8443
To examine the role of this CE2 element in regulating Hoxa1 expression in vivo , transgenic mice were generated which express a Hoxa1 beta - galactosidase reporter gene that contains a mutation in the CE2 element .
 Hoxa1, Hoxa1, beta - galactosidase
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 Hoxa1, Hoxa1, beta - galactosidase