A platform of large-scale in vivo CRISPR screens is described in Science this week. Despite CRISPR-Cas9's ability to be scaled up for large-scale screens in cultured cells, its use in animals is limited by the need to generate, validate, and track large numbers of mutant animals. To address this, a University of Utah team developed MIC-Drop — short for multiplexed intermixed CRISPR droplets — that combines droplet microfluidics, single-need en masse CRISPR ribonucleoprotein infections, and DNA barcoding to enable large-scale functional genetics screens in zebrafish. "The MIC-Drop platform enables in vivo vertebrate CRISPR experiments to be performed with speed, efficiency, and scale previously available only to in vitro systems," the authors write.
An analysis of the seadragon genome is published in Science Advances this week, providing insights into this animal's evolutionary novelties and identifying its sex-determining locus. Seadragons are best known for their leaf-like appendages, toothless tubular mouth, and male pregnancy involving incubation of fertilized eggs on an open brood patch. To better understand the basis for such characteristics, a group led by scientists from the Chinese Academy of Sciences generated and analyzed high-quality, chromosome-level genome assemblies of the male and a female common seadragon, as well as a chromosome-scale, genome assembly for the closely related alligator pipefish. Transcription profiles show that a set of genes typically involved in fin development have been co-opted for the development of the seadragon's leaf-like appendages, as well as reveal an enrichment of transcripts for potential tissue repair and immune defense genes. The investigators also identify a putative sex-determining locus encoding a male-specific gene shared by common seadragon and alligator pipefish.