Cdan1 Is Essential for Primitive Erythropoiesis

Abstract

Congenital dyserythropoietic anemia type I (CDA I) is an autosomal recessive disease characterized by moderate to severe macrocytic anemia and pathognomonic morphologic abnormalities of the erythroid precursors, including spongy heterochromatin. The disease is mainly caused by mutations in CDAN1 (encoding for Codanin-1). No patients with homozygous null type mutations have been described, and mouse null mutants die during early embryogenesis prior to the initiation of erythropoiesis. The cellular functions of Codanin-1 and the erythroid specificity of the phenotype remain elusive. To investigate the role of Codanin-1 in erythropoiesis, we crossed mice carrying the Cdan1 floxed allele (Cdanfl/fl) with mice expressing Cre-recombinase under regulation of the erythropoietin receptor promoter (ErGFPcre). The resulting CdanΔEry transgenic embryos died at mid-gestation (E12.5–E13.5) from severe anemia, with very low numbers of circulating erythroblast. Transmission electron microscopy studies of primitive erythroblasts (E9.5) revealed the pathognomonic spongy heterochromatin. The morphology of CdanΔEry primitive erythroblasts demonstrated progressive development of dyserythropoiesis. Annexin V staining showed increases in both early and late-apoptotic erythroblasts compared to controls. Flow cytometry studies using the erythroid-specific cell-surface markers CD71 and Ter119 demonstrated that CdanΔEry erythroid progenitors do not undergo the semi-synchronous maturation characteristic of primitive erythroblasts. Gene expression studies aimed to evaluate the effect of Cdan1 depletion on erythropoiesis revealed a delay of ζ to α globin switch compared to controls. We also found increased expression of Gata2, Pu.1, and Runx1, which are known to inhibit terminal erythroid differentiation. Consistent with this data, our zebrafish model showed increased gata2 expression upon cdan1 knockdown. In summary, we demonstrated for the first time that Cdan1 is required for primitive erythropoiesis, while providing two experimental models for studying the role of Codanin-1 in erythropoiesis and in the pathogenesis of CDA type I.

The congenital dyserythropoieitic anemias: genetics and pathophysiology

“…Therefore, studying the pathogenesis of the CDAs remains critical to advance the field. The development of novel CDA cell [31 ▪ ,51 ▪ ,96 ▪▪ ,137,138] and animal models [33 ▪▪ ,51 ▪ ] as well as advances in iPSC technology, including differentiation of iPSC from CDA patients into erythroid cells that recapitulate the erythroid defects of the disease [109,131 ▪▪ ], are expected to result in improvement of our understanding of the pathophysiology of these disorders, which will ultimately lead to novel therapies.…”

“…To define the role of Codanin-1 in erythropoiesis, a mouse with a conditional Cdan1 allele was generated, demonstrating that Codanin-1 is essential for primitive erythropoiesis [33 ▪▪ ]. Deletion of Cdan1 in the erythroid compartment resulted in mid-embryonic lethality, with the mutant embryos exhibiting several of the CDA I features [33 ▪▪ ].…”

“…To define the role of Codanin-1 in erythropoiesis, a mouse with a conditional Cdan1 allele was generated, demonstrating that Codanin-1 is essential for primitive erythropoiesis [33 ▪▪ ]. Deletion of Cdan1 in the erythroid compartment resulted in mid-embryonic lethality, with the mutant embryos exhibiting several of the CDA I features [33 ▪▪ ]. Unlike previous reports that suggested that human CDA I erythroblasts exhibit cell cycle arrest at the S phase [34,35], Codanin-1 deficiency in murine erythroid cells appeared to result in cell cycle arrest at the GO/G1 phase [33 ▪▪ ].…”

“…Deletion of Cdan1 in the erythroid compartment resulted in mid-embryonic lethality, with the mutant embryos exhibiting several of the CDA I features [33 ▪▪ ]. Unlike previous reports that suggested that human CDA I erythroblasts exhibit cell cycle arrest at the S phase [34,35], Codanin-1 deficiency in murine erythroid cells appeared to result in cell cycle arrest at the GO/G1 phase [33 ▪▪ ]. Possible explanations for these discrepant cell cycle findings observed in human and mouse CDA I erythroblasts include species-specific differential roles of Codanin-1 in cell cycle regulation or disparate roles of Codanin-1 in primitive versus definitive erythroid cells.…”

Using the Zebrafish as a Genetic Model to Study Erythropoiesis

“…This disease is caused by mutations in CDAN1 gene. In zebrafish embryos, knockdown of cdan1 resulted in reduced gata1a expression, increased gata2a expression, and impaired primitive erythropoiesis [ 143 ]. These results complement the data obtained from mice and suggest that cdan1 deficiency may cause CDAI via misregulation of the erythroid transcription factors gata1 and gata2 [ 143 ].…”