7970
However , genetically engineered mice ( GEM ) in which mono - allelic germline Nf1 gene loss is coupled with bi - allelic somatic ( glial progenitor cell ) Nf1 gene inactivation develop brain tumors that do not fully recapitulate the neuropathological features of the human condition .
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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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