Diferenciación genética de poblaciones atlánticas de charcos de marea del copépodo intermareal Tigriopus brevicornis

The Harpacticoid copepod Tigriopus brevicornis belongs to the meiofauna of intertidal rock pools and is distributed widely along European coasts. Sixteen sites were sampled from the Irish Sea to the coasts of Spain. We used the ITS1 marker to analyse the relationship between the populations because it shows low intrapopulational variation (mean pairwise difference: 1.00 ± 0.8) and high interpopulational divergence (mean pairwise difference: 16.38 ± 7.39). A total of 57 bp out of 433 bp were recognised as informative nucleotides among the 61 individuals analysed. The analysis of the genetic relationships highlighted a north-south split in the distribution of the natural populations and showed a genetic break point around the Gironde estuary, which is probably due to differences in the geomorphologic characteristics of the coastal area on the two different sides of this estuary. Various populations were isolated and the ITS1 sequences indicated that there are specific genetic signatures in these populations. The northern set of populations, which was sampled along a large rocky coastline, had a metapopulation structure with genetic exchanges between geographically close populations and also between geographically far ones. The southern set of populations, which was sampled in small rocky pools on large sandy beaches, showed isolated populations as a consequence of the geomorphology of the area.Los copépodos harpacticoides Tigriopus brevicornis pertenecen a la meiofauna intermareal y están ampliamente distribuídos a lo largo de las costas europeas. Dieciséis lugares fueron muestreados desde el Mar de Irlanda hasta las costas de España. Nosotros usamos el marcador ITSI para analizar la relación entre poblaciones porque se mostró una variación interpoblacional baja (promedio diferencia de pares: 1.00 ± 0.8) y una divergencia interpoblacional alta (promedio diferencia de pares: 16.38 ± 7.39). Un total de 57 bp entre 433 bp fueron reconocidos como nucleótidos informativos entre los 61 individuos analizados. El análisis de relación genética resalta una partición Norte-Sur en la distribución de las poblaciones naturales y mostraba un punto de rotura genético alrededor del estuario de Gironde, probablemente debido a las diferencias en las características geomorfológicas de esta área costera en ambos lados del estuario. Algunas poblaciones fueron aisladas: las secuencias ITSI indicaban que había unas señales genéticas específicas en estas poblaciones. La población de la parte norte, que fue muestreada a lo largo de una línea rocosa de costa, evidencia la estructura de una metapoblación con intercambios genéticos entre poblaciones geográficamente próximas, pero también entre poblaciones geográficamente lejanas. La población de la parte sur, que fue muestreada en pequeños charcos de marea sobre vastas playas arenosas, mostraban poblaciones aisladas, destacando las consecuencias de la geomorfología del área

Germinal centers in human lymph nodes contain reactivated memory B cells

To reveal migration trails of antigen-responsive B cells in lymphoid tissue, we analyzed immunoglobulin (Ig)M-VH and IgG-VH transcripts of germinal center (GC) samples microdissected from three reactive human lymph nodes. Single B cell clones were found in multiple GCs, one clone even in as many as 19 GCs. In several GCs, IgM and IgG variants of the same clonal origin were identified. The offspring of individual hypermutated IgG memory clones were traced in multiple GCs, indicating repeated engagement of memory B cells in GC reactions. These findings imply that recurring somatic hypermutation progressively drives the Ig repertoire of memory B cells to higher affinities and infer that transforming genetic hits in non-Ig genes during lymphomagenesis do not have to arise during a single GC passage, but can be collected during successive recall responses

Effect of hyperosmotic shock on phosphoenolpyruvate carboxykinase gene expression and gluconeogenic activity in the crab muscle

AbstractChasmagnathus granulata phosphoenolpyruvate carboxykinase (PEPCK) cDNA from jaw muscle was cloned and sequenced, showing a specific domain to bind phosphoenolpyruvate in addition to the kinase-1 and kinase-2 motifs to bind guanosine triphosphate (GTP) and Mg2+, respectively, specific for all PEPCKs. In the kinase-1 motifs the GK was changed to RK. The first 19 amino acids of the putative enzyme contain hydrophobic amino acids and hydroxylated residues specific to a mitochondrial type signal. The PEPCK is expressed in hepatopancreas, muscles, nervous system, heart, and gills. Hyperosmotic stress for 24 h increased the PEPCK mRNA level, gluconeogenic and PEPCK activities in muscle

Lymphoma-associated mutations in autoreactive memory B cells of patients with Sjögren's syndrome

We recently demonstrated that normal memory B lymphocytes carry a substantial number of de novo mutations in the genome. Here, we performed exome-wide somatic mutation analyses of bona fide autoreactive rheumatoid factor (RF)-expressing memory B cells retrieved from patients with Sjӧgren's syndrome (SS). The amount and repertoire of the de novo exome mutations of RF B cells were found to be essentially different from those detected in healthy donor memory B cells. In contrast to the mutation spectra of normal B cells, which appeared random and non-selected, the mutations of the RF B cells were greater in number and enriched for mutations in genes also found mutated in B-cell non-Hodgkin lymphomas. During the study, one of the SS patients developed a diffuse large B-cell lymphoma (DLBCL) out of an RF clone that was identified 2 years earlier in an inflamed salivary gland biopsy. The successive oncogenic events in the RF precursor clone and the DLBCL were assessed. In conclusion, our findings of enhanced and selected genomic damage in growth-regulating genes in RF memory B cells of SS patients together with the documented transformation of an RF-precursor clone into DLBCL provide unique novel insight into the earliest stages of B-cell derailment and lymphomagenesis.</p

Lymphoma-associated mutations in autoreactive memory B cells of patients with Sjögren's syndrome

We recently demonstrated that normal memory B lymphocytes carry a substantial number of de novo mutations in the genome. Here, we performed exome-wide somatic mutation analyses of bona fide autoreactive rheumatoid factor (RF)-expressing memory B cells retrieved from patients with Sjӧgren's syndrome (SS). The amount and repertoire of the de novo exome mutations of RF B cells were found to be essentially different from those detected in healthy donor memory B cells. In contrast to the mutation spectra of normal B cells, which appeared random and non-selected, the mutations of the RF B cells were greater in number and enriched for mutations in genes also found mutated in B-cell non-Hodgkin lymphomas. During the study, one of the SS patients developed a diffuse large B-cell lymphoma (DLBCL) out of an RF clone that was identified 2 years earlier in an inflamed salivary gland biopsy. The successive oncogenic events in the RF precursor clone and the DLBCL were assessed. In conclusion, our findings of enhanced and selected genomic damage in growth-regulating genes in RF memory B cells of SS patients together with the documented transformation of an RF-precursor clone into DLBCL provide unique novel insight into the earliest stages of B-cell derailment and lymphomagenesis.</p

Salivary Gland Mucosa-Associated Lymphoid Tissue-Type Lymphoma From Sjogren's Syndrome Patients in the Majority Express Rheumatoid Factors Affinity-Selected for IgG

Objective: Patients with Sjӧgren's syndrome (SS) have an increased risk of developing malignant B cell lymphomas, particularly mucosa-associated lymphoid tissue (MALT)–type lymphomas. We have previously shown that a predominant proportion of patients with SS-associated salivary gland MALT lymphoma express somatically hypermutated IgM with strong amino acid sequence homology with stereotypic rheumatoid factors (RFs). The present study was undertaken in a larger cohort of patients with SS-associated MALT lymphoma to more firmly assess the frequency of RF reactivity and the significance of somatic IGV-region mutations for RF reactivity. Methods: B cell antigen receptors (BCRs) of 16 patients with SS-associated salivary gland MALT lymphoma were analyzed. Soluble recombinant IgM was produced of 12 MALT lymphoma samples, including 1 MALT lymphoma sample that expressed an IgM antibody fitting in a novel IGHV3-30–encoded stereotypic IGHV subset. For 4 of the 12 IgM antibodies from MALT lymphoma samples, the somatically mutated IGHV and IGKV gene sequences were reverted to germline configurations. Their RF activity and binding affinity were determined by enzyme-linked immunosorbent assay and surface plasmon resonance, respectively. Results: Nine (75%) of the 12 IgM antibodies identified in patients with SS-associated salivary gland MALT lymphoma displayed strong monoreactive RF activity. Reversion of the IGHV and IGKV mutations to germline configuration resulted in RF affinities for IgG that were significantly lower for 3 of the 4 somatically mutated IgM antibodies. In stereotypic IGHV3-7/IGKV3-15–encoded RFs, a recurrent replacement mutation in the IGKV3-15–third complementarity-determining region was found to play a pivotal role in the affinity for IgG-Fc. Conclusion: A majority of patients with SS-associated salivary gland MALT lymphoma express somatically mutated BCRs that are selected for monoreactive, high-affinity binding of IgG-Fc. These data underscore the notion that soluble IgG, most likely in immune complexes in inflamed tissues, is the principal autoantigen in the pathogenesis of a variety of B cell lymphomas, particularly SS-associated MALT lymphomas