CoDysAn: A Telemedicine Tool to Improve Awareness and Diagnosis for Patients With Congenital Dyserythropoietic Anemia

Congenital dyserythropoietic anemias

Congenital dyserythropoietic anemias (CDAs) are a heterogeneous group of inherited anemias that affect the normal differentiation-proliferation pathways of the erythroid lineage. They belong to the wide group of ineffective erythropoiesis conditions that mainly result in monolinear cytopenia. CDAs are classified into the 3 major types (I, II, III), plus the transcription factor-related CDAs, and the CDA variants, on the basis of the distinctive morphological, clinical, and genetic features. Next-generation sequencing has revolutionized the field of diagnosis of and research into CDAs, with reduced time to diagnosis, and ameliorated differential diagnosis in terms of identification of new causative/modifier genes and polygenic conditions. The main improvements regarding CDAs have been in the study of iron metabolism in CDAII. The erythroblast-derived hormone erythroferrone specifically inhibits hepcidin production, and its role in the mediation of hepatic iron overload has been dissected out. We discuss here the most recent advances in this field regarding the molecular genetics and pathogenic mechanisms of CDAs, through an analysis of the clinical and molecular classifications, and the complications and clinical management of patients. We summarize also the main cellular and animal models developed to date and the possible future therapies.

Genetics and Genomics Approaches for Diagnosis and Research Into Hereditary Anemias

The hereditary anemias are a relatively heterogeneous set of disorders that can show wide clinical and genetic heterogeneity, which often hampers correct clinical diagnosis. The classical diagnostic workflow for these conditions generally used to start with analysis of the family and personal histories, followed by biochemical and morphological evaluations, and ending with genetic testing. However, the diagnostic framework has changed more recently, and genetic testing is now a suitable approach for differential diagnosis of these patients. There are several approaches to this genetic testing, the choice of which depends on phenotyping, genetic heterogeneity, and gene size. For patients who show complete phenotyping, single-gene testing remains recommended. However, genetic analysis now includes next-generation sequencing, which is generally based on custom-designed targeting panels and whole-exome sequencing. The use of next-generation sequencing also allows the identification of new causative genes, and of polygenic conditions and genetic factors that modify disease severity of hereditary anemias. In the research field, whole-genome sequencing is useful for the identification of non-coding causative mutations, which might account for the disruption of transcriptional factor occupancy sites and cis-regulatory elements. Moreover, advances in high-throughput sequencing techniques have now resulted in the identification of genome-wide profiling of the chromatin structures known as the topologically associating domains. These represent a recurrent disease mechanism that exposes genes to inappropriate regulatory elements, causing errors in gene expression. This review focuses on the challenges of diagnosis and research into hereditary anemias, with indications of both the advantages and disadvantages. Finally, we consider the future perspectives for the use of next-generation sequencing technologies in this era of precision medicine.

Severe anemia caused by dominant mutations in Krüppel-like factor 1 (KLF1)

The etiology and severity of anemia, a common blood disorder, are diverse. Dominant mutations in Krüppel-like factor 1 (KLF1/EKLF) underlie the molecular basis for some of them. KLF1 is a zinc finger transcription factor that plays an essential role in red blood cell proliferation and differentiation. Mutations have been identified in the KLF1 gene that cause hematologic diseases. Two of these alter one allele but generate an extreme phenotype: the mouse Nan mutation (E339D) leads to hemolytic neonatal anemia with hereditary spherocytosis, and the human CDA mutation (E325K) causes congenital dyserythropoietic anemia (CDA) type IV. These modify functionally important amino acids in the zinc finger DNA-binding domain at positions involved in direct interactions with regulatory elements of KLF1's target genes. Although the two dominant mutations alter the same evolutionarily conserved glutamic acid residue, the substitutions are not equivalent and lead to divergent consequences for the molecular mechanisms underlying activity of these mutants, particularly in recognition and interaction with their unique binding sites. Consequently, the properties of the protein are transformed such that it acquires novel dominant characteristics whose effects may not be limited to the erythroid compartment. KLF1 mutants cause loss-of-function/haploinsufficiency effects on some KLF1 wild-type target genes, while at the same time gain-of-function effects activate ectopic sites and neomorphic gene expression. Such anomalies not only lead to intrinsic red cell problems, but also to expression of non-erythroid genes that systemically disturb organ development. This review highlights recent molecular, biochemical, and genetic studies of KLF1 mutants, particularly the dramatic consequences that come from just a single amino acid change. The study of these variants provides an important contribution to the overall understanding of the DNA-protein interface of the zinc finger subtype of transcription factors, and the potential clinical consequences of what might appear to be a minor change in sequence.