Expanding the spectrum of FAT1 nephropathies by novel mutations that affect hippo signaling


  • F. Fabretti
  • N. Tschernoster
  • F. Erger
  • A. Hedergott
  • A.K. Buescher
  • C. Dafinger
  • B. Reusch
  • V.K. Köntges
  • S. Kohl
  • M.P. Bartram
  • L.T. Weber
  • H. Thiele
  • J. Altmueller
  • B. Schermer
  • B.B. Beck
  • S. Habbig


  • Kidney International Reports


  • Kidney Int Rep 6 (5): 1368-1378


  • INTRODUCTION: Disease-causing mutations in the protocadherin FAT1 have been recently described both in patients with a glomerulotubular nephropathy and in patients with a syndromic nephropathy. METHODS: We identified 4 patients with FAT1-associated disease, performed clinical and genetic characterization, and compared our findings to the previously published patients. Patient-derived primary urinary epithelial cells were analyzed by quantitative polymerase chain reaction (qPCR) and immunoblotting to identify possible alterations in Hippo signaling. RESULTS: Here we expand the spectrum of FAT1-associated disease with the identification of novel FAT1 mutations in 4 patients from 3 families (homozygous truncating variants in 3, compound heterozygous missense variants in 1 patient). All patients show an ophthalmologic phenotype together with heterogeneous renal phenotypes ranging from normal renal function to early-onset end-stage kidney failure. Molecular analysis of primary urine-derived urinary renal epithelial cells revealed alterations in the Hippo signaling cascade with a decreased phosphorylation of both the core kinase MST and the downstream effector YAP. Consistently, we found a transcriptional upregulation of bona fide YAP target genes. CONCLUSION: A comprehensive review of the here identified patients and those previously published indicates a highly diverse phenotype in patients with missense mutations but a more uniform and better recognizable phenotype in the patients with truncating mutations. Altered Hippo signaling and de-repressed YAP activity might be novel contributing factors to the pathomechanism in FAT1-associated renal disease.