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Retinoids exert their physiological activities through retinoid receptor nuclear proteins that belong to the superfamily of steroid / thyroid hormone receptors , of which there are two classes , retinoic acid receptors ( RARs ) and the retinoic - X receptors ( RXRs ) , each of which has three subtypes , alpha , beta , and gamma [ 23 ] , [ 24 ] .
 Anatomy: nuclear
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Anatomy 
Text: {0} 
Answer:
 Anatomy: nuclear