RESUMO
Most eukaryotic cell types use a common program to regulate the process of cell division. During mitosis, successful partitioning of the genetic material depends on spatially coordinated chromosome movement and cell cleavage. Here we characterize a zebrafish mutant, retsina (ret), that exhibits an erythroid-specific defect in cell division with marked dyserythropoiesis similar to human congenital dyserythropoietic anemia. Erythroblasts from ret fish show binuclearity and undergo apoptosis due to a failure in the completion of chromosome segregation and cytokinesis. Through positional cloning, we show that the ret mutation is in a gene (slc4a1) encoding the anion exchanger 1 (also called band 3 and AE1), an erythroid-specific cytoskeletal protein. We further show an association between deficiency in Slc4a1 and mitotic defects in the mouse. Rescue experiments in ret zebrafish embryos expressing transgenic slc4a1 with a variety of mutations show that the requirement for band 3 in normal erythroid mitosis is mediated through its protein 4.1R-binding domains. Our report establishes an evolutionarily conserved role for band 3 in erythroid-specific cell division and illustrates the concept of cell-specific adaptation for mitosis.
Assuntos
Proteína 1 de Troca de Ânion do Eritrócito/deficiência , Proteína 1 de Troca de Ânion do Eritrócito/genética , Eritropoese/genética , Mitose/genética , Mutação , Peixe-Zebra/embriologia , Peixe-Zebra/genética , Sequência de Aminoácidos , Anemia Diseritropoética Congênita/genética , Animais , Animais Geneticamente Modificados , Regulação da Expressão Gênica no Desenvolvimento , Humanos , Hibridização in Situ Fluorescente , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Dados de Sequência Molecular , Fenótipo , Peixe-Zebra/sangueRESUMO
In addition to creating the DNA double strand breaks that initiate V(D)J recombination, the RAG proteins are thought to play a critical role in the joining phase of the reaction. One such role, suggested by in vitro studies, might be to ensure the structural integrity of postcleavage complexes, but the significance of such a function in vivo is unknown. We have identified RAG1 mutants that are proficient in DNA cleavage but defective in their ability to interact with coding ends after cleavage and in the capture of target DNA for transposition. As a result, these mutants exhibit severe defects in hybrid joint formation, hairpin coding end opening, and transposition in vitro, and in V(D)J recombination in vivo. Our results suggest that the RAG proteins have an architectural function in facilitating proper and efficient V(D)J joining, and a protective function in preventing degradation of broken ends prior to joining.