Winkler, J. D. | bioRxiv Science

bioRxiv2023

Biliatresone treatment of pregnant mice causes changes in bile metabolism and liver inflammation in their offspring

Background & AimsBiliary atresia is a neonatal disease characterized by bile duct and liver damage, fibrosis, inflammation and abnormal bile metabolism. It appears to result from a prenatal exposure that spares the mother and affects the fetus. Our aim was to define the phenotype in neonatal mice after maternal exposure to low-dose biliatresone, a plant toxin implicated in biliary atresia in livestock. MethodsPregnant mice were treated orally with low-doses of biliatresone. Histological changes, bile acid profiles and immune profiles were analyzed in postnatal day 5 and 21 pups born to treated mothers. ResultsThe pups of mothers treated with this dose of biliatresone had no evidence of significant liver or ductular injury or fibrosis at postnatal day 5 or 21 and they grew normally. However, serum levels of glycocholic acid were elevated at postnatal day 5, suggesting altered bile metabolism, and bile metabolism became increasingly abnormal through postnatal day 21, with enhanced glycine conjugation of bile acids. There was also immune cell activation observed in the liver at postnatal day 21. ConclusionPrenatal exposure to low doses of an environmental toxin can cause liver inflammation and aberrant bile metabolism even in the absence of histological changes. Lay summaryPrenatal exposure to low doses of an environmental toxin can cause changes in bile metabolism in neonatal mice.

pharmacology and toxicology↗

bioRxiv2017

Refactoring the Genetic Code for Increased Evolvability

The standard genetic code is robust to mutations and base-pairing errors during transcription and translation. Point mutations are most likely to be synonymous or preserve the chemical properties of the original amino acid. Saturation mutagenesis experiments suggest that in some cases the best performing mutant requires a replacement of more than a single nucleotide within a codon. These replacements are essentially inaccessible to common error-based laboratory engineering techniques that alter single nucleotide per mutation event, due to the extreme rarity of adjacent mutations. In this theoretical study, we suggest a radical reordering of the genetic code that maximizes the mutagenic potential of single nucleotide replacements. We explore several possible genetic codes that allow a greater degree of accessibility to the mutational landscape and may result in a hyper-evolvable organism serving as an ideal platform for directed evolution experiments. We then conclude by evaluating potential applications for recoded organisms within the synthetic biology field.\n\nSignificance StatementThe conservative nature of the genetic code prevents bioengineers from efficiently accessing the full mutational landscape of a gene using common error-prone methods. Here we present two computational approaches to generate alternative genetic codes with increased accessibility. These new codes allow mutational transition to a larger pool of amino acids and with a greater degree of chemical differences, using a single nucleotide replacement within the codon, thus increasing evolvability both at the single gene and at the genome levels. Given the widespread use of these techniques for strain and protein improvement along with more fundamental evolutionary biology questions, the use of recoded organisms that maximize evolvability should significantly improve the efficiency of directed evolution, library generation and fitness maximization.

bioengineering↗