ABSTRACT
Krüppel-like factor 1 (KLF1) is an essential transcription factor for erythroid development, as demonstrated by Klf1 knockout mice which die around E14 due to severe anemia. In humans, >65 KLF1 variants, causing different erythroid phenotypes, have been described. The Klf1 Nan variant, a single amino acid substitution (p.E339D) in the DNA binding domain, causes hemolytic anemia and is dominant over wildtype KLF1. Here we describe the effects of the Nan variant during fetal development. We show that Nan embryos have defects in erythroid maturation. RNA-sequencing of the Nan fetal liver cells revealed that Exportin 7 (Xpo7) was among the ~780 deregulated genes. This nuclear exportin is implicated in terminal erythroid differentiation; in particular it is involved in nuclear condensation. Indeed, KLF1 Nan fetal liver cells had larger nuclei and reduced chromatin condensation. Knockdown of XPO7 in wildtype erythroid cells caused a similar phenotype. We conclude that reduced expression of XPO7 is partially responsible for the erythroid defects observed in Nan erythroid cells.
Acknowledgements
TvD and HvdW were supported by the Netherlands Genomics Initiative (NGI Zenith 93511036); IC, TvD, FG and SP by the Landsteiner Foundation for Blood Transfusion Research (LSBR 1040); SH, MvL and SP by the Netherlands Organization for Health Research and Development (ZonMw TOP 40-00812-98-12128); IC, TvD, FG and SP by the EU fp7 Specific Cooperation Research Project THALAMOSS (306201). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Author contributions
I.C., T.v.D,. H.J.G.v.d.W, R.S., M.v.L., F.G. and S.P. designed the experiments. I.C., N.G, R.S., S.H., A.M. and T.v.D. performed the experiments. H.J.G.v.d.W analyzed the 4C-seq and RNA-seq data and wrote the bioinformatics section. Z.O. and W.F.J.v.IJ. performed next generation sequencing experiments. The paper was written by I.C., H.J.G.v.d.W, M.v.L., F.G., T.v.D. and S.P. The authors have no conflicts of interest to declare.