The studies presented in this thesis focused on the identification of genes that play a central role in the pathogenesis of myelodysplastic syndromes with a deletion of the short arm (q) of chromosome 5, the del(5q) MDS. The overall goal of the projects was to gain a better understanding of how gene haploinsufficiency in (del)5q MDS leads to a clonal advantage, ineffective hematopoiesis and how haploinsufficiency can be targeted.
Heterozygous deletion of RPS14 occurs in del(5q) myelodysplastic syndrome (MDS) and has been linked to impaired erythropoiesis, characteristic of this disease subtype. So far, it was not well understood how ribosomal haploinsufficiency affects protein synthesis and if differentially translated proteins have a impact on the erythroid differentiation defect (chapter 1). We generated a murine model with conditional inactivation of Rps14 and demonstrated a p53-dependent erythroid differentiation defect with apoptosis at the transition from polychromatic to orthochromatic erythroblasts resulting in age- and erythroid stress dependent progressive anemia, megakaryocyte dysplasia, and loss of hematopoietic stem cell (HSC) quiescence (chapter 2). Protein synthesis was significantly reduced in Rps14 haploinsufficient hematopoietic stem cells and in particular in erythroid progenitor cells relative to wild-type cells. As assessed by quantitative proteomics, Rps14 haploinsufficient erythroblasts expressed higher levels of proteins involved in innate immune signaling, notably the heterodimeric S100 calcium-binding proteins S100a8 and S100a9 (alarmins). S100a8 is functionally involved in the erythroid defect caused by the Rps14 deletion, as addition of recombinant S100a8 was sufficient to induce an erythroid differentiation defect in wild-type erythroid cells (phenocopy), and genetic inactivation of S100a8 expression rescued the erythroid differentiation defect of Rps14-haploIn the current study it was our goal to focus on important design criteria including
(1) the opportunity for reproducible and user-defined properties such as the choice of substrate, extracellular matrix, cell types, and degradability;
(2) the ability to induce vascularisation;
(3) accessibility and suitability for complementary histological/cytological analysis; and, most importantly,
(4) the functional ability to capture and retrieve endogenous hematopoietic cells efficiently
