Biomedical subjects

Alfonso Martinez-Arias

Publications and source records attributed to Alfonso Martinez-Arias.

3 recordsLinked to original sources

PubMed2006

Notch signaling pathway.

Notch is a receptor that mediates intercellular signaling through a pathway conserved across the metazoa. It is involved in cell fate assignation and pattern formation during development. The receptor acts as a membrane-tethered transcription factor and is activated by members of the Delta, Serrate, Lag-2 family of Notch ligands, which trigger two successive proteolytic cleavages of the receptor. The second cleavage releases the intracellular domain of Notch, which translocates to the nucleus, where it interacts with the CSL family of transcriptional regulators and forms part of a Notch target gene-activating complex. In the absence of signaling, CSL [CBF1, Su(H), Lag-1] regulators repress Notch target genes through interactions with several transcriptional co-repressors that recruit histone deacetylases and other chromatin-modifying enzymes. After forming, the transcription-activating binary Notch intracellular domain-CSL complex recruits several proteins that facilitate transcription, among them the coactivator MAM and histone acetylases. Transcription of target genes is terminated when the Notch intracellular domain is degraded in a proteasome-dependent manner.

Animals↗

PubMed2002

Dynamic analysis of actin cable function during Drosophila dorsal closure.

Throughout development, a series of epithelial movements and fusions occur that collectively shape the embryo. They are dependent on coordinated reorganizations and contractions of the actin cytoskeleton within defined populations of epithelial cells. One paradigm morphogenetic movement, dorsal closure in the Drosophila embryo, involves closure of a dorsal epithelial hole by sweeping of epithelium from the two sides of the embryo over the exposed extraembryonic amnioserosa to form a seam where the two epithelial edges fuse together. The front row cells exhibit a thick actin cable at their leading edge. Here, we test the function of this cable by live analysis of GFP-actin-expressing embryos in which the cable is disrupted by modulating Rho1 signaling or by loss of non-muscle myosin (Zipper) function. We show that the cable serves a dual role during dorsal closure. It is contractile and thus can operate as a "purse string," but it also restricts forward movement of the leading edge and excess activity of filopodia/lamellipodia. Stripes of epithelium in which cable assembly is disrupted gain a migrational advantage over their wild-type neighbors, suggesting that the cable acts to restrain front row cells, thus maintaining a taut, free edge for efficient zippering together of the epithelial sheets.

Actins↗

PubMed1986

The Antennapedia gene is required and expressed in parasegments 4 and 5 of the Drosophila embryo.

Transcripts homologous to the 5' exon of the Antp gene accumulate in parasegments 4 and 5 of the Drosophila embryo, where analysis of the cuticular phenotype of Antennapedia (Antp) embryos shows that there is a genetic requirement for the Antp gene. The pattern of Antp expression is different in different germ layers; the mesoderm expresses Antp only in parasegment 5; in the developing nervous system and the epidermis the pattern of expression is complex and suggests that interactions between different selector genes take place during wild-type development. Both genetic requirements and gene expression indicate that Antennapedia is the main morphological determinant in parasegment 4; in parasegment 5 it probably acts in concert with other selector genes.

Journal Article↗