The Journal of Neuroscience, November 3, 2004, ():
An Early Broad Competence of Motoneurons to Express ER81 Is Later Sculpted by the Periphery
J. Neurosci. Wang and Scott
24: 9789
Supplemental data
Files in this Data Supplement:
- supplemental material
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Supplemental Figure: Summary and model. Left: Summary of ER81 expression and motoneuron connectivity. Axon trajectories and muscle location are highly schematic. In control embryos ER81 is expressed in adductor (blue) and femorotibialis (red) motoneurons that innervate muscles in pre-axial limb (light blue). Following rostral limb shifts most adductor motoneurons and some femorotibialis motoneurons express ER81 and innervate their appropriate muscles in pre-axial limb. In constrast, most femorotibialis motoneurons do not express ER81 (black cells opposite LS2 and LS3) and innervate muscles in post-axial limb (pink region). Some thoracic motoneurons (black cells opposite T7) also innervate the adductor and femorotibialis muscles, but do not express ER81. Following A-P limb reversal, adductor motoneurons express ER81, even though they innervate post-axial muscles. Femorotibialis motoneurons and LLMC motoneurons in LS4-LS5 (but not more caudal segments) express ER81 when they innervate the femorotibialis muscle.
Right: Model of developmental regulation of ER81 expression. Left: As yet unidentified signals from tissues surrounding and within the neural tube (yellow – brown arrows) establish a broad, but restricted, competence of motoneurons in MLMC and LLMC (open blue and red boxes, respectively in the middle panel) to respond to ER81-inducing signals. Middle: Prior to axon outgrowth nascent motoneurons are exposed to a rostrocaual gradient of ER81-inducing signals (blue and red arrows), leading to onset of expression in adductor motoneurons prior to expression in femorotibialis motoneurons. Right: As axons grow out, enter the limb, and project to targets they encounter specific, spatially restricted cues (red and blue +) required for ER81 expression. LLMC motoneurons in segments LS4-LS5, while competent to express ER81, never encounter these cues. Additional inhibitory signals (-) may be produced by posterior limb, accounting for the caudal shift in expression patterns following A-P limb reversal.
