Send to

Choose Destination
Neuron. 1999 Aug;23(4):675-87.

Active suppression of interneuron programs within developing motor neurons revealed by analysis of homeodomain factor HB9.

Author information

Gene Expression Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA.


Sonic hedgehog (Shh) specifies the identity of both motor neurons (MNs) and interneurons with morphogen-like activity. Here, we present evidence that the homeodomain factor HB9 is critical for distinguishing MN and interneuron identity in the mouse. Presumptive MN progenitors and postmitotic MNs express HB9, whereas interneurons never express this factor. This pattern resembles a composite of the avian homologs MNR2 and HB9. In mice lacking Hb9, the genetic profile of MNs is significantly altered, particularly by upregulation of Chx10, a gene normally restricted to a class of ventral interneurons. This aberrant gene expression is accompanied by topological disorganization of motor columns, loss of the phrenic and abducens nerves, and intercostal nerve pathfinding defects. Thus, MNs actively suppress interneuron genetic programs to establish their identity.

Comment in

[Indexed for MEDLINE]
Free full text

Supplemental Content

Full text links

Icon for Elsevier Science
Loading ...
Support Center