Date of Award

7-9-2009

Document Type

Thesis

Degree Name

Medical Doctor (MD)

First Advisor

Diane S. Krause

Abstract

The t(1;22)(p13;q13) translocation creates a fusion of the genes RBM15 and MKL1 and is exclusively associated with the infantile form of Acute Megakaryoblastic Leukemia, or AML variant M7. Although MKL1 is a known coactivator of the Serum Response Factor (SRF) pathway, it is not known whether MKL1 plays an important role in megakaryocytic commitment or differentiation. This project investigated the role of MKL1 in normal megakaryocytopoiesis by using a human CD34+ hematopoietic stem cell (HSC) model. Human CD34+ HSCs were transduced with lentiviral vectors expressing either MKL1 or dominant negative MKL1 (DN-MKL1) and were cultured in conditions promoting megakaryocytopoiesis. After nine days, cells transduced with MKL1-expressing virus had increased expression of the megakaryocyteassociated markers CD41a (52±10% vs. 28±15%), CD61 (56±15% vs. 26±13%) and CD42b (46±17% vs. 14±5%) when compared to cells transduced with the vector alone (all p < 0.05). Transduction with the DN-MKL1 lentivirus was unexpectedly also associated with an increase in these same markers, though this experiment was only performed once and will require further investigation. In separate megakaryocyte progenitor assays, MKL1 was associated with an increased frequency of megakaryocyte colony forming units (CFU-Mk) (263±111 vs. 164±61 CFU-Mk per 10,000 cells), though these data did not reach statistical significance. These findings suggest that MKL1 may be an important regulator of megakaryocytopoiesis, and that abnormal MKL1 function may be involved in megakaryoblastic leukemogenesis.

Comments

This thesis is restricted to Yale network users only. This thesis is permanently embargoed from public release.

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