Summary The zinc-finger associated domain (ZAD)-containing C2H2 zinc-finger proteins (ZAD-ZnFs) represent the most abundant class of transcription factors that emerged during insect evolution, yet their molecular diversity and biological functions remain largely unclear. Here, we established a systematic CRISPR-based protein-tagging approach that enables direct, unambiguous comparison of nuclear localization and genome-wide binding profiles of endogenous ZAD-ZnFs in developing Drosophila embryos. Evidence is provided that a subset of ZAD-ZnFs forms nuclear condensates through the stacking of the N-terminal ZAD dimerization surface. Disruption of condensation activity leads to misregulation of genome-wide binding profiles and lethality, underscoring its functional and physiological significance in development. Importantly, integrative ChIP-seq and Micro-C data analyses reveal that many ZAD-ZnFs colocalize with core insulator proteins such as CTCF and CP190 to strengthen the formation of topological boundaries. We suggest that the diverse molecular functions of ZAD-ZnFs have evolutionally arisen from their ancestral role as insulator-binding proteins.

Bioplastics represent promising alternatives to petroleum-based plastics, yet their biodegradation remains insufficiently understood. Identifying bacteria capable of degrading bioplastics extracellularly could enhance end-of-life management practices. To investigate Burkholderia ’s capacities for the degradation of medium-chain-length polyhydroxyalkanoate (mcl-PHA), we screened a panel of Burkholderia strains and identified such capacity in some strains of B. gladioli , B. multivorans, and B. vietnamiensis . To elucidate the genetic basis of this activity, we performed transposon mutagenesis followed by activity-based screening and Tn-seq on B. vietnamiensis LMG 16232. Transposon insertions with negative phenotype were identified in genes encoding a triacylglycerol lipase, a lipase chaperone, type II secretion system components, HTH-type transcriptional activators, and a polyhydroxyalkanoate synthesis repressor. To validate the involvement of these genetic elements in mcl-PHA degradation, we generated insertional mutants using a CRISPR-associated transposase system (CAST). Complete loss or reduced extracellular mcl-PHA depolymerase activity was observed in the CAST mutants, validating their involvement in mcl-PHA degradation. In addition, the interruption of these genetic elements showed a loss of lipase activity, suggesting that the enzymes responsible for mcl-PHA depolymerase are lipases with substrate ambiguity; moreover, docking experiments supported these findings. Together, we identify B. vietnamiensis as a source of enzymes capable of degrading extracellular mcl-PHA and demonstrate the power of combining activity-based screening, Tn-seq, and CAST to rapidly establish gene-to-function links. Importance Due to their versatile metabolism, Burkholderia strains play critical roles in degradation of multiple compounds in the environment. Here we show that several Burkholderia species can degrade medium-chain-length polyhydroxyalkanoates (mcl-PHAs), a promising class of bioplastics. By integrating transposon mutagenesis, Tn-seq, and CRISPR-associated transposase (CAST) technologies, we identify and validate key genetic determinants involved in mcl-PHA degradation in B. vietnamiensis. These genes encode a lipase, a secretion system component, and regulatory factors, underscoring the complexity and specificity of microbial bioplastic degradation pathways. The findings not only advance our understanding of PHA biodegradation but also identifies B. vietnamiensis as as a source of enzymes capable of degrading extracellular mcl-PHA.

Duchenne muscular dystrophy (DMD) is a progressive muscle wasting disease for which there is no cure. There is a critical need for additional therapeutics. Human genome-wide association studies (GWAS) have identified candidate DMD genetic modifiers that could serve as therapeutic targets. Because many GWAS-identified single nucleotide polymorphisms (SNPs) lie in noncoding, putative regulatory regions, it can be challenging to identify which gene(s) are regulated by these SNPs and how gene expression is altered to modify disease severity even with extensive in silico modeling. We analyzed expression of zebrafish orthologs of putative DMD modifiers and showed almost all are comparably expressed in wild-type and dmd mutant zebrafish at three different stages of disease. To model decreased expression of candidate modifiers, we pursued a zebrafish CRISPR-based screening approach, which we validated by testing zebrafish orthologs of two extensively studied DMD modifiers, LTBP4 and THBS1. We then tested candidates from the most recent GWAS and demonstrate that galntl6, man1a1, etaa1a;etaa1b, and adamts17 are bona fide DMD modifiers. Our findings demonstrate the utility of zebrafish for DMD genetic modifier screening and characterizing modifier function.

CRISPR base editors enable scalable targeted DNA mutagenesis and are a powerful tool for the interpretation of gene function, the study of variants of unknown significance, and disease modelling. Existing guide RNA (gRNA) design tools focus on engineering a small number of targeted variants in a given gene or lack comprehensive functional annotation of target sequences. Here we developed BEstimate, a flexible computational pipeline that systematically specifies base editor gRNA target sites, generates gRNA off-target predictions, and rich functional, structural and clinical annotations of targeted edits. BEstimate accommodates custom gRNA design against variant alleles, improving editing accuracy and facilitating the programmed reversion of disease variants. BEstimate is a freely available, versatile tool for designing gRNA libraries and analysing base editor screens.

Computational models have become essential tools for understanding signalling networks and their non-linear dynamics. However, these models are typically constructed manually using prior knowledge and can be over-reliant on study bias. These limitations hinder their ability to make accurate predictions and incorporate new evidence. Scaling up the construction of models to take advantage of increasingly abundant ‘omics data can bridge these gaps by providing a comprehensive view of signalling events and how they influence cellular phenotypes. In this study, we present MAGELLAN, a method leveraging message passing graph neural networks to build computational models directly from pathway data and discrete rules representing experimental results. We used this to construct a computational model of breast cancer signalling and re-parameterize a previously published non-small cell lung cancer (NSCLC) model, showing that MAGELLAN can predict genetic dependencies and achieve comparable model quality to expert-curated and manually trained models. Our approach enables the integration of prior knowledge networks and experimental data to build predictive models that are mechanistically interpretable. This approach simplifies model creation, making it more accessible and practical for experimentalists, and supports broader applications in drug discovery and biological research.

Abstract The developmentally dynamic stem cell-like subpopulation in cancers known as cancer stem cells (CSCs) metastasize efficiently, form new tumours, and are resistant to current therapeutics. Understanding the molecular mechanisms of the stem cell-like state could help eliminate CSCs via novel therapeutic applications in aggressive cancers such as pancreatic ductal adenocarcinoma (PDAC). Here, we performed a compound screen uncovering that inhibition of Hypoxia-inducible factor prolyl hydroxylase 2 (PHD2) supports CSCs, whereas a novel proline-uncompetitive glutamyl-prolyl-tRNA synthetase (GluProRS) inhibitor NCP26 eliminates CSCs. By using a multiomic strategy with transcriptomics and quantitative secretomic analyses, we uncovered that TGFβ/Activin signalling induces HIF1A-mediated pseudohypoxia via ɑ-Ketoglutarate depletion due to P4HA1 intracellular upregulation. In turn, HIF1A and SMAD2/3 form a transcriptional complex that regulates CSC self-renewal, invasiveness and chemoresistance. NCP26 has several anti-tumour effects, including direct activation of the Integrated Stress Response (ISR) and indirect inhibition of the pseudo-hypoxia circuitry mediated by SMAD2/3-HIF1A that deposits collagen in ECM. Furthermore, GluProRS is secreted from PDAC cells and elevated in PDAC patient blood compared to healthy and pancreatitis patients. Collectively, the secreted GluProRS protein could be a useful biomarker for early PDAC detection, and its inhibitor NCP26 is an attractive candidate for combined chemotherapeutic applications.

Abstract Background BRAT1 (BRCA1-associated ataxia telangiectasia mutated activator 1) plays a crucial role in several vital biological processes, including the DNA damage response and the maintenance of mitochondrial homeostasis. Dysfunction in BRAT1 leads to a range of clinical phenotypes, with the majority of affected individuals succumbing before reaching one year of age. Results Through an analysis of previous literature, the homozygous BRAT1 p.V62E mutation (GTG to GAG) was selected to construct a mouse model. Homozygous BRAT1 p.V62E knock-in mice with a C57BL/6J background were generated using CRISPR/Cas9 technology, and the point mutation was confirmed by Sanger sequencing. The results revealed no significant differences between the mutant mice and wild-type controls during low-intensity testing. However, the mutant mice exhibited enhanced endurance during high-intensity testing. RNA sequencing analysis identified ten differentially expressed genes in the gastrocnemius muscle and four differentially expressed genes in the brain tissue of the mutant mice. Conclusions This represents the first successful construction of a BRAT1 mutant mouse model. This achievement not only provides confidence for developing additional mouse models but also offers a valuable perspective for understanding the relationship between BRAT1 and mitochondrial function. The mouse model demonstrates a degree of consistency with the clinical phenotypes observed in patients and may serve as a predictive tool for patient prognosis.

ABSTRACT Phosphorylation, a crucial post-translational modification (PTM), plays a central role in cellular signaling and disease mechanisms. Mass spectrometry-based phosphoproteomics is widely used for system-wide characterization of phosphorylation events. However, traditional methods struggle with accurate phosphorylated site localization, complex search spaces, and detecting sequences outside the reference database. Advances in de novo peptide sequencing offer opportunities to address these limitations, but have yet to become integrated and adapted for phosphoproteomics datasets. Here, we present InstaNovo-P, a phosphorylation specific version of our transformer-based InstaNovo model, fine-tuned on extensive phosphoproteomics datasets. InstaNovo-P significantly surpasses existing methods in phosphorylated peptide detection and phosphorylated site localization accuracy across multiple datasets, including complex experimental scenarios. Our model robustly identifies peptides with single and multiple phosphorylated sites, effectively localizing phosphorylation events on serine, threonine, and tyrosine residues. We experimentally validate our model predictions by studying FGFR2 signaling, further demonstrating that InstaNovo-P uncovers phosphorylated sites previously missed by traditional database searches. These predictions align with critical biological processes, confirming the model’s capacity to yield valuable biological insights. InstaNovo-P adds value to phosphoproteomics experiments by effectively identifying biologically relevant phosphorylation events without prior information, providing a powerful analytical tool for the dissection of signaling pathways.

Classification of high-dimensional information is a ubiquitous computing paradigm across diverse biological systems, including organs such as the brain, down to signaling between individual cells. Inspired by the success of artificial neural networks in machine learning, the idea of engineering genetic circuits that operate as neural networks emerges as a strategy to expand the classification capabilities of living systems. In this work, we design these biomolecular neural networks (BNNs) based on the molecular sequestration reaction, and experimentally characterize their behavior as linear classifiers for increasing levels of complexity. Initially, we demonstrate that a static, DNA-based system can effectively prototype a linear classifier, though we also identify its limitations to easily tune the slope of the decision boundary it generates. We then propose and experimentally validate a BNN at the protein level using a cell-free transcription–translation (TXTL) system, which overcomes the DNA-based system’s limitation and behaves as a linear classifier even before it reaches its steady state (or, equivalently, out-of-equilibrium). Ultimately, we test a CRISPR-based design and its out-of-equilibrium behavior in a biological context by successfully constructing a linear classifier within mammalian cells. Overall, by leveraging mathematical modeling and experimental automation, we establish molecular sequestration as a universal scheme for implementing neural networks within living systems, paving the way for transformative advances in synthetic biology and programmable biocomputing systems.

Lipid nanoparticles (LNPs) have emerged as a transformative platform for mRNA delivery, enabling vaccines and gene editing with transient expression and high cargo capacity. However, their potential for ocular gene editing remains underexplored. In this study, we assessed the transduction efficiency, inflammatory response, and gene editing capability of LNP-encapsulated mRNA in murine eyes. Intravitreal delivery of LNPs achieved targeted mRNA expression in the trabecular meshwork (TM) with superior specificity and efficiency compared to adenoviral or adeno-associated viral vectors, while inducing minimal microglial activation in the retina. Using LNPs co-encapsulating SpCas9 mRNA and sgRNA, we demonstrated efficient CRISPR-mediated knockout (KO) of Matrix Gla Protein (Mgp), a key inhibitor of TM calcification. Mgp-KO eyes exhibited sustained intraocular pressure (IOP) elevation and anterior chamber deepening with normal anterior chamber angle, recapitulating key features of primary open-angle glaucoma (POAG). Chronic IOP elevation led to reactive Müller gliosis and ganglion cell complex thinning, reflecting retinal stress and progressive neurodegeneration. Our findings establish LNP-CRISPR as a safe and efficient system for TM-targeted gene editing, with broad applicability in glaucoma pathogenesis modelling and therapeutic discovery.

ABSTRACT Retinitis Pigmentosa (RP) is an inherited retinal dystrophy characterized by the progressive loss of rod photoreceptors. Sector RP is a form of RP, where degeneration originates in the inferior retina, mainly influenced by light exposure. Over 200 RHO variants are pathogenic and associated with autosomal dominant RP. RHO M39R is one of the most common RHO variants linked to sector RP in the UK. A knock-in (KI) mouse model expressing Rho M39R was generated and characterized to investigate the mechanisms of degeneration associated with this variant and explore novel therapeutic strategies for rhodopsin sector RP. Under ambient light, Rho M39R/+ KI mice exhibited impaired retinal function by ERG, with some defects in OS ultrastructure, but retained normal outer nuclear layer (ONL) thickness. Repeated exposure to bright light led to photoreceptor loss. In contrast, Rho M39R/M39R KI mice in ambient light displayed severe retinal dysfunction, ONL thinning, and grossly abnormal OS ultra structure. In homozygous mice, a single bright light exposure significantly reduced ONL thickness within 48 h. The rescue of these models was achieved through reduced light exposure and pharmacological intervention. Rearing in dim red light (red cage condition) restored ERG responses in Rho M39R/+ KI mice and improved ONL thickness in Rho M39R/M39R KI mice. Transcriptomic analysis in Rho M39R/M39R KI mice revealed upregulation of Sphingosine 1-P Receptor (S1PR) transcripts. Treatment with the S1PR agonist Fingolimod (FTY720) before bright light exposure significantly reduced degeneration, demonstrating a protective effect in both heterozygous and homozygous models and suggesting potential a therapeutic approach for sector RP patients.

Delayed diagnosis of Mendelian disease substantially prevents early therapeutic intervention that could improve symptoms and prognosis. One major contributing challenge is the functional interpretation of non-coding variants that cause disease by altering splicing and/or gene expression. We identified two siblings with glycogen storage disease (GSD) type IX γ2, both of whom had a classic clinical presentation, enzyme deficiency, and a known pathogenic splice acceptor variant on one allele of PHKG2 . Despite the autosomal recessive nature of the disease, no variant on the second allele was identified by gene panel sequencing. To identify a potential missing second pathogenic variant, we completed whole genome sequencing (WGS) and detected putative deep intronic splicing variant in PHKG2 in both siblings. We confirmed the functional splicing effects of this variant using short-read and long-read RNA-seq on patient blood and a HEK293T cell model in which we installed the variant using CRISPR editing. Using the cell model, we demonstrated multiple biochemical and cellular impacts that are consistent with GSD IX γ2, and a reversal of aberrant splicing using antisense splice-switching oligonucleotides. In doing so, we demonstrate a novel and robust pathway for detecting, validating, and reversing the impacts of novel non-coding causes of rare disease.

The United Kingdom (UK) is home to many local and rare livestock breeds. The local breed populations are highly adapted to specific environments in the UK and these and other rare breeds provide solutions to niche needs. Rare breeds often contribute more than expected to overall species genetic diversity, which is important because genetic variation is needed for adapting to new challenges. It is therefore very important from both UK and global perspectives to maintain genetic diversity of rare livestock breeds in the UK, and to do this, we need to evaluate the monitoring of genetic diversity to identify gaps in our knowledge and prioritise resources reserved for conservation purposes. The objectives of this study were to survey the literature to: (1) summarise genetic/genomic characterisation (effective population size (N e ) and inbreeding) of domestic populations (livestock and equine) in the UK and Ireland; (2) compare number of populations on the UK’s Rare Breed Survival Trust (RBST) watch list and the number of UK and Irish populations in the peer-reviewed literature with inbreeding, genetic diversity and/or N e estimates; and (3) compare annually reported (census-based) estimates of N e with (inbreeding and DNA-based) estimates from peer-reviewed literature. We found a total of 37 publications with N e or inbreeding estimates for UK or Ireland livestock populations, published from 1975 to 2024. While many (42%) of the breeds on the RBST watchlist have been included in publications, there are still many breeds, and a few species (turkey, duck and geese) with no publicly available pedigree- or DNA-based genetic diversity measures. We found census-based N e estimates were, on average, higher than DNA-based estimates, likely due to violated assumptions when estimating N e with census-based data because of the way livestock mating systems are designed. Most peer-reviewed papers estimated genetic diversity measures using pedigree, microsatellite markers, or SNP markers. To identify breed-unique variants responsible for adaptive traits in rare breeds, more studies using whole-genome sequencing will be needed. Altogether, we have summarised the genetic diversity estimates on UK livestock populations, identifying gaps in knowledge.

Pseudomonas aeruginosa is a major pathogen associated with hospital-acquired infections, and the spread of carbapenem-resistant isolates highlights the urgency of developing non-conventional therapies, such as phage therapy. For this alternative to be effective, un-derstanding phage-host interactions is crucial for the selection of candidate phages and offers new insights into these dynamics. Background/Objectives: This study aimed to characterize prophage diversity in clinical P. aeruginosa genomes, assess the relationship between phages and the CRISPR/Cas system, and investigate the potential role of phages in disseminating resistance genes. Methods: A total of 141 genomes from Brazilian hos-pitals were analyzed. Prophage detection was performed using VIBRANT, and in silico analyses were conducted to evaluate taxonomic diversity, presence of resistance genes, phage life cycle, genomic distribution, and the presence of the CRISPR/Cas system. Re-sults: In total, 841 viral sequences were identified, with a predominance of the class Cau-doviricetes and high overall phage diversity. No statistically significant difference was ob-served in the number of prophages between isolates with and without CRISPR/Cas sys-tems. Phages carrying resistance genes were detected in isolates harboring the type I-C CRISPR/Cas system. Additionally, prophages showed no preference for specific insertion sites along the bacterial genome. Conclusions: These findings provide evidence of a well-established phage-host relationship. The dual role of phages—as vectors of antimi-crobial resistance and as potential therapeutic agents—reflects their dynamic impact on bacterial communities and reinforces their importance in developing new strategies to combat antimicrobial resistance.

Invasive species inflict major ecological, economic, social, and cultural harm worldwide, highlighting the urgent need for innovative and effective control strategies. Genome editing offers exciting possibilities for creating highly targeted control methods for invasive species. Here, we demonstrate CRISPR-Cas9 genome editing in the cane toad ( Rhinella marina ), one of Australia’s most notorious invasive species, by targeting the tyrosinase gene to produce albino phenotypes that provide clear visual markers for assessing editing efficiency. Microinjection of Cas9 protein and guide RNAs into one-cell zygotes resulted in 87.6% of mosaic larvae displaying nearly complete albinism, with 2.3% exhibiting complete albinism. For completely albino individuals, genomic analysis confirmed predominantly frameshift mutations or large deletions at the target site, with no wild-type alleles detected. Germline transmission rates reflected the extent of albinism in the mosaic adult, where we achieved maternal germline transmission rates of almost 100%. This technology, representing the first application of CRISPR-Cas9 in the Bufonidae family, opens possibilities for exploring both basic research questions and strategies for population control.

ABSTRACT Cellular resource limitations create unintended interactions among synthetic gene circuit modules, compromising circuit modularity. This challenge is particularly pronounced in circuits with positive feedback, where uneven resource allocation can lead to Winner-Takes-All (WTA) behavior, favoring one module at the expense of others. In this study, we experimentally implemented a Negatively Competitive Regulatory (NCR) controller using CRISPR interference (CRISPRi) and evaluated its effectiveness in mitigating WTA behavior in two gene circuits: dual self-activation and cascading bistable switch. We chromosomally integrated a tunable dCas9 gene and designed module-specific gRNAs, with each module encoding its own gRNA to self-repress via competition for limited dCas9. This configuration introduces strong negative feedback to the more active module while reallocating resources to the less active one, promoting balanced module activation. Compared to the control group lacking dCas9-mediated repression, the NCR controller significantly increased module coactivation and suppressed WTA behavior. Our quantitative results demonstrate that NCR provides an effective strategy for regulating resource competition and improving the modularity of synthetic gene circuits.

Zoonotic viruses such as hantaviruses and influenza A viruses present a threat to humans and livestock. There is thus a need for methods that are rapid, sensitive, and relatively cheap to detect infections with these pathogens early. Here we use an amplification-free CRISPR-Cas13-based assay, which is simple, cheap and field-deployable, to detect the presence or absence of genomic hantavirus or influenza A virus RNA. In addition, we evaluate whether the use of multiple CRISPR RNAs (crRNAs) can improve the sensitivity of this amplification-free method. We demonstrate that for the hantaviruses Tula Virus (TULV) and Andes Virus (ANDV) a combination of two or three crRNAs provides the best sensitivity for detecting viral RNA, whereas for influenza virus RNA detection, additional crRNAs provide no benefit. We also show that the amplification-free method can be used to detect TULV and ANDV RNA in tissue culture infection samples and influenza A virus RNA in clinical nasopharyngeal swabs. In clinical samples, the Cas13 assay has an 85% agreement with RT-qPCR for identifying a positive sample. Overall, these findings indicate that amplification-free CRISPR-Cas13 detection of viral RNA has potential as a tool for rapidly detecting zoonotic virus infections.

Abstract Generating mammalian gametes with a skewed sex ratio has thus far eluded empirical confirmation. The utilization of such genetically engineered organisms would offer the potential to curtail the necessity for culling animals of undesirable sex, mitigate resource wastage, and alleviate superfluous labor burdens. In this study, we introduce a transgenic male mouse lineage, which consistently yields predominantly female progeny (comprising up to ~90% of the total offspring). This accomplishment was made possible by integrating a controllable genetic cassette onto the Y chromosome. The cassette encodes dCas9 and RNA guides that selectively silence a spermatid maturation gene. After the separation of X and Y gametes during meiosis, gametes containing an X chromosome develop normally, while those harboring the engineered Y chromosome, subjected to dCas9 silencing of the spermatid maturation gene, do not mature properly. Indeed, some spermatozoa from the transgenic mice exhibit a unique morphology, associated with the absence of the maturation gene. Notably, the resultant female offspring do not inherit the genetically engineered Y chromosome and are thus not genetically modified. Importantly, the litter size of the transgenic mice remains unchanged compared to the wild type. These findings represent the potential of genetic engineering to yield sex-biased litters of full size without compromising genetic integrity, marking a pioneering advancement in this field of study.

Background: Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-associated protein 13a (Cas13a) has been described as a superior tool to short-interfering RNAs (siRNAs) for specific gene silencing. Cas13 targets RNAs through Watson-Crick binding of the target CRISPR RNA (crRNA) and activation of nuclease activity. In bacteria, once Leptotrichia wadei Cas13a (LwCas13a) has cut its specific target, the trans-collateral activity of the protein degrades any single-stranded RNA present in the cell independent of its sequence or homology to the crRNA. This transcollateral activity has been reported to be absent in mammalian cells. Therefore, in this study, we aimed to downregulate mRNAs expression in mammalian cells (HaCaT and HEK293T) using LwaCas13a. Methods We developed a doxycycline-inducible system to express LwaCas13a in HEK293T cells. The off-target activity of LwaCas13a in HEK293T cells was analyzed using RNA-seq. Results In this study, we observed that activation of LwaCas13a in HEK293T cells led to non-specific targeting of RNAs, which caused cell toxicity and death. Conclusion This study provides evidence of the off-target activity of LwaCas13a in HEK293T cells, making it an unsuitable tool for the specific downregulation of RNAs.

Fibromyalgia syndrome (FMS) is characterized by elevated levels of immunoglobulin G (IgG), altered bowel habits, and increased pain sensitivity, suggesting immune dysregulation, but the exact mechanism remains unclear. Here, we found that FMS-IgG binds to mast cells in a MRGPRX2/b2-dependent manner, leading to mast cell recruitment and IL-6 secretion. Transferring serum-IgG from FMS patients to mice induced FMS-like symptoms and increased skin mast cells, indicating that FMS-IgG acts through mast cell activation. The ablation of mice Mrgprb2 mast cells or deleting Mrgprb2 receptors prevented IgG-induced heightened sensitivity to mechanical and cold stimuli. Stimulating human LAD2 cells with FMS IgG elicited MRGPRX2-dependent IL-6 production. Consistent with mice findings, mast cell density and tryptase levels increased in human FMS skin samples compared to healthy controls. Taken together our results suggests that FMS IgG mediates hypersensitivity via activation of mast cells bearing the MRGPRX2 receptor and that these cells are a potential therapeutic target.

Parathyroid hormone 4 (Pth4) is an evolutionarily conserved member of the PTH family, expressed in hypothalamic neurons and lost in eutherian mammals. In order to elucidate its role in mineral homeostasis and skeletal development, a pth4 knockout ( pth4 KO ) zebrafish line was generated using CRISPR/Cas9 and transcriptomic profiling was conducted across six key tissues: brain, kidney, intestine, gills, scales, and bone. The results obtained demonstrated that the loss of Pth4 led to pronounced disturbances in calcium and phosphate homeostasis, skeletal deformities, and widespread tissue-specific transcriptional alterations. Notably, dysregulation of mineral regulatory genes— such as fgf23, phex , and slc34a1a was particularly evident in the kidney, suggesting disruption of the FGF23-Klotho axis. In parallel, differential expression of extracellular matrix genes ( col1a1a, col10a1a, col11a1 ) and matrix remodeling enzymes ( mmp9, mmp13a, mmp2 ) in bone and scales indicated impaired skeletal remodeling. Together, these findings highlight a pivotal role for Pth4 in the endocrine and local regulation of mineral metabolism and skeletal integrity, expanding our understanding of PTH family functions in vertebrate physiology.

ABSTRACT High-temperature requirement protein A1 (HTRA1) is a secreted serine protease with diverse substrates, including extracellular matrix proteins, proteins involved in amyloid deposition, and growth factors. Accordingly, HTRA1 has been implicated in a variety of neurodegenerative diseases including a leading cause of blindness in the elderly, age-related macular degeneration (AMD). In fact, genome wide association studies have identified that the 10q26 locus which contains HTRA1 confers the strongest genetic risk factor for AMD. A recent study has suggested that AMD-associated risk alleles in HTRA1 correlate with a significant age-related defect in HTRA1 synthesis in the retinal pigmented epithelium (RPE) within the eye, possibly accounting for AMD susceptibility. Thus, we sought to identify small molecule enhancers of HTRA1 transcription and/or protein abundance using an unbiased high-throughput screening approach. To accomplish this goal, we used CRISPR/Sp.Cas9 engineering to introduce an 11 amino acid luminescent peptide tag (HiBiT) onto the C-terminus of HTRA1 in immortalized ARPE-19 cells. Editing was very efficient (∼88%), verified by genomic DNA analysis, short interfering RNA (siRNA), and HiBiT blotting. Nineteen-hundred and twenty compounds from two libraries were screened. An azo compound with reported anti-amyloidogenic and cardioprotective activity, Chicago Sky Blue 6B (CSB), was identified as an enhancer of endogenous HTRA1 secretion (2.0 ± 0.3 fold) and intracellular levels (1.7 ± 0.2 fold). These results were counter-screened using HiBiT complement factor H (CFH) edited ARPE-19 cells, verified using HiBiT blotting, and were not due to HTRA1 transcriptional changes. Importantly, serine hydrolase activity-based protein profiling (SH-ABPP) demonstrated that CSB does not affect HTRA1’s specific activity. However, interestingly, in follow-up studies, Congo Red, another azo compound structurally similar to CSB, also substantially increased intracellular HTRA1 levels (up to 3.6 ± 0.3 fold) but was found to significantly impair HTRA1 enzymatic reactivity (0.45 ± 0.07 fold). Computational modeling of potential azo dye interaction with HTRA1 suggests that CSB and Congo Red can bind to the non-catalytic face of the trimer interface but with different orientation tolerances and interaction energies. These studies identify select azo dyes as HTRA1 chemical probes which may serve as starting points for future HTRA1-centered small molecule therapeutics.

SUMMARY While cortical organoids have been used to model different facets of neurodevelopmental conditions and human brain evolution, cerebellar organoids have not yet featured so prominently in the same context, despite increasing evidence of this brain regions importance for cognition and behavior. Here, we provide a longitudinal characterization of cerebellar organoids benchmarked against human fetal data and identify at very early stages of development a significant number of dynamically expressed genes relevant for neurodevelopmental conditions such as autism and attention deficit hyperactivity disorders. Then, we model an ASD mutation impacting CHD8, showing both granule cell and oligodendrocyte lineages prominently affected, resulting in altered network activity in more mature organoids. Lastly, using CRISPR/Cas9 editing, we also model an evolution-relevant mutation in a regulatory region of the CADPS2 gene. We investigate the effect of the derived allele exclusive to Homo sapiens, identifying a rerouting of the CADPS2-expression in rhombic lip cells, coupled with a different sensitivity to hypoxia which in turn lead to a differential timing of granule cell differentiation. HIGHLIGHTS Longitudinal characterization of cerebellar organoids uncovers disorder related genes especially at early stages of development Mutation in CHD8 alter rhombic lip and oligodendrocytes differentiation via WNT pathway Rerouting of CADPS2 expression, delaying differentiation and migration, in recent human evolution IN BRIEF Aprile and colleagues longitudinally profiled cerebellar organoids, benchmarking them against a fetal human atlas and identified a highly dynamic expression of genes related to cognitive and behavioral disorders especially at early stages of differentiation. Organoids were used to model the impact of a high-penetrance mutation associated with autism spectrum disorder and a high-frequency derived allele in Homo sapiens predicted to have played a role in recent brain evolution.

1-deoxy-sphingolipids (1-deoxySLs) are atypical sphingolipids synthesized by the serine palmitoyltransferase (SPT) when L-alanine is used instead of its canonical substrate L-serine. Increased 1-deoxySLs are associated with sensory neuropathies such as Hereditary Sensory and Autonomic Neuropathy type 1 (HSAN1) and diabetic polyneuropathy (DPN). Despite their known cellular, mitochondrial, and neurotoxic effects, the mechanisms underlying their toxicity remain poorly understood. Using a CRISPR interference (CRISPRi) screening approach, we identified CERS2, ELOVL1, ACACA, HSD17B12, and PTPLB as key mediators of 1-deoxySL-induced toxicity. All genes are integral to the biosynthesis of very long-chain (VLC) fatty acids and VLC-ceramides. We validated these findings through genetic knockdown experiments, cytotoxicity assays, and stable isotope-resolved lipidomics via LC-MS/MS. Pharmacological inhibition of ELOVL1 using a preclinical tested compound alleviated the cellular, mitochondrial, and neuronal toxicity induced by 1-deoxySLs. Supplementation experiments combining 1-deoxySLs with various VLC fatty acids revealed that 1-deoxyDHceramide conjugated to nervonic acid (m18:0/24:1) is the principal toxic specie. Further mechanistic studies showed that m18:0/24:1 induces apoptosis through the mitochondrial permeability transition pore (mPTP) formation. Inhibition of BAX or blocking mPTP formation with cyclosporin A effectively prevented toxicity. In conclusion, our findings demonstrate that 1-deoxyDHCeramides conjugated to nervonic acid are the primary mediators of 1-deoxySL toxicity, acting through mitochondrial dysfunction and BAX-dependent apoptosis.

Resistance to targeted therapy in BRAF-mutant melanomas can arise from drug-tolerant persister cells, which can non-genetically escape drug-induced quiescence to resume proliferation. To investigate how melanoma cells escape drug to re-enter the cell cycle within 3-4 days of BRAF and MEK inhibition, we computationally reconstructed single-cell lineages from time-lapse imaging data, linking key signaling pathways to cell-cycle fate outcomes. We found that ERK reactivation, while necessary, is insufficient for cell-cycle re-entry under MAPK inhibition. Instead, mTORC1 emerged as an additional critical mediator, enhancing translation and cell growth in cells destined for drug escape. We further found that ERK and mTORC1 signaling converge to produce Cyclin D1 protein levels, a key bottleneck for cell-cycle re-entry. Using CRISPR to tag endogenous Cyclin D1, we found that future escapees markedly upregulate Cyclin D1 at least 15 hours prior to drug escape, compared to non-escapees. Importantly, this early upregulation enables accurate prediction of future escapees from non-escapees, underscoring how differences in Cyclin D1 accumulation precede and govern the timing and likelihood of cell-cycle re-entry in persister cells. Our findings suggest that variability in ERK and mTORC1 activity underlies the heterogeneous Cyclin D1 levels observed, influencing the proliferative potential of persister cells and ultimately shaping the diverse cell-cycle behaviors observed under drug treatment. Cyclin D1 protein therefore emerges as both a critical biomarker and a therapeutic target for preventing cell-cycle re-entry in BRAF/MEK-treated melanoma. One Sentence Summary Cyclin D1 accumulation, driven by the integration of heterogeneous MAPK and mTORC1 signaling, is a critical bottleneck for cell-cycle re-entry in drug-treated melanoma cells.