Objective:In order to study the expression of estrogen receptor-α(ERα)in mouse embryo,the sense and anti-sense RNA probes for hybridization of ERα were prepared.Methods:The ERα fragment which was obtained by RT-PCR was subcloned into plasmids pGEM-3Z,and then the recombinant plasmids ERα/pGEM-3Z were linearized with the restriction enzymes,Hind Ⅲ and EcoRⅠ.Using T7 and Sp6 RNA polymerase,respectively,the digoxigenin(dig)labeled sense and antisense probes were transcribed in vitro.Then the expression of ERα in mouse embryo was examined with the probes by whole mount in situ hybridization.Results:The gene fragment of ERα was cloned and the cRNA probes were prepared with digoxigenin-labeled.ERα gene was expressed in the forebrain,spinal neural tube,genital ridge,limb bud,mandibular arch of 10.5 dpc embryo and was also expressed in the telencephalon,mesencephalon,spinal cord,limb bud,and reproductive system of 13.5 dpc embryo.