Caracterización molecular y funcional de las anemias congénitas

Abstract

Congenital anemias are classified into two main groups: hemolytic anemias due to intrinsic alterations of the red blood cell and anemias due to bone marrow failure. The first group includes: membranopathies, enzymopathies and hemoglobinopathies, including sickle cell disease (SCD) and thalassemia syndromes; the second group includes congenital sideroblastic anemias (CSA) and congenital dyserythropoietic anemia. These are diseases with multisystemic involvement and great phenotypic variety, in which patients with the same mutation can present from mild-moderate anemia to severe anemia with transfusion dependence from infancy. Despite a good knowledge of their etiology, there are many unknown factors associated with this clinical heterogeneity, and it is necessary to study these possible modulators of the disease further to better understand the gene signature of these patients. These are rare diseases, frequently underdiagnosed, which makes it difficult to study the true population incidence of these diseases. In this work, we will attempt to further study SCD, ACS and thalassemia, trying to clarify some of the issues raised. As mentioned, SCD is an autosomal recessive hemoglobinopathy, characterized by a chronic inflammatory state and repeated vaso-occlusive crises, presenting multiorgan damage and high infant mortality. Due to the need to establish early treatment and due to the increase of the endemic population in our country, newborn screening was established in 2016 in the Region of Murcia. In this study, we have tried to determine the incidence of SCD and to evaluate its benefit in the neonatal population of the Region of Murcia. In our region, the prevalence of SCD was similar to other regions of Spain except Madrid and Catalonia, with a greater migratory flow. All newborns with SCD early therapeutic care and all carrier couples received genetic counseling. Within the group of bone marrow failure anemias, we find CSA as described. CSA encompasses a heterogeneous group of rare, hereditary hematopoietic disorders characterized by an accumulation of mitochondrial iron in erythroid precursors, leading to iron overload and ineffective erythropoiesis characteristic of this disease. Recently, it has been described in animal models that NLRP1 inhibition can have a significant impact on erythropoiesis. Thus, in this study, we have tried to characterize the possible involvement of the inflammasome in the pathophysiology of a patient with CSA due to mutation in the mitochondrial transporter SLC25A38. With this study, we have demonstrated, on the one hand, that inhibition of the inflammasome increases erythrocyte formation in a patient with CSA due to mutation in the SLC25A38 gene; and on the other hand, we have identified in this patient by NGS a variant of NLRP1 that in combination with other factors such as ferroptosis could aggravate his clinical phenotype, thus providing significant data on the possible involvement of the inflammasome in CSA. Despite their different etiologies, hemoglobinopathies (SCD and thalassemia syndromes) and CSA have a common pathophysiological origin in congenital alteration in erythropoiesis. To study them in depth, we have analyzed the transcriptome of ten patients with thalassemia syndromes, four patients with SCD, and one patient with CSA using the Quant 3' mRNA-Sequencing technique. Our results have shown a clearly differentiated expression between patients and healthy controls, revealing an increased expression in genes related to glycolytic and oxidative metabolism, membrane genes, and erythropoiesis in all the patients studied except the patient with CSA, who shows a unique gene expression pattern compared to the rest of the congenital anemias studied.