Mice with mutant Inf2 show impaired podocyte and slit diaphragm integrity in response to protamine-induced kidney injury

Kidney Int. 2016 Aug;90(2):363-372. doi: 10.1016/j.kint.2016.04.020. Epub 2016 Jun 24.


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.

Keywords: cytoskeleton; focal segmental glomerulosclerosis; glomerulus.

MeSH terms

  • Actins / metabolism
  • Acute Kidney Injury / chemically induced
  • Acute Kidney Injury / metabolism*
  • Animals
  • Cells, Cultured
  • Disease Models, Animal
  • Formins
  • Glomerulosclerosis, Focal Segmental / genetics*
  • Glomerulosclerosis, Focal Segmental / metabolism*
  • Heparin / pharmacology
  • Humans
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Membrane Proteins / metabolism
  • Mice
  • Microfilament Proteins / genetics*
  • Microfilament Proteins / metabolism
  • Microscopy, Electron, Transmission
  • Phenotype
  • Phosphorylation
  • Podocytes / drug effects
  • Podocytes / metabolism*
  • Podocytes / pathology
  • Podocytes / ultrastructure
  • Point Mutation
  • Protamines / toxicity
  • Signal Transduction
  • rho GTP-Binding Proteins / metabolism
  • rhoA GTP-Binding Protein


  • Actins
  • Formins
  • INF2 protein, mouse
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • Microfilament Proteins
  • NPHS2 protein
  • Protamines
  • nephrin
  • Heparin
  • RhoA protein, mouse
  • rho GTP-Binding Proteins
  • rhoA GTP-Binding Protein