Wild-derived mouse strains exhibit large variation of home-cage activity among strains. The wild strain MSM/Ms (MSM) exhibits different activity in the home-cage comparing to C57BL/6 (B6), a commonly used laboratory strain. We have previously analyzed consomic strains derived from B6 and MSM to elucidate genetic mechanism responsible for strain differences in the regulation of home-cage activity. We have found that a consomic strain of chromosomes 6 exhibits low level of activity. Further genetic mapping of the QTL using congenic strains revealed that at least four loci are clustered in 14.5 Mbp chromosomal region. Among these loci, one locus significantly increases activity of B6 when the congenic strain carries the genomic region derived from MSM. There are three candidate genes which exist in the mapped region. We previously reported that one of the candidate genes, ER degradation enhancer, mannosidase alpha-like 1 (Edem1), exhibits lower expression level than B6, suggested Edem1 as a strong candidate gene of increased activity. In this study, we conducted genetic and molecular analyses, and found that Edem1 may not associate with the increased home-cage activity in mice.