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Abstract: FR-PO327

Quantifiable Phenotyping of an Existing Nphs1 Knockout Mouse Model

Session Information

Category: Genetic Diseases of the Kidneys

  • 1102 Genetic Diseases of the Kidneys: Non-Cystic

Authors

  • Lemberg, Katharina, Boston Children's Hospital, Boston, Massachusetts, United States
  • Yousef, Kirollos, Boston Children's Hospital, Boston, Massachusetts, United States
  • Mertens, Nils David, Boston Children's Hospital, Boston, Massachusetts, United States
  • Buerger, Florian, Boston Children's Hospital, Boston, Massachusetts, United States
  • Schneider, Ronen, Boston Children's Hospital, Boston, Massachusetts, United States
  • Mansour, Bshara, Boston Children's Hospital, Boston, Massachusetts, United States
  • Merz, Lea Maria, Boston Children's Hospital, Boston, Massachusetts, United States
  • Kolvenbach, Caroline Maria, Boston Children's Hospital, Boston, Massachusetts, United States
  • Saida, Ken, Boston Children's Hospital, Boston, Massachusetts, United States
  • Nicolas Frank, Camille H., Boston Children's Hospital, Boston, Massachusetts, United States
  • Shril, Shirlee, Boston Children's Hospital, Boston, Massachusetts, United States
  • Hildebrandt, Friedhelm, Boston Children's Hospital, Boston, Massachusetts, United States
Background

Steroid resistant nephrotic syndrome (SRNS) is the second leading cause of chronic kidney disease in the first three decades of life. The majority of children with SRNS progress to ESRD requiring dialysis or transplantation. The identification of monogenic causes of SRNS has revealed ~60 single-gene etiologies. Monogenic causes of SRNS predominantly cause glomerular podocyte dysfunction (Lovric NDT 31:1802-1813, 2015). Congenital nephrotic syndrome (CNS) is the most severe monogenic form of nephrotic syndrome. The second most frequent gene causing CNS when harboring biallelic mutations is NPHS1, which encodes the protein nephrin. Nephrin is located at the slit diaphragm and essential for the renal filtration barrier. There is no causal therapy so far. In order to enable eventual gene replacement therapy for CNS, we are developing quantifiable phenotyping in Nphs1-/- mouse models of CNS to provide a reproducible reference of evaluation for in vivo studies.

Methods

We developed a breeding colony for a previously published unconditional Nphs1-/- knockout mouse model (Nphs1tm1Rk/J) and performed phenotypic evaluation, comparing homozygous mice to heterozygous controls. We quantitatively evaluated them for three independent conditions: Kaplan-Meier survival curves, frequency of proteinaceous casts in proximal tubules upon light microscopy and foot process effacement upon electron microscopy.

Results

Mice were born in Mendelian ratios. Homozygous segregation of the Nphs1-KO allele led to a) a perinatally lethal phenotype with a median survival of 1.0 day (n=18), b) light microscopic changes by counting the ratio between proteinaceous casts in proximal tubules per mature glomerulus in coronal equatorial sections, with a ratio of 0.38 in homozygous mice (n=5) vs 0.0 in heterozygous mice (n=5) and c) TEM studies revealed reduced number of podocytes, which we quantified by counting foot process cross sections (fp) over a defined length of the glomerular basement membrane, with 0.49 fp/µm Nphs1-/- (n=2) and 2.5 fp/µm in Nphs1+/- (n=3).

Conclusion

We hereby provide a quantifiable phenotyping of Nphs1 tm1Rk/ tm1Rk KO mice which can be useful for further in vivo studies of CNS.

Funding

  • Other NIH Support