Smoothened-mediated Hedgehog signalling is required for the maintenance of the anterior-posterior lineage restriction in the developing wing of Drosophila

• DOI: 10.1242/dev.124.20.4053
• Publication Date: 2021-04-26T03:00:48Z
• Authors: Seth S. Blair; Amy Ralston
• Keywords: Homeodomain Proteins; 0303 health sciences; Gene Expression Regulation, Developmental; Genes, Insect; Receptors, Cell Surface; Smoothened Receptor; Receptors, G-Protein-Coupled; 03 medical and health sciences; Animals; Drosophila Proteins; Wings, Animal; Cell Lineage; Drosophila; Signal Transduction; Transcription Factors

ABSTRACT It is thought that the posterior expression of the ‘selector’ genes engrailed and invected control the subdivision of the growing wing imaginal disc of Drosophila into anterior and posterior lineage compartments. At present, the cellular mechanisms by which separate lineage compartments are maintained are not known. Most models have assumed that the presence or absence of selector gene expression autonomously drives the expression of compartment-specific adhesion or recognition molecules that inhibit intermixing between compartments. However, our present understanding of Hedgehog signalling from posterior to anterior cells raises some interesting alternative models based on a cell’s response to signalling. We show here that anterior cells that lack smoothened, and thus the ability to receive the Hedgehog signal, no longer obey a lineage restriction in the normal position of the anterior-posterior boundary. Rather these clones extend into anatomically posterior territory, without any changes in engrailed/invected gene expression. We have also examined clones lacking both en and inv; these too show complex behaviors near the normal site of the compartment boundary, and do not always cross entirely into anatom-ically anterior territory. Our results suggest that compart-mentalization is a complex process involving intercom-partmental signalling; models based on changes in affinity or growth will be discussed.