Role of Par1 Polarity Proteins in Podocyte Development and Glomerular Disease

DESCRIPTION (provided by applicant): This proposal describes a five year program for development of an academic career in podocyte biology and glomerular disease. The PI has completed an NIH-supported, structured fellowship training program in Pediatric and Developmental Nephrology and will now expand upon her scientific skills through a unique integration of interdepartmental resources. This program will promote expertise in use of molecular genetics and cell biology to investigate mechanisms that maintain podocyte polarity in the setting of glomerular disease. Drs. Katalin Susztak and Anne Muesch will mentor the PI's scientific development. Her primary mentor, Dr. Susztak, is an Associate Professor of Internal Medicine/ Nephrology and a leader in her field in identifying novel mechanisms of glomerular disease. The internal co-mentor, Dr. Muesch, an Associate Professor in Development and Molecular Biology, is an expert in mechanisms that establish cell polarity, which will be examined in the context of glomerular disease. In addition, to expand the PI's repertoire and facilitate her study of the development of podocyte polarity, the PI is receiving hands-on training in embryonic kidney culture from an external advisor, Dr. Jonathan Barasch, who is located nearby at Columbia University. Drs. Susztak, Muesch, Barasch and several other highly regarded developmental nephrologists will form an advisory committee to provide scientific and career advice. Research will focus on the role of apical-basal polarity proteins Par1a/b in establishing podocyte polarity during kidney development and in maintaining podocyte polarity in the setting of glomerular disease. Recent work performed under the guidance of her mentors demonstrated that Par1a/b is expressed in developing nephrons and in rodent and human podocytes. Dominant negative suppression of Par1a/b function in cultured podocytes induced changes of cell shape and altered expression of slit diaphragm proteins, which are key podocyte components that support glomerular filter structure and function. Glomerular Par1a/b expression was altered in rodent models of diabetic nephropathy, nephrotic syndrome and glomerulosclerosis. The proposed experiments will entail doxycycline-inducible, podocyte-specific suppression of Par1a/b function using an in vivo mouse model, which will allow study of Par1a/b function during nephron development (induction during embyrogenesis) and in adult mice. Adenoviral infection of constructs suppressing Par1a/b function in embryonic kidney culture will be used to further study the function of Par1a/b in vitro. In addition, Par1a/b expression in an experimental model of nephrotic syndrome and glomerulosclerosis, using puromycin aminonucleoside nephrosis (PAN) induced in rats, and in human nephrotic syndrome, using a collection of control and diseased human kidney specimens. Specific aims include: Examine Par1a/b function during nephron development on podocyte differentiation, 2) Examine Par1a/b function in maintaining a polarized podocyte structure and glomerular filter function, and 3) Examine expression of Par1a/b in human and experimental models of nephrotic syndrome and glomerulosclerosis. PUBLIC HEALTH RELEVANCE: Chronic and end-stage kidney disease (CKD and ESKD) results in significant morbidity and mortality. We propose to examine novel pathways that may provide insight into mechanisms of proteinuric kidney disease and focal glomerulosclerosis (FSGS), a leading cause of childhood CKD and ESKD. We will examine the role of Par1a/b in establishing and maintaining podocyte structure and define polarity protein expression in human nephrotic syndrome and glomerulosclerosis, potentialy identifying new targets for therapeutic intervention or biomarkers for progressive kidney disease. !