We reported that targeted overexpression of human sCSF1, human mCSF1 or both (s/mCSF1) in osteoblasts in vivo results in significant osteopenia in all three genotypes.41 When analyzed by sex, sCSF1 transgenic and m/sCSF1 double-transgenic female animals, but not mCSF1 transgenic female mice, were found to have lower bone mass than their male littermates.41 By breeding CSF1 isoform-selective transgenic mice to an op/op background, mice were generated in which a single CSF1 isoform was the only source of the cytokine (sCSF1op/op and mSCF1op/op). The gene discussed is CSF1; the disease is Osteopenia.