Coordinate roles for LIM homeobox genes in directing the dorsoventral trajectory of motor axons in the vertebrate limb.
Motor neurons extend axons along specific trajectories, but the molecules that control their pathfinding remain poorly defined. We show that two LIM homeodomain transcription factors, Lim1 and Lmx1b, control the initial trajectory of motor axons in the developing mammalian limb. The expression of Lim1 by a lateral set of lateral motor column (LMC) neurons ensures that their axons select a dorsal trajectory in the limb. In a complementary manner, the expression of Lmx1b by dorsal limb mesenchymal cells controls the dorsal and ventral axonal trajectories of medial and lateral LMC neurons. In the absence of these two proteins, motor axons appear to select dorsal and ventral trajectories at random. Thus, LIM homeodomain proteins act within motor neurons and cells that guide motor axons to establish the fidelity of a binary choice in axonal trajectory.
Kania
A
A
Howard Hughes Medical Institute, Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA.
Johnson
R L
RL
Jessell
T M
TM
D000818:Animals; D001369:Axons / Q000502:physiology*; D002478:Cells, Cultured; D005121:Extremities / Q000196:embryology / Q000294:innervation*; D005260:Female; D018507:Gene Expression Regulation, Developmental; D005801:Genes, Homeobox; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D060850:LIM-Homeodomain Proteins; D007763:Lac Operon; D008297:Male; D051379:Mice; D009046:Motor Neurons / Q000502:physiology*; D014157:Transcription Factors; D014714:Vertebrates
D018398:Homeodomain Proteins; C112149:LIM homeobox transcription factor 1 beta; D060850:LIM-Homeodomain Proteins; C499523:Lhx1 protein, mouse; D014157:Transcription Factors