Biology subjects

Donoughe, S.

Publications and source records attributed to Donoughe, S..

6 recordsLinked to original sources

bioRxiv2022

Fat2 polarizes the WAVE complex in trans to align cell protrusions for collective migration

For a group of cells to migrate together, each cell must couple the polarity of its migratory machinery with that of the other cells in the cohort. Although collective cell migrations are common in animal development, little is known about how protrusions are coherently polarized among groups of migrating epithelial cells. We address this problem in the collective migration of the follicular epithelial cells in Drosophila melanogaster. In this epithelium, the cadherin Fat2 localizes to the trailing edge of each cell and promotes the formation of lamellipodia at the leading edge of the cell behind. We show that Fat2 performs this function by acting in trans to restrict WAVE complex activity to one long-lived region along each cells leading edge. Without Fat2, the WAVE complex distribution expands around the cell perimeter and fluctuates over time, resulting in reduced, unpolarized protrusive activity. We further show that Fat2s influence is very local, with sub-micron-scale puncta of Fat2 concentrating the WAVE complex in corresponding puncta just across the leading-trailing cell-cell interface. These findings demonstrate that a trans interaction between Fat2 and the WAVE complex creates stable regions of protrusive activity in each cell and aligns the cells protrusions across the epithelium for directionally persistent collective migration.

developmental biology↗

bioRxiv2020

Repeated loss of variation in insect ovary morphology highlights the role of developmental constraint in life-history evolution

The number of offspring an organism can produce is a key component of its evolutionary fitness and life-history. Here we perform a test of the hypothesized trade off between the number and size of offspring using thousands of descriptions of the number of egg-producing compartments in the insect ovary (ovarioles), a common proxy for potential offspring number in insects. We find evidence of a negative relationship between egg size and ovariole number when accounting for adult body size. However in contrast to prior claims, we note that this relationship is not generalizable across all insect clades, and we highlight several factors that may have contributed to this size-number trade off being stated as a general rule in previous studies. We reconstruct the evolutionary history of the nurse cell arrangement within the ovariole, and show that the diversification of ovariole number and egg size have both been largely independent of nurse cell presence or position within the ovariole. Instead we show that ovariole number evolution has been shaped by a series of transitions between variable and invariant states, with multiple independent lineages evolving to have almost no variation in ovariole number. We highlight the implications of these invariant lineages on our understanding of the specification of ovariole number during development, as well as the importance of considering developmental processes in theories of life-history evolution.

evolutionary biology↗

bioRxiv2018

Insect egg size and shape evolve with ecology, not developmental rate

1The evolution of organism size is hypothesized to be predicted by a combination of development, morphological constraints, and ecological pressures. However, tests of these predictions using phylogenetic methods have been limited by taxon sampling. To overcome this limitation, we generated a database of more than ten thousand observations of insect egg size and shape from the entomological literature and combined them with published genetic and novel life-history datasets. This enabled us to perform phylogenetic tests of long-standing predictions in size evolution across hexapods. Here we show that across eight orders of magnitude in egg volume variation, the relationship between egg shape and size itself evolves, such that predicted universal patterns of scaling do not adequately explain egg shape diversity. We test the hypothesized relationship between size and development, and show that egg size is not correlated with developmental rate across insects, and that for many insects egg size is not correlated with adult body size either. Finally, we show that the evolution of parasitism and aquatic oviposition both help to explain the diversification of egg size and shape across the insect evolutionary tree. Our study challenges assumptions about the evolutionary constraints on egg morphology, suggesting that where eggs are laid, rather than universal mathematical allometric constants, underlies egg size and shape evolution.

evolutionary biology↗

bioRxiv2018

Size, shape and structure of insect wings

The size, shape and structure of insect wings are intimately linked to their ability to fly. However, there are few systematic studies of the variability of the natural patterns in wing morphology across insects. We assemble a comprehensive dataset of insect wings and analyze their morphology using topological and geometric notions in terms of i) wing size and contour shape, ii) vein geometry and topology, and iii) shape and distribution of wing membrane domains. These morphospaces are a first-step in defining the diversity of wing patterns across insect orders and set the stage for investigating their functional consequences.

evolutionary biology↗

bioRxiv2018

A database of egg size and shape from more than 6,700 insect species

1Offspring size is a fundamental trait in disparate biological fields of study. This trait can be measured as the size of plant seeds, animal eggs, or live young, and it influences ecological interactions, organism fitness, maternal investment, and embryonic development. Although multiple evolutionary processes have been predicted to drive the evolution of offspring size, the phylogenetic distribution of this trait remains poorly understood, due to the difficulty of reliably collecting and comparing offspring size data from many species. Here we present a database of 10,449 morphological descriptions of insect eggs, with records for 6,706 unique insect species and representatives from every extant hexapod order. The dataset includes eggs whose volumes span more than eight orders of magnitude. We created this database by partially automating the extraction of egg traits from the primary literature. In the process, we overcame challenges associated with large-scale phenotyping by designing and employing custom bioinformatic solutions to common problems. We matched the taxa in this database to the currently accepted scientific names in taxonomic and genetic databases, which will facilitate the use of this data for testing pressing evolutionary hypotheses in offspring size evolution.

evolutionary biology↗

bioRxiv2017

High-throughput live-imaging of embryos in microwell arrays using a modular, inexpensive specimen mounting system

Live-imaging embryos in a high-throughput manner is essential for shedding light on a wide range of questions in developmental biology, but it is difficult and costly to mount and image embryos in consistent conditions. Here, we present OMMAwell, a simple, reusable device that makes it easy to mount up to hundreds of embryos in arrays of agarose microwells with customizable dimensions and spacing. OMMAwell can be configured to mount specimens for upright or inverted microscopes, and includes a reservoir to hold live-imaging medium to maintain constant moisture and osmolarity of specimens during time-lapse imaging. All device components can be cut from a sheet of acrylic using a laser cutter. Even a novice user will be able to cut the pieces and assemble the device in less than an hour. At the time of writing, the total materials cost is less than five US dollars. We include all device design files in a commonly used format, as well as complete instructions for its fabrication and use. We demonstrate a detailed workflow for designing a custom mold and employing it to simultaneously live-image dozens of embryos at a time for more than five days, using embryos of the cricket Gryllus bimaculatus as an example. Further, we include descriptions, schematics, and design files for molds that can be used with 14 additional vertebrate and invertebrate species, including most major traditional laboratory models and a number of emerging model systems. Molds have been user-tested for embryos including zebrafish (Danio rerio), fruit fly (Drosophila melanogaster), coqui frog (Eleutherodactylus coqui), annelid worm (Capitella teleta), amphipod crustacean (Parhyale hawaiensis), red flour beetle (Tribolium castaneum), and three-banded panther worm (Hofstenia miamia), as well mouse organoids (Mus musculus). Finally, we provide instructions for researchers to customize OMMAwell inserts for embryos or tissues not described herein.\n\nSummary StatementThis Techniques and Resources article describes an inexpensive, customizable device for mounting and live-imaging a wide range of tissues and species; complete design files and instructions for assembly are included.

developmental biology↗