(A) Cx43ΔCT/fl were mated with Cx43fl/fl;DMP1-8kb-Cre mice and 4 different genotypes were obtained: 1) Cx43fl/fl mice have both alleles of Cx43 gene flanked by LoxP sites and are similar to wild-type mice, 2) Cx43ΔCT/fl mice have one allele of Cx43 replaced by a Cx43 truncated at amino acid 258, which can generate functional channel but lacks the scaffolding ability, and the other allele is the full length floxed Cx43, 3) Cx43fl/fl;DMP1-8kb-Cre mice have both alleles flanked by LoxP sites and are recognized and excised by the Cre recombinase under control of a DNA fragment containing 8kb of the murine dentin matrix protein 1 promoter (DMP1), thus lacking Cx43 protein in osteocytes, and 4) Cx43ΔCT/fl;DMP1-Cre mice, expressing ubiquitously Cx43ΔCT and lacking osteocytic full length Cx43. (B) Body weight from mice of all genotypes was measured monthly from 1 to 4 months of age. Symbols represent mean ± s.d., n=12–28. (C) Total body, spinal, and femoral BMD was measured monthly from 1 to 4 months of age by dual-DXA. Symbols represent mean ± s.d., n=12–28.