David M. Meredith

OBJECTIVE: There is an increased interest in rheumatology in mesenchymal progenitor/stem cells (MPCs) and their roles in rheumatic diseases, but little is known about the phenotype of these cells in vivo. The aim of this study was to isolate and characterize human bone marrow (BM) MPCs. METHODS: Fluorescence microscopy was used to identify putative MPCs among adherent BM cells. To purify them, a positive selection with antifibroblast microbeads was used, combined with fluorescence-activated cell sorting (FACS) for microbead+,CD45(low) cells. A more detailed phenotype of these cells was determined using 4-color flow cytometry, and standard chondrogenic, osteogenic, and adipogenic assays were used to investigate their differentiation potentials. RESULTS: Putative MPCs microscopically identified as large, fibroblast-like, D7-FIB+ cells were purified using positive selection with D7-FIB-conjugated (antifibroblast) microbeads followed by FACS for specifically bound microbead+,CD45(low) cells. These cells represented 0.01% of mononuclear cells in the BM. They were uniformly positive for CD105, LNGFR, HLA-DR, CD10, CD13, CD90, STRO-1, and bone morphogenetic protein receptor type IA (BMPRIA) and were negative for CD14, CD34, CD117, and CD133. Only cells with this phenotype could proliferate and produce adherent cell monolayers capable of chondrogenic, osteogenic, and adipogenic differentiation. D7-FIB- cells in the BM lacked any MPC activity. Uncultured skin fibroblasts had a phenotype similar to that of BM MPCs, but were negative for LNGFR, STRO-1, HLA-DR, and BMPRIA. CONCLUSION: This study shows the distinct phenotype, morphology, and method of isolation of BM MPCs. The findings may have implications for defining the physiologic roles of MPCs in arthritis, bone diseases, and joint regeneration.

Primary central nervous system lymphomas (PCNSLs) and primary testicular lymphomas (PTLs) are extranodal large B-cell lymphomas (LBCLs) with inferior responses to current empiric treatment regimens. To identify targetable genetic features of PCNSL and PTL, we characterized their recurrent somatic mutations, chromosomal rearrangements, copy number alterations (CNAs), and associated driver genes, and compared these comprehensive genetic signatures to those of diffuse LBCL and primary mediastinal large B-cell lymphoma (PMBL). These studies identify unique combinations of genetic alterations in discrete LBCL subtypes and subtype-selective bases for targeted therapy. PCNSLs and PTLs frequently exhibit genomic instability, and near-uniform, often biallelic, CDKN2A loss with rare TP53 mutations. PCNSLs and PTLs also use multiple genetic mechanisms to target key genes and pathways and exhibit near-uniform oncogenic Toll-like receptor signaling as a result of MYD88 mutation and/or NFKBIZ amplification, frequent concurrent B-cell receptor pathway activation, and deregulation of BCL6. Of great interest, PCNSLs and PTLs also have frequent 9p24.1/PD-L1/PD-L2 CNAs and additional translocations of these loci, structural bases of immune evasion that are shared with PMBL.

The role of phosphorylation in the dissociation of structural components of the herpes simplex virus type 1 (HSV-1) tegument was investigated, using an in vitro assay. Addition of physiological concentrations of ATP and magnesium to wild-type virions in the presence of detergent promoted the release of VP13/14 and VP22. VP1/2 and the UL13 protein kinase were not significantly solubilized. However, using a virus with an inactivated UL13 protein, we found that the release of VP22 was severely impaired. Addition of casein kinase II (CKII) to UL13 mutant virions promoted VP22 release. Heat inactivation of virions or addition of phosphatase inhibited the release of both proteins. Incorporation of radiolabeled ATP into the assay demonstrated the phosphorylation of VP1/2, VP13/14, VP16, and VP22. Incubation of detergent-purified, heat-inactivated capsid-tegument with recombinant kinases showed VP1/2 phosphorylation by CKII, VP13/14 phosphorylation by CKII, protein kinase A (PKA), and PKC, VP16 phosphorylation by PKA, and VP22 phosphorylation by CKII and PKC. Proteolytic mapping and phosphoamino acid analysis of phosphorylated VP22 correlated with previously published work. The phosphorylation of virion-associated VP13/14, VP16, and VP22 was demonstrated in cells infected in the presence of cycloheximide. Use of equine herpesvirus 1 in the in vitro release assay resulted in the enhanced release of VP10, the homolog of HSV-1 VP13/14. These results suggest that the dissociation of major tegument proteins from alphaherpesvirus virions in infected cells may be initiated by phosphorylation events mediated by both virion-associated and cellular kinases.