Tamoxifen-Induced Conditional Deletion of Igf1 in CX3CR1+ Microglia

CX3CR1^CreER [14 (link)] and Igf1^flox [15 (link)] were obtained from The Jackson Laboratory and maintained as a breeding colony in the Biomedical Laboratory, University of Southern Denmark (Odense, Denmark), to obtain CX3CR1^CreER/WT: Igf1^flox/flox (MG-Igf1^KO) (Figure 1A). Cre recombinase was activated by the daily subcutaneous (s.c.) administration of Tamoxifen (TAM) (Sigma Aldrich, St. Louis, MO, USA, 75 mg/kg) to newborn pups from postnatal day 1 to postnatal day 4 (PN1-PN4) (Figure 1B). For control purposes, CX3CR1^CreER/WT mice (Igf1^WT) were also injected with TAM. This control setup was critical to ensure that any observed effects in the MG-Igf1^KO group were attributable specifically to the absence of Igf1 rather than to the previously reported effects of TAM administration [16 (link)]. Animal experiments were conducted on female mice in their adulthood (13 weeks old) and were approved by the Danish Animal Experiments Inspectorate (approval number: 2020-15-0201-0065).