Efficient genome-wide first-generation phenotypic screening system in mice using the piggyBac transposon

Abstract

Significance Genome-wide, phenotype-driven mutagenesis in animal models could provide an unbiased way to decode a gene’s functions and its role in diseases. Here we have generated a piggyBac (PB) transposon-based first-generation (F1) dominant screening system in mice, which provides unprecedented opportunities to conduct a highly efficient and affordable genome-wide phenotypic screen for an individual investigator in a single laboratory. Using this system, we carried out an F1 dominant screen for growth retardation and discovered 5 isolated mutants that carry transposon insertions hitting the genes Rin2, Rbm39, Mll, Zeb2, and Six1/4. The Six1/4PB/+ mutant animals exhibit abnormalities in nipple recognition and milk ingestion during the breastfeeding period and also exhibit cranial nerve defects. Genome-wide phenotypic screens provide an unbiased way to identify genes involved in particular biological traits, and have been widely used in lower model organisms. However, cost and time have limited the utility of such screens to address biological and disease questions in mammals. Here we report a highly efficient piggyBac (PB) transposon-based first-generation (F1) dominant screening system in mice that enables an individual investigator to conduct a genome-wide phenotypic screen within a year with fewer than 300 cages. The PB screening system uses visually trackable transposons to induce both gain- and loss-of-function mutations and generates genome-wide distributed new insertions in more than 55% of F1 progeny. Using this system, we successfully conducted a pilot F1 screen and identified 5 growth retardation mutations. One of these mutants, a Six1/4PB/+ mutant, revealed a role in milk intake behavior. The mutant animals exhibit abnormalities in nipple recognition and milk ingestion, as well as developmental defects in cranial nerves V, IX, and X. This PB F1 screening system offers individual laboratories unprecedented opportunities to conduct affordable genome-wide phenotypic screens for deciphering the genetic basis of mammalian biology and disease pathogenesis.