RESUMEN
Structure and developmental expression are described for amphioxus AmphiVent, a homolog of vertebrate Vent genes. In amphioxus, AmphiVent-expressing ventral mesoderm arises at midneurula by outgrowth from the paraxial mesoderm, but in vertebrates, Vent-expressing ventral mesoderm originates earlier, at the gastrula stage. In other embryonic tissues (nascent paraxial mesoderm, neural plate, endoderm, and tailbud), AmphiVent and its vertebrate homologs are expressed in similar spatiotemporal domains, indicating conservation of many Vent gene functions during chordate evolution. The ventral mesoderm evidently develops precociously in vertebrates because their relatively large embryos probably require an early and extensive deployment of the mesoderm-derived circulatory system. The vertebrate ventral mesoderm, in spite of its strikingly early advent, still resembles the nascent ventral mesoderm of amphioxus in expressing Vent homologs. This coincidence may indicate that Vent homologs in vertebrates and amphioxus play comparable roles in ventral mesoderm specification.
Asunto(s)
Cordados no Vertebrados/genética , Proteínas de Unión al ADN/genética , Proteínas de Homeodominio/genética , Mesodermo/metabolismo , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Cordados no Vertebrados/embriología , Cordados no Vertebrados/ultraestructura , Embrión no Mamífero/metabolismo , Embrión no Mamífero/ultraestructura , Evolución Molecular , Duplicación de Gen , Expresión Génica , Genes Homeobox , Proteínas de Homeodominio/química , Proteínas de Homeodominio/clasificación , Proteínas de Homeodominio/fisiología , Hibridación in Situ , Datos de Secuencia Molecular , Cresta Neural/metabolismo , Filogenia , Treonina/químicaRESUMEN
The osa gene of Drosophila melanogaster encodes a nuclear protein that is a component of the Brahma chromatin-remodeling complex. Osa is required for embryonic segmentation, development of the notum and wing margin, and photoreceptor differentiation. In these tissues, osa mutations have effects opposite to those caused by wingless (wg) mutations, suggesting that osa functions as an antagonist of wg signaling. Here we describe the cloning and characterization of mammalian orthologues of osa. Three evolutionarily conserved domains were identified in Osa family members: the N-terminal Bright domain and C-terminally located Osa homology domains 1 and 2. RNase protection analysis indicates a widespread expression of the Osa1 gene during mouse development, in adult tissues, and in cultured cell lines. The Osa1 gene was localized to mouse chromosome 4, within the region syntenic to chromosomal position 1p35-p36 of its human counterpart. We present evidence that the OSA1 product is localized in the nucleus and associates with human Brahma complex, which suggests evolutionarily conserved function for Osa in gene regulation between mammals and Drosophila.
