In the sentence extracted from biomedical literature, identify all the disease entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="disease"> to denote a disease.

### Input Text: We have generated a mouse model for ataxia - telangiectasia by using gene targeting to generate mice that do not express the Atm protein .
### Output Text:
We have generated a mouse model for <span class="disease">ataxia - telangiectasia</span> by using gene targeting to generate mice that do not express the Atm protein . 