Biology subjects

King, N.

Publications and source records attributed to King, N..

6 recordsLinked to original sources

bioRxiv2018

Glycosyltransferase homologs prevent promiscuous cell aggregation and promote multicellular development in the choanoflagellate S. rosetta

The mechanisms underlying multicellular development in the animal stem lineage may be reconstructed through the study of choanoflagellates, the closest living relatives of animals. To determine the genetic underpinnings of multicellularity in the emerging model choanoflagellate S. rosetta, we performed a screen for mutants with defects in multicellular rosette development. In two of the mutants, Jumble and Couscous, single cells failed to develop into orderly rosettes but instead aggregated promiscuously into amorphous clumps of cells. Both mutants mapped to lesions in genes encoding glycosyltransferases and the mutations perturbed glycosylation patterns in the extracellular matrix (ECM). In animals, glycosyltransferases transfer activated sugars to donor molecules and thereby sculpt the polysaccharide-rich ECM, regulate integrin and cadherin activity, and, when disrupted, contribute to tumorigenesis. The finding that glycosyltransferases promote proper rosette development and prevent cell aggregation in S. rosetta suggests a pre-metazoan role for glycosyltransferases in regulating development and preventing abnormal tumor-like multicellularity.\n\nIMPACT STATEMENTA genetic screen reveals that glycosyltransferases are required for proper rosette development and the prevention of cell clumping in one of the closest living relatives of animals, the choanoflagellate S. rosetta.

genetics↗

bioRxiv2018

A robust method for transfection in choanoflagellates illuminates their cell biology and the ancestry of animal septins

As the closest living relatives of animals, choanoflagellates offer unique insights into animal origins and core mechanisms underlying animal cell biology. However, unlike traditional model organisms, such as yeast, flies and worms, choanoflagellates have been refractory to DNA delivery methods for expressing foreign genes. Here we report the establishment of a robust method for expressing transgenes in the choanoflagellate Salpingoeca rosetta, overcoming barriers that have previously hampered DNA delivery and expression. To demonstrate how this method accelerates the study of S. rosetta cell biology, we engineered a panel of fluorescent protein markers that illuminate key features of choanoflagellate cells. We then investigated the localization of choanoflagellate septins, a family of GTP-binding cytoskeletal proteins that are hypothesized to regulate the multicellular rosette development in S. rosetta. Fluorescently tagged septins localized to the basal pole of S. rosetta single cells and rosettes in a pattern resembling septin localization in animal epithelia. The establishment of transfection in S. rosetta and its application to the study of septins represent critical advances in the growth of S. rosetta as an experimental model for investigating choanoflagellate cell biology, core mechanisms underlying animal cell biology, and the origin of animals.

cell biology↗

bioRxiv2017

The ancestral animal genetic toolkit revealed by diverse choanoflagellate transcriptomes

The changes in gene content that preceded the origin of animals can be reconstructed by comparison with their sister group, the choanoflagellates. However, only two choanoflagellate genomes are currently available, providing poor coverage of their diversity. We sequenced transcriptomes of 19 additional choanoflagellate species to produce a comprehensive reconstruction of the gains and losses that shaped the ancestral animal gene repertoire. We find roughly 1,700 gene families with origins on the animal stem lineage, of which only a core set of 36 are conserved across animals. We find more than 350 gene families that were previously thought to be animal-specific actually evolved before the animal-choanoflagellate divergence, including Notch and Delta, Toll-like receptors, and glycosaminoglycan hydrolases that regulate animal extracellular matrix (ECM). In the choanoflagellate Salpingoeca helianthica, we show that a glycosaminoglycan hydrolase modulates rosette colony size, suggesting a link between ECM regulation and morphogenesis in choanoflagellates and animals.\n\nData AvailabilityRaw sequencing reads: NCBI BioProject PRJNA419411 (19 choanoflagellate transcriptomes), PRJNA420352 (S. rosetta polyA selection test)\n\nTranscriptome assemblies, annotations, and gene families: https://dx.doi.org/10.6084/m9.figshare.5686984\n\nProtocols: https://dx.doi.org/10.17504/protocols.io.kwscxee

evolutionary biology↗

bioRxiv2017

Lessons from simple marine models on the bacterial regulation of eukaryotic development

Molecular cues from environmental bacteria influence important developmental decisions in diverse marine eukaryotes. Yet, relatively little is understood about the mechanisms underlying these interactions, in part because marine ecosystems are dynamic and complex. With the help of simple model systems, including the choanoflagellate Salpingoeca rosetta, we have begun to uncover the bacterial cues that shape eukaryotic development in the ocean. Here, we review how diverse bacterial cues - from lipids to macromolecules - regulate development in marine eukaryotes. It is becoming clear that there are networks of chemical information circulating in the ocean, with both eukaryotes and bacteria acting as nodes; one eukaryote can precisely respond to cues from several diverse environmental bacteria, and a single environmental bacterium can regulate the development of different eukaryotes.\n\nHighlightsO_LICues from environmental bacteria influence the development of many marine eukaryotes\nC_LIO_LIThe molecular cues produced by environmental bacteria are structurally diverse\nC_LIO_LIEukaryotes can respond to many different environmental bacteria\nC_LIO_LISome environmental bacteria act as \"information hubs\" for diverse eukaryotes\nC_LIO_LIExperimentally tractable systems, like the choanoflagellate S. rosetta, promise to reveal molecular mechanisms underlying these interactions\nC_LI

microbiology↗

bioRxiv2017

The origin of animal multicellularity and cell differentiation

How animals evolved from their single-celled ancestors over 600 million years ago is poorly understood. Comparisons of genomes from animals and their closest relatives - choanoflagellates, filastereans and ichthyosporeans - have recently revealed the genomic landscape of animal origins. However, the cell and developmental biology of the first animals have been less well examined. Using principles from evolutionary cell biology, we reason that the last common ancestor of animals and choanoflagellates (the Urchoanozoan) used a collar complex - a flagellum surrounded by a microvillar collar - to capture bacterial prey. The origin of animal multicellularity likely occurred through the modification of pre-existing mechanisms for extracellular matrix synthesis and regulation of cytokinesis. The progenitors of animals likely developed clonally through serial division of flagellated cells, giving rise to sheets of cells that folded into spheres by a morphogenetic process comparable to that seen in modern choanoflagellate rosettes and calcareous sponge embryos. Finally, we infer that cell differentiation evolved in the animal stem-lineage by a combination of three mechanisms: division of labor from ancient plurifunctional cell types, conversion of temporally segregated phenotypes into spatially segregated cell types, and functional innovation.

evolutionary biology↗

bioRxiv2017

An Aphrodisiac Produced By Vibrio fischeri Stimulates Mating In The Closest Living Relatives Of Animals

We serendipitously discovered that the marine bacterium Vibrio fischeri induces sexual reproduction in one of the closest living relatives of animals, the choanoflagellate Salpingoeca rosetta. Although bacteria influence everything from nutrition and metabolism to cell biology and development in eukaryotes, bacterial regulation of eukaryotic mating was unexpected. Here we show that a single V. fischeri protein, the previously uncharacterized EroS, fully recapitulates the aphrodisiac activity of live V. fischeri. EroS is a chondroitin lyase; although its substrate, chondroitin sulfate, was previously thought to be an animal synapomorphy, we demonstrate that S. rosetta produces chondroitin sulfate and thus extend the ancestry of this important glycosaminoglycan to the premetazoan era. Finally, we show that V. fischeri, purified EroS, and other bacterial chondroitin lyases induce S. rosetta mating at environmentally-relevant concentrations suggesting that bacterially-produced aphrodisiacs likely regulate choanoflagellate mating in nature.

microbiology↗