Here, we produced cell-type-specific profiles of genome-wide histone modifications including H3K27ac and H3K4me3 in basal, luminal progenitor, mature luminal and stromal cells extracted from a small pilot cohort of pre-cancer BRCA1 mutation carriers (BRCA1mut/+) and non-carriers (BRCA1+/+), using a low-input ChIP-seq technology that we developed. The gene discussed is BRCA1; the disease is cancer.