B-cell specific in vivo roles of a novel long non-coding RNA in Chronic Lymphocytic Leukemia and Richter Syndrome
Introduction
The ultraconserved regions (UCRs) are the genomic segments manifesting perfect conservation between the orthologous genomes of human, rat, and mouse that get transcribed into mono-exonic long non-coding RNAs (lncRNAs) known as transcribed ultraconserved regions (T-UCRs). Increasing evidence demonstrates the importance of T-UCRs in human cancers, however, their involvement in the pathogenesis of Chronic Lymphocytic Leukemia (CLL) is poorly understood. Our lab has recently identified a lncRNA transcribed from a UCR and named it TRUC-16 (Translational Regulatory UltraConserved gene affecting p16), which is overexpressed in CLL and correlates with treatment-free survival.
Methods
A transgenic CRISPR knock-in mouse model was generated to overexpress TRUC-16 specifically in B cells. The number and development of B cell subsets were monitored over time in peripheral blood and lymphoid organs (lymph nodes, spleen, and bone marrow), and immunophenotyping was performed to assess clonality and proportion of the cells considered to be the origin for CLL (i.e. B1 cells and IgM memory B cells that are CD5+). Mice survival (n=30/per group) was followed and necropsy was performed with histopathologic and immunophenotypic analysis. Transcriptional profiling using single-cell RNA sequencing will be performed followed by multiplex immunohistochemistry to dissect the factors driving the disease upon B-cell-specific overexpression of TRUC-16.
Results
We have validated the TRUC-16 overexpression specific to the B-cell compartment in both the mice cohorts and have observed lymphoma in several organs (including the spleen, liver, mesenteric, and cervical Lymph nodes). Interestingly, TRUC-16 overexpressing mice showed significantly higher splenic weights compared to controls. Further, we plan to understand the molecular underpinnings driving this aggressive disease and the mechanistic roles of TRUC-16 overexpression.
Conclusion
Validation of the functional correlation between the TRUC-16 phenotype with CLL patients’ clinical data will provide a valuable resource to pursue a multitude of preclinical studies to find targets that might help in a better understanding of the disease pathophysiology.