Role of mir-15a/16-1 in early B cell development in a mouse model of chronic lymphocytic leukemia.

Chingiz Underbayev,Diego Fraidenraich,Marilyn M Lightfoote,Joel Solomon Schneider,Heba Degheidy,Vijay Parashar,William Ruezinsky,Mona Batish,Steven R Bauer,Elizabeth Raveche,Siddha Kasar,Gerald Marti

doi:10.18632/oncotarget.11290

Chingiz Underbayev, Diego Fraidenraich + Show 10 more

Open Access

https://doi.org/10.18632/oncotarget.11290

Copy DOI

Abstract

In both human chronic lymphocytic leukemia (CLL) and the New Zealand Black (NZB) murine model of CLL, decreased levels of microRNAs miR-15a/16 play an important role in the disease. Here we investigate the effects of this microRNA on early steps of B cell development and the capacity of miR-15a-deficient hematopoietic stem cells (HSC) and B1 progenitor cells (B1P) to reproduce CLL-like phenotype both in vitro and in vivo. Our results demonstrate that both miR-15a deficient HSC and B1P cells are capable of repopulating irradiated recipients and produce higher numbers of B1 cells than sources with normal miR-15a/16 levels. Furthermore, induced pluripotent stem (iPS) cells derived for the first time from NZB mice, provided insights into the B cell differentiation roadblock inherent in this strain. In addition, exogenously delivered miR-15a into the NZB derived B cell line provided valuable clues into novel targets such as Mmp10 and Mt2. Our data supports the hypothesis that miR-15a/16 deficient stem cells and B1Ps experience a maturation blockage, which contributes to B1 cells bias in development. This work will help understand the role of miR-15a in early events of CLL and points to B1P cells as potential cells of origin for this incurable disease.

Highlights

chronic lymphocytic leukemia (CLL) is the most common blood malignancy in the Western hemisphere associated with accumulation of malignant CD5+CD19+CD20dullCD23+IgMdull B cells in peripheral organs [1, 2]
We found that the level of miR-15a was decreased in both B1 and B2 cells derived from New Zealand Black (NZB) and DBA congenics (DBA-/-) when compared to the wild-type DBA (Figure 1A), which positively correlated with Dleu2 levels in splenocytes
The percentage of B-1 cells was increased in DBA congenic mice with mutated mir-15a/16 loci whereas the numbers of conventional B2 cells decreased relative to the DBA wild-type control spleens (Figure 1C)

Summary

Introduction

CLL is the most common blood malignancy in the Western hemisphere associated with accumulation of malignant CD5+CD19+CD20dullCD23+IgMdull B cells in peripheral organs [1, 2]. In the indolent form of CLL, the most frequent abnormality is a decreased expression of microRNA miR-15a/16-1 [3] from the host Dleu gene located in the frequently deleted 13q14 region. Deletion of this region in mice (MDR-/-) has been shown to lead to the accumulation of CD5+B220dull B1 cells in peritoneal cavities (PerC) by 12 months of age in a B cell autonomous manner [4]. The microRNA processing pathway is a multistep process which starts with RNA-pol II mediated transcription of primary transcript (pri-miR) followed by its cleavage by an enzymatic complex Drosha [7] which results in a precursor pre-miR molecule. We have demonstrated that mir-15a mutation and deletion in NZB mouse are responsible for its decreased expression levels and this is due to a blockage of Drosha-mediated cleavage of primary transcript [9]

Methods

Results

Conclusion