Belt and braces: two escape ways to maintain the cassette reservoir of large chromosomal integrons
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PROVIDER: PRJEB65866 | ENA |
REPOSITORIES: ENA
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Project description:Integrons are genetic elements that enable bacterial adaptation by collecting new genes encoded in integron cassettes (ICs) to create a reservoir of adaptive functions. These cassettes typically lack their own promoters and rely on the integron platform for their expression. Integrons, well-known for spreading antibiotic resistance genes in clinically relevant Gram-negative species, include Mobile Integrons (MIs), that transport over 170 resistance genes. In contrast, Sedentary Chromosomal Integrons (SCIs), ubiquitous in Vibrio species, are primarily found within bacterial chromosomes. However, their functions are not related to antimicrobial resistance and are largely unexplored. SCIs, typified by the Superintegron (SI) in Vibrio cholerae, represent ancient and highly variable regions in bacterial genomes. The SI is extensive, housing 179 integron cassettes, mostly with unknown functions. Although 19 cassettes encode toxin-antitoxin (TA) systems, which stabilize the array, the intricacies of the SI are challenging to study due to its size and unique integrase. To investigate the SI's impact on V. cholerae, we developed the SeqDelTA approach, enabling the gradual deletion of the SI. This deletion facilitates the use of standard genetic tools without SI interference. Our in-depth analysis of the resulting ∆SI strain, covering various aspects, demonstrated no significant alterations in V. cholerae's physiology. Despite their extended coevolution, SCIs appear to be genetically isolated from the host genome.
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Project description:Integrons are genetic platforms that acquire new genes encoded in integron cassettes (ICs), building arrays of adaptive functions for bacteria. ICs generally encode promoterless genes, whose expression relies on the PC promoter within the integron platform. Cassette arrays are assumed to be operon-like structures in which expression is dependent on the distance to the Pc. This is especially relevant in large sedentary chromosomal integrons (SCIs,) like the ones in Vibrio species. We have identified 29 gene-less cassettes in 4 Vibrio SCIs, and explored whether their function could be related to regulating the transcription of adjacent ICs. We show that most gene-less cassettes have promoter activity on the sense strand, enhancing the expression of downstream cassettes. Accordingly, we found that most of the superintegron in Vibrio cholerae is not silent. These promoter cassettes can trigger the expression of a silent dfrB9 resistance cassette downstream, increasing trimethoprim resistance >512-fold in V. cholerae and Escherichia coli. Additionally, one cassette had an antisense promoter capable of reducing trimethoprim resistance through transcriptional interference. Our findings highlight the regulatory role of gene-less cassettes in the expression of adjacent cassettes, emphasizing their significance in large SCIs and their clinical importance if captured by mobile integrons.
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Project description:Delamination of neural progenitor cells (NPCs) from the ventricular surface is a crucial prerequisite to form the subventricular zone, the germinal layer linked to the expansion of the mammalian neocortex in development and evolution. Here, we dissect the molecular mechanism by which the transcription factor Insm1 promotes the generation of basal progenitors (BPs). Insm1 protein is most highly expressed in newborn BPs in mouse and human developing neocortex. Forced Insm1 expression in embryonic mouse neocortex causes NPC delamination, converting apical to basal radial glia. Insm1 represses the expression of the apical adherens junction belt-specific protein Plekha7. CRISPR/Cas9-mediated disruption of Plekha7 expression suffices to cause NPC delamination. Plekha7 overexpression impedes the intrinsic, and counteracts the Insm1-induced, NPC delamination. Our findings uncover a novel molecular mechanism underlying NPC delamination in which a BP-genic transcription factor specifically targets the integrity of the apical adherens junction belt, rather than adherens junction components as such.
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Project description:Belt electrode-skeletal muscle electrical stimulation (B-SES) involves the use of belt-shaped electrodes to simultaneously contract multiple muscle groups. Twitch contractions have been demonstrated to protect against denervation-induced muscle atrophy in rats, possibly via mitochondrial biosynthesis. In this study, we examined whether inducing tetanus contractions with B-SES suppresses muscle atrophy and identified the underlying molecular mechanisms. We evaluated the effects of acute (60 Hz, 5 min) and chronic (60 Hz, 5 min, every alternate day for 1 week) B-SES on the tibialis anterior (TA) and gastrocnemius (GAS) muscles in Sprague Dawley rats using belt electrodes attached to both ankle joints. In acute stimulation, a significant decrease in glycogen content in the left and right TA and GAS was observed, suggesting that B-SES causes simultaneous contractions in multiple muscle groups. B-SES also enhanced p70S6K phosphorylation, an indicator of the mechanistic target of rapamycin complex 1 activity. During chronic stimulations, rats were divided into control (CONT), denervation-induced atrophy (DEN), and DEN+electrically stimulated with B-SES (DEN＋ES) groups. After 7 days of treatment, muscle wet weight (n = 8-11 for each group) and muscle fiber cross-sectional area (CSA, n = 6 for each group) of the TA and GAS muscles were reduced in the DEN and DEN+ES groups compared to those in the CON group. The DEN+ES group showed significantly higher muscle weight and CSA than the DEN group. Although RNA-seq and pathway analysis suggested that mitochondrial and ribosome biogenesis are key events in this phenomenon, mitochondrial content showed no difference. In contrast, ribosomal RNA 28S and 45S (n = 6) levels in the DEN+ES group were higher than those in the DEN group. The mRNA levels of the muscle proteolytic molecules Atrogin-1 and MuRF1 were significantly higher in DEN than in CONT but were suppressed in DEN+ES. In conclusion, tetanic electrical stimulation of both ankles using belt electrodes was effective in preventing denervation-induced atrophy in multiple muscle groups. Unlike twitch contractions, ribosomal biosynthesis plays a key role in tetanic contractions to prevent muscle atrophy.
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Project description:The Sahel/Savannah belt harbours diverse populations with different demographic histories and different subsistence patterns. However, populations from this large African region are notably under-represented in genomic research. To investigate the population structure and adaptation history of populations from the Sahel/Savannah space, we generated dense genome-wide genotype data of 327 individuals—comprising 14 ethnolinguistic groups, including ten previously unsampled populations. DNA samples were genotyped on the Illumina H3Africa Consortium Array (BeadChip type: H3Africa_2017_20021485_A2; designed for SNP-genotyping of 2,267,346 SNPs) at the SNP&SEQ Technology Platform, NGI/SciLifeLab Genomics (Sweden). Reference: Demographic and Selection Histories of Populations Across the Sahel/Savannah Belt. Fortes-Lima C, Tříska P, Čížková M, Podgorná E, Diallo MY, Schlebusch CM, Černý V. Molecular Biology and Evolution 2022 39(10):msac209. doi: 10.1093/molbev/msac209. PMID: 36173804 .
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