Trem2 Splicing and Expression are Preserved in a Human Aβ-producing, Rat Knock-in Model of Trem2-R47H Alzheimer’s Risk Variant

Generation of Trem2
^R47H rats carrying humanized App alleles (App
^h/h)

F0-Trem2^R47H rats were crossed to Long-Evans rats to generate F1- Trem2^R47H/w rats. These crossings were repeated four more times to obtain F5-Trem2^R47H/w rats. The probability that F5 rats carry unidentified off-target mutations (except those, if present, on Chr. 9) is ~1.5625%. To generate Trem2^R47H rats on a background in which rat App has a humanized Aβ region, F5-Trem2^R47H/w and App^h/h rats¹⁷ were crossed to generate F1-Trem2^R47H/w; App^h/w rats. Progeny were crossed to remove the App^w allele. Henceforth, all Trem2^R47H rats have an App^h/h background and therefore produce human and not rodent Aβ species, and only these rats were used in all experiments.

To verify that the Trem2^R47H mutations were correctly inserted into Trem2 exon-2, we amplified by PCR the Trem2 gene exon-2 from Trem2^w/w, Trem2^R47H/w and…