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Abstract: PO1407

A Novel Mouse Model for Familial Hypomagnesemia with Hypercalciuria and Nephrocalcinosis (FHHNC) Bearing the Most Frequent Human CLDN16 Mutation

Session Information

Category: Fluid, Electrolyte, and Acid-Base Disorders

  • 901 Fluid, Electrolyte, and Acid-Base Disorders: Basic

Authors

  • Prot-Bertoye, Caroline, Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, CNRS, ERL8228, Paris, France
  • Griveau, Camille, Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, CNRS, ERL8228, Paris, France
  • Cheval, Lydie, Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, CNRS, ERL8228, Paris, France
  • Langlais, Honoré A., Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, CNRS, ERL8228, Paris, France
  • Brideau, Gaëlle, Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, CNRS, ERL8228, Paris, France
  • Houillier, Pascal, Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, CNRS, ERL8228, Paris, France
Background

Mutations of claudin (CLDN) 16 and CLDN19 cause FHHNC, characterized by a urinary loss of calcium (Ca) and magnesium (Mg), hypomagnesemia, nephrocalcinosis and renal failure. Cldn16 and Cldn 19 are co-expressed at the tight junction (TJ) of the thick ascending limb (TAL) of Henle’s loop and play a key role in paracellular reabsorption of Ca and Mg. Here, 25% of filtered Ca and 70% of filtered Mg are reabsorbed. Cldn16 knock-out mouse model failed to faithfully recapitulate the human disease, as it was complicated by neither nephrocalcinosis nor renal failure. Cldn 16 knock-down mice have a renal loss of NaCl and hyperaldosteronism. We hypothesized that a knock-in model bearing the most frequent human CLDN 16 mutation (p.L151F) would be helpful to delineate the abnormalities caused by mutated Cldn16.

Methods

Cldn 16L151F/ L151Fmice were generated by CRISPR Cas9-based mutagenesis. Cldn 16+/+and Cldn 16L151F/ L151Ffemale mice were housed in metabolic cages at 3 months of age. Daily food and water intake, body weight were recorded. Blood and urine composition were analyzed. Nephrocalcinosis and Cldn expression in TAL were studied on kidney sections by alizarin red coloration and immunofluorescence.

Results

At 3 months, weight, food and water intake, blood parameters (Na, Cl, Ca, Mg, Pi, creatinine) did not differ between Cldn 16+/+and Cldn 16L151F/ L151Fmice. Cldn 16L151F/ L151Fmice had significantly higher urinary excretions of Ca, Mg and Pi and a lower urinary pH; urine volume, osmolality, Na, K and aldosterone were unaltered. At 6 months calcitriol was significantly increased in Cldn 16L151F/ L151Fmice. No nephrocalcinosis was seen at 12 months. Cldn 16 was almost never seen at TJ and Cldn 19 seems to be less expressed at TJ in Cldn 16L151F/ L151Fmice suggesting that Cldn 16L151Fhas a negative effect on Cldn19 expression.

Conclusion

Cldn 16L151F/ L151Fmice have a urinary loss of Ca and Mg, as typically observed in patients with FHHNC. No evidence of NaCl wasting was found. Further studies are ongoing on male mice, renal function and PTH, bone and dental phenotypes. This model will help to better understand the link between an altered CLDN 16 and defective Ca and Mg handling.

Funding

  • Private Foundation Support