CHD5 and breast neoplasm: Interestingly, in the breast tumor sample showing HD for DEAR1, one copy of Chromosome 1p contains a microdeletion of DEAR1, while the second copy deletes the entire short arm, including CHD5, but the breakpoint for the deletion lies within DEAR1. CHD5 maps to a genomic interval associated with LOH in late-stage tumors; thus, the finding that DEAR1 seems to play a role in the earliest stages of breast tumorigenesis would suggest a mechanism for mutation or deletion of DEAR1 as an initiating event that could lead to the LOH for distal Chromosome 1p loci and thus haploinsufficiency of CHD5.