The widely usedUcp1-CreEvdrtransgene elicits complex developmental and metabolic phenotypes

Abstract

SummaryBacterial artificial chromosome transgenic models, including mostCre-recombinases, enable potent interrogation of gene functionin vivobut require rigorous validation as limitations emerge. Due to its high relevance to metabolic studies, we performed comprehensive analysis of theUcp1-CreEvdrline which is widely used for brown fat research. Hemizygotes exhibited major brown and white fat transcriptomic dysregulation, indicating potential altered tissue function.Ucp1-CreEvdrhomozygotes also show high mortality, growth defects, and craniofacial abnormalities. Mapping the transgene insertion site revealed insertion in chromosome 1 accompanied by large genomic alterations disrupting several genes expressed in a range of tissues. Notably,Ucp1-CreEvdrtransgene retains an extraUcp1gene copy that may be highly expressed under high thermogenic burden. Our multi-faceted analysis highlights a complex phenotype arising from the presence of theUcp1-CreEvdrtransgene independently of the intended genetic manipulations. Overall, comprehensive validation of transgenic mice is imperative to maximize discovery while mitigating unexpected, off-target effects.HighlightsHemizygousUcp1-CreEvdrmice exhibit substantial brown and white fat tissue dysregulation.HomozygousUcp1-CreEvdrmice display high mortality, growth defects, and craniofacial abnormalities.TheUcp1-CreEvdrtransgene integration resulted in major genomic disruptions affecting multiple genes.TheUcp1-CreEvdrtransgene retains a possibly functional extraUcp1copy.