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Hepatocyte nuclear factor 1A deficiency causes hemolytic anemia in mice by altering erythrocyte sphingolipid homeostasis

Karin von Wnuck Lipinski, Sarah Weske, Petra Keul, Susann Peters, Hideo A. Baba, Gerd Heusch, Markus H. Gräler and Bodo Levkau

Key points

  • HNF1A deficiency in mice leads to non-cell autonomous anemia caused by altered RBC sphingolipids leading to hemolysis.

  • Sphingosine loading of wild type RBC phenocopies HNF1A-/- RBC with high osmotic fragility, PS exposure and calcium due to PMCA suppression.

Abstract

The Hepatocyte Nuclear Factor (HNF) family regulates complex networks of metabolism and organ development. Human mutations in its prototypical member HNF1A cause maturity-onset of diabetes of the young (MODY) type 3. In this study, we identified an important role for HNF1A in the preservation of erythrocyte membrane integrity, calcium homeostasis and osmotic resistance through a yet unrecognized link of HNF1A to sphingolipid homeostasis. HNF1A-/- mice displayed microcytic hypochromic anemia with reticulocytosis that was partially compensated by avid extramedullary erythropoiesis at all erythroid stages in the spleen thereby excluding erythroid differentiation defects. Morphologically, HNF1A-/- erythrocytes resembled acanthocytes and displayed increased phosphatidylserine exposure, high intracellular calcium, and elevated osmotic fragility. Sphingolipidome analysis by mass spectrometry revealed substantial and tissue-specific sphingolipid disturbances in several tissues including erythrocytes with the accumulation of sphingosine as most prominent common feature. All HNF1A-/- erythrocyte defects could be simulated by exposure of wild type erythrocytes to sphingosine in vitro and attributed in part to sphingosine-induced suppression of the plasma-membrane Ca2+-ATPase activity. Bone marrow transplantation rescued the anemia phenotype in vivo, whereas incubation with HNF1A-/- plasma increased the osmotic fragility of wild type erythrocytes in vitro. Our data suggest a non-cell autonomous erythrocyte defect secondary to the sphingolipid changes caused by HNF1A deficiency. Transcriptional analysis revealed four important genes involved in sphingolipid metabolism to be deregulated in HNF1A deficiency: ORMLD1, sphingosine kinase-2, neutral ceramidase and ceramide synthase-5. The considerable erythrocyte defects in murine HNF1A deficiency encourage clinical studies to explore the hematological consequences of HNF1A deficiency in human MODY3 patients.

  • Submitted March 22, 2017.
  • Accepted October 25, 2017.