Gene targeting in mouse embryos mediated by RecA and modified single-stranded oligonucleotides

Genomic perspectives of transcriptional regulation in forebrain development

The forebrain is the seat of higher-order brain functions, and many human neuropsychiatric disorders are due to genetic defects affecting forebrain development, making it imperative to understand the underlying genetic circuitry. Recent progress now makes it possible to begin fully elucidating the genomic regulatory mechanisms that control forebrain gene expression. Herein, we discuss the current knowledge of how transcription factors drive gene expression programs through their interactions with cis-acting genomic elements, such as enhancers; how analyses of chromatin and DNA modifications provide insights into gene expression states; and how these approaches yield insights into the evolution of the human brain.

Gene editing activity on extrachromosomal arrays in C. elegans transgenics

Gene editing by modified single-stranded oligonucleotides is a strategy aimed at inducing single base changes into the genome, generating a permanent genetic change. The work presented here explores gene editing capabilities in the model organism Caenorhabditis elegans. Current approaches to gene mutagenesis in C. elegans have been plagued by non-specificity and thus the ability to induce precise, directed alterations within the genome of C. elegans would offer a platform upon which structure/function analyses can be carried out. As such, several in vivo assay systems were developed to evaluate gene editing capabilities in C. elegans. Fluorescence was chosen as the selectable endpoint as fluorescence can be easily detected through the transparent worm body even from minimal expression. Two tissue specific fluorescent expression vectors containing either a GFP or mCherry transgene were mutagenized to create a single nonsense mutation within the open reading frame of each respective fluorescent gene. These served as the target site to evaluate the frequency of gene editing on extrachromosomal array transgenic lines. Extrachromosomal arrays can carry hundreds of copies of the transgene, therefore low frequency events (like those in the gene editing reaction) may be detected. Delivery of the oligonucleotide was accomplished by microinjection into the gonads of young adult worms in an effort to induce repair of the mutated fluorescent gene in the F1 progeny. Despite many microinjections on the transgenic strains with varying concentrations of ODNs, no gene editing events were detected. This result is consistent with the previous research, demonstrating the difficulties encountered in targeting embryonic stem cells and the pronuclei of single-celled embryos.