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To investigate mechanisms regulating chromatin distribution , we analyzed heterochromatin organization in different tissues and species , including mice with mutations in the lamin B receptor ( Lbr ) and lamin A ( Lmna ) genes that encode nuclear envelope ( NE ) proteins .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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