Abstract
CUL4A and CUL4B are closely related members in Cullin family and can each assemble a Cullin-RING E3 ligase complex (Cullin-RING Ligase 4A or 4B, CRL4A, or CRL4B) and participate in a variety of biological processes. Previously we showed that zebrafish cul4a, but not cul4b, is essential for cardiac and pectoral fin development. Here, we have identified cul4a as a crucial regulator of primitive erythropoiesis in zebrafish embryonic development. Depletion of cul4a resulted in a striking reduction of erythroid cells due to the inhibition of erythroid differentiation. Transcript levels for early hematopoietic regulatory genes including scl, lmo2, and gata1 are significantly reduced in cul4a-deficient embryos. Mechanistically, we demonstrated that scl and gata1, the central regulators of primitive hematopoiesis for erythroid determination, are transcriptionally upregulated by cul4a. These findings demonstrate an important role for cul4a in primitive erythropoiesis and may bear implications in regeneration medicine of anemia and related diseases.
Highlights
Zebrafish (Danio rerio) has become a powerful model for investigating hematopoiesis because its transparency greatly facilitates the visualization of hematopoietic system
To assess whether cul4a is involved in the blood cell development in zebrafish, we firstly examined the expression pattern of cul4a during zebrafish embryonic development using whole-mount in situ hybridization (WISH)
To determine whether the hematopoietic defects observed in cul4a morphants resulted from a nonspecific morpholino effect, we performed rescue experiments using a mismatch cul4a mRNA to avoid targeting by cul4a-MO
Summary
Zebrafish (Danio rerio) has become a powerful model for investigating hematopoiesis because its transparency greatly facilitates the visualization of hematopoietic system. The first wave generates primitive erythrocytes (primitive erythropoiesis) and macrophages (primitive myelopoiesis), and the second wave produces hematopoietic stem cells (HSCs)[4]. The primitive myelopoiesis occurs at the anterior lateral plate mesoderm, while primitive erythropoiesis takes place at the posterior lateral plate mesoderm (PLPM), Pu.[1], a transcription factor that contains an ETS domain, plays an indispensable role in primitive myelopoiesis[10,11]. Definitive hematopoiesis is initiated by the transcription factors of Runx[1] and c-Myb[6]. The importance of these transcription factors has been demonstrated in cell-based ex vivo assays as well as in knockout mouse models, the regulation of their expression remains poorly understood
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