22902
To investigate whether the IGF system is required for germ cell ( GC ) and SC development and function , we inactivated the insulin receptor ( Insr ) , the IGF1 receptor ( Igf1r ) , or both receptors specifically in the GC lineage or in SCs .
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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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