Reverse genetic screening reveals poor correlation between morpholino-induced and mutant phenotypes in zebrafish

Area of Science:

• Genetics
• Developmental Biology
• Zebrafish Models

Background:

• Programmable site-specific nucleases facilitate targeted gene disruption in zebrafish.
• Understanding gene function relies on accurate phenotype assessment in model organisms.

Purpose of the Study:

• To generate zebrafish lines with targeted mutations in over 20 genes using site-specific nucleases.
• To compare observed mutant phenotypes with previously reported Morpholino-induced phenotypes (morphants).
• To establish reliable standards for defining gene function in zebrafish.

Main Methods:

• Application of site-specific nucleases for targeted gene disruption in zebrafish.
• Generation of zebrafish lines with individual gene mutations.
• Phenotypic analysis of mutant embryos during embryogenesis.
• Comparison of mutant phenotypes with published Morpholino data.

Main Results:

• Mutations in a small subset of genes resulted in observable embryogenesis defects.
• Mutants for ten genes did not replicate published Morpholino-induced phenotypes.
• Approximately 80% of published morphant phenotypes were not observed in mutant embryos.
• Absence of phenotypes in mutants was unlikely due to maternal effects or incomplete gene function elimination.

Conclusions:

• Mutant phenotypes should serve as the primary standard for defining gene function in zebrafish.
• Morpholinos can be reliably used for ancillary analyses once they recapitulate established mutant phenotypes.
• This study highlights discrepancies between Morpholino-based and knockout-based functional genomics in zebrafish.