Mild dyserythropoiesis and ß-like globin gene expression imbalance due to the loss of histone chaperone ASF1B.

The expression of the human ß-like globin genes follows a well-orchestrated developmental pattern, undergoing two essential switches, the first one during the first weeks of gestation (ε to γ), and the second one during the perinatal period (γ to ß). The γ- to ß-globin gene switching mechanism includes suppression of fetal (γ-globin, HbF) and activation of adult (ß-globin, HbA) globin gene transcription. In hereditary persistence of fetal hemoglobin (HPFH), the γ-globin suppression mechanism is impaired leaving these individuals with unusual elevated levels of fetal hemoglobin (HbF) in adulthood. Recently, the transcription factors KLF1 and BCL11A have been established as master regulators of the γ- to ß-globin switch. Previously, a genomic variant in the KLF1 gene, identified by linkage analysis performed on twenty-seven members of a Maltese family, was found to be associated with HPFH. However, variation in the levels of HbF among family members, and those from other reported families carrying genetic variants in KLF1, suggests additional contributors to globin switching. ASF1B was downregulated in the family members with HPFH. Here, we investigate the role of ASF1B in γ- to ß-globin switching and erythropoiesis in vivo. Mouse-human interspecies ASF1B protein identity is 91.6%. By means of knockdown functional assays in human primary erythroid cultures and analysis of the erythroid lineage in Asf1b knockout mice, we provide evidence that ASF1B is a novel contributor to steady-state erythroid differentiation, and while its loss affects the balance of globin expression, it has no major role in hemoglobin switching.

Apheresis causes complement deposition on red blood cells (RBCs) and RBC antigen alterations, possibly inducing enhanced clearance.

BACKGROUND: Apheresis is increasingly being applied to collect cells or plasma, even allowing the collection of multiple blood components during one procedure. Although the quality of the cellular and plasma products that are obtained by apheresis have been extensively studied and shown to be of high quality, the impact of apheresis on the red blood cells (RBCs) that are returned to the donor has not been investigated. STUDY DESIGN AND METHODS: The effect of the plasma- or plateletpheresis procedures by four different devices-MCS+ (Haemonetics), PCS2 (Haemonetics), Trima Accel (Terumo BCT), and Autopheresis-C (Auto-C, Fresenius Kabi)-on the RBCs that are returned to the donor was tested in a blinded, prospective trial in a cohort of 25 donors. RESULTS: A rheologic analysis of donor RBCs before and after plasma- or plateletpheresis showed no differences in outcome. However, a strong increase in hemolysis was found in samples from the Trima Accel devices after plateletpheresis, compared to all other machines tested. Furthermore, an increase in complement deposition on RBCs was seen after all plasmapheresis procedures (MCS+, PCS2, and Auto-C). Finally, a significant decrease in the expression of the complement-regulating protein CD59 was seen in all postapheresis samples as well as a significant decrease of the adhesion molecule CD147. CONCLUSION: The increase in complement deposition and the decrease in the expression of CD59 suggests that RBC clearance might be enhanced after return to the donor. Possible side effects due to an increase in hemolysis after Trima Accel plateletpheresis should be further investigated.

Hemoglobin analyses in the Netherlands reveal more than 80 different variants including six novel ones.

More than 20,000 blood samples of individuals living in The Netherlands and suspected of hemolytic anemia or diabetes were analyzed by high resolution cation exchange high performance liquid chromatography (HPLC). Besides common disease-related hemoglobins (Hbs), rare variants were also detected. The variant Hbs were retrospectively analyzed by capillary zone electrophoresis (CZE) and by isoelectric focusing (IEF). For unambiguous identification, the globin genes were sequenced. Most of the 80 Hb variants detected by initial screening on HPLC were also separated by capillary electrophoresis (CE), but a few variants were only detectable with one of these methods. Some variants were unstable, had thalassemic properties or increased oxygen affinity, and some interfered with Hb A2 measurement, detection of sickle cell Hb or Hb A1c quantification. Two of the six novel variants, Hb Enschede (HBA2: c.308G > A, p.Ser103Asn) and Hb Weesp (HBA1: c.301C > T, p.Leu101Phe), had no clinical consequences. In contrast, two others appeared clinically significant: Hb Ede (HBB: c.53A > T, p.Lys18Met) caused thalassemia and Hb Waterland (HBB: c.428C > T, pAla143Val) was related to mild polycytemia. Hb A2-Venlo (HBD: c.193G > A, p.Gly65Ser) and Hb A2-Rotterdam (HBD: c.38A > C, p.Asn13Thr) interfered with Hb A2 quantification. This survey shows that HPLC analysis followed by globin gene sequencing of rare variants is an effective method to reveal Hb variants.