Expanding the biosensor horizon

At an amazing pace, synthetic biology, bio-informatics and systems biology are expanding the applications of industrial biotechnology contributing to the transition towards a bio-economy due to economic and ecological advantages. Additionally, new-to-nature compounds have been commercialized using biotechnology, showing its enormous potential. Despite these recent advances, the transformation and optimization of wild type organisms into highly efficient microbial cell factories still undergoes slow design-build-test-learn cycles, especially in the last two steps. The testing phase requires high-throughput screening methods to keep up with the ever-increasing size of strain libraries, while the learning phase is still hampered by the immensely complex bacterial metabolisms. To overcome these hurdles, transcriptional biosensors have the potential to become a key enabling tool in synthetic biology and metabolic engineering. The repertoire of industrially useful biosensors is however still lacking and their true potential has not been fully characterized. A better understanding in the development of new-to-nature biosensors will be pursued through novel strategies and engineering principles to obtain portable and orthogonal biosensor parts with defined specificity and response. The process of biosensor-driven optimization of microbial cell factories will be applied to the production of perfectly defined chitooligosaccharides as proof of concept. These molecules are rising in popularity due to their numerous applications in healthcare, pharma, feed and food sectors

Chimeric LysR-type transcriptional biosensors for customizing ligand specificity profiles toward flavonoids

Transcriptional biosensors enable key applications in both metabolic engineering and synthetic biology. Due to nature's immense variety of metabolites, these applications require biosensors with a ligand specificity profile customized to the researcher's needs. In this work, chimeric biosensors were created by introducing parts of a donor regulatory circuit from Sinorhizobium meliloti, delivering the desired luteolin-specific response, into a nonspecific biosensor chassis from Herbaspirillum seropedicae. Two strategies were evaluated for the development of chimeric LysR-type biosensors with customized ligand specificity profiles toward three closely related flavonoids, naringenin, apigenin, and luteolin. In the first strategy, chimeric promoter regions were constructed at the biosensor effector module, while in the second strategy, chimeric transcription factors were created at the biosensor detector module. Via both strategies, the biosensor repertoire was expanded with luteolin-specific chimeric biosensors demonstrating a variety of response curves and ligand specificity profiles. Starting from the nonspecific biosensor chassis, a shift from 27.5% to 95.3% luteolin specificity was achieved with the created chimeric biosensors. Both strategies provide a compelling, faster, and more accessible route for the customization of biosensor ligand specificity, compared to de novo design and construction of each biosensor circuit for every desired ligand specificity

A homozygous CREB3L1 missense mutation expands the mutational spectrum of CREB3L1-related osteogenesis imperfecta

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A homozygous pathogenic missense variant broadens the phenotypic and mutational spectrum of CREB3L1-related osteogenesis imperfecta

The cyclic adenosine monophosphate (AMP) responsive element binding protein 3-like 1 (CREB3L1) gene codes for the endoplasmic reticulum stress transducer old astrocyte specifically induced substance (OASIS), which has an important role in osteoblast differentiation during bone development. Deficiency of OASIS is linked to a severe form of autosomal recessive osteogenesis imperfecta (OI), but only few patients have been reported. We identified the first homozygous pathogenic missense variant (p.(Ala304Val)) in a patient with lethal OI, which is located within the highly conserved basic leucine zipper domain, four amino acids upstream of the DNA binding domain. In vitro structural modeling and luciferase assays demonstrate that this missense variant affects a critical residue in this functional domain, thereby decreasing the type I collagen transcriptional binding ability. In addition, overexpression of the mutant OASIS protein leads to decreased transcription of the SEC23A and SEC24D genes, which code for components of the coat protein complex type II (COPII), and aberrant OASIS signaling also results in decreased protein levels of SEC24D. Our findings therefore provide additional proof of the potential involvement of the COPII secretory complex in the context of bone-associated disease

Whole-exome sequencing as a powerful tool to unravel the molecular pathogenesis of osteogenesis imperfecta

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