Multiplex genome editing in using Mb3Cas12a.

The use of CRISPR-Cas proteins for the creation of multiplex genome engineering represents an important avenue for crop improvement, and further improvements for creation of knock-in plant lines via CRISPR-based technologies may enable the high-throughput creation of designer alleles. To circumvent limitations of the commonly used CRISPR-Cas9 system for multiplex genome engineering, we explored the use of Cas12a (Mb3Cas12a) for multiplex genome editing in . We identified optimized cis-regulatory sequences for driving expression of single-transcript multiplex crRNA arrays in , resulting in stable germline transmission of Mb3Cas12a-edited alleles at multiple target sites.

Targeting of the Dosage-Compensated Male X-Chromosome during Early Drosophila Development.

Dosage compensation, which corrects for the imbalance in X-linked gene expression between XX females and XY males, represents a model for how genes are targeted for coordinated regulation. However, the mechanism by which dosage compensation complexes identify the X chromosome during early development remains unknown because of the difficulty of sexing embryos before zygotic transcription using X- or Y-linked reporter transgenes. We used meiotic drive to sex Drosophila embryos before zygotic transcription and ChIP-seq to measure the dynamics of dosage compensation factor targeting.

TET-mediated epimutagenesis of the Arabidopsis thaliana methylome.

DNA methylation in the promoters of plant genes sometimes leads to transcriptional repression, and the loss of DNA methylation in methyltransferase mutants results in altered gene expression and severe developmental defects. However, many cases of naturally occurring DNA methylation variations have been reported, whereby altered expression of differentially methylated genes is responsible for agronomically important traits. The ability to manipulate plant methylomes to generate epigenetically distinct individuals could be invaluable for breeding and research purposes.

Histone locus regulation by the dosage compensation adaptor protein CLAMP.

The conserved histone locus body (HLB) assembles prior to zygotic gene activation early during development and concentrates factors into a nuclear domain of coordinated histone gene regulation. Although HLBs form specifically at replication-dependent histone loci, the and factors that target HLB components to histone genes remained unknown. Here we report that conserved GA repeat elements within the bidirectional promoter direct HLB formation in In addition, the CLAMP (chromatin-linked adaptor for male-specific lethal [MSL] proteins) zinc finger protein binds these GA repeat motifs, increases chromatin accessibility, enhances histone gene transcription, and promotes HLB formation.

The essential Drosophila CLAMP protein differentially regulates non-coding roX RNAs in male and females.

Heterogametic species require chromosome-wide gene regulation to compensate for differences in sex chromosome gene dosage. In Drosophila melanogaster, transcriptional output from the single male X-chromosome is equalized to that of XX females by recruitment of the male-specific lethal (MSL) complex, which increases transcript levels of active genes 2-fold. The MSL complex contains several protein components and two non-coding RNA on the X ( roX) RNAs that are transcriptionally activated by the MSL complex.

The shocking consequences of hybrid epigenomes.

The formation of spontaneous epialleles is poorly understood. A new study describes how the formation of epihybrids can lead to the appearance of novel epialleles.