Grn mice

Wild type C57/BL6, Cx3cr1^+/CreER [56 (link)], Grn^flox/flox, and Grn^−/− mice [88 (link)] were obtained from the Jackson Laboratory. Cx3cr1^+/CreERGrn^flox/flox mice were fed Tamoxifen at 3 weeks of age to delete PGRN in microglia[56 (link)]. Cx3cr1^+/CreER mice were also fed Tamoxifen to be used as controls. Tamoxifen (Sigma T5648, 10mg/ml) was dissolved in filter-sterilized corn oil by incubating overnight at 37°C. The solution was protected from light and was administered to mice (75 mg /kg) via oral gavage every other day 7 times total. CNS demyelination was induced by supplementing the diet of 10-week-old mice with 0.2% (w/w) cuprizone (bis [cyclohexanone] oxaldihydrazone) in powdered rodent chow [72 (link)]). The rodent chow (5 g/mouse/day) was replaced every other day for 5 weeks. For the remyelination period, mice were returned to normal chow for 3 weeks. Untreated control mice were fed normal crushed chow for 5 weeks or 8 weeks. All the mice were housed in the Weill Hall animal facility at Cornell. All animal procedures have been approved by the Institutional Animal Care and Use Committee (IACUC) at Cornell.

Grn^+/− and Grn^−/− mice (Jackson Laboratory #036771) (Martens et al., 2012 (link)) were compared to wild-type littermates for initial validation of progranulin microdialysis. Conditional Grn knockout mice were generated by crossing Grn^fl/fl mice (Jackson Laboratory #036770) (Martens et al., 2012 (link)) with mice expressing CaMKII-Cre (Jackson Laboratory #005359) (Tsien et al., 1996 (link)) or Cx3Cr1-Cre-ER (Jackson Laboratory #020940) (Yona et al., 2013 (link)) to produce Grn^fl/fl:Cre+ or Cre− littermates. All mouse lines were maintained on a congenic C57Bl6/J background. Young adult mice were used for microdialysis studies, with most mice aged 2–6 months. Cx3Cr1-Cre-ER was induced by daily injections of 2 mg tamoxifen (MilliporeSigma) in 0.1 mL corn oil (MilliporeSigma) for five days, followed by a minimum wait of four weeks before microdialysis sampling to allow turnover of peripheral mono-nuclear cells (Goldmann et al., 2013 (link)). Mice were housed on a 12 h light/dark cycle with lights on from 6 AM to 6 PM in a facility accredited by the Association for Assessment and Accreditation of Laboratory Animal Care. Mice had free access to food (Envigo #7917) and water throughout the study, including during microdialysis sampling. All experiments were approved by the Institutional Animal Care and Use Committee of the University of Alabama at Birmingham.