Biology subjects

Hulett, R. E.

Publications and source records attributed to Hulett, R. E..

4 recordsLinked to original sources

bioRxiv2026

CRISPR/Cas9-mutagenesis reveals that varying dependence on HSF1 is associated with differences in coral heat tolerance

Coral reefs face declines due to increasing water temperatures associated with climate change. Major research efforts have focused on determining the mechanisms corals can use to adapt to heat stress and identifying molecular indicators for this adaptation. CRISPR/Cas9-based genomic editing promises a new avenue to study gene function in corals; however, these methods are limited by the annual spawning of corals in the wild. Here, we shifted spawning of the reef-building coral Galaxea fascicularis to access gametes multiple times a year in the lab. We discovered the remarkable plasticity and programmability in coral spawning, which enabled the development of a genetically tractable model coral. To investigate the molecular responses of corals to heat stress, we profiled transcriptional changes in heat-tolerant G. fascicularis and heat-sensitive Acropora millepora during acute heat stress. Comparison of the transcriptional responses to heat stress in larvae of the two species revealed that A. millepora has a stronger magnitude of the early heat stress response than G. fascicularis. This increased response in A. millepora included the upregulation of the conserved transcriptional regulator of heat stress response, Heat Shock Transcription Factor 1 (HSF1), and its predicted targets. CRISPR/Cas9 mutagenesis of HSF1 in both species showed that the heat-tolerant G. fascicularis is less dependent on HSF1 than A. millepora for survival during acute heat stress. These results suggest that differences in HSF1 expression after heat exposure contribute to variation in coral heat tolerance and may be used as biomarkers to predict heat tolerance in wild corals.

genetics↗

bioRxiv2023

A wound-induced differentiation trajectory for neurons

Animals capable of whole-body regeneration can replace any missing cell type and regenerate fully-functional new organs, de novo. The regeneration of a new brain requires the formation of diverse neuronal cell types and their assembly into an organized structure and correctly-wired circuits. Recent work in various regenerative animals has revealed transcriptional programs required for the differentiation of distinct neuronal subpopulations, however how these transcriptional programs are initiated upon amputation remains unknown. Here, we focused on the highly regenerative acoel worm, Hofstenia miamia, to study wound-induced transcriptional regulatory events that lead to the production of neurons. Footprinting analysis using chromatin accessibility data on an improved genome assembly revealed that binding sites for the NFY transcription factor complex were significantly bound during regeneration, showing a dynamic increase in binding within one hour upon amputation specifically in tail fragments, which will regenerate a new brain. Strikingly, NFY targets were highly enriched for genes with neuronal functional. Single-cell transcriptome analysis combined with functional studies identified sox4+stem cells as the likely progenitor population for multiple neuronal subtypes. Further, we found that wound-induced sox4 expression is likely under direct transcriptional control by NFY, uncovering a mechanism for how early wound-induced binding of a transcriptional regulator results in the initiation of a neuronal differentiation pathway. HighlightsO_LIA new chromosome-scale assembly for Hofstenia enables comprehensive analysis of transcription factor binding during regeneration C_LIO_LINFY motifs become dynamically bound by 1hpa in regenerating tail fragments, particularly in the loci of neural genes C_LIO_LIA sox4+ neural-specialized stem cell is identified using scRNA-seq C_LIO_LIsox4 is wound-induced and required for differentiation of multiple neural cell types C_LIO_LINFY regulates wound-induced expression of sox4 during regeneration C_LI

developmental biology↗

bioRxiv2022

Acoel single-cell atlas reveals expression dynamics and heterogeneity of a pluripotent stem cell population

Pluripotent adult stem cell populations underlie whole-body regeneration in many distantly related animal lineages. These collectively pluripotent populations of cells share some features across species, such as the expression of piwi and other germline-related genes. Studies of how these cells operate during regeneration are needed in diverse systems to determine how underlying cellular and molecular mechanisms of renewal and differentiation compare. Here, we sought to characterize stem cells and their dynamics in the acoel Hofstenia miamia, a highly regenerative marine worm with a piwi-expressing stem cell population called neoblasts. Transcriptome profiling at single cell resolution revealed cell types shared across postembryonic stages, including stem cells and differentiated cell types such as neural, epidermal, muscle, and digestive cells. Reconstruction of single-cell differentiation trajectories followed by functional studies confirmed that neoblasts are the source of differentiated cells and identified transcription factors needed for the formation of major cell types. Next, analysis of single-cell transcriptomes from regenerating worms showed that both differentiated cells and stem cells dynamically alter gene expression in response to amputation. Further analysis of the stem cells recovered subpopulations of neoblasts, each with specific transcriptional profiles suggesting that the majority of neoblasts are specialized to differentiated lineages, reflecting putatively lineage-primed progenitors. Notably, neoblast subsets in Hofstenia were identifiable consistently across postembryonic stages and also displayed differential expression dynamics in response to wounding. Altogether, these data suggest that whole-body regeneration is accomplished by the coordination of cells with distinct and dynamic transcriptomic profiles through time. Furthermore, the data generated here will enable the study of how this coordination is achieved, enhancing our understanding of pluripotent stem cells and their evolution across metazoans.

developmental biology↗

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↗