Biology subjects

Hahn, L.

Publications and source records attributed to Hahn, L..

3 recordsLinked to original sources

bioRxiv2024

Single cells can resolve graded stimuli

Cells use signalling pathways as windows into the environment to gather information, transduce it into their interior, and use it to drive behaviours. MAPK (ERK) is a highly conserved signalling pathway in eukaryotes, directing multiple fundamental cellular behaviours such as proliferation, migration, and differentiation, making it of few central hubs in the signalling circuitry of cells. Despite this versatility of behaviors, population-level measurements have reported low information content (<1 bit) relayed through the ERK pathway, rendering the population barely able to distinguish the presence or absence of stimuli. Here, we contrast the information transmitted by a single cell and a population of cells. Using a combination of optogenetic experiments, data analysis based on information theory framework, and numerical simulations we quantify the amount of information transduced from the receptor to ERK, from responses to singular, brief and sparse input pulses. We show that single cells are indeed able to resolve between graded stimuli, yielding over 2 bit of information, however showing a large population heterogeneity.

biophysics↗

bioRxiv2024

Species identity and composition shape productivity of stony corals

Coral biodiversity has an enhancing but saturating effect on community productivity, however, the direct effects of neighbouring coral colonies on productivity remain poorly understood due to the complex interplay of biotic and abiotic factors. We set up a fully controlled aquarium experiment, in which we quantified the effects of species identity and composition on the productivity of nine stony coral species from three families. Baseline productivity and the response to neighbouring organisms strongly differed between species. Regardless of whether species increased or decreased productivity, the responses were consistently more pronounced and positive towards conspecific than heterospecific neighbours, indicating kin selection effects between closely related species. Species productivity in monoculture and productivity in polyculture were inversely correlated, with inherently less productive species overperforming in polyculture and vice versa. Our results highlight that contact-free interactions in marine animals shape biodiversity-productivity effects otherwise known from plant communities.

ecology↗

bioRxiv2023

Deprivation of arginine and lysine interferes with growth of patient-derived tumor xenografts

In recent years, a novel treatment method for cancer emerged, which is based on the starvation of tumors of amino acids like arginine. The deprivation of arginine in serum is based on enzymatic degradation and can be realized by arginine deaminases like the L-amino acid oxidase found in the ink toxin of the sea hare Aplysia punctata. Previously isolated from the ink, the L-amino acids oxidase was described to oxidate the essential amino acid L-lysine and L-arginine to their corresponding deaminated alpha-keto acids. Here, we present the recombinant production and functionalization of amino acid oxidase Aplysia Punctata ink toxin (APIT). PEGylated APIT (APIT-PEG) increased the blood circulation time. APIT-PEG treatment of patient-derived xenografted mice shows a significant dose dependent reduction of tumor growth over time mediated by amino acid starvation of the tumor. Treatment of mice with APIT-PEG which lead to deprivation of arginine was well tolerated.

cancer biology↗