To test whether complement-mediated microglial synaptic elimination could occur in premanifest HD, we performed quantitative RT–PCR on RNA extracted from two rare samples of caudate nucleus from premanifest HD patients and found that levels of C3 and CR3 transcripts were elevated relative to controls (Extended Data Fig. 1i,j), consistent with a previous study that used unbiased transcriptomic profiling in the BA9 region of premanifest HD patients55. The gene discussed is C3; the disease is Huntington disease.