M in the Mpl gene of African American patients with MPD that leads to substitution of the 39th amino acid Lysine, with Asparagine in the extra PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/25957400 cellular domain of the protein. Patients with this polymorphism exhibited high platelet counts and low platelet Mpl protein. African Americans were however not represented amongst our patients tested. We also performed in vitro transcription/ translation with the cloned cDNA from the AMM patients. Similar levels of proteins were formed irrespective of the source of the cDNA, indicating that the cDNA from AMM patients had no structural defects preventing its translation. There was no difference in the extent of glycosylation of the protein either when the reaction was performed in the presence of microsomal membranes capable of post-translational modification in vitro. To further confirm this in vivo, these cDNAs were transfected into 293 T human embryonic kidney cells and the cell lysates analysed by western blots for Mpl expression. Irrespective of the source of the cDNA, similar level of Valsartan/sacubitril msds expression of Mpl protein was observed. Two bands were however detected. Since the antibody used can react with both glycosylated and non-glycosylated forms of Mpl, it is likely that the second band corresponds to non-glycosylated form. As the in vivo system is saturated with the over-expressed protein, the system for modification of the protein could be exhausted. Overall, Mpl gene from AMM patients does not seem to have any impaired structural features to prevent its transcription/translation. Our present study shows elevated TPO level; reduced Mpl platelet protein level; absence of Mpl transcriptional inhibition and absence of any structural defects in Mpl coding region in AMM patients. However, there was no co-relation between TPO level and Mpl expression, similar to the observation of Harrison CN et al. [22] in ET patients. Plasma TPO level is regulated by platelet counts and MK mass [23]. TPO binds to its receptor Mpl on platelets/MKs and gets internalised. This receptor mediated endocytosis of TPO leads to its catabolism by the lysozymes, without any recycling of the receptors to the surface [24]. In AMM patients there is initial MK hyperplasia and thrombocytosis that leads to enhanced release of growth factors such as Platelet Derived Growth Factor, bFibroblast Growth Factor and Transforming Growth Factor 1 [25-27]. This may lead to increase in TPO transcription, since these growth factors have been shown to stimulate the transcription of TPO from the bone marrow stromal cells in cultures [28,29]. Our earlier observation that elevated plasma TPO level is not associated with its enhanced transcription inthe bone marrow cells [17] could be due to the fact that our cultures predominantly consisted of fibroblasts and not stromal cells. Enhanced expression of TPO and absence of an accompanying increase in Mpl transcription or re-cycling of the internalised receptor may be responsible for persistence of high plasma TPO level in AMM patients. Reduced Mpl level seen in AMM patients may be due to exhaustion of the Mpl pool by binding to the enhanced TPO and its subsequent catabolism. This gains support from an earlier observation in thrombocythemic mice wherein very high and persistent level of TPO due to its induced over expression were found to be associated with reduced platelet Mpl protein without any reduction in Mpl transcription [30]. Also in other MPDs such as ET/PV, high plasma TPO level is associated w.
