Biology subjects

Ayala, M. V.

Publications and source records attributed to Ayala, M. V..

4 recordsLinked to original sources

bioRxiv2024

A mouse model of cardiac AL amyloidosis unveils mechanisms of tissue accumulation and toxicity of amyloid fibrils

AL amyloidosis is one of the most common types of systemic amyloidosis, caused by the deposition in tissues of fibrillar aggregates of abnormal immunoglobulin (Ig) light chain (LC), leading to organ dysfunction. The most frequent and severe forms affect the kidneys and heart, the latter being associated with a poor prognosis. Despite extensive efforts to decipher the mechanisms of fibril formation and their toxicity, the lack of reliable in vivo models hinders the study of the disease in its physiological context. We developped a transgenic mouse model producing high amounts of a human AL light chain (LC). While mice exceptionnaly develop spontaneous AL amyloidosis and do not exhibit organ toxicity due to the circulating amyloidogenic free LC, a single injection of amyloid fibrils, made up of the variable domain (VL) of the human LC, or soluble VL led to amyloid deposits in the heart, vessels, spleen and, to a lesser extent, in the kidney and other visceral tissues. AL fibrils in mice contain both full length and fragmented LC with a fragmentation pattern highly superposable to that of human AL fibrils from the same LC subgroup (IGLV6-57). They also develop an early cardiac dysfunction closely resembling the human disease with increased NT-proBNP,and activation of pathways involved in the extracellular matrix remodeling and fibrosis. Overall, this transgenic AL model closely reproduces human cardiac AL amyloidosis and shares with humans the biochemical composition of the deposits, arguing for a conserved mechanism of amyloid fibrils formation. It also shows that a partial degradation of the LC is likely required to initiate amyloid fibril formations. This model offers a new avenue for research on AL amyloidosis and fills an important gap for the preclinical evaluation of new therapies.

pathology↗

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

Full-length immunoglobulin high-throughput sequencing reveals specific novel mutational patterns in POEMS syndrome

POEMS syndrome is a rare multisystem disease due to an underlying plasma cell (PC) dyscrasia. The pathophysiology of the disease remains unclear but the role of the monoclonal immunoglobulin (Ig) light chain (LC) is strongly suspected, due to the highly restrictive usage of two {lambda} variable (V) domains (IGLV1-40 and IGLV1-44) and the general improvement of clinical manifestations following PC clone-targeted treatment. However, the diagnostic value of Ig LC sequencing, especially in case of incomplete forms of the disease, remains to be determined. Using a sensitive high-throughput Ig repertoire sequencing on RNA (RACE-RepSeq), we detected a {lambda} LC monoclonal expansion in the bone marrow (BM) of 85% of patients with POEMS syndrome, including some in whom bone marrow tests routinely performed to diagnose plasma cell dyscrasia failed to detect {lambda}+ monoclonal PCs. Twenty-four of the 30 LC clonal sequences found (80%) were derived from the IGLV1-40 and IGLV1-44 germline genes, two from the closely related IGLV1-36 gene, and all were associated with an IGLJ3*02 junction (J) gene, confirming the high restriction of VJ region usage in POEMS syndrome. RACE-RepSeq VJ full-length sequencing additionally revealed original mutational patterns, the strong specificity of which might crucially help establish or eliminate the diagnosis of POEMS syndrome in uncertain cases. Thus, RACE-RepSeq appears as a sensitive, rapid and specific tool to detect low-abundance PC clones in BM, and assign them to POEMS syndrome, with all the consequences for therapeutic options hereby.

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↗