Biology subjects

Ashi, M. O.

Publications and source records attributed to Ashi, M. O..

3 recordsLinked to original sources

bioRxiv2024

Selective killing of plasma cell clones using splice-switching oligonucleotides targeting immunoglobulin variable exons.

Deregulated proliferation of a plasma cell (PC) clone is accompanied by an excess production of a monoclonal immunoglobulin (mo-Ig) component with unique V(D)J rearrangement features. In systemic Ig light chain (AL) amyloidosis, organ dysfunction is due to the deposition of amyloid fibrils composed of mo-Ig light chains in target tissues. Recent advances in exon skipping therapy using splice-switching antisense oligonucleotides (ASO) prompted us to examine a new antisense strategy targeting the variable (V) exon in myeloma cells. Indeed, we previously observed that the production of truncated Ig light chains, encoded by alternatively spliced mRNAs lacking V exon, heightened endoplasmic reticulum (ER) stress and triggered apoptosis of antibody-secreting plasma cells. We designed ASO hybridizing donor or acceptor V exon splice sites on mo-Ig pre-mRNAs. These compounds were very potent alternative splicing inducers and increased the production of V-domain-less truncated Ig chains. Remarkably, in vitro experiments and tumor xenograft models revealed that myeloma cells were highly sensitive to specific ASO treatment, compared to an irrelevant control-ASO. RNA-seq experiments further confirmed that the production of truncated Ig induced upon ASO treatment provoked a massive myeloma cell death through ER stress-associated apoptosis. In addition, high throughput sequencing of Ig repertoire demonstrated that ASO targeting JH2 or J{kappa}1 donor splice site induced massive elimination of VDJH2- or VJ{kappa}1-rearranged clones respectively, while sparing the others. Collectively, these data provide evidence that ASO targeting V exon on mo-Ig pre-mRNAs can emerge as new weapons to induce selective killing of plasma cell clones.

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↗

bioRxiv2019

Glomerulosclerosis and kidney failure in a mouse model of monoclonal immunoglobulin light-chain deposition disease

Light chain deposition disease (LCDD) is a rare disorder characterized by glomerular and peritubular amorphous deposits of a monoclonal immunoglobulin (Ig) light chain (LC), leading to nodular glomerulosclerosis and nephrotic syndrome. We developed a transgenic model using site-directed insertion of the variable domain of a pathogenic human LC gene into the mouse Ig kappa locus, ensuring its production by all plasma cells. High free LC levels were achieved after backcrossing with mice presenting increased plasma cell differentiation and no Ig heavy chain (HC) production. Our mouse model recapitulates the characteristic features of LCDD, including progressive glomerulosclerosis, nephrotic-range proteinuria and finally, kidney failure. The variable domain of the LC bears alone the structural properties involved in its pathogenicity. RNA sequencing conducted on plasma cells demonstrated that LCDD LC induces endoplasmic reticulum stress, likely accounting for the high efficiency of proteasome inhibitor-based therapy. Accordingly, reduction of circulating pathogenic LC was efficiently achieved and not only preserved renal function, but partially reversed kidney lesions. Finally, transcriptome analysis of pre-sclerotic glomeruli revealed that proliferation and extracellular matrix remodelling represented the first steps of glomerulosclerosis, paving the way for future therapeutic strategies in LCDD and other kidney diseases featuring diffuse glomerulosclerosis, particularly diabetic nephropathy.

pathology↗