miR-181c is up-regulated in monoMAC cells related to increased cell death

Somatic and germline mutations in GATA2 were recently identified in patients diagnosed with monoMAC, the hallmarks of which include monocytopenia, B-cell and NK-cell lymphopenia, susceptibility to opportunistic infections (e.g. MAC), and a strong propensity to develop hypocellular MDS/AML or CMML. GATA2 mutations are thought to result in loss of function or haploinsufficiency, but the precise mechanism for the development of cytopenias, immunodeficiency, and susceptibility to MDS remains to be elucidated. MicroRNA (miR) represents a unique mechanism of post-transcriptional gene regulation. In this study we generated microRNA profiles of patient derived monoMAC cell lines followed by functional studies to identify aberrant miRs and their targets, which could potentially cooperate with GATA2 deficiency in generating cytopenias and hematologic disease. In our study, eight miRs were significantly differentially expressed (≥ 2-fold; p ≤ 0.05) as determined by microRNA microarray profiles; miR-9, miR-181a-2-3p, miR-181c, miR-181c-3p, miR-486-3p, and miR-582-5p showed increased expression in monoMAC cell lines compared to controls, while miR-223 and miR-424-3p showed significantly decreased expression. Among the differentially expressed miRs that were validated by quantitative RT-PCR was miR-181c, which demonstrated a 2.2 fold increase in expression in monoMAC cell lines (p = 0.013). Among the target transcripts potentially regulated by miR-181c, MCL1 expression was significantly decreased (2 fold; p = 0.018) in monoMAC cell lines in comparison to control cell lines. Transient transfection of miR-181c in Ly8 cells resulted in 40% decrease of MCL1 mRNA level, suggesting that miR-181c negatively regulates MCL1 in MonoMAC. These findings indicate that monoMAC/GATA2 deficiency is associated with significantly decreased expression of MCL1 possibly through negative regulation involving miR-181c. Deletion of Mcl1 is known to cause apoptosis, loss of HSCs, and cytopenias in murine studies. Thus, down-regulation of MCL1 seen in monoMAC/GATA2 deficiency may similarly favor unregulated apoptosis and the depletion of hematopoietic progenitors resulting in cytopenias, immunodeficiency, and risk of MDS/AML. miRNA profiling was performed using Agilent miRNA array platform with RNAs isolated from EBV-immortalized human B cells of healthy controls and monoMAC patients