Methylation in Growth and Differentiation. Protein methylation was recently found by systems biology approaches to play a major role in regulating yeast cell growth. Consistent with this finding, we found that disruption of the gene encoding S-adenosylhomocysteine (SAH1) hydrolase markedly inhibited growth. S-adenosylmethionine (SAM) is the universal methyl donor,and SAH1 is the product of all methyltransferase(MTase) reactions.The SAH1 disruption leads to a 50% decrease in protein synthesis which,in turn leads to major decreases in the levels of Cln3p.Unexpectedly,when cells were transfected with a modified gene for Cln3 ,that desreased its rate of degradation,growth rates were normal.This result was unexpected because the basic defect of lacking SAH1 remained.We are currently testing the hypothesis that normal rates of growth are due to increased gene expression for multiple enzymes known to be involved in Met and SAM synthesis. We are also identifying substrates for specific MTases in yeast. Copper deficiency is known to affect brain development, and Menkes disease is fatal due to impaired brain development from low brain copper. A reduction in (SAH1) levels, as occurs in copper deficiency, may affect brain development by inhibiting protein methylation.We demonstrated that inhibiting SAH1 maredly inhibited development of two nerve cell models.
Neurology; Cytoskeleton and cell motility; Molecular and Cellular Biology; Molecular Basis of Disease; Molecular genetics; Neurobiology; Signal Transduction; Inherited Metabolic Disorders; Transgenic organisms
My laboratory seeks to understand the molecular basis of myelination and myelin diseases. Myelin is a multi-lamellar sheath that invests large axons and permits rapid conduction of nerve signals. Failure in myelin synthesis and myelin breakdown cause several important neurological diseases, including multiple sclerosis, leukodystrophies and peripheral dysmyelinating neuropathies. In some of these diseases, genetic mutations cause defects in cytoskeletal, adhesion and signaling molecules. I work with a team of undergraduate and graduate students, postdoctoral fellows, technicians, senior scientists and many international collaborators to discover how these molecules normally coordinate cell-cell and cell-extracellular matrix interactions to generate the cytoarchitecture of myelinated axons. We use a variety of approaches, including generation of mice carrying genetic abnormalities, cultures of myelinating glia and neurons, imaging, biochemistry and morphology to understand the role of these molecules in normal and pathological development. By comparing normal myelination to the abnormalities occurring in human diseases, we aim to identify molecular mechanisms that pharmacological intervention might correct. For example, we described how the protein dystroglycan associates with different proteins, some of which impact human neuropathies, depending on a proteolitic cleavage that can be regulated to improve the disease. Similarly, we found that molecules such as integrins and RhoGTPAses are required for glia to extend large processes that will become myelin around axons. In certain neuromuscular disorders, defective signaling pathways that converge on these molecules cause failure to produce or mantain an healthy myelin Finally, in collaborations with scientists and clinicians in the Hunter J. Kelly Research Institute, we are generating transgenic forms of GalC, an enzyme deficient in Krabbe leukodystrophy, to investigate which cells requires the enzyme. Investigating how GalC is handled may help find a cure for this devastating disease.
Apoptosis and cell death; Inherited Metabolic Disorders; Molecular Basis of Disease; Molecular and Cellular Biology; Neurobiology; Regulation of metabolism; Transgenic organisms; Vision science
Our lab is focused on studies of retinal degenerations caused by metabolic defects, particularly dyslipidemias involving defective cholesterol metabolism (e.g., Smith-Lemli-Opitz syndrome), using pharmacological and transgenic animal models. Current studies are focused on the role of lipid and protein oxidation in the underlying mechanisms of photoreceptor cell death in such retinal degenerations, using a combination of genomic, proteomic, and lipidomic approaches.
Inherited Metabolic Disorders; Membrane Transport (Ion Transport); Molecular Basis of Disease; Molecular and Cellular Biology; Molecular genetics; Protein Function and Structure; Transgenic organisms; Vision science
Most physiological processes and numerous disease states influence or are influenced by pH. Even relatively small deviations in whole body pH can have devastating consequences for our health. Our bodies are subject to a constant challenge from dietary and metabolic acids, thus it is critical for the body to have mechanisms that tightly regulate pH. Blood plasma pH is maintained at a value close to 7.4, predominantly thanks to the buffering action of 24 mM bicarbonate (HCO3-). HCO3- neutralizes acid, generating carbon dioxide and water (HCO3- + H+ to CO2 + H2O), preventing lethal acidosis. I study the SLC4 family of membrane proteins that move HCO3- across cell membranes. Notable members include  the Na/2HCO3 cotransporter NBCe1-A that reclaims HCO3- from filtered blood plasma in kidney tubules (preventing loss of vital plasma HCO3- to the urine),  NBCe1-B that promotes fluid removal from the corneal stroma (preventing corneal edema and vision loss),  the Cl-HCO3 exchanger AE1 that promotes O2-CO2 exchange in red blood cells, and  SLC4A11 that conducts H+ and promotes corneal clarity. Dysfunction of SLC4 family members is associated with renal tubular acidosis, blindness, cancer, deafness, epilepsy, and hypertension.
Cell growth, differentiation and development; Membrane Transport (Ion Transport); Molecular and Cellular Biology; Signal Transduction; Inherited Metabolic Disorders; RNA
Regulation of Kidney Epithelial Cell Growth, Transport and Differentiation Our laboratory is investigating the molecular mechanisms by which hormones, growth factors and extracellular matrix proteins regulate kidney tubule epithelial cell growth and functional differentiation in vitro. An established canine kidney epithelial cell line, MDCK, and isolated "mutants" are currently being utilized to examine the actions of growth regulatory on the expression of several proteins including the Na+, K+-ATPase and laminin, a glycoprotein in the extracellular matrix. The effects of novel growth regulatory factors on the expression of proteins involved in gluconeogenesis, membrane transport, renal disease and growth control in primary renal cell cultures are being examined. Primary kidney epithelial cells differentiate into nephrons in a reconstituted extracellular matrix proteins is the subject of study.