Project Grant F31HL184589

INTERROGATING THE ROLE OF NUCLEAR HEPARAN SULFATES IN HEMATOPOIETIC CELLS - PROJECT SUMMARY HEMATOPOIESIS INVOLVES THE SELF-MAINTENANCE AND DIFFERENTIATION OF HEMATOPOIETIC STEM AND PROGENITOR CELLS (HSPCS) THROUGH VARIOUS STAGES, ULTIMATELY YIELDING TERMINALLY DIFFERENTIATED BLOOD CELLS WITH DIVERSE MORPHOLOGIES AND FUNCTIONS. OUR RESEARCH, ALONG WITH OTHERS, HAS EMPHASIZED THE IMPORTANCE OF HEPARAN SULFATE PROTEOGLYCANS (HSPGS) IN THIS COMPLEX PROCESS, SPECIFICALLY, THE LOSS OF HEPARAN SULFATED CHAINS ON THE PROTEINS TO WHICH THEY ARE ATTACHED DISRUPTS DIFFERENTIATION IN HEMATOPOIETIC STEM CELLS. HOWEVER, THE PRECISE CONTRIBUTION OF HEPARAN SULFATE (HS) IN HEMATOPOIETIC DIFFERENTIATION IS POORLY UNDERSTOOD. THE DEVELOPMENT OF DERIVATIZED SCFV ANTIBODIES TARGETING UNIQUE HEPARAN SULFATE EPITOPES HAS ENABLED A QUANTUM LEAP FORWARD TO STUDY THIS MORE CLOSELY. INTERESTINGLY, MASS SPECTROMETRY AND IMMUNOFLUORESCENCE EXPERIMENTS UTILIZING THESE SCFV ANTIBODIES HAVE REVEALED THE PRESENCE OF HEPARAN SULFATES IN DISTINCT SUBCELLULAR COMPARTMENTS, INCLUDING THE NUCLEUS, CHALLENGING THE CONVENTIONAL BELIEF THAT ALL HEPARAN- SULFATED PROTEINS ARE LOCALIZED ON THE CELL SURFACE. THIS UNEXPECTED FINDING ALIGNS WITH EARLIER STUDIES SUGGESTING THE PRESENCE OF HS IN THE NUCLEUS, THOUGH THE BIOLOGICAL SIGNIFICANCE OF THESE OBSERVATIONS HAS REMAINED ELUSIVE. I HYPOTHESIZE THAT NUCLEAR HS INFLUENCE TRANSCRIPTIONAL PROGRAMS THAT GUIDE HEMATOPOIETIC DIFFERENTIATION. IN THIS WORK, I WILL (1) UNCOVER THE IDENTITY OF NUCLEAR HEPARAN-SULFATED PROTEINS IN HSPCS, (2) DETERMINE THE FUNCTIONAL SIGNIFICANCE OF NUCLEAR HS IN HSPC DIFFERENTIATION, AND (3) DELINEATE THE MECHANISMS BY WHICH NUCLEAR HS REGULATES HSPC FUNCTION. COLLECTIVELY, OUR PROPOSED STUDIES WILL HAVE A BROAD IMPACT ON THE FIELD BY DISSECTING THE FUNCTIONAL ROLE OF A NOVEL UNDEREXPLORED PATHWAY IN HEMATOPOIESIS. IN THE LONG TERM, THESE STUDIES COULD ULTIMATELY OPEN NOVEL AVENUES FOR POSSIBLE THERAPEUTIC INTERVENTIONS TO TREAT DISORDERS OF THE HEMATOPOIETIC SYSTEM AND OTHER ORGAN SYSTEMS.