Biology subjects

Kornberg, T. B.

Publications and source records attributed to Kornberg, T. B..

6 recordsLinked to original sources

bioRxiv2020

Cytonemes with complex geometries and composition extend into invaginations of target cells

Cytonemes are specialized filopodia that mediate paracrine signaling in Drosophila and other animals. Studies using fluorescence confocal microscopy (CM) established their general paths, cell targets, and essential roles in signaling. To investigate details unresolvable by CM, we used high pressure freezing and electron microscopy to visualize cytoneme structures, paths, contents, and contacts. We observed cytonemes previously seen by CM in the Drosophila wing imaginal disc system, including in disc, tracheal air sac primordium (ASP), and myoblast cytonemes, and identified cytonemes extending into invaginations of target cells and cytonemes connecting ASP cells and connecting myoblasts. Diameters of cytoneme shafts vary between wide (206 {+/-} 51.8 nm) and thin (55.9 {+/-}16.2 nm) segments at regular intervals. Actin, ribosomes, and membranous compartments are present throughout; rough endoplasmic reticulum and mitochondria are in wider proximal sections. These results reveal novel structural features of filopodia and provide a basis for understanding cytoneme cell biology and function. SummaryCytoneme signaling filopodia of Drosophila cells have regions defined by oscillating diameters, and contents that include ER, mitochondria and ribosomes, and form contacts along invaginations of target cell membranes.

cell biology↗

bioRxiv2020

Regulated delivery controls Drosophila Hedgehog, Wingless and Decapentaplegic signaling

Morphogen signaling proteins disperse across tissues to activate signal transduction in target cells. We investigated dispersion of Hedgehog (Hh), Wingless (Wg), and Bone morphogenic protein homolog Decapentaplegic (Dpp) in the Drosophila wing imaginal disc, and found that delivery to targets is regulated. Cells take up <5% Hh produced, and neither amounts taken up nor extent of signaling changes under conditions of Hh production from 50-200% normal amounts. Similarly, cells take up <25% Wg produced, and variation in Wg production from 50-700% normal has no effect on amounts taken up or signaling. Similar properties were observed for Dpp. Wing disc-produced Hh signals to disc-associated tracheal and myoblast as well as an approximately equal number of disc cells, but the extent of signaling in the disc is unaffected by the presence or absence of the tracheal cells and myoblasts. These findings show that target cells do not take up signaling proteins from a common pool and that both the amount and destination of delivered morphogens are regulated.. SummaryThe extent of Hh, Wg, and Dpp signaling is independent of the amount of signal produced or the number of recipient cells.

developmental biology↗

bioRxiv2020

Hedgehog produced by the Drosophila wing imaginal disc induces distinct expression responses in three target tissues

Hedgehog (Hh) is an evolutionarily conserved signaling protein that has essential roles in animal development and homeostasis. We investigated Hh signaling in the region of the Drosophila wing imaginal disc that produces Hh and is near the tracheal air sac primordium (ASP) and myoblasts. Hh distributes in concentration gradients in the wing disc anterior compartment, ASP, and myoblasts and activates different sets of genes in each tissue. Some transcriptional targets of Hh signal transduction are common to the disc, ASP, and myoblasts, whereas others are tissue-specific. Signaling in the three tissues is cytoneme-mediated and cytoneme-dependent. We conclude that a single source of Hh in the wing disc regulates cell type-specific responses in three discreet target tissues. SummaryHedgehog produced by the wing imaginal disc signals to wing disc, myoblast and tracheal cells

developmental biology↗

bioRxiv2020

Fusion of Drosophila oocytes with specified germline sister cells

In many animals, oocytes develop together with sister germline cells that pass products to the developing oocyte. In Drosophila, fifteen sister germline (nurse) cells in each egg chamber are known to apoptose by stage 12-13, but we discovered that two specific nurse cells that are juxtaposed to the oocyte are eliminated precociously at stage 10B. These nurse cells fuse with the oocyte and their nuclei extrude through an opening that forms in the oocyte. These nuclei extinguish in the ooplasm, and at stage 11, egg chambers have thirteen nucleated nurse cells and the plasma membrane of the oocyte is mostly restored. In infrequent egg chambers in which nurse cells are not eliminated, oocytes do not develop normally and are not fertilized. Precocious elimination is common to other Drosophila species. We conclude that nurse cells are distinguished by position and identity, and that nurse cell dissolution proceeds in two stages.

developmental biology↗

bioRxiv2018

Glutamate signaling at cytoneme synapses

We investigated the roles of neuronal synapse components for development of the Drosophila air sac primordium (ASP). The ASP, an epithelial tube, extends specialized signaling filopodia called cytonemes that take up signals such as Dpp from the wing imaginal disc. Dpp signaling in the ASP requires that disc cells express Dpp, Synaptobrevin, Synaptotagmin-1, the glutamate transporter, and a voltage-gated calcium channel, and that ASP cells express the Dpp receptor, Synaptotagmin-4 and the AMPA-type glutamate receptor GluRII. Calcium transients in ASP cytonemes correlate with signaling activity. Calcium transients in the ASP require GluRII, are activated by L-glutamate and by stimulation of an optogenetic ion channel expressed in the wing disc, and are inhibited by EGTA and NASPM. Activation of GluRII is essential but not sufficient for signaling. Cytoneme-mediated signaling is glutamatergic.\n\nSummaryParacrine signals transfer between Drosophila epithelial cells at glutamatergic synapses.

developmental biology↗

bioRxiv2018

Cytoneme-mediated signaling essential for tumorigenesis

Communication between neoplastic cells and cells of their microenvironment is critical to cancer progression. To investigate the role of cytoneme-mediated signaling as a mechanism for distributing growth factor signaling proteins between tumor and tumor-associated cells, we analyzed EGFR and RET Drosophila tumor models. We tested several genetic loss-of-function conditions that impair cytoneme-mediated signaling. diaphanous, Neuroglian, SCAR, capricious are genes that cytonemes require during normal development. Genetic inhibition of cytonemes restored apical basal polarity to tumor cells, reduced tumor growth, and increased organism survival. These findings suggest that cytonemes traffic the signaling proteins that move between tumor and stromal cells, and that cytoneme-mediated signaling is required for tumor growth and malignancy.\n\nSummaryEssential cytonemes for paracrine signaling in Drosophila tumors

cancer biology↗