Biology subjects

Rasmussen, T. L.

Publications and source records attributed to Rasmussen, T. L..

3 recordsLinked to original sources

bioRxiv2022

EZ Clear for simple, rapid, and robust mouse whole organ clearing

Tissue clearing for whole organ cell profiling has revolutionized biology and imaging for exploration of organs in three-dimensional space without compromising tissue architecture. But complicated, laborious procedures, or expensive equipment, as well as the use of hazardous, organic solvents prevents the widespread adoption of these methods. Here we report a simple and rapid tissue clearing method, EZ Clear, that can clear whole adult mouse organs in 48 hours in just three simple steps. Samples stay at room temperature and remain hydrated throughout the clearing process, preserving endogenous and synthetic fluorescence, without altering sample size. After wholemount clearing and imaging, EZ Cleared samples can be further processed for downstream embedding and cryosectioning followed by standard histology or immunostaining, without loss of endogenous or synthetic fluorescence signal. Overall, the simplicity, speed, and flexibility of EZ Clear make it easy to adopt and apply to diverse approaches in biomedical research.

developmental biology↗

bioRxiv2021

FOXO1 represses Sprouty2 and Sprouty4 expressionin endothelial cells to promote arterial specification and vascular remodeling in the mouse yolk sac

The establishment of a functional circulatory system is required for post-implantation development during murine embryogenesis. Previous studies in loss of function mouse models have shown that FOXO1, a Forkhead family transcription factor, is required for yolk sac vascular remodeling and survival beyond embryonic day (E) 11. Here, we demonstrate that loss of FoxO1 in E8.25 endothelial cells results in increased Sprouty2 and Sprouty4 transcripts, reduced expression of arterial genes, and decreased Flk1/Vegfr2 mRNA levels without affecting overall endothelial cell identity, survival, or proliferation. Using a Dll4-BAC-nlacZ reporter line, we found that one of the earliest expressed arterial genes, Delta like 4 (Dll4), is significantly reduced in the yolk sac of FoxO1 mutants without being substantially affected in the embryo proper. We show that in the yolk sac, FOXO1 not only binds directly to a subset of previously identified Sprouty2 gene regulatory elements (GREs), as well as newly identified, evolutionarily conserved Sprouty4 GREs, but can also repress their expression. Additionally, over expression of Sprouty4 in transient transgenic embryos largely recapitulates reduced expression of arterial genes seen in endothelial FoxO1 mutant mouse embryos. Together, these data reveal a novel role for FOXO1 as a key early transcriptional repressor controlling both pre-flow arterial specification and subsequent vessel remodeling within the murine yolk sac.

developmental biology↗

bioRxiv2021

Decadal trend of plankton community change and habitat shoaling in the Arctic gateway recorded by planktonic foraminifera

The Fram Strait plays a crucial role in regulating the heat and sea-ice dynamics in the Arctic. In response to the ongoing global warming, the marine biota of this Arctic gateway is experiencing significant changes with increasing advection of Atlantic species. The footprint of this "Atlantification" has been identified in isolated observations across the plankton community, but a systematic, multi-decadal perspective on how regional climate change facilitates the invasion of Atlantic species and affects the ecology of the resident species is lacking. Here we evaluate a series of 51 depth-resolved plankton profiles collected in the Fram Strait during seven surveys between 1985 and 2015, using planktonic foraminifera as a proxy for changes in both the pelagic community composition and species vertical habitat depth. The time series reveals a progressive shift towards more Atlantic species, occurring independently of changes in local environmental conditions. We conclude that this trend is reflecting higher production of the Atlantic species in the "source" region, from where they are advected into the Fram Strait. At the same time, we observe that the ongoing extensive sea-ice export from the Arctic and associated cooling-induced decline in density and habitat shoaling of the subpolar Turborotalita quinqueloba, whereas the resident Neogloboquadrina pachyderma persists. As a result, the planktonic foraminiferal community and vertical structure in the Fram Strait shifts to a new state, driven by both remote forcing of the Atlantic invaders and local climatic changes acting on the resident species. The strong summer export of Arctic sea ice has so far buffered larger plankton transformation. We predict that if the sea-ice export will decrease, the Arctic gateway will experience rapid restructuring of the pelagic community, even in the absence of further warming. Such a large change in the gateway region will likely propagate into the Arctic proper.

ecology↗