CDAN1 is necessary for embryonal erythropoiesis

Congenital dyserythropoietic anemia type I (CDA I), is an autosomal recessive disease with moderate-to severe macrocytic anemia in which erythroid precursors in the bone marrow exhibit pathognomonic abnormalities including spongy heterochromatin. We have shown that the CDAN1 gene, which is mutated in CDA I, encodes Codanin-1, a ubiquitously expressed and evolutionary conserved protein. Mutations in CDA I patients are always hypomorphic, and mouse null mutants die during early embryogenesis. Even though Codanin-1 is an essential protein, the cellular functions of Codanin-1 remains elusive, and it is not clear why the erythroid lineage is highly sensitive to lower activity of Codanin-1.

To Investigate of the role of Codanin-1 in erythropoiesis we crossed mice with Cdan1 floxed allele (Cdan^fl/fl) with mice that express Cre-recombinase under regulation of the Erythropoietin receptor promoter (EpoRcre). The resulting CdanΔEry transgenics die at mid-gestation (E11.5-E13.5) from severe anemia.

To monitor erythroid differentiation in circulating primitive erythroid cells we used both morphological analysis and flow cytometry. Cytospins of CdanΔEry primitive erythroblasts show abnormal morphology and dyserythropoiesis. TEM analysis of E9.5 erythroblasts demonstrates the characteristic spongy heterochromatin. By day E12.5 most of the cells are dying. We assessed for apoptosis using AnnexinV staining. CdanΔEry E10.5 embryos have an increase in both early- and late-apoptotic erythroblasts compared to controls. Flow cytometry using erythroid-specific cell-surface markers reveals that CdanΔEry peripheral blood erythroblasts do not undergo the synchronous maturation characteristic of primitive erythroblasts.

In summary, we demonstrate for the first time that Cdan1 is required for erythropoiesis, while providing an experimental model for the human disease.