Biology subjects

Lahn, B. T.

Publications and source records attributed to Lahn, B. T..

6 recordsLinked to original sources

bioRxiv2026

MuteFree: A novel AAV vector system featuring mutation-free ITRs

Instability of the inverted terminal repeats (ITRs) in AAV transfer plasmids has long hindered consistent and efficient production of therapeutic AAV vectors. The palindromic, GC-rich ITR sequence readily forms secondary structures, making them highly mutable in transfer plasmids. Indeed, a recent survey observed mutated ITRs in [~]40% of AAV transfer plasmids from labs around the world. Conventional strategies to mitigate this issue - such as using specialized E. coli strains, suboptimal culture conditions, or modified ITR sequences - have limited effect and often compromise plasmid and AAV yield. Here, by combinatorial optimization of the plasmid backbone structure and ITR flanking sequences, we established MuteFree, an AAV transfer plasmid system that eliminated ITR mutations for both single-stranded AAV (ssAAV) and self-complementary AAV (scAAV). Specifically, MuteFree reduced ITR mutation rates from a range of 32-100% in various transfer plasmids tested to 0% after serial passage of host E. coli for >160 population doublings. Moreover, in three GMP-grade AAV plasmid manufacturing projects initially cancelled due to severe and incurable ITR mutations, replacing conventional backbone with MuteFree completely solved the problem, reducing mutation occurrence to zero under standard GMP manufacturing conditions. Notably, MuteFree supports the packaging of potent AAV virus. The MuteFree system thus presents a robust solution to ITR instability, enabling high-fidelity and high-yield AAV production of AAV-based gene therapy vectors that is fully compatible with existing GMP manufacturing workflows.

molecular biology↗

bioRxiv2025

miniVec: A miniaturized plasmid backbone supporting antibiotic-free and additive-free fermentation with enhanced yield and functionality

Plasmids are a foundational research reagent and a key material in biopharmaceutical manufacturing. Plasmids require a backbone for propagation in E. coli, which typically contains an antibiotic resistance gene alongside a replication origin. As plasmids increasingly enter clinical applications, concerns are raised on the safety risks of antibiotic resistance genes. Additionally, these protein-coding genes occupy long stretches of DNA that incur significant metabolic burdens on host cells, which negatively impacts plasmid manufacturability and functionality, leading to high production cost and compromised clinical efficacy. Here, we describe miniVec, a novel miniaturized plasmid backbone devoid of protein-coding sequence, and instead expresses a small RNA to provide constant selective pressure capable of sustaining high plasmid copy numbers in plain culture media devoid of antibiotics or other chemical additives. This simplifies large-scale fermentation and greatly increases plasmid yield. Notably, miniVec confers enhanced functionality in a variety of applications such as chemical transfection, electroporation, virus packaging, transposon-or CRISPR-mediated genome integration, and in vivo naked DNA transfection and vaccination, while exhibiting no detectable immunogenicity or toxicity. These advantages establish miniVec as the next-generation plasmid platform for clinical applications, featuring improved safety that aligns with regulatory expectations, enhanced manufacturability leading to much higher yield and dramatic cost reduction, and augmented functionality in diverse applications.

bioengineering↗

bioRxiv2025

Exogenous Photoreceptor-Specific N-Glycosylated PROM1 Rescues Retinal Degeneration in Patient and Mouse Models

PROM1 is widely expressed across various tissues. However, its pathogenic mutations are exclusively associated with inherited retinal dystrophy (IRD). The mechanisms underlying this retina-specific vulnerability remain poorly understood, and no effective treatment currently exists for PROM1-IRD. Here, we utilized urine cells, hiPSCs, hiPSC-RPE cells, retinal organoids (ROs) and Prom1-/- mice to address these challenges. During photoreceptor development in ROs, PROM1 co-localized with ciliary marker ARL13B and outer segment (OS) marker PRPH2. It exhibited photoreceptor-specific mRNA splicing isoforms and unique N-glycosylation. In IRD patient-specific models with the PROM1 c.619G>T (p.E207X) homozygous mutation, we observed nonsense-mediated mRNA decay and altered splicing, leading to complete loss of PROM1 protein and OS-like structure disruption, faithfully recapitulating PROM1-IRD pathology. To rescue these defects, we engineered a photoreceptor-specific AAV7m8-CRXp-hPROM1, which successfully restored PROM1 expression and OS-like structures in patient-derived ROs. Therapeutic efficacy was further validated in Prom1-/- mice, where subretinal delivery of AAV8-CRXp-hPROM1 led to photoreceptor-specific expression of human PROM1, significantly preserving OS morphology and improving visual function. These findings not only provide the first solid preclinical evidence supporting gene therapy for PROM1-IRD, but also reveal photoreceptor-specific vulnerability to PROM1 mutations, offering a novel conceptual framework for investigating and treating related IRDs.

neuroscience↗

bioRxiv2024

Mechanistic basis of lineage restriction

Lineage restriction is the biological phenomenon where cells lose developmental potency during differentiation for all except their adopted lineages. Lineage restriction is foundational to multicellularity as it secures the functional identities of the myriad cell types in the body. As yet, the mechanisms of lineage restriction remain enigmatic. By developing Potency-Seq to systematically map transcriptional potency of genes across the genome, we uncovered a link between the restriction of developmental potency of cells and the occlusion of transcriptional potency of their genomes. We further showed that, strikingly, genes can undergo irreversible occlusion of their transcriptional potency simply by chromatinization into the nucleosomal form with unmodified histones. These findings led to a comprehensive mechanistic account of lineage restriction as driven by gene occlusion. Specifically, naive pluripotent stem cells at the onset of development possess the unique capacity to erase occlusion globally to reset full transcriptional potency of the genome, which in turn establishes full developmental potency of the cells. Such deocclusion capacity is abolished when cells progress from naive to primed pluripotency. From this stage onward, lineage-inappropriate genes can undergo nucleosome-mediated occlusion in an irreversible manner when their cognate transcription factors (TFs) and/or placeholder factors (PFs) no longer exist in cells to protect them. Consequently, the transcriptionally potent portion of the genome shrinks progressively and irreversibly during differentiation, thus permanently restricting the developmental potency of differentiating cells. ONE-SENTENCE SUMMARYDevelopmental potency of cells is linked to transcriptional potency of their genomes

developmental biology↗

bioRxiv2024

Prevalence of errors in lab-made plasmids across the globe

Plasmids are indispensable in life sciences research and therapeutics development. Currently, most labs custom-build their plasmids. As yet, no systematic data on the quality of lab-made plasmids exist. Here, we report a broad survey of plasmids from hundreds of academic and industrial labs worldwide. We show that nearly half of them contained design and/or sequence errors. For transfer plasmids used in making AAV vectors, which are widely used in gene therapy, about 40% carried mutations in the inverted terminal repeat (ITR) regions due to their inherent instability, which is influenced by flanking GC content. We also list genes difficult to clone into plasmid or package into virus due to their toxicity. Our finding raises serious concerns over the trustworthiness of lab-made plasmids, which parallels the underappreciated mycoplasma contamination and misidentified mammalian cell lines reported previously, and highlights the need for community-wide standards to uphold the quality of this ubiquitous reagent in research and medicine. Accordingly, we propose the concept of good vector practice (GVP) that covers the proper design, construction, in-process QC, final QC, banking and management of plasmids in research and medicine to uphold their quality.

molecular biology↗

bioRxiv2021

Capacity to erase gene occlusion is a defining feature distinguishing naive from primed pluripotency

Pluripotent stem cells can exist in either the naive state representing a developmental blank slate or the downstream primed state poised for differentiation. Currently, known differences between these two states are mostly phenomenological, and none can adequately explain why the two states should differ in developmental priming. Gene occlusion is a mode of epigenetic inactivation that renders genes unresponsive to their cognate transcriptional activators. It plays a crucial role in lineage restriction. Here, we report that a defining feature distinguishing the two pluripotent states lies in the ability of naive but not primed cells to erase occlusion. This "deocclusion" capacity requires Esrrb, a gene expressed only in the naive but not primed state. Notably, Esrrb silencing in the primed state is itself due to occlusion. Collectively, our data argue that the Esrrb-dependent deocclusion capacity in naive cells is key for sustaining naive pluripotency, and the loss of this capacity in the primed state via the occlusion of Esrrb poises cells for differentiation.

molecular biology↗