CRISPR Editing Enables Consequential Tag-Activated MicroRNA-Mediated Endogene Deactivation.

Molecular therapies and functional studies greatly benefit from spatial and temporal precision of genetic intervention. We therefore conceived and explored tag-activated microRNA (miRNA)-mediated endogene deactivation (TAMED) as a research tool and potential lineage-specific therapy. For proof of principle, we aimed to deactivate γ-globin repressor BCL11A in erythroid cells by tagging the 3' untranslated region (UTR) of BCL11A with miRNA recognition sites (MRSs) for the abundant erythromiR miR-451a. To this end, we employed nucleofection of CRISPR/Cas9 ribonucleoprotein (RNP) particles alongside double- or single-stranded oligodeoxynucleotides for, respectively, non-homologous-end-joining (NHEJ)- or homology-directed-repair (HDR)-mediated MRS insertion. NHEJ-based tagging was imprecise and inefficient (≤6%) and uniformly produced knock-in- and indel-containing MRS tags, whereas HDR-based tagging was more efficient (≤18%), but toxic for longer donors encoding concatenated and thus potentially more efficient MRS tags. Isolation of clones for robust HEK293T cells tagged with a homozygous quadruple MRS resulted in 25% spontaneous reduction in BCL11A and up to 36% reduction after transfection with an miR-451a mimic. Isolation of clones for human umbilical cord blood-derived erythroid progenitor-2 (HUDEP-2) cells tagged with single or double MRS allowed detection of albeit weak γ-globin induction. Our study demonstrates suitability of TAMED for physiologically relevant modulation of gene expression and its unsuitability for therapeutic application in its current form.

Solitary extramedullary plasmacytoma of the nasopharynx: The role of flow cytometry.

Extramedullary plasmacytoma (EMP) represents a distinct yet rare entity among the plasma cell neoplasms. Given its rarity, no therapeutic consensus has been met. We report the case of a 57-year-old man with a one-year history of nasal congestion and occasional dyspnoea. Imaging showed a hypermetabolic mass in the right nasopharynx extending backward towards the adjacent oropharynx, infiltrating the epiglottis. As incisional biopsy showed histologic and immunophenotypic features consistent with plasma cell neoplasm, whereas the possibility of a marginal zone lymphoma with plasmacytic differentiation was included in the differential diagnosis. A final diagnosis of EMP was reached by using flow cytometry (FC) of a cell suspension from the neoplastic tissue. The patient received local radiotherapy (RT) which resulted to complete remission. In conclusion, flow cytometry might serve as an auxiliary method in cases where immunohistochemistry cannot differentiate between a plasma cell dyscrasia and a B-non-Hodgkin lymphoma. In cases of an established diagnosis of solitary nasopharyngeal EMP RT represents an excellent treatment modality offering prolonged disease-free survival.

Rapid and Sensitive Assessment of Globin Chains for Gene and Cell Therapy of Hemoglobinopathies.

The ß-hemoglobinopathies sickle cell anemia and ß-thalassemia are the focus of many gene-therapy studies. A key disease parameter is the abundance of globin chains because it indicates the level of anemia, likely toxicity of excess or aberrant globins, and therapeutic potential of induced or exogenous ß-like globins. Reversed-phase high-performance liquid chromatography (HPLC) allows versatile and inexpensive globin quantification, but commonly applied protocols suffer from long run times, high sample requirements, or inability to separate murine from human ß-globin chains. The latter point is problematic for in vivo studies with gene-addition vectors in murine disease models and mouse/human chimeras. This study demonstrates HPLC-based measurements of globin expression (1) after differentiation of the commonly applied human umbilical cord blood-derived erythroid progenitor-2 cell line, (2) in erythroid progeny of CD34+ cells for the analysis of clustered regularly interspaced short palindromic repeats/Cas9-mediated disruption of the globin regulator BCL11A, and (3) of transgenic mice holding the human ß-globin locus. At run times of 8 min for separation of murine and human ß-globin chains as well as of human γ-globin chains, and with routine measurement of globin-chain ratios for 12 nL of blood (tested for down to 0.75 nL) or of 300,000 in vitro differentiated cells, the methods presented here and any variant-specific adaptations thereof will greatly facilitate evaluation of novel therapy applications for ß-hemoglobinopathies.