Cellular and Molecular Characterization of the Effects of the Zebrafish Embryo Genotyper Protocol

Standardization of zebrafish drug testing parameters for muscle diseases

Skeletal muscular diseases predominantly affect skeletal and cardiac muscle, resulting in muscle weakness, impaired respiratory function and decreased lifespan. These harmful outcomes lead to poor health-related quality of life and carry a high healthcare economic burden. The absence of promising treatments and new therapies for muscular disorders requires new methods for candidate drug identification and advancement in animal models. Consequently, the rapid screening of drug compounds in an animal model that mimics features of human muscle disease is warranted. Zebrafish are a versatile model in preclinical studies that support developmental biology and drug discovery programs for novel chemical entities and repurposing of established drugs. Due to several advantages, there is an increasing number of applications of the zebrafish model for high-throughput drug screening for human disorders and developmental studies. Consequently, standardization of key drug screening parameters, such as animal husbandry protocols, drug compound administration and outcome measures, is paramount for the continued advancement of the model and field. Here, we seek to summarize and explore critical drug treatment and drug screening parameters in the zebrafish-based modeling of human muscle diseases. Through improved standardization and harmonization of drug screening parameters and protocols, we aim to promote more effective drug discovery programs.

Improved selection of zebrafish CRISPR editing by early next-generation sequencing based genotyping

Despite numerous prior attempts to improve knock-in (KI) efficiency, the introduction of precise base pair substitutions by the CRISPR-Cas9 technique in zebrafish remains challenging. In our efforts to generate KI zebrafish models of human CACNA1C mutations, we have tested the effect of several CRISPR determinants on KI efficiency across two sites in a single gene and developed a novel method for early selection to ameliorate KI efficiency. We identified optimal KI conditions for Cas9 protein and non-target asymmetric PAM-distal single stranded deoxynucleotide repair templates at both cacna1c sites. An effect of distance to the cut site on the KI efficiency was only observed for a single repair template conformation at one of the two sites. By combining minimally invasive early genotyping with the zebrafish embryo genotyper (ZEG) device and next-generation sequencing, we were able to obtain an almost 17-fold increase in somatic editing efficiency. The added benefit of the early selection procedure was particularly evident for alleles with lower somatic editing efficiencies. We further explored the potential of the ZEG selection procedure for the improvement of germline transmission by demonstrating germline transmission events in three groups of pre-selected embryos.