On December 18th, 2017, a new paper was published by The Jackson Laboratory (Bar Harbor, ME, USA) and Cergentis (Utrecht, The Netherlands) entitled: "Large-scale discovery of mouse transgenic integration sites reveals frequent structural variation and insertional mutagenesis”.

The paper, published on BioRXiv, describes the TLA-based analysis of 40 widely used transgenic mouse lines. The Targeted Locus Amplification technology was used to map the integration sites of the transgenes and to verify potentially harmful sequence variation.

The transgene integration site(s) were identified in all 40 lines. In 20 of the 40 lines, the integration site was found to have occurred in an endogenous mouse gene. Almost all lines were found to contain structural variation of the mouse genome as a result of the integration event. Furthermore, in 25% of the lines, evidence of co-integrated E.coli sequence was found.

The paper shows that transgene insertions can have effect on the phenotype of widely used transgenic animal models and highlights the importance of a complete genetic characterisation.