Abstract
Immune thrombocytopenia (ITP) is widely accepted as an acquired autoimmune disorder characterised by autoantibody-induced platelet destruction. A New Zealand family with a recently defined MYB gene variant show familial ITP along with hereditary persistence of fetal haemoglobin (HPFH). MYB is known to play a critical role in the differentiation of megakaryocyte-erythroid precursors and some mutations in MYB are oncogenic. HPFH indicates aberrant development of erythroid precursors and suggests that platelets, which are closely related, might also show an aberrant phenotype. The long-term goal of the study on this family is to determine the mechanism of ITP. This research project aimed to identify differences in the platelets between family members who carry the MYB variant and controls. Three hypotheses were proposed in this study: 1. The MYB variant causes the platelet to express a “fetal” like phenotype. 2. The MYB variant is associated with differences in platelet morphology. 3. Differences in platelet RNA are associated with the effects of the MYB variant on platelet development. In this project, we developed two flow cytometric methods to assess candidate fetal markers, the i-antigen and CD71, on the platelet surface. CD71 and i-antigen expression was not observed on the family members’ platelets. One of the family members showed abnormal platelet morphology with increased hypo-granulated platelets by light microscopy. We refined the platelet isolation and fixation methods for platelet transmission electron microscopy. By electron microscopy of the platelet, the family member showed an increased area of the canalicular system structures and decreased numbers of mitochondria. Isolation methods for platelet RNA were investigated and optimized in preparation for platelet transcriptome studies. Each of the aims was strongly based on the requirement of method development and this is described in chapter two. The final results are shown in chapter three.