title: Mice with mutant Inf2 show impaired podocyte and slit diaphragm integrity in response to protamine-induced kidney injury.
abstract: Mutations in the INF2 (inverted formin 2) gene, encoding a diaphanous formin family protein that regulates actin cytoskeleton dynamics, cause human focal segmental glomerulosclerosis (FSGS). INF2 interacts directly with certain other mammalian diaphanous formin proteins (mDia) that function as RhoA effector molecules. FSGS-causing INF2 mutations impair these interactions and disrupt the ability of INF2 to regulate Rho/Dia-mediated actin dynamics in vitro. However, the precise mechanisms by which INF2 regulates and INF2 mutations impair glomerular structure and function remain unknown. Here, we characterize an Inf2 R218Q point-mutant (knockin) mouse to help answer these questions. Knockin mice have no significant renal pathology or proteinuria at baseline despite diminished INF2 protein levels. INF2 mutant podocytes do show impaired reversal of protamine sulfate-induced foot process effacement by heparin sulfate perfusion. This is associated with persistent podocyte cytoplasmic aggregation, nephrin phosphorylation, and nephrin and podocin mislocalization, as well as impaired recovery of mDia membrane localization. These changes were partially mimicked in podocyte outgrowth cultures, in which podocytes from knockin mice show altered cellular protrusions compared to those from wild-type mice. Thus, in mice, normal INF2 function is not required for glomerular development but normal INF2 is required for regulation of the actin-based behaviors necessary for response to and/or recovery from injury.
authors.affiliation: Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA; Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Balajikarthick
authors.initials: B
authors.lastname: Subramanian
authors.affiliation: Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA; Harvard Medical School, Boston, Massachusetts, USA; University of Children's Hospital, Iowa City, Iowa, USA.
authors.forename: Hua
authors.initials: H
authors.lastname: Sun
authors.affiliation: Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Yan
authors.affiliation: Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA.
authors.forename: Victoria T
authors.initials: VT
authors.lastname: Charoonratana
authors.affiliation: Department of Biochemistry, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire, USA.
authors.forename: Henry N
authors.initials: HN
authors.lastname: Higgs
authors.affiliation: Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA; Department of Pediatrics, Peking University First Hospital, Beijing, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Wang
authors.affiliation: Regeneron Pharmaceuticals, Tarrytown, New York, USA.
authors.forename: Ka-Man V
authors.initials: KV
authors.lastname: Lai
authors.affiliation: Regeneron Pharmaceuticals, Tarrytown, New York, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Valenzuela
authors.affiliation: Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA; Harvard Medical School, Boston, Massachusetts, USA; Division of Nephrology, Department of Pediatrics, Children's Hospital, Boston, Massachusetts, USA; Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Brown
authors.affiliation: Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA; Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Johannes S
authors.initials: JS
authors.lastname: Schlöndorff
authors.affiliation: Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA; Harvard Medical School, Boston, Massachusetts, USA; Broad Institute of Harvard and Massachusetts Institute of Technology, Cambridge, Massachusetts, USA. Electronic address: mpollak@bidmc.harvard.edu.
authors.forename: Martin R
authors.initials: MR
authors.lastname: Pollak
mesh_terms: D000199:Actins / Q000378:metabolism; D058186:Acute Kidney Injury / Q000139:chemically induced / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D004195:Disease Models, Animal; D000080865:Formins; D005923:Glomerulosclerosis, Focal Segmental / Q000235:genetics* / Q000378:metabolism*; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008840:Microfilament Proteins / Q000235:genetics* / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D010641:Phenotype; D010766:Phosphorylation; D050199:Podocytes / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology / Q000648:ultrastructure; D017354:Point Mutation; D011479:Protamines / Q000633:toxicity; D015398:Signal Transduction; D020741:rho GTP-Binding Proteins / Q000378:metabolism; D020742:rhoA GTP-Binding Protein
chemical_list: D000199:Actins; D000080865:Formins; C515509:INF2 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; C407223:NPHS2 protein; D011479:Protamines; C113267:nephrin; D006493:Heparin; C526380:RhoA protein, mouse; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein
keywords: cytoskeleton; focal segmental glomerulosclerosis; glomerulus