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Hereditary spherocytosis is a common inherited disorder that is characterised by anaemia, jaundice, and splenomegaly. It is reported worldwide and is the most common inherited anaemia in individuals of northern European ancestry. Clinical severity is variable with most patients having a well-compensated haemolytic anaemia. Some individuals are asymptomatic, whereas others have severe haemolytic anaemia requiring erythrocyte transfusion. The primary lesion in hereditary spherocytosis is loss of membrane surface area, leading to reduced deformability due to defects in the membrane proteins ankyrin, band 3, beta spectrin, alpha spectrin, or protein 4.2. Many isolated mutations have been identified in the genes encoding these membrane proteins; common hereditary spherocytosis-associated mutations have not been identified. Abnormal spherocytes are trapped and destroyed in the spleen and this is the main cause of haemolysis in this disorder. Common complications are cholelithiasis, haemolytic episodes, and aplastic crises. Splenectomy is curative but should be undertaken only after careful assessment of the risks and benefits.

Hereditary xerocytosis (HX, MIM 194380)is an autosomal dominant hemolytic anemia characterized by primary erythrocyte dehydration. Copy number analyses, linkage studies, and exome sequencing were used to identify novel mutations affecting PIEZO1, encoded by the FAM38A gene, in 2 multigenerational HX kindreds. Segregation analyses confirmed transmission of the PIEZO1 mutations and cosegregation with the disease phenotype in all affected persons in both kindreds. All patients were heterozygous for FAM38A mutations, except for 3 patients predicted to be homozygous by clinical and physiologic studies who were also homozygous at the DNA level. The FAM38A mutations were both in residues highly conserved across species and within members of the Piezo family of proteins. PIEZO proteins are the recently identified pore-forming subunits of channels that mediate mechanotransduction in mammalian cells. FAM38A transcripts were identified in human erythroid cell mRNA, and discovery proteomics identified PIEZO1 peptides in human erythrocyte membranes. These findings, the first report of mutation in a mammalian mechanosensory transduction channel-associated with genetic disease, suggest that PIEZO proteins play an important role in maintaining erythrocyte volume homeostasis. IntroductionHereditary xerocytosis (also known as HX or dehydrated stomatocytosis, DHSt; OMIM 194380) is an autosomal dominant hemolytic anemia characterized by primary erythrocyte dehydration. 1 HX erythrocytes exhibit decreased total cation and potassium content that are not accompanied by a proportional net gain of sodium and water. HX patients typically exhibit mild to moderate, compensated hemolytic anemia. Erythrocyte mean corpuscular hemoglobin concentration is increased and erythrocyte osmotic fragility is decreased, both reflecting cellular dehydration.A locus for HX on chromosome 16 (16q23-q24) was first identified in a large, 3-generation Irish family. 2 This locus was refined to D16S511-16qter via study of 10 kindreds with variants of HX, pseudohyperkalemia, or nonimmune hydrops fetalis. 3,4 Recent studies of one of the original HX families from Rochester, NY, 5 and of a large HX family from Manitoba, Canada 6 confirmed the linkage of the disease phenotype to chromosome 16q, and refined the candidate region to 16q24.2-16qter, a 2.4 million-bp interval containing 51 known or predicted genes. 6 To identify the HXassociated genetic locus, we performed high-resolution single nucleotide polymorphism (SNP) typing and whole-exome sequencing on selected persons from both the New York and Canadian HX kindreds.In the refined candidate region, no regions of copy number variation were detected at 16q24.2-16qter. A large region of homozygosity was detected in this region in DNA from a presumed homozygote from the New York kindred. Exome sequencing identified novel mutations affecting PIEZO1 (encoded by the FAM38A gene) in both HX kindreds. Segregation analyses confirmed transmission of the PIEZO1 mutations and cosegregation with the disease phenotype in all...

• Transcriptome analyses of human and murine reveal significant stage and speciesspecific differences across stages of terminal erythroid differentiation.• These transcriptomes provide a significant resource for understanding mechanisms of normal and perturbed erythropoiesis.We recently developed fluorescence-activated cell sorting (FACS)-based methods to purify morphologically and functionally discrete populations of cells, each representing specific stages of terminal erythroid differentiation. We used these techniques to obtain pure populations of both human and murine erythroblasts at distinct developmental stages. RNA was prepared from these cells and subjected to RNA sequencing analyses, creating unbiased, stage-specific transcriptomes. Tight clustering of transcriptomes from differing stages, even between biologically different replicates, validated the utility of the FACSbased assays. Bioinformatic analyses revealed that there were marked differences between differentiation stages, with both shared and dissimilar gene expression profiles defining each stage within transcriptional space. There were vast temporal changes in gene expression across the differentiation stages, with each stage exhibiting unique transcriptomes. Clustering and network analyses revealed that varying stage-specific patterns of expression observed across differentiation were enriched for genes of differing function. Numerous differences were present between human and murine transcriptomes, with significant variation in the global patterns of gene expression. These data provide a significant resource for studies of normal and perturbed erythropoiesis, allowing a deeper understanding of mechanisms of erythroid development in various inherited and acquired erythroid disorders. (Blood. 2014;123(22):3466-3477) IntroductionMammalian erythropoiesis is an excellent example of the complex changes in temporal, developmental, and differentiation stage-specific gene expression exhibited by a single cell type.1,2 In the mammalian embryo and fetus, erythroid cells have differing developmental origins, with the primitive erythroid cell lineage developing from yolk sac-derived erythroid progenitors, and the definitive cell lineage maturing from 2 different developmentally regulated stem and progenitor cell populations. [3][4][5][6] These cells have different programs of regulation, with variation in spatial, temporal, and site-specific differentiation.In the adult, mature erythrocytes are the terminally differentiated final cellular product derived from hematopoietic stem and progenitor cells (HSPC). HSPCs undergo a series of lineage choice fate decisions, with increasingly restricted potential, ultimately committing to the erythroid lineage and beginning erythropoiesis. Traditionally, erythropoiesis has been divided into 3 stages: early erythropoiesis, terminal erythroid differentiation, and reticulocyte maturation.2 Early erythropoiesis involves commitment of multi-lineage progenitors into erythroid progenitor cells, with proliferation and d...

The demographics, pathogens, and outcome associated with neonatal sepsis continue to change. The increase in late-onset sepsis in preterm infants who required prolonged intensive care indicates that strategies to prevent infection are urgently needed for this population of infants.