RESUMEN
Hibris (Hbs) is a transmembrane immunoglobulin-like protein that shows extensive homology to Drosophila Sticks and stones (Sns) and human kidney protein Nephrin. Hbs is expressed in embryonic visceral, somatic and pharyngeal mesoderm among other tissues. In the somatic mesoderm, Hbs is restricted to fusion competent myoblasts and is regulated by Notch and Ras signaling pathways. Embryos that lack or overexpress hbs show a partial block of myoblast fusion, followed by abnormal muscle morphogenesis. Abnormalities in visceral mesoderm are also observed. In vivo mapping of functional domains suggests that the intracellular domain mediates Hbs activity. Hbs and its paralog, Sns, co-localize at the cell membrane of fusion-competent myoblasts. The two proteins act antagonistically: loss of sns dominantly suppresses the hbs myoblast fusion and visceral mesoderm phenotypes, and enhances Hbs overexpression phenotypes. Data from a P-homed enhancer reporter into hbs and co-localization studies with Sns suggest that hbs is not continuously expressed in all fusion-competent myoblasts during the fusion process. We propose that the temporal pattern of hbs expression within fusion-competent myoblasts may reflect previously undescribed functional differences within this myoblast population.
Asunto(s)
Proteínas de Drosophila , Drosophila/genética , Regulación del Desarrollo de la Expresión Génica , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Músculo Esquelético/embriología , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Diferenciación Celular/genética , Fusión Celular , Clonación Molecular , Drosophila/embriología , Embrión no Mamífero , Inmunoglobulinas/genética , Inmunoglobulinas/metabolismo , Proteínas de Insectos/genética , Proteínas de Insectos/metabolismo , Mesodermo , Datos de Secuencia Molecular , Músculo Esquelético/citología , Mutación , Receptores Notch , Homología de Secuencia de Aminoácido , Transducción de Señal , Vísceras/anomalías , Vísceras/embriología , Proteínas ras/metabolismoRESUMEN
saliva (slv) transcription begins at the salivary gland placodes and continues on throughout development as salivary glands invaginate and reach their final location and morphology. saliva is located cytogenetically in 76A/B, and encodes a 226-amino-acid protein with four hydrophobic domains. A Northern blot detects a 1.6-kb transcript throughout development. Database similarity searches reveal homology to proteins from Caenorhabditis, Lilium, Medicago and mouse.
Asunto(s)
Proteínas de Drosophila , Drosophila melanogaster/genética , Genes de Insecto/genética , Genes de Plantas/genética , Glándulas Salivales/embriología , Proteínas y Péptidos Salivales/genética , Vertebrados/genética , Secuencia de Aminoácidos , Animales , ADN Complementario/química , ADN Complementario/genética , ADN de Plantas/química , ADN de Plantas/genética , Drosophila melanogaster/química , Drosophila melanogaster/embriología , Embrión no Mamífero/metabolismo , Regulación del Desarrollo de la Expresión Génica , Hibridación in Situ , Datos de Secuencia Molecular , Plantas/genética , Glándulas Salivales/metabolismo , Alineación de Secuencia , Análisis de Secuencia de ADN , Homología de Secuencia de AminoácidoRESUMEN
The homeotic gene Ultrabithorax encodes a family of six homeoproteins translated from alternatively spliced mRNAs. The structures of these UBX isoforms have been conserved among anciently diverged Drosoph-ila species and functional distinctions between some isoforms have been reported that suggest subtle but important roles in Ubx action. We present a detailed analysis of the expression patterns of Ubx mRNAs and proteins during embryogenesis, using isoform-specific monoclonal antibodies and synthetic oligonucleotide probes. These patterns are remarkably complex, each mRNA and corresponding protein isoform being expressed in a partially overlapping but distinct stage and tissue-specific pattern. The complexity is greatest in the central nervous system, where different isoforms predominate during successive developmental stages and where their relative proportions differ from one metamere to another and even among individual neurons within a given metamere. The distributions of UBX isoforms are consistent with those functional distinctions that have been described; they also suggest that different isoforms may be specialized or optimized to control different aspects of central nervous system development. The close correspondence between the mRNA and protein patterns indicates that the mRNAs do not differ strongly in translatability, despite the abundance of rare codons in the optional exons. There is a delay between the detection of particular splicing events in the nucleus and the detection of the 3' end of the message or the appearance of the corresponding mRNAs and proteins in the cytoplasm. This delay is consistent with the size of the Ubx introns and indicates a cotranscriptional mechanism of splicing.
Asunto(s)
Clonación Molecular/métodos , Proteínas de Drosophila , Drosophila/genética , Hormonas de Insectos/genética , Proteínas de la Membrana , Proteínas del Tejido Nervioso , Poli C/genética , Animales , Artefactos , Composición de Base , Secuencia de Bases , Cartilla de ADN , ADN Complementario/genética , Bases de Datos Factuales , Datos de Secuencia Molecular , Reacción en Cadena de la PolimerasaRESUMEN
We describe a method for the in situ detection of specific splicing variants. The method is based on the use of antisense oligonucleotides designed to span splice junctions labelled with digoxigenin by terminal transferase tailing. We find that the spatial patterns of Ubx splicing variants Ia and IIa are similar in early embryos, but differ in late embryos. Variant IVa is only detected in the CNS (ps6) at stages 16 and 17. We also present evidence indicating that the first splicing event is cotranscriptional.