Mutations affecting the secretory COPII coat component SEC23B cause congenital dyserythropoietic anemia type II

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Congenital dyserythropoietic anemias (CDAs) are phenotypically and genotypically heterogeneous diseases1,2,3,4. CDA type II (CDAII) is the most frequent CDA. It is characterized by ineffective erythropoiesis and by the presence of bi- and multinucleated erythroblasts in bone marrow, with nuclei of equal size and DNA content, suggesting a cytokinesis disturbance5. Other features of the peripheral red blood cells are protein and lipid dysglycosylation and endoplasmic reticulum double-membrane remnants4,6. Development of other hematopoietic lineages is normal. Individuals with CDAII show progressive splenomegaly, gallstones and iron overload potentially with liver cirrhosis or cardiac failure. Here we show that the gene encoding the secretory COPII component SEC23B is mutated in CDAII. Short hairpin RNA (shRNA)-mediated suppression of SEC23B expression recapitulates the cytokinesis defect. Knockdown of zebrafish sec23b also leads to aberrant erythrocyte development. Our results provide in vivo evidence for SEC23B selectivity in erythroid differentiation and show that SEC23A and SEC23B, although highly related paralogous secretory COPII components, are nonredundant in erythrocyte maturation.

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Figure 1: SEC23B mutation analysis.
Figure 2: SEC23B expression and function in erythroid cells.
Figure 3: Analysis of sec23b zebrafish morphants.

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NCBI Reference Sequence

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We acknowledge the technical assistance of S. Braun, I. Janz, T. Kersten, G. Baur, T. Becker and R. Leichtle. Anti-ts-O45-G monoclonal antibody 'VG' was a gift from K. Simons (Max Planck Institute of Molecular Cell Biology and Genetics). HeLa-Kyoto cells (human cervix carcinoma cells) were from S. Narumiya (Kyoto University) and T. Hirota (Institute of Molecular Pathology). These studies were supported by the German Red Cross Blood Service Baden-Wuerttemberg-Hessen to K.S., by the University of Ulm to H.H. and by the Else Kröner Fresenius Stiftung to K.S. and H.H. Additional support was provided by the Italian Ministero dell'Università e della Ricerca, by Telethon (Italy), by grants MUR-P35/126/IND and by grants Convenzione CEINGE-Regione Campania-Ass. Sanità to A.I. University of Utah Core facilities were supported by an US National Institutes of Health grant. K.-P.H. acknowledges support from the Deutsche Forschungsgemeinschaft (SFB 684). We thank the DIM Facility for imaging microscopy and the Flow Cytometry Facility for cell cycle analyses at CEINGE Institute.

Author information

K.S., A.I. and H.H. designed the study. H.H., A.I., S.P. and J. Delaunay treated subjects, collected clinical data and, together with J. Denecke, performed clinical laboratory analyses. K. Holzmann performed and K. Holzmann and K.S. analyzed the chip experiments. K.S., F.V., R.R., M.R.E., D.S., L.D.F., K. Heinrich, B.J., U.P. and R.P. performed the molecular, protein and cell analyses. K.-P.H. modeled the SEC23B structure. N.S.T. and W.H. performed zebrafish morpholino injections, blood cell preparations and electron microscopy. W.C. and B.H.P. performed the zebrafish western blot analysis. M.T.R. did the FACS analyses and fibroblast differentiation. K.S., A.I. and H.H. wrote the paper.

Correspondence to Klaus Schwarz or Achille Iolascon.

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