Investigation of the Significance of Son Isoform mRNA Expression in Patients with Blood Cytopenias with/without Evidence of Myeloid Neoplasia

Myelodysplastic Syndrome (MDS) is a clonal hematopoietic disorder related to ineffective hematopoiesis and hematopoietic stem cell dysplasia. Cytogenetic information regarding MDS to help guide diagnosis and prognostics is limited; therefore, further research into new tools and biological targets for this disease entity are of significant interest to the medical community. While major RNA splicing components have been found to be key players in the pathogenesis of MDS, there is not a large reservoir of data for the use of such pathophysiology in the clinical care of MDS. SON Protein has been described as an RNA splicing co-factor and transcriptional repressor that regulates expression of multiple genes involved in cell cycle progression, stem cell pluripotency maintenance, and leukemogenesis. We have recently discovered that SON short isoforms (SON E and SON B) generated by alternative RNA splicing are aberrantly upregulated in MDS and AML. These short isoforms are associated with antagonism of full-length SON-mediated transcriptional repression of the MLL-menin complex, which plays a significant role in inhibition of leukemia-associated gene expression. Consequently, aberrant upregulation of SON short isoforms has been shown to enhance replating potential of hematopoietic progenitors. Considering the splicing pathophysiology that may be involved in MDS along with the association of SON short isoforms with myeloid neoplasia progression, we designed a study that would investigate the variable expression of SON isoforms in a variety of clinical circumstances related to myeloid disorders. Expanded data on the expression of SON short isoforms in various myeloid pathologies combined with clinical markers of disease progression/severity (such as cell counts) and treatment modalities will allow for further analysis of SON B/E as potential markers of pathology severity or treatment response. It was originally postulated that different SON short isoforms (both SON E and SON B) might exhibit a progression in myeloid dysplasia/neoplasia because MDS occasionally progresses into AML. However, it was decided that myeloproliferative neoplasms, such as Polycythemia Vera (PV), might also demonstrate a SON-manifested pathophysiology due to phenotypic dysregulation of myeloid hematopoiesis. We collected Peripheral Blood Mononuclear Cells (PBMCs) and Bone Marrow specimens (BM) from consented patients at Mitchell Cancer Institute that were identified as ideal candidates for inclusion based upon some degree of myeloid pathology. Investigation with RNA extraction and RT-qPCR demonstrated a noticeable difference in SON isoform mRNA expression in all patient samples obtained with comparison to normal/healthy donor PBMCs. Patient samples included diagnoses of MDS, anemia, neutropenia, PV, and AML (all myeloid hematopoietic pathologies). SON E levels were significantly elevated compared to normal patient samples. Additionally, considerable differences were noted in SON B isoform expression. These findings demonstrate an interesting and potentially noteworthy correlation between SON mRNA alternative splicing and the pathophysiology of myeloid hematopoietic disorders. Although further research is necessary to confirm a relationship and illuminate its specific significance, this discovery is an early promising link between the biology of splicing dynamics and the clinical manifestations of myeloid neoplasia.