CSF1R and osteopetrosis: Csf1r null mutant mice reveal severe osteopetrosis due to deficient osteoclast activation (Dai et al., 2002; Li, Chen, Zhu, & Pollard, 2006) and structural brain abnormalities with impact on microglia and neural progenitor cells (Erblich, Zhu, Etgen, Dobrenis, & Pollard, 2011; Nandi et al., 2012), but it was not possible to proof neurodegeneration because of early onset high lethality.