OBJECTIVETo breed estrogen receptor beta (ERbeta) gene knock-out female mice for studying postmenopausal osteoporotic fracture.

METHODSThree pairs of ERbeta gene knock-out mice were bred for 3 months, and 14 2-month-old female wild-type C57BL/6J mice with the same genetic background were paired at the ratio of 2:1 and mated with the male ERbeta gene knock-out homozygote mice. After further breeding to obtain sufficient number of mice, the genome DNA was extracted from the tail of the mice for genotyping by PCR. Ten 4-month-old female filial mice with ERbeta gene knock-out and 10 wild-type female mice were randomly selected and sacrificed, and the right proximal tibiae were removed and subjected to micro CT for measuring the parameters of trabecular bone histomorphometry.

RESULTSA total of 340 filial generation mice were reproduced in 2 months and genotypic identification revealed a proportion of ERbeta+ or + mice of 23.5%, ERbeta+ or - mice of 48.27 percent; and homozygous mutant (ERbeta- or -) mice of 28.3% (in which 54 were female). The MicroCT data revealed that the micro-architecture of the proximal tibiae was significantly different between ERbeta gene knock-out mice selected from the filial generation and wild type mice (P<0.05).

CONCLUSIONIt is feasible to breed ERbeta knock-out female mice by introducing female wild-type mice to pair and mate with ERbeta knock-out homozygote male mice. This approach allows breeding of sufficient number of female ERbeta knock-out mice as the animal models for studying the role of ERbeta.