Daniel Hesselson

Per- and polyfluoroalkyl substances (PFAS) threaten ecosystems worldwide due to their persistence, bioaccumulation, and toxicity. Through a global-scale meta-analysis of 119 aquatic and terrestrial food webs from 64 studies, we analyse 1009 trophic magnification factors (TMFs) for 72 PFAS and identify key variability drivers. On average, PFAS concentrations double with each trophic level increase (mean TMF = 2.00, 95% CI:1.64-2.45), though magnification varies considerably by compound. Notably, the industrial alternative F-53B exhibits the highest magnification (TMF = 3.07, 95% CI:2.41-3.92), a critical finding given its expanding use and minimal regulatory scrutiny. Methodological disparities across studies emerge as the dominant source of TMF variability. Our models explain 85% of the variation in TMFs, underscoring predictive capacity. This synthesis establishes PFAS as persistent trophic multipliers and provides a framework to prioritise high-risk compounds and harmonise biomagnification assessments. Our results call for consideration of stricter PFAS regulation to curb cascading ecological and health impacts.

Proteins and peptides underpin essential biological functions and technological applications, from targeting disease-relevant interactions to providing broad enzymatic activities. However, engineering molecules with desired properties remains difficult, owing to complex sequence-structure-function relationships and the lack of data on specific systems. Experimental selection strategies, including directed evolution, phage display, and mRNA display, address this challenge by leveraging high diversity libraries and iterative enrichment under defined selection pressures. This allows for the identification of candidates without requiring extensive prior knowledge, and can generate extensive datasets for use in machine learning. While many selection systems exist, comparisons across different selection approaches are hindered by the lack of a unifying analytical framework. Here, we present a set of broadly applicable analyses for assessing selection dynamics in multi-round or multi-condition experiments, ranging from position level analysis of sequence properties to full sequence space mappings through protein language model embeddings. Using the toolset to analyze a variety of different datasets in parallel, we explore the potential effects of diversity, coverage, and reproducibility, offering generalizable insights to guide experimental design, interpretation, and troubleshooting across protein and peptide discovery platforms.

Directed evolution is a process of mutation and artificial selection to breed biomolecules with new or improved activity. Directed evolution platforms are primarily prokaryotic or yeast-based, and stable mammalian systems have been challenging to establish and apply. To this end, we develop PROTein Evolution Using Selection (PROTEUS), a platform that uses chimeric virus-like vesicles to enable extended mammalian directed evolution campaigns without loss of system integrity. This platform is stable and can generate sufficient diversity for directed evolution in mammalian systems. Using PROTEUS, we alter the doxycycline responsiveness of tetracycline-controlled transactivators, generating a more sensitive TetON-4G tool for gene regulation with mammalian-specific adaptations. PROTEUS is also compatible with intracellular nanobody evolution, and we use it to evolve a DNA damage-responsive anti-p53 nanobody. Overall, PROTEUS is an efficient and stable platform to direct evolution of biomolecules within mammalian cells.

Per- and polyfluoroalkyl substances (PFAS) threaten ecosystems worldwide due to their persistence, bioaccumulation, and toxicity. Through a global-scale meta-analysis of 122 aquatic and terrestrial food webs from 64 studies, we analyse 1,009 trophic magnification factors (TMFs) for 72 PFAS and identify key variability drivers. PFAS concentrations systematically doubled with each trophic level increase (mean TMF=2.00, 95% CI:1.64-2.45), confirming widespread biomagnification across ecosystems. Methodological disparities across studies emerged as the dominant source of TMF variability. Our models explained 84% of the variation in TMFs, underscoring predictive capacity. Notably, the industrial alternative F-53B exhibited the highest magnification (TMF=3.07, 95% CI:2.41-3.92), a critical finding given its expanding use and minimal regulatory scrutiny. This synthesis establishes PFAS as persistent trophic multipliers and provides a framework to prioritise high-risk compounds and harmonise biomagnification assessments. Our results call for consideration of stricter PFAS regulation to curb cascading ecological and health impacts.

For over two decades pluripotent stem cells have promised a renewable source of β cells to treat patients with type 1 diabetes. Major efforts to optimize the differentiation, survival, and function of transplanted stem cell-derived tissue have recently delivered clinically meaningful metabolic benefits using a perforated encapsulation device that promotes integration with recipient vasculature under the protection of systemic immunosuppression. Despite this success, the journey is not over as a universal cure will require a larger β cell mass. Here, we summarize recent interdisciplinary advances that could maximize the functional β cell mass within transplanted devices and provide an immune privileged niche that could eliminate the need for systemic immunosuppression.

Background Per- and polyfluoroalkyl substances (PFAS) are a class of widely used anthropogenic chemicals. Concerns regarding their persistence and potential adverse effects have led to multiple secondary research publications. Here, we aim to assess the resulting evidence base in the systematic secondary literature by examining research gaps, evaluating the quality of reviews, and exploring interdisciplinary connections. Methods This study employed a systematic evidence-mapping approach to assess the secondary literature on the biological, environmental, and medical aspects of exposure to 35 fluorinated compounds. The inclusion criteria encompassed systematic reviews published in peer-reviewed journals, pre-prints, and theses. Comprehensive searches across electronic databases and grey literature identified relevant reviews. Data extraction and synthesis involved mapping literature content and narrative descriptions. We employed a modified version of the AMSTAR2 checklist to evaluate the methodological rigour of the reviews. Furthermore, we conducted bibliometric data analysis to uncover patterns and trends in the academic literature. A research protocol for this study was previously pre-registered (osf.io/2tpn8) and published (Vendl et al., Environment International 158 (2022) 106973). The database is accessible for free on the online, interactive, and user-friendly systematic evidence map at https://hi-this-is-lorenzo.shinyapps.io/PFAS_SEM_Shiny_App/. Results Our map includes a total of 175 systematic reviews that met the eligibility criteria. Over the years, there has been a steady increase in the annual number of publications, with a notable surge in 2021. The majority of reviews focused on human exposure, whereas environmental and animal-related reviews were fewer and often lacked a rigorous systematic approach to literature search and screening. Review outcomes were predominantly associated with human health, particularly focusing on children's reproductive and developmental health. Animal reviews primarily focused on studies conducted in controlled laboratory settings, and wildlife reviews were characterised by a taxonomic bias. Recent reviews increasingly incorporated quantitative synthesis methodologies. The methodological strengths of the reviews included detailed descriptions of study selection processes and disclosure of potential conflicts of interest. However, weaknesses were observed in the critical lack of detail in reporting methods. A bibliometric analysis showed a bias in research toward certain geographical areas. Some regions were highly productive in terms of research, mainly with authors from within the country, but they had limited and clustered international collaborations. Conclusions In this overview of the available systematic secondary literature, we map literature content, assess reviews’ methodological quality, highlight data gaps, and draw research network clusters, aiming to guide future research initiatives, facilitate literature reviews, and enhance opportunities for cross-country collaboration. Furthermore, we discuss how this systematic evidence map and its publicly available database benefit scientists, regulatory agencies, and other stakeholders by providing access to current systematic secondary literature on PFAS exposure.

Directed evolution (DE) is a process of mutation and artificial selection to breed biomolecules with new or improved activity ^1,2 . DE platforms are primarily prokaryotic or yeast-based, and stable mutagenic mammalian systems have been challenging to establish and apply ³ . To this end, we developed PROTein Evolution Using Selection (PROTEUS), a new platform that uses chimeric virus-like vesicles (VLVs) to enable extended mammalian DE campaigns without loss of system integrity. This platform is stable and can generate sufficient diversity for DE in mammalian systems. Using PROTEUS, we altered the doxycycline responsiveness of tetracycline-controlled transactivators, generating a more sensitive TetON-4G tool for gene regulation. PROTEUS is also compatible with intracellular nanobody evolution, and we use it to design a DNA damage-responsive anti-p53 nanobody. Overall, PROTEUS is an efficient and stable platform to direct evolution of biomolecules within mammalian cells.

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease characterized by the degeneration of motor neurons. Mutations in the cyclin F (CCNF) and fused in sarcoma (FUS) genes have been associated with ALS pathology. In this study, we aimed to investigate the functional role of CCNF and FUS in ALS by using genome editing techniques to generate zebrafish models with genetic disruptions in these genes. Sequence comparisons showed significant homology between human and zebrafish CCNF and FUS proteins. We used CRISPR/Cas9 and TALEN-mediated genome editing to generate targeted disruptions in the zebrafish ccnf and fus genes. Ccnf-deficient zebrafish exhibited abnormal motor neuron development and axonal outgrowth, whereas Fus-deficient zebrafish did not exhibit developmental abnormalities or axonopathies in primary motor neurons. However, Fus-deficient zebrafish displayed motor impairments in response to oxidative and endoplasmic reticulum stress. The Ccnf-deficient zebrafish were only sensitized to endoplasmic reticulum stress, indicating that ALS genes have overlapping as well as unique cellular functions. These zebrafish models provide valuable platforms for studying the functional consequences of CCNF and FUS mutations in ALS pathogenesis. Furthermore, these zebrafish models expand the drug screening toolkit used to evaluate possible ALS treatments.

Per‐ and polyfluoroalkyl substances (PFAS) are a large group of synthetic chemicals that have been in use for over 70 years. Their ubiquitous distribution and harmful effects pose a threat to wildlife worldwide. To provide a comprehensive synopsis and show the gaps and gluts of existing research on PFAS exposure in wildlife, we created a systematic map and bibliographic analysis of the literature. We followed our protocol to conduct a systematic literature search on Scopus, Web of Science and five other databases. In two steps (title/abstract/keywords and full‐text), we screened peer‐reviewed empirical articles, preprints and theses in English that studied the concentration of at least one of 34 PFAS compounds in free‐ranging wildlife or their parts/products. Following the protocol, we extracted data and performed a critical appraisal. We included 581 publications. From the first and only paper in 2001, there was a linear annual increase to 54 papers in 2021. While PFOS (97% of studies), PFOA (91%) and long‐chain PFAS in general were the most measured, few studies investigated new‐generation PFAS (e.g. GenX and ADONA). Across the studied 1042 species from 26 taxonomic classes, the most frequent were the common carp (Cyprinus carpio, 8%), polar bear (Ursus maritimus, 6%) and European perch (Perca fluviatilis, 5%). Most sampling took place in the United States (17%), Norway (13%), Canada (12%) and China (10%), which were also the main publishing countries. Polar regions attracted significant research interest from countries all around the globe. Aquatic habitats (marine: 31%, freshwater: 28%) of temperate zones were the most common locations for sample collection. We encourage researchers to work towards closing the following gaps: investigating new‐generation PFAS, assessing PFAS in mid‐ and low‐income countries and performing more long‐term studies, especially on invertebrates. We note the recent rise in studies on the physiological consequences of PFAS exposure and encourage further work on this crucial topic. Furthermore, we recommend that the statement of potential and actual conflicts of interest, and the provision of raw data and analysis code should be made compulsory by all journals and routinely enforced. This practice will mitigate conflict of interest and ensure reproducibility.