Differential expression of a transcription regulatory factor, the LIM domain only 4 protein Lmo4, in muscle sensory neurons.
In the stretch-reflex system, proprioceptive sensory neurons make selective synaptic connections with different subsets of motoneurons, according to the peripheral muscles they supply. To examine the molecular mechanisms that may influence the selection of these synaptic targets, we constructed single-cell cDNA libraries from sensory neurons that innervate antagonist muscles. Differential screening of these libraries identified a transcription regulatory co-factor of the LIM homeodomain proteins, the LIM domain only 4 protein Lmo4, expressed in most adductor but few sartorius sensory neurons. Differential patterns of Lmo4 expression were also seen in sensory neurons supplying three other muscles. A subset of motoneurons also expresses Lmo4 but the pattern of expression is not specific for motor pools. Differential expression of Lmo4 occurs early, as neurons develop their characteristic LIM homeodomain protein expression patterns. Moreover, ablation of limb buds does not block Lmo4 expression, suggesting that an intrinsic program controls the early differential expression of Lmo4. LIM homeodomain proteins are known to regulate several aspects of sensory and motor neuronal development. Our results suggest that Lmo4 may participate in this differentiation by regulating the transcriptional activity of LIM homeodomain proteins.
Chen
Hsiao-Huei
HH
Department of Neurobiology, University of Pittsburgh, PA 15261, USA.
Yip
Joseph W
JW
Stewart
Alexandre F R
AF
Frank
Eric
E
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation; D002642:Chick Embryo; D018076:DNA, Complementary / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D005121:Extremities / Q000196:embryology; D005727:Ganglia, Spinal / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D060588:LIM Domain Proteins; D051379:Mice; D008969:Molecular Sequence Data; D009046:Motor Neurons / Q000166:cytology / Q000378:metabolism; D018482:Muscle, Skeletal / Q000294:innervation*; D009475:Neurons, Afferent / Q000166:cytology / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics*
D048868:Adaptor Proteins, Signal Transducing; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; C095239:ETV1 protein, human; C490641:Etv1 protein, mouse; D018398:Homeodomain Proteins; D060588:LIM Domain Proteins; C114905:LMO4 protein, human; C491976:Lmo4 protein, mouse; D014157:Transcription Factors; C065788:transcription factor PEA3