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Consistent with Ark2C - modulated BMP signaling influencing motor axons , motor pools in the spinal cord were found to harbor phosphorylated Smad1 / 5 / 8 ( pSmad ) and treatment of primary MN with BMP inhibitor diminished axon length .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
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