Bone Morphogenetic Protein-2 expression is sexually dimorphic in the adult zebra finch forebrain: an immunocytological study.
Bradley J. Walters, Colin J. Saldanha
Songbirds are excellent models towards understanding the estrogenic modulation of constitutive and induced neurogenesis, synaptic plasticity and learning. Bone morphogenetic proteins (BMPs), which are critical for the establishment of the vertebrate CNS, also affect neurogenesis and synaptic plasticity later in development and adulthood. Several BMPs are expressed in the adult zebra finch brain, and telencephalic BMP2 transcription is increased following brain injury and aromatization. However, whether (or not) BMP2 is translated constitutively or in association with injury is unclear. Adult finches (4 per sex) received unilateral, penetrating brain injuries and were perfused 3 or 7 days later. The brains were stained using an antibody specific to a recombinant BMP2 peptide. BMP2 expression was prominent in cells clustered around the damaged meso- and nidopallia. Immunopositive cells were also seen in many other areas including the neurogenic subventricular zone (SVZ), and song nuclei Area X and RA. A comparison of cell densities across these areas and the entopallium (an undamaged nucleus ventral to the needle tract) revealed significant differences due to sex, brain area and the interaction of these variables. All these effects appear to be driven by immunoreactive cells that define Area X in males but fail to distinguish it from the surrounding medial striatum in females. Thus, BMP2 is expressed in a sexually dimorphic manner in areas involved in song learning and immediately surrounding areas of brain damage in the zebra finch. Future studies will focus on the role(s) of BMP2 in synaptic plasticity, learning and injury-induced neurogenesis.
Supported by NS042767.