Mitochondrial Changes in β0-Thalassemia/Hb E Disease
My topic is Thalassemia. Thalassemia is an inherited blood disorder where someone has less hemoglobin (substance in your red blood cells that carries oxygen) and fewer red blood cells in their body than normal. It is caused by mutations in the DNA of cells that make hemoglobin. There are several types of thalassemia and signs and symptoms depend on the type and severity. I am interested in this topic because I have Thalassemia minor. I am a carrier of this trait and it was passed down to me by my mother. I am curious what Thalassemia does on a cellular level. The research study was about Mitochondrial Changes in β0-Thalassemia/Hb E Disease. Mitochondria are subcellular organelles that are crucial in several cellular processes including oxidative phosphorylation and apoptosis (which is known to be dysregulated in differentiating erythrocytes from β°-thalassemia/Hb E patients). Mitochondria were evaluated through several different methods such as western blotting, Mitotracker Staining, AlamarBlue Assay, Quantitative Real-Time PCR, and statistical analysis.
A mitochondrial protein enriched proteome was determined and verified from erythroblasts from normal controls and β°-thalassemia/Hb E patients of different severities. Fifty differentially regulated mitochondrial proteins were identified. Mitotracker staining revealed differences in staining between normal control erythroblasts and those from β°-thalassemia/Hb E patients. In day 10 cells, there were differences in mitochondria number and gene expression. There were differences seen in redox status as determined by alamarBlue staining in newly isolated CD34+ cells. There are differences in these cells as early as the erythroid progenitor cell stage and high levels of globin gene expression. Figure 1 shows the mitochondrial protein enriched proteome of erythroid cells. Day 10 erythroid cells from normal controls and β°-thalassemia/Hb E patients (mild and severe) were subjected to GelC-MS/MS analysis. Figure 2 shows validation of proteome data. Based on the proteome data, two differentially regulated mitochondrial proteins were selected for validation in an independent cohort of controls and patients. The proteins were hsp60 and prohibitin 2. Figure 3 showed the quantity of mitochondria in erythroid precursor cells. The levels of mitochondrial genomes were determined using quantitative PCR. Results from figure 3 show equal numbers of mitochondria on days 7 and 14, but higher levels of mitochondria in cells from β°-thalassemia/Hb E patients (both mild and severe) on day 10. There was a gradual loss of mitochondria during differentiation. Figure 4 showed the activity of mitochondria in erythroid precursor cells. Results from figure 4 showed differences during differentiation for all three genes investigated. Expression of ATP6 and CTY were reduced in erythroblasts from severe β°-thalassemia patients when compared to normal controls on day 10. ATP6 and ATP8 were increased in expression in both mild and severe β°-thalassemia when compared to normal controls on day 14. The increased expression of hsp60 and the decreased expression of prohibitin2 seen in severe cases of β°-thalassemia/HbE at day 10 of differentiation correlate with the main physio pathological process in severe cases of β°-thalassemia/HbE. Mitochondria removal is slightly slower in thalassemic cells than in normal controls. Cellular redox state through the alamarBlue assay showed decreased signal on day ten in the cells from β°-thalassemia/Hb E patients as compared to normal controls. Newly isolated CD34+ erythroid progenitor cells by the alamarBlue assay showed a higher redox status in both mild and severe β°-thalassemia cells as compared to normal controls and difference between cells from mild and severe patients. Results suggest an association between mitochondria and the pathology of β°-thalassemia/Hb E as mediated by erythroid differentiation. The results suggest that there is a different redox state in newly isolated CD34+ cells. This may result from the differing levels of erythropoietin in these patients as compared to normal controls. These results suggest that the unpaired globin chains are directly affecting the integrity of mitochondria. There are more mitochondria present in cells from thalassemia patients on day 10 which suggests that the effect is magnified with damage to the mitochondria with the onset of apoptosis in ineffective erythropoiesis.
Over the course of the semester we have learned many different things about the structures and functions of cells. Many terms in this study show what we have learned. In chapter 5 we studied mitochondria and oxidative phosphorylation. In chapter 15 we studied cell signaling and apoptosis. We also learned about gene expression in chapter 12. This study describes things that are different with thalassemic cells than a typical erythrocyte. It shows how thalassemic cells function differently.
Citations
Mayo Clinic. (2018). Thalassemia – Symptoms and causes. [online] Available at: https://www.mayoclinic.org/diseases-conditions/thalassemia/symptoms-causes/syc-20354995 [Accessed 10 Dec. 2018].
Www-ncbi-nlm-nih-gov.proxy.lib.odu.edu. (2018). Old Dominion University Libraries – Remote login. [online] Available at: https://www-ncbi-nlm-nih-gov.proxy.lib.odu.edu/pmc/articles/PMC4836671/ [Accessed 10 Dec. 2018].
MedicineNet. (2018). The Beta Thalassemia Trait: Symptoms, Treatment & Diagnosis. [online] Available at: https://www.medicinenet.com/beta_thalassemia/article.htm#what_is_the_difference_between_thalassemia_minor_and_major [Accessed 10 Dec. 2018].
Sciencedirect.com. (2018). Erythropoiesis – an overview | ScienceDirect Topics. [online] Available at: https://www.sciencedirect.com/topics/medicine-and-dentistry/erythropoiesis [Accessed 10 Dec. 2018].