Biology subjects

Lambert, J.-M.

Publications and source records attributed to Lambert, J.-M..

2 recordsLinked to original sources

bioRxiv2020

New models to study plasma cells in mouse based on the restriction of IgJ expression to antibody secreting cells.

Plasma cells (PC) represent the last stage of B cell development and are mainly characterized by their capacity of secreting large quantities of antibodies. They can be implicated in a broad-spectrum of neoplastic disorders, including Multiple Myeloma, Waldenstrom macroglobulinemia or Monoclonal Gammopathy of Clinical Significance, all characterized by the abnormal proliferation of a PC clone. Up to date, there are only few reporter models to specifically follow PC development, migration and homing in mouse and none allowing the genetic manipulation of these cells. We created a transgenic mouse model in which a green fluorescent protein gene was placed under the control of the well-characterized regulatory elements of the murine immunoglobulin J (IgJ) chain locus. Thanks to this model, we demostrated that IgJ is an early and specific marker of antibody secreting cells (ASCs) and appears before the expression of CD138, making it a good candidate to targeted genetic modifications of plasma cells. Therefore, a conditional deletion model using a Tamoxifen-dependent Cre recombinase inserted into the IgJ locus was characterized. Using a reporter model, we showed that, in contrast with existing models of B cell lineage genetic modification, the activity of the CRE recombinase only affects ASCs after tamoxifen treatment. Additionally, we used this model in a functional in vitro assay, to show that Ig modifications directly affect plasma cell survival. These two new mouse models, IgJGFP and IgJCreERT2 represent exquisite tools to study PCs. In pathology, the IgJCreERT2model opens new frontiers for in vivo genetic modifications of PCs to better reflect the pathophysiology of PC-related diseases.

immunology↗

bioRxiv2019

Uncoupling splicing from transcription using antisense oligonucleotides reveals a dual role for I exon donor splice sites in antibody class switching

Class switch recombination (CSR) changes antibody isotype by replacing C constant exons with different constant exons located downstream on the immunoglobulin heavy (IgH) locus. During CSR, transcription through specific switch (S) regions and processing of noncoding germline transcripts (GLTs) are essential for the targeting of Activation-Induced cytidine Deaminase (AID). While CSR to IgG1 is abolished in mice lacking I{gamma}1 exon donor splice site (dss), many questions remain regarding the importance of I exon dss recognition in CSR. To further clarify the role of I exon dss in CSR, we first evaluated RNA polymerase II (RNA pol II) loading and chromatin accessibility in S regions after activation of mouse B cells lacking I{gamma}1 dss. We found that deletion of I{gamma}1 dss markedly reduced RNA pol II pausing and active chromatin marks in the S{gamma}1 region. We then challenged the post-transcriptional function of I exon dss in CSR by using antisense oligonucleotides (ASO) masking I exon dss on GLTs. Treatment of stimulated B cells with an ASO targeting I{gamma}1 dss, in the acceptor S{gamma}1 region, or I dss, in the donor S region, did not decrease germline transcription but strongly inhibited constitutive splicing and CSR to IgG1. Altogether, this study reveals that the recognition of I exon dss first supports RNA pol II pausing and the opening of chromatin in targeted S regions and that GLTs splicing events using constitutive I exon dss appear mandatory for the later steps of CSR, most likely by guiding AID to S regions.

immunology↗