Revisiting the specificity of the MHC class II transactivator CIITA in classical murine dendritic cells in vivo

• Published in: European journal of immunology 2017-08, Vol.47 (8), p.1317-1323
• Main Authors: Anderson, David A., Grajales‐Reyes, Gary E., Satpathy, Ansuman T., Vasquez Hueichucura, Carlos E., Murphy, Theresa L., Murphy, Kenneth M.
• Format: Article
• Language: English
• Subjects: Animals; Ciita; Dendritic cell; Dendritic Cells - classification; Dendritic Cells - immunology; Dendritic Cells - physiology; Gene Expression Regulation; Genes, MHC Class II; Histocompatibility Antigens Class II - genetics; Interferon-gamma - genetics; Mice; Nuclear Proteins - deficiency; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; Trans-Activators - deficiency; Trans-Activators - genetics; Trans-Activators - metabolism; Transcription factor; Transcription Factors - genetics; Transcription Factors - metabolism; Transcriptome; Zbtb46
• ISSN: 0014-2980; 1521-4141
• DOI: 10.1002/eji.201747050

Ciita was discovered for its role in regulating transcription of major histocompatibility complex class II (MHCII) genes. Subsequently, CIITA was predicted to control many other genes based on reporter and ChIP‐seq analysis but few such predictions have been verified in vivo using Ciita–/– mice. Testing these predictions for classical dendritic cells (cDCs) has been particularly difficult, since Ciita–/– mice lack MHCII expression required to identify cDCs. However, recent identification of the cDC‐specific transcription factor Zbtb46 allows the identification of cDCs independently of MHCII expression. We crossed Zbtb46gfp mice onto the Ciita–/– background and found that all cDC lineages developed in vivo in the absence of Ciita. We then compared the complete transcriptional profile of wild‐type and Ciita–/– cDCs to define the physiological footprint of CIITA for both immature and activated cDCs. We find that CIITA exerts a highly restricted control over only the MHCII, H2‐DO and H2‐DM genes, in DC1 and DC2 cDC subsets, but not over other proposed targets, including Ii. These findings emphasize the caveats needed in interpreting transcription factor binding sites identified by in‐vitro reporter analysis, or by ChIP‐seq, which may not necessarily indicate their functional activity in vivo. Chromatin binding by CIITA and the presence of SXY modules across the genome has led to the hypothesis that CIITA regulates a transcriptional program beyond the MHC locus (illustrated under red X). Testing this hypothesis in classical dendritic cells revealed that the transcriptional program regulated by CIITA is highly restricted to the MHC locus (illustrated in green square).