In vivo Modeling Implicates APOL1 in Nephropathy: Evidence for Dominant Negative Effects and Epistasis under Anemic Stress.

Abstract

African Americans have a disproportionate risk for developing nephropathy. This disparity has been attributed to coding variants (G1 and G2) in apolipoprotein L1 (APOL1); however, there is little functional evidence supporting the role of this protein in renal function. Here, we combined genetics and in vivo modeling to examine the role of apol1 in glomerular development and pronephric filtration and to test the pathogenic potential of APOL1 G1 and G2. Translational suppression or CRISPR/Cas9 genome editing of apol1 in zebrafish embryos results in podocyte loss and glomerular filtration defects. Complementation of apol1 morphants with wild-type human APOL1 mRNA rescues these defects. However, the APOL1 G1 risk allele does not ameliorate defects caused by apol1 suppression and the pathogenicity is conferred by the cis effect of both individual variants of the G1 risk haplotype (I384M/S342G). In vivo complementation studies of the G2 risk allele also indicate that the variant is deleterious to protein function. Moreover, APOL1 G2, but not G1, expression alone promotes developmental kidney defects, suggesting a possible dominant-negative effect of the altered protein. In sickle cell disease (SCD) patients, we reported previously a genetic interaction between APOL1 and MYH9. Testing this interaction in vivo by co-suppressing both transcripts yielded no additive effects. However, upon genetic or chemical induction of anemia, we observed a significantly exacerbated nephropathy phenotype. Furthermore, concordant with the genetic interaction observed in SCD patients, APOL1 G2 reduces myh9 expression in vivo, suggesting a possible interaction between the altered APOL1 and myh9. Our data indicate a critical role for APOL1 in renal function that is compromised by nephropathy-risk encoding variants. Moreover, our interaction studies indicate that the MYH9 locus is also relevant to the phenotype in a stressed microenvironment and suggest that consideration of the context-dependent functions of both proteins will be required to develop therapeutic paradigms.

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Published Version (Please cite this version)

10.1371/journal.pgen.1005349

Publication Info

Anderson, Blair R, David N Howell, Karen Soldano, Melanie E Garrett, Nicholas Katsanis, Marilyn J Telen, Erica E Davis, Allison E Ashley-Koch, et al. (2015). In vivo Modeling Implicates APOL1 in Nephropathy: Evidence for Dominant Negative Effects and Epistasis under Anemic Stress. PLoS Genet, 11(7). p. e1005349. 10.1371/journal.pgen.1005349 Retrieved from https://hdl.handle.net/10161/10832.

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Scholars@Duke

Katsanis

Nicholas Katsanis

Jean and George W. Brumley, Jr., M.D. Professor of Developmental Biology
Telen

Marilyn Jo Telen

Wellcome Clinical Distinguished Professor of Medicine in Honor of R. Wayne Rundles, M.D.

Dr. Telen is recognized as an expert in the biochemistry and molecular genetics of blood group antigens and the pathophysiological mechanisms of vaso-occlusion in sickle cell disease. She is the Director of the Duke Comprehensive Sickle Cell Center.

Dr. Telen's laboratory focuses on structure/function analysis of membrane proteins expressed by erythroid cells, as well as the role of these proteins in non-erythroid cells. Proteins are also studied in transfectant systems, and research focuses especially on adhesion receptors. The goals of this work are (1) to understand the mechanism and role of red cell adhesion to leukocytes and endothelium in sickle cell disease; (2) to understand the signaling mechanisms leading to activation (and inactivation) of red cell adhesion molecules; (3) to understand the molecular basis of blood group antigen expression, and (4) to understand the interactions of erythroid membrane proteins with other cells and with extracellular matrix..

Recent investigations have focused on the role of signaling pathways in the upregulation of sickle red cell adhesion. Present studies include (1) investigation of beta-adrenergic signaling pathway responsible for activation of B-CAM/LU and LW adhesion receptors; (2) understanding how nitric oxide and ATP downregulate sickle red cell adhesion; (3) studying the effect of these processes in animal models.

Dr. Telen is also involved in a large multicenter study looking for genetic polymorphisms that affect clinical outcomes in sickle cell disease, as well as a multi-center study investigating the mechanisms and treatment of pulmonary hypertension in sickle cell disease.


Key Words:

Adhesion molecules
Erythrocyte membrane
Sickle cell disease
Transfusion medicine
Immunohematology
CD44
B-CAM/LU
Genetic polymorphisms


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