From Behaviour To Genes: Sex in the Japanese Quail

Abstract

In Japanese quail (Coturnix japonica) like in most vertebrates, testosterone (T) activates male copulatory behaviour through its action in the preoptic area (POA). The transformation of T into estradiol by the enzyme aromatase localized in the POA is critical for this behavioral activation. We studied the distribution of aromatase in the quail brain and its regulation by steroids by radioenzyme assays on microdissected brain areas (quantification of enzymatic activity), by immunocytochemistry (visualization of the protein) and by RT PCR/in situ hybridization (quantification and visualization of the corresponding mRNA). Partial cloning of the aromatase gene in quail also allowed us to produce a specific antibody to this enzyme raised against the quail sequence expressed in Escherichia coli. Aromatase synthesis in the POA is controlled at the pre-translational level by T and its metabolite estradiol, but estradiol receptors alpha (ERα) are not normally co-localized with aromatase. A new form of ER (ERβ) has been identified and we have recently cloned this receptor in quail. It is located in all brain regions that contain aromatase but whether ERβ is specifically present in aromatase-immunoreactive cells still needs to be investigated.