A homing rescue gene drive with multiplexed gRNAs reaches high frequency in cage populations but generates functional resistance.

CRISPR homing gene drives have considerable potential for managing populations of medically and agriculturally significant insects. They operate by Cas9 cleavage followed by homology-directed repair, copying the drive allele to the wild-type chromosome and thus increasing in frequency and spreading throughout a population. However, resistance alleles formed by end-joining repair pose a significant obstacle. To address this, we create a homing drive targeting the essential hairy gene in Drosophila melanogaster. Nonfunctional resistance alleles are recessive lethal, while drive carriers have a recoded "rescue" version of hairy. The drive inheritance rate is moderate, and multigenerational cage studies show drive spread to 96%-97% of the population. However, the drive does not reach 100% due to the formation of functional resistance alleles, despite using four gRNAs. These alleles have a large deletion but likely utilize an alternate start codon. Thus, revised designs targeting more essential regions of a gene may be necessary to avoid such functional resistance. Replacement of the rescue element's native 3' UTR with a homolog from another species increases drive inheritance by 13%-24%. This was possibly because of reduced homology between the rescue element and surrounding genomic DNA, which could also be an important design consideration for rescue gene drives.

Yunpi Tongbian Fang alleviates slow transit constipation induced by loperamide by regulating intestinal microbiota and short-chain fatty acids in rats.

Slow transit constipation (STC) is a prevalent chronic colonic dysfunction disease that significantly impairs the quality of life for affected individuals. Yunpi Tongbian Fang (YPTBF), a traditional Chinese medicine compound, has demonstrated promising clinical efficacy; however, its underlying mechanism remains elusive. In order to assess the laxative properties of YPTBF, which encompasses the influence on gut microbiota, gut metabolites, gut neurotransmitters, and colon histology, an oral administration of YPTBF was conducted for a duration of two consecutive weeks on STC rats induced by loperamide hydrochloride. The results showed that YPTBF improved the symptoms of STC, alleviated the decrease in total fecal volume and fecal water content caused by loperamide-induced constipation, restored intestinal transport function, and HE staining showed the recovery of pathological damage to the colon mucosa. In addition, YPTBF increased the concentrations of 5-HT and ACHE, while reducing the concentrations of VIP and NO. YPTBF adjusted the diversity and abundance of gut microbiota in STC rats, enabling the recovery of beneficial bacteria and promoting the production of acetic acid, propionic acid, and butyric acid. We found that YPTBF can improve constipation in STC rats, possibly by regulating the intestinal microbiota structure and improving SCFAs metabolism.

Mutagenesis and Resistance Development of Bacteria Challenged by Silver Nanoparticles.

Because of their extremely broad spectrum and strong biocidal power, nanoparticles of metals, especially silver (AgNPs), have been widely applied as effective antimicrobial agents against bacteria, fungi, and so on. However, the mutagenic effects of AgNPs and resistance mechanisms of target cells remain controversial. In this study, we discover that AgNPs do not speed up resistance mutation generation by accelerating genome-wide mutation rate of the target bacterium Escherichia coli. AgNPs-treated bacteria also show decreased expression in quorum sensing (QS), one of the major mechanisms leading to population-level drug resistance in microbes. Nonetheless, these nanomaterials are not immune to resistance development by bacteria. Gene expression analysis, experimental evolution in response to sublethal or bactericidal AgNPs treatments, and gene editing reveal that bacteria acquire resistance mainly through two-component regulatory systems, especially those involved in metal detoxification, osmoregulation, and energy metabolism. Although these findings imply low mutagenic risks of nanomaterial-based antimicrobial agents, they also highlight the capacity for bacteria to evolve resistance.