| dc.description.abstract | Hb9 (Mnx1) is a transcription factor described as a spinal cord motor neuron-specific marker in embryonic development and a critical factor for the post-mitotic specification of these cells. As such, transgenic mice with mutations in the Hb9 gene are commonly used for the study of spinal cord motor neurons. To date, the expression of Hb9 in other cell types has not previously been reported. We performed a fate-mapping approach to examine the localization of Hb9-expressing cells and their progeny (‘Hb9-lineage cells’) within the embryonic and adult spinal cord. We found that Hb9-lineage cells are distributed in a gradient of increasing abundance throughout the rostro-caudal spinal cord axis during developmental and postnatal stages. Furthermore, although the majority of Hb9-lineage cells at cervical spinal cord levels are motor neurons, at more caudal levels, Hb9-lineage cells include astrocytes and oligodendrocytes, the macroglial cells of the central nervous system. In the peripheral nervous system, we observed a similar phenomenon with Hb9-lineage Schwann cells present in an increasing rostro-caudal gradient throughout the body. These observations have several exciting implications. Hb9 may play an important role not only in astrocyte and oligodendrocyte development, but also in development of Schwann cells, which are the glial cells associated with the peripheral nerves. Additionally, characterization of Hb9-lineage glial cells may reveal new functional roles for glia throughout the developing spinal cord. Through characterizing the role of Hb9 in glial cell development, describing the molecular pathways involved, and determining the differences in gene expression between Hb9+ and Hb9- spinal cord glial cells, the developmental function of Hb9 can be better understood. | |
