Bernardo Reina San Martin

Introduction

 During the immune response, the generation of highly specific and adapted humoral responses is achieved by mechanisms initiated by DNA damage inflicted by Activation-induced cytidine deaminase (AID), an enzyme that deaminates cytosines to uracils in DNA. These lesions are processed to introduce mutations in immunoglobulin (Ig) variable regions during somatic hypermutation (SHM) or to generate double stranded DNA break intermediates in Ig switch regions during class switch recombination (CSR). While on-target DNA lesions are crucial for triggering antibody diversification, off-target lesions and/or aberrant DNA repair can initiate malignancy. Although DNA deamination by AID has been clearly established as the mechanism that initiates antibody diversification, the questions of how AID selects its genomic targets and how AID-induced DNA damage is accurately repaired, remain largely unanswered.

The core activity of Bernardo Reina-San-Martin’s lab is directed towards elucidation of the molecular mechanisms driving antibody diversification, with a specific focus on the protein complexes involved in mediating AID targeting and in repairing AID-induced DNA damage in vivo.

Projects

The projects currently developed in Bernardo Reina-San-Martin’s laboratory aim at increasing our knowledge about the molecular mechanisms driving the diversification of the B cell repertoire during immune responses through somatic hypermutation (SHM) and class switch recombination (CSR). In addition, they would like to further understand the mechanisms that enforce genome stability and integrity in response to programmed DNA damage induced by AID.

Some of the specific questions that they address are:

1/ How is the function of AID function regulated in vivo ?

2/ What are the proteins that associate with AID and what is their functional role in CSR and SHM ?

3/ By which mechanism is the access of AID to chromatin controlled ?

4/ What is the role of transcription in the genome-wide recruitment of AID ?

5/ How is AID-induced DNA damage efficiently repaired ?

6/ How is the outcome of AID recruitment differentially regulated between immunoglobulin (Ig) and non-Ig loci ?

7/ What are the protein complexes involved in repairing AID-induced DNA damage?

    The approaches they use to address these questions include: molecular and cellular techniques, gene targeting/transgenesis in mice, shRNA-mediated knockdown, in vitro cell differentiation assays, protein identification by mass spectrometry, flow cytometry, chromatin immunoprecipitation (ChIP), ChIP-Seq analysis, and more recently CRISPR/Cas9 genome editing.