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James Castelli Gair

Universidad Pablo de Olavide
Carretera de Utrera Km1
Seville, Seville 41013

00 34 954348942

Taxa Studied: Invertebrate Animals
Techniques Employed: In Situ Hybridization, Antibody Staining, Confocal Microscopy, Time-Lapse Microscopy, Transgenesis, Mutagenesis
Research Description: Our group studies how two-dimensional epithelial sheets of cells reorganize during development to make specific organs. To address this issue we are using two models: The ectodermal endocrine glands (corpora allata and prothoracic glands), and the external respiratory organ of the larva (the posterior spiracles). The glands allow studying the morphogenesis and evolution of a migratory organ, while the spiracles allow studying how cell shape changes and cell rearrangements contribute to the formation of a tube. Both structures are regulated by complex gene-networks activated by Hox genes. Dfd, Scr and the endocrine glands: The endocrine control of metamorphosis in insects is mediated by the corpora allata and the prothoracic glands. In diptera these fuse to the corpora cardiaca giving rise to the ring gland. We found that the corpora allata and the prothoracic gland arise from ectoderm cells homologous to those that in other segments give rise to the trachea. This is one of the most extreme cases of divergent evolution known to date. Both trachea and glands use similar genes for their early development, but soon they start diverging by the activation of specific genes that result in the formation of morphologically and functionally different structures. While the trachea maintain their polarized structure, the glands suffer an epithelial to mesenchymal transition. We analyze the genes controlling this transition as well as the signals directing their migration. We have shown that trachea and glands can be converted into each other, suggesting they originated from an ancient repeated metameric structure. This model allows the study of how divergent evolution may have occurred. Abd-B and the posterior spiracles: We have shown that during spiracle formation, the Hox transcription factor ABD-B activates a unique transcriptional cascade in the eighth abdominal segment that induces the cells to change shape and rearrange their relative positions leading to the invagination of the posterior spiracles. We have found that the targets of this Hox transcriptional cascade include apico-basal cell polarity genes, cadherins and GAP and GEF regulators of the small GTPase Rho, which control the actin cytoskeleton in the spiracle. We are currently analyzing how all these fundamental proteins are co-ordinately modulated to induce the characteristic elongation and rearrangement cell behaviours of the developing spiracles. We have proposed a model to explain how Abd-B recruited during evolution the complex gene network that gives rise to the spiracles.
Lab Web Page: http://www.cabd.es/en-research_groups-11-21-cell-integration-of-diverse-genetic-inputs-during-the-morphogenesis-of-complex-organs-summary.html
Willing to Host Undergraduates: YES
Actively Seeking Undergraduates: YES
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