Human cardiovascular and pulmonary dysfunction is often life threatening and generates a huge economic burden. Such conditions can arise from abnormal development, or post-natal, from infection, acute injury or exposure to environmental allergen. The high incidence of these conditions provides a clear rationale for long- term basic research to understand the molecular basis for normal development and homeostasis of cardiovascular and pulmonary systems. The long-term goal of this research is to understand the function of the novel protein fibronectin type-III domain containing 3B (FNDC3B) in mammalian cardiovascular and pulmonary development and homeostasis. Fndc3b is expressed in cardiovascular and pulmonary systems and mice mutant for Fndc3b display respiratory distress and die shortly after birth. The cardiovascular system of Fndc3b mice is malformed and hearts display ventricular septal defects and non-compaction. Lung development is also affected and the conducting airway epithelium has abnormal morphology. FNDC3 proteins contain a highly conserved consensus binding site for WW-domain containing proteins. Based on these, and additional, findings we hypothesize that FNDC3B functions in pulmonary epithelial cells, and in vascular endothelial cells to modulate cell-cell adhesion required for normal pulmonary and cardiovascular function. We also hypothesize that FNDC3B is required for secretion of surfactant and that FNDC3B accomplishes each of these functions by binding to specific WW-domain containing proteins. To test these hypotheses, three sets of experiments are proposed. First, we will identify which cells express FNDC3B in the lung and heart of mice. Second, we will analyze the anatomy and function of epithelial cells lining the bronchiolar airway and alveoli and investigate whether the expression of proteins required for normal pulmonary function is affected in Fndc3b mutant and control animals. We shall also investigate whether cell- cell junctions are intact, and if unique secretory organelles required for normal function of airway epithelial cells, atrial myocytes and vascular endothelial cells such as lamellar bodies, secretory granules, caveolae and Weibel-Palade bodies are abnormal in Fndc3b mutant animals. Third, we will investigate which WW-proteins interact with FNDC3B using (a) an array based method and (b) by tandem-affinity purification of epitope- tagged FNDC3B expressed in mouse airway epithelial MEL15 cells and HUVEC endothelial cells followed by mass spectrometry and database analysis. These studies will provide new information about the function of FNDC3B in cardiovascular and pulmonary development in mice. The long-term benefit of this basic research will be to improve our knowledge of the molecular and cellular basis for cardiovascular and pulmonary development and homeostasis, which in turn will offer new opportunities for diagnosis, and ultimately treatment, of human conditions associated with dysfunction of these essential systems.

Public Health Relevance

Abnormal cardiovascular and lung function in newborn infants is a common cause of morbidity and mortality that generates significant human suffering, and financial burden on the health-care system. Understanding the causes of these disorders is an important step towards the long- term goals of improved diagnosis and treatment for such conditions. We are investigating the function of a novel protein, FNDC3B, which is required for normal heart and lung development and post-natal survival of mice. The long-term benefit of this basic research will be to increase our knowledge of the molecular and cellular basis for cardio-pulmonary development in mammals, which in turn will offer improved diagnosis, and ultimately treatment, of human conditions associated with abnormal cardiovascular and pulmonary function.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Exploratory/Developmental Grants (R21)
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Special Emphasis Panel (ZRG1-VH-F (90))
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Schramm, Charlene A
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University of California Irvine
Anatomy/Cell Biology
Schools of Arts and Sciences
United States
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