The transcription regulator Lmo3 is required for cell fate specification in the external globus pallidus.

The external globus pallidus (GPe) is an essential component of the basal ganglia, a group of subcortical nuclei that are involved in control of action. Changes in the firing of GPe neurons are associated with both passive and active body movements. Aberrant activity of GPe neurons has been linked to motor symptoms of a variety of movement disorders, such as Parkinsons Disease, Huntingtons disease and dystonia. Recent studies have helped delineate functionally distinct sub types of GABAergic GPe projection neurons. However, little remains known about specific molecular mechanisms underlying the development of GPe neuronal subtypes. We show that the transcriptional regulator Lmo3 is required for the development of medial ganglionic eminence derived Nkx2.1+ and PV+ GPe neurons, but not FoxP2+ neurons or Npas1+ neurons. As a consequence of the reduction in PV+ neurons, Lmo3-null mice have a reduced pallidal input to the subthalamic nucleus. SIGNIFICANCE STATEMENTThe external globus pallidus (GPe) is a critical component of the basal ganglia and can coordinate neuronal activity across the basal ganglia by virtue of its widespread projections to almost all other basal ganglia nuclei. Aberrant activity of GPe neurons has been linked to motor symptoms of a wide variety of movement disorders. Recent advances have delineated functionally distinct sub types of GABAergic GPe projection neurons. However, little remains known about molecular mechanisms underlying their development. Here, we demonstrate that the transcription regulator Lmo3 is required for the development of specific subtypes of GPe neurons, and for their appropriate connectivity with other parts of the basal ganglia.