Biology subjects

Bostock, M. P.

Publications and source records attributed to Bostock, M. P..

4 recordsLinked to original sources

bioRxiv2026

Glia generate distinct visual processing centres by locally inhibiting ERK activity in an optic lobe neuroepithelium

Epithelial patterning is fundamental to organ development. Extensive work has focused on how neuroepithelia are patterned to generate diverse progenitors, yet how a single neuroepithelium is partitioned to produce distinct processing centres is poorly understood. Here, we focus on the Drosophila outer proliferation centre neuroepithelium, which generates the medulla and lamina visual processing centres. Medulla neuroblasts are produced by a proneural wave that initiates at the medial margin of the neuroepithelium and moves laterally propagated by EGFR-ERK signalling, whereas lamina precursors arise at the lateral neuroepithelial margin and have been proposed to require photoreceptor-derived Hedgehog. Here, we show that Hedgehog signalling is dispensable for lamina precursor specification but instead promotes their survival. In contrast, suppressing ERK and apoptosis together is sufficient to drive ectopic lamina precursor development. We find that cortex glia secrete the EGF antagonist Argos, which accumulates at the lateral neuroepithelium, thus repressing ERK activity locally. Together, our findings reveal a glia-mediated, extrinsic patterning mechanism that suppresses EGFR-ERK signalling in the lateral neuroepithelium, protecting these cells from the proneural wave and instructing lamina over medulla fate. Summary statementGlial cells locally control ERK signalling to partition a developing tissue, enabling distinct structures to arise from a common neuroepithelium.

developmental biology↗

bioRxiv2022

Photoreceptors generate neuronal diversity in their target field through a Hedgehog morphogen gradient in Drosophila

Defining the origin of neuronal diversity is a major challenge in developmental neurobiology. The Drosophila visual system is an excellent paradigm to study how cellular diversity is generated. Photoreceptors from the eye disc grow their axons into the optic lobe and secrete Hedgehog (Hh) to induce the lamina, such that for every unit eye there is a corresponding lamina unit made up of post-mitotic precursors stacked into columns. Each differentiated column contains five lamina neuron types (L1-L5), making it the simplest neuropil in the optic lobe, yet how this diversity is generated was unknown. Here, we found that Hh pathway activity is graded along the distal-proximal axis of lamina columns and further determined that this gradient in pathway activity arises from a gradient of Hh ligand. We manipulated Hh pathway activity cell-autonomously in lamina precursors and non-cell autonomously by inactivating the Hh ligand, and by knocking it down in photoreceptors. These manipulations showed that different thresholds of activity specify unique cell identities, with more proximal cell types specified in response to progressively lower Hh levels. Thus, our data establish that Hh acts as a morphogen to pattern the lamina. Although, this is the first such report during Drosophila nervous system development, our work uncovers a remarkable similarity with the vertebrate neural tube, which is patterned by Sonic Hedgehog. Altogether, we show that differentiating neurons can regulate the neuronal diversity of their distant target fields through morphogen gradients.

developmental biology↗

bioRxiv2021

Differentiation signals from glia are fine-tuned to set neuronal numbers during development

Neural circuit formation and function require that diverse neurons are specified in appropriate numbers. Known strategies for controlling neuronal numbers involve regulating either cell proliferation or survival. We used the Drosophila visual system to probe how neuronal numbers are set. Photoreceptors from the eye-disc induce their target field, the lamina, such that for every unit eye there is a corresponding lamina unit (column). Although each column initially contains [~]6 post-mitotic lamina precursors, only 5 differentiate into neurons, called L1-L5; the extra precursor, which is invariantly positioned above the L5 neuron in each column, undergoes apoptosis. Here, we showed that a glial population called the outer chiasm giant glia (xgO), which resides below the lamina, secretes multiple ligands to induce L5 differentiation in response to EGF from photoreceptors. By forcing neuronal differentiation in the lamina, we uncovered that though fated to die, the extra precursor is specified as an L5. Therefore, two precursors are specified as L5s but only one differentiates during normal development. We found that the row of precursors nearest to xgO differentiate into L5s and, in turn, antagonise differentiation signalling to prevent the extra precursors from differentiating, resulting in their death. Thus, an intricate interplay of glial signals and feedback from differentiating neurons defines an invariant and stereotyped pattern of neuronal differentiation and programmed cell death to ensure that lamina columns each contain exactly one L5 neuron.

developmental biology↗

bioRxiv2020

An immobilization technique for long-term time-lapse imaging of explanted Drosophila tissues

Time-lapse imaging is an essential tool to study dynamic biological processes that cannot be discerned from fixed samples alone. However, imaging cell- and tissue-level processes in intact animals poses numerous challenges if the organism is opaque and/or motile. Explant cultures of intact tissues circumvent some of these challenges, but sample drift remains a considerable obstacle. We employed a simple yet effective technique to immobilize tissues in medium-bathed agarose. We applied this technique to study multiple Drosophila tissues from first-instar larvae to adult stages in various orientations and with no evidence of anisotropic pressure or stress damage. Using this method, we were able to image fine features for up to 18 hours and make novel observations. Specifically, we report that fibers characteristic of quiescent neuroblasts are inherited by their basal daughters during reactivation; that the lamina in the developing visual system is assembled roughly 2-3 columns at a time; that lamina glia positions are dynamic during development; and that the nuclear envelopes of adult testis cyst stem cells do not break down completely during mitosis. In all, we demonstrate that our protocol is well-suited for tissue immobilization and long-term live imaging, enabling new insights into tissue and cell dynamics in Drosophila.

developmental biology↗