Joshi, Pushkar S.Molyneaux, Bradley JohnFeng, LiangXie, XiaoliangMacklis, JeffreyGan, Lin2013-09-062008Joshi, Pushkar S, Bradley Molyneaux, Liang Feng, Xiaoliang Xie, Jeffrey Macklis, and Lin Gan. Bhlhb5 regulates the postmitotic acquisition of area identities in layers II-V of the developing neocortex. Neuron, 2008Bhlhb5 regulates the postmitotic acquisition of area identities in layers II-V of the developing neocortex. Neuron 60(2): 258-72.0896-6273http://nrs.harvard.edu/urn-3:HUL.InstRepos:11006839While progenitor-restricted factors broadly specify area identities in developing neocortex, the downstream regulatory elements involved in acquisition of those identities in post-mitotic neurons are largely unknown. Here, we identify Bhlhb5, a transcription factor expressed in layers II–V, as a post-mitotic regulator of area identity. Bhlhb5 is initially expressed in a high caudomedial to low rostrolateral gradient that transforms into a sharp border between sensory and rostral motor cortices. Bhlhb5-null mice exhibit aberrant expression of area-specific genes and structural organization in the somatosensory and caudal motor cortices. In somatosensory cortex, Bhlhb5-null mice display post-synaptic disorganization of vibrissal barrels. In caudal motor cortex, Bhlhb5-null mice exhibit anomalous differentiation of corticospinal motor neurons, accompanied by failure of corticospinal tract formation. Together, these results demonstrate Bhlhb5’s function as an area-specific transcription factor that regulates the post-mitotic acquisition of area identities and elucidate the genetic hierarchy between progenitors and post-mitotic neurons driving neocortical arealization.en-USJournal Article2013-08-02Joshi PS, Molyneaux BJ, Feng L, Xie X, Macklis JD, Gan L2013-09-0610.1016/j.neuron.2008.08.006