Erythroid Tissues Research Articles

Neuronal nitric oxide synthase required for erythropoietin modulation of heart function in mice.

Introduction: Erythropoietin (EPO) acts primarily in regulating red blood cell production mediated by high EPO receptor (EPOR) expression in erythroid progenitor cells. EPO activity in non-erythroid tissue is evident in mice with EPOR restricted to erythroid tissues (ΔEPORE) that become obese, glucose-intolerant, and insulin-resistant. In animal models, nitric oxide synthase (NOS) contributes to EPO activities including erythropoiesis, neuroprotection, and cardioprotection against ischemia-reperfusion injury. However, we found that extended EPO treatment to increase hematocrit compromised heart function, while the loss of neuronal NOS (nNOS) was protective against the deleterious activity of EPO to promote heart failure. Methods: Wild-type (WT) mice, ΔEPORE mice, and nNOS-knockout mice (nNOS-/-) were placed on a high-fat diet to match the ΔEPORE obese phenotype and were treated with EPO for 3weeks. Hematocrit and metabolic response to EPO treatment were monitored. Cardiac function was assessed by echocardiography and ultrasonography. Results: ΔEPORE mice showed a decrease in the left ventricular outflow tract (LVOT) peak velocity, ejection fraction, and fractional shortening, showing that endogenous non-erythroid EPO response is protective for heart function. EPO treatment increased hematocrit in all mice and decreased fat mass in male WT, demonstrating that EPO regulation of fat mass requires non-erythroid EPOR. EPO treatment also compromised heart function in WT mice, and decreased the pulmonary artery peak velocity (PA peak velocity), LVOT peak velocity, ejection fraction, and fractional shortening, but it had minimal effect in further reducing the heart function in ΔEPORE mice, indicating that the adverse effect of EPO on heart function is not related to EPO-stimulated erythropoiesis. ΔEPORE mice had increased expression of heart failure-associated genes, hypertrophic cardiomyopathy-related genes, and sarcomeric genes that were also elevated with EPO treatment in WT mice. Male and female nNOS-/- mice were protected against diet-induced obesity. EPO treatment in nNOS-/- mice increased the hematocrit that tended to be lower than WT mice and decreased the PA peak velocity but did not affect the LVOT peak velocity, ejection fraction, and fractional shortening, suggesting that nNOS is required for the adverse effect of EPO treatment on heart function in WT mice. EPO treatment did not change expression of heart failure-associated gene expression in nNOS-/- mice. Discussion: Endogenous EPO has a protective effect on heart function. With EPO administration, in contrast to the protective effect to the cardiac injury of acute EPO treatment, extended EPO treatment to increase hematocrit in WT mice adversely affected the heart function with a corresponding increase in expression of heart failure-associated genes. This EPO activity was independent of EPO-stimulated erythropoiesis and required EPOR in non-erythroid tissue and nNOS activity, while nNOS-/- mice were protected from the EPO-associated adverse effect on heart function. These data provide evidence that nNOS contributes to the negative impact on the heart function of high-dose EPO treatment for anemia.

A Review on Scianna Blood Group System

The Scianna blood group system consists of seven antigens expressed on erythrocyte membrane-associated protein (ERMAP) which is encoded by the gene present on the short arm of chromosome 1 at 1p36.2-p22.1 locus which is close to but distinct from Rh locus. The 475 amino acid ERMAP glycoprotein belongs to immunoglobulin superfamily containing a single IgSF domain. It is highly expressed in erythroid tissues. The antibodies of Scianna blood group are clinically less significant. ERMAP glycoprotein is thought to be involved in cell adhesion/receptor, immune recognition and signal transduction.

Hydroxyurea Decouples Persistent F-Cell Elevation and Induction of γ-Globin

Mechanisms that control the fetal-to-adult hemoglobin switch are attractive therapeutic targets in sickle cell disease. In this study, we investigated developmental γ-globin silencing in the Townes humanized knock-in mouse model, which harbors a construct containing the human γ-, βA-, and βS-globin genes, and examined the utility of this model in evaluation of pharmacologic induction of fetal hemoglobin (HbF). We studied mouse pups on the day of delivery (P0) to 28 days after birth (P28). Regardless of the hemoglobin genotype (SS, AS, or AA), the proportion of F cells in peripheral blood was 100% at P0, declined sharply to 20% at P2, and was virtually undetectable at P14. Developmental γ-globin silencing in Townes mice was complete at P4 in association with significantly increased BCL11A expression in the primary erythropoietic organs of the mouse. Hydroxyurea given at P2 significantly sustained elevated percentages of F cells in mice at P14. However, the percentage of F cells declined at P14 for treatment begun at P4. A lack of augmentation of γ-globin mRNA in erythroid tissues suggests that the apparent increase in HbF in red cells caused by hydroxyurea was not due to sustained or re-activation of γ-globin transcription, but was instead a function of erythropoiesis suppression. Thus, we provide new details of the hemoglobin switch in the Townes murine model that recapitulates postnatal γ- to β-globin switch in humans and identify the myelosuppressive toxicity of hydroxyurea as a superseding factor in interpreting pharmacologic induction of HbF.

1402-P: Endogenous Erythropoietin Is Protective in Mice during High-Fat Diet to Obesity and Cardiac Function while Exogenous Erythropoietin Exacerbates Cardiac Function

Endogenous Erythropoietin (EPO) provides protection against obesity and heart function. Mice with EPO receptor restricted to erythroid tissue (ΔEPORE mice) become obese, glucose intolerant and insulin resistant. In male mice at 4 months of age, after three weeks of high fat diet feeding, ΔEPORE mice showed an increase in fat mass from to 13 grams compared to fat mass in wild type mice that more than doubled from 4 to grams. EPO treatment (i.p. 3000 U/kg, 3 times/week for three weeks) during high fat diet feeding in wild type mice reduced the increase in fat mass to 3 grams and had a minimal effect on fat mass in ΔEPORE mice. The EPO stimulated increase in hematocrit was comparable in wild type and ΔEPORE mice. Using echocardiography to measure cardiac systolic function and cardiac output after high fat diet feeding, without EPO treatment ejection fraction (%) and fractional shortening (%) of left ventricular contractility were decreased in ΔEPORE mice compared with wild type mice, suggesting that endogenous EPO provided a cardioprotective effect mediated by EPO receptor expression in non-erythroid cells. EPO treatment in wild type mice decreased peak velocity and left ventricular outflow tract velocity but there were no significant changes in ΔEPORE mice, indicating that the decreases in these parameters with EPO administration are independent of EPO stimulated erythropoiesis and mediated by EPO receptor in non-erythroid cells. EPO treatment also decreased ejection fraction and fractional shortening in wild type mice and had no further significant effect in ΔEPORE mice. These data provide evidence that while endogenous EPO may be protective for heart function, high dose EPO administration during high fat diet feeding in wild type mice compromises cardiac function. EPO modulation of heart function requires EPO receptor expression beyond erythroid cells and is distinct from EPO stimulated erythropoiesis. Disclosure J.Lee: None. H.Rogers: None. C.T.Noguchi: None.

Erythroid‐specific inactivation of Slc12a6/Kcc3 by EpoR promoter‐driven Cre expression reduces K‐Cl cotransport activity in mouse erythrocytes

Investigation of erythrocytes from spontaneous or engineered germ‐line mutant mice has been instrumental in characterizing the physiological functions of components of the red cell cytoskeleton and membrane. However, the red blood cell expresses some proteins whose germline loss‐of‐function is embryonic‐lethal, perinatal‐lethal, or confers reduced post‐weaning viability.Promoter regions of erythroid‐specific genes have been used to engineer erythroid‐specific expression of Cre recombinase. Through breeding with mice carrying appropriately spaced insertions of loxP sequences, generation of erythroid‐specific knockouts has been carried out for signaling enzymes, transcription factors, peptide hormones, and single transmembrane span signaling receptors. We report here the use of Cre recombinase expression driven by the erythropoietin receptor (EpoR) promoter to generate EpoR‐Cre;Kcc3f / f mice, designed to express erythroid‐specific knockout of the KCC3 K‐Cl cotransporter encoded by Kcc3/Slc12A6. We confirm KCC3 as the predominant K‐Cl cotransporter of adult mouse red cells in mice with better viability than previously exhibited by Kcc3 −/− germline knockouts. We demonstrate roughly proportionate preservation of K‐Cl stimulation by hypotonicity, staurosporine, and urea in the context of reduced, but not abrogated, K‐Cl function in EpoR‐Cre;Kcc3f / f mice. We also report functional evidence suggesting incomplete recombinase‐mediated excision of the Kcc3 gene in adult erythroid tissues.

Recognized and Emerging Features of Erythropoietic and X-Linked Protoporphyria.

Erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP) are inherited disorders resulting from defects in two different enzymes of the heme biosynthetic pathway, i.e., ferrochelatase (FECH) and delta-aminolevulinic acid synthase-2 (ALAS2), respectively. The ubiquitous FECH catalyzes the insertion of iron into the protoporphyrin ring to generate the final product, heme. After hemoglobinization, FECH can utilize other metals like zinc to bind the remainder of the protoporphyrin molecules, leading to the formation of zinc protoporphyrin. Therefore, FECH deficiency in EPP limits the formation of both heme and zinc protoporphyrin molecules. The erythroid-specific ALAS2 catalyses the synthesis of delta-aminolevulinic acid (ALA), from the union of glycine and succinyl-coenzyme A, in the first step of the pathway in the erythron. In XLP, ALAS2 activity increases, resulting in the amplified formation of ALA, and iron becomes the rate-limiting factor for heme synthesis in the erythroid tissue. Both EPP and XLP lead to the systemic accumulation of protoporphyrin IX (PPIX) in blood, erythrocytes, and tissues causing the major symptom of cutaneous photosensitivity and several other less recognized signs that need to be considered. Although significant advances have been made in our understanding of EPP and XLP in recent years, a complete understanding of the factors governing the variability in clinical expression and the severity (progression) of the disease remains elusive. The present review provides an overview of both well-established facts and the latest findings regarding these rare diseases.

218-LB: Age, Sex, and Fat Mass Affects Erythropoietin Metabolic Response in Mice

Erythropoietin (EPO) is required for erythrocyte production. However, EPO receptor (EpoR) extends beyond erythroid tissue and ΔEpoR mice with EpoR restricted to hematopoietic tissue show an increase in fat mass. At 3 months of age, ΔEpoR mice show no difference in body weight compared with wild type (WT, C57BL/6) mice. By 6 months of age, male body weights of ΔEpoR mice are greater than WT mice, and at 8+ months body weights of male and female ΔEpoR mice are greater than their WT counterparts. To assess EPO activity on glucose homeostasis and fat mass, mice were fed a high fat diet (HFD, 60% kCal fat) and treated with EPO (3000U/kg 3X per week) or saline for 3 weeks at age 3, 6, and 8+ months. EPO increased hematocrit in all mice. EPO treatment in male WT mice reduces weight and fat mass at 6 and 8+ months of age, when their fat mass is 35% or greater with saline treatment. Female WT mice treated with EPO do not show significantly less weight or fat mass at any age. EPO treatment does not affect weight or fat mass in ΔEpoR mice. With HFD feeding and EPO treatment in 3 month old mice, body weights are not different between WT and ΔEpoR mice although fat mass is significantly higher in ΔEpoR mice. At 6 months, body weight and fat mass in males are greater in ΔEpoR than WT, while ΔEpoR females show no difference in body weight but significantly more fat mass compared with WT females. In the older mice (8+ months old), both sexes of ΔEpoR mice are significantly heavier and fatter than WT mice. EPO treatment improves glucose tolerance in female ΔEpoR mice at 3 and 6 months but not at 8+months, whereas male ΔEpoR mice only showed improvement at 3 months, not at 6 and 8+months. In male and female WT mice, EPO improves glucose metabolism at 3 and 6 months, and to a lesser extent at 8+ months with greater improvement in mice with <35% fat mass. These data show that EPO regulates metabolism in a sex and age dependent manner mediated via EpoR expression in non-hematopoietic tissue and is influenced by level of fat mass. Disclosure H. Rogers: None. C. T. Noguchi: None.

Erythropoietin signaling in osteoblasts is required for normal bone formation and for bone loss during erythropoietin-stimulated erythropoiesis.

Erythropoietin (EPO) regulates erythropoiesis by binding to erythropoietin receptor (Epor) on erythroid progenitor cells. Epor is also expressed on bone forming osteoblasts and bone loss accompanies EPO-stimulated erythropoiesis in mice. Mice with Epor restricted to erythroid tissue exhibit reduced bone and increased marrow adipocytes; in contrast, transgenic mice (Tg) with osteoblastic-specific deletion of Epor exhibit reduced trabecular bone with age without change in marrow adipocytes. By 12weeks, male Tg mice had 22.2% and female Tg mice had 29.6% reduced trabecular bone volume (BV) compared to controls. EPO administration (1200U/kg) for 10days reduced trabecular bone in control mice but not in Tg mice. There were no differences in numbers of osteoblasts, osteoclasts, and marrow adipocytes in Tg mice, suggesting independence of EPO signaling in mature osteoblasts, osteoclasts, and adipocytes. Female Tg mice had increased number of dying osteocytes and male Tg mice had a trend for more empty lacunae. Osteogenic cultures from Tg mice had reduced differentiation and mineralization with reduced Alpl and Runx2 transcripts. In conclusion, endogenous EPO-Epor signaling in osteoblasts is important in bone remodeling, particularly trabecular bone and endogenous Epor expression in osteoblasts is required for bone loss accompanying EPO-stimulated erythropoiesis.

1950-P: Fat Mass Affects Metabolic Response to Erythropoietin in Mice

Erythropoietin (EPO) is required for erythrocyte production. However, EPO receptor (EpoR) expression extends beyond erythroid tissue. To assess EPO activity on glucose homeostasis and fat mass accumulation, wild type (WT, C57BL/6) mice, ΔEpoRE mice with EpoR restricted to hematopoietic tissue and ΔEpoRWAT mice with targeted EpoR deletion in fat tissue were fed a high fat diet (HFD, 60% kCal fat) and treated with EPO (3000U/kg 3X per week) or saline for 3 weeks at age 3, 4, and 6 months. EPO increased hematocrit in all mice and improved glucose tolerance when fat mass was less than 35% which included all female mice. In male WT mice EPO improved glucose tolerance and reduced fat mass which at 6 months was 40% on HFD and below 35% with HFD/EPO treatment. In female mice, estrogen interferes with EPO fat mass regulation. EPO treatment did not affect fat mass in ΔEpoRE mice, indicating that EPO regulation of fat mass is a non-hematopoietic response. EPO improved glucose tolerance in female and only age 3 month male ΔEpoRE mice when fat mass was less than 35%. In male ΔEpoRWAT mice, EPO minimally reduced fat mass indicating that EPO fat mass regulation in males is largely a direct fat tissue response. EPO treatment improved glucose tolerance in male ΔEpoRWAT mice when fat mass was below 35% but not at 6 months when fat mass exceeded 40%. These data demonstrate that EPO improved glucose tolerance when fat mass was below 35%, that the sex-dimorphic EPO regulation of fat mass is primarily mediated by EpoR in fat, and that EPO activity in glucose metabolism and fat mass is differentially regulated and does not follow EPO stimulated erythropoiesis. Disclosure H. Rogers: None. C.T. Noguchi: None. Funding National Institutes of Health

1997-P: Cross Talk between EPO and Estrogen Signaling in Regulation of Fat Mass

Erythropoietin (EPO), the cytokine that regulates erythropoiesis, contributes to metabolic regulation in rodents. The increase in red blood cell production with EPO treatment in mice was accompanied by improved glycemic control, and by attenuated body weight gain via reducing fat mass in male mice. No change in body weight was observed in mice with EPO receptor restricted to erythroid tissue, suggesting that EPO regulation of body weight is a non-erythroid response. EPO stimulated decrease in fat mass was observed in ovariectomized female mice on high fat diet, but not after estradiol supplementation or in ovariectomized female mice on normal chow, providing evidence for estrogen related gender specific EPO action in metabolic regulation beyond erythropoiesis. Here we determine the contribution of estrogen response in EPO metabolic regulation by assessing EPO treatment in estrogen receptor α knockout (ERαKO) mice. Male and female ERαKO mice exhibit decreased glucose tolerance, increased fat mass and, in female ERαKO mice, increased lean mass compared with WT control mice. Overall, EPO stimulated increase in hematocrit in male and female ERαKO mice on high fat diet was accompanied by improvement in glucose tolerance comparable to that observed in WT control mice treated with EPO. EPO treatment in male ERαKO and WT mice show significantly reduced the increase in fat mass while on high fat diet compared with saline treatment. Similarly, EPO treatment in female ERαKO mice on high fat diet show reduced fat mass gain compared to saline treatment. In contrast, EPO treatment did not affect fat mass in female WT mice on high fat diet. We also observed that on normal chow diet, EPO treatment was able to reduce fat mass in female ERαKO mice, but not in female WT mice, confirming the role of estrogen in mediating the sex-differential effect of EPO in regulating fat mass. These results are evidence of cross talk between EPO and estrogen for metabolic homeostasis and regulation of body mass in female mice. Disclosure J. Lee: None. H. Rogers: None. C.T. Noguchi: None.

The Metabolic Effect of Chronic Elevated Erythropoietin in Tg6 Mice

Erythropoietin (EPO) is the cytokine required for erythrocyte production. However, EPO receptor (EpoR) expression is not restricted to erythroid tissue and non-hematopoietic EPO action has been associated with the regulation of glucose homeostasis and fat mass accumulation in animal models. The hemizygous transgenic tg6 mouse (PDGF- promoter/human EPO cDNA) overexpresses EPO, allowing for the study of chronic elevated levels of EPO. Tg6 mice exhibit a hematocrit of 80-90%, almost twice that of their wild type (wt) littermates. The elevated EPO also alters their glucose metabolism. In both males and females, tg6 mice exhibit significantly lower fasting glucose and improved glucose tolerance with significantly reduced blood glucose levels during a 2-hour glucose tolerance test (GTT). EPO treatment in male wt mice reduces fat mass and body weight compared to saline treatment. Similarly, tg6 mice with chronic elevated EPO have been reported to exhibit reduced body mass compared with control mice. We find that male tg6 mice tend to have reduced body weight, becoming significant with age and due to an associated decrease in fat mass, and a trend toward reduced food intake. In contrast, while female tg6 mice show significant decreases in fat mass, their total body weight is similar to control mice due in part to an increase in lean body mass. These data suggest that metabolically, tg6 mice show improved glucose metabolism compared to control mice associated with a decrease fat store in both male and female mice, and with a sex-specific reduction in body weight in male mice. In addition, the increase in lean body mass in female mice counters the weight loss associated with decrease fat mass resulting in no apparent change in body weight. Disclosure H. Rogers: None. O. Gavrilova: None. C.T. Noguchi: None.

Using the Zebrafish as an Approach to Examine the Mechanisms of Vertebrate Erythropoiesis.

The zebrafish, Danio rerio, is a powerful model for the study of erythropoiesis and defining the genetic basis of hematological diseases. The mechanisms of erythroid differentiation are highly conserved in the zebrafish, permitting translational research studies and the modeling of erythropoiesis in higher vertebrates. An advantage of the system is the ability to manipulate gene expression and observe the effect on erythroid development in vivo, with relative ease and rapidity. The production of optically transparent embryos also makes it an attractive tool for visual analysis of circulating erythrocytes that can be used to study erythropoiesis. Through large-scale chemical mutagenesis screens, a variety of zebrafish blood mutants have been identified that are used for gene discoveries and the recapitulation of human diseases. Experimental techniques including in situ hybridization, o-dianisidine staining, flow cytometry, and microinjection are now commonly employed to study red blood cell biochemistry and erythropoiesis in the zebrafish. These techniques have been applied for identifying novel genes required for the hemoglobin synthesis, isolating blood cell lineages, visualizing genetic expression within erythroid tissues, and characterizing the phenotype of blood disorders. The applications of zebrafish methodology to the study of erythropoiesis and optimized step-by-step protocols are discussed in this chapter.

Whole transcriptome analysis of human erythropoietic cells during ontogenesis suggests a role of VEGFA gene as modulator of fetal hemoglobin and pharmacogenomic biomarker of treatment response to hydroxyurea in \u03b2-type hemoglobinopathy patients

BackgroundHuman erythropoiesis is characterized by distinct gene expression profiles at various developmental stages. Previous studies suggest that fetal-to-adult hemoglobin switch is regulated by a complex mechanism, in which many key players still remain unknown. Here, we report our findings from whole transcriptome analysis of erythroid cells, isolated from erythroid tissues at various developmental stages in an effort to identify distinct molecular signatures of each erythroid tissue.ResultsFrom our in-depth data analysis, pathway analysis, and text mining, we opted to focus on the VEGFA gene, given its gene expression characteristics. Selected VEGFA genomic variants, identified through linkage disequilibrium analysis, were explored further for their association with elevated fetal hemoglobin levels in β-type hemoglobinopathy patients. Our downstream analysis of non-transfusion-dependent β-thalassemia patients, β-thalassemia major patients, compound heterozygous sickle cell disease/β-thalassemia patients receiving hydroxyurea as fetal hemoglobin augmentation treatment, and non-thalassemic individuals indicated that VEGFA genomic variants were associated with disease severity in β-thalassemia patients and hydroxyurea treatment efficacy in SCD/β-thalassemia compound heterozygous patients.ConclusionsOur findings suggest that VEGFA may act as a modifier gene of human globin gene expression and, at the same time, serve as a genomic biomarker in β-type hemoglobinopathy disease severity and hydroxyurea treatment efficacy.

IGF2BP1 overexpression causes fetal-like hemoglobin expression patterns in cultured human adult erythroblasts

Here we investigated in primary human erythroid tissues a downstream element of the heterochronic let-7 miRNA pathway, the insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1), for its potential to affect the hemoglobin profiles in human erythroblasts. Comparison of adult bone marrow to fetal liver lysates demonstrated developmental silencing in IGF2BP1. Erythroid-specific overexpression of IGF2BP1 caused a nearly complete and pancellular reversal of the adult pattern of hemoglobin expression toward a more fetal-like phenotype. The reprogramming of hemoglobin expression was achieved at the transcriptional level by increased gamma-globin combined with decreased beta-globin transcripts resulting in gamma-globin rising to 90% of total beta-like mRNA. Delta-globin mRNA was reduced to barely detectable levels. Alpha-globin levels were not significantly changed. Fetal hemoglobin achieved levels of 68.6 ± 3.9% in the IGF2BP1 overexpression samples compared with 5.0 ± 1.8% in donor matched transduction controls. In part, these changes were mediated by reduced protein expression of the transcription factor BCL11A. mRNA stability and polysome studies suggest IGF2BP1 mediates posttranscriptional loss of BCL11A. These results suggest a mechanism for chronoregulation of fetal and adult hemoglobin expression in humans.

Erythropoietin and Hypothalamic-Pituitary Axis.

Erythropoietin (EPO), known primarily for its erythropoietic activity, is commonly used clinically to treat anemia of chronic kidney disease. However, the expression of EPO receptor (EpoR) beyond erythroid tissue provides for potential extrahematopoietic effects of EPO, including EPO regulation of metabolic homeostasis (Zhang et al., 2014). Small clinical studies have shown that EPO treatment in patients with end-stage renal disease improved glycemic control and insulin sensitivity. Studies in animal models have shown that EPO regulation of metabolism is mainly attributed to its response in fat, and the hypothalamus-pituitary axis (Dey et al., 2016; Dey, Scullen, & Noguchi, 2015; Teng, Gavrilova, et al., 2011; Wang et al., 2013) and is not dependent on its hematopoietic activity. EpoR expression in the hypothalamus is localized to the neurons expressing proopiomelanocortin (POMC) in the arcuate nucleus region, the most important site in the brain for the regulation of physiological energy expenditure. EPO treatment increases POMC production in anorexigenic POMC neurons in the hypothalamus. In the pituitary, EPO modulates the secretion of the POMC-derived peptide, adrenocorticotropic hormone (ACTH) that regulates physiological and metabolic stress response. With EPO produced by cells in the brain, such as astrocytes, and with EPO-stimulated POMC expression in the hypothalamus and EPO-inhibited ACTH secretion in the pituitary, EPO signaling contributes to the hypothalamic-pituitary axis as a major regulator of glucose metabolism and energy homeostasis.

Metabolic Burden of Erythropoietin Stimulated Erythropoiesis in Mice

Erythropoietin (EPO) promotes erythroid differentiation and increases glucose uptake in erythroid progenitor cells in culture. The metabolic burden associated with EPO treatment in adult mice is suggested by a decrease in body weight concomitant with increased hematocrit. Wild type male mice (C57Bl/6, age 8 months) treated with EPO showed the expected increase in hematocrit accompanied by a fall in blood glucose level and a decrease in body weight and fat mass. However, the decrease in body weight is even more evident in obese mice on a high fat diet and has also been linked to non-hematopoietic response, particularly with EPO receptor (EpoR) expression in white adipose tissue. We examined the metabolic burden of EPO treatment (3000U/kg for 3 weeks) in young, lean male mice (3 months) placed on high fat diet at the time of EPO administration. The increase in hematocrit was accompanied by decreased blood glucose level and improved glucose tolerance. However, no difference in body weight was observed between mice treated with EPO and the saline treated group, suggesting that the EPO stimulated decrease in body weight is evident primarily in older animals with greater fat mass. To determine the contribution of EpoR expression in non-hematopoietic tissue to the metabolic EPO response, young male mice with EpoR restricted to erythroid tissue (TgEpoR) were placed on high fat diet and treated with EPO. The expected increased hematocrit was also accompanied by decreased blood glucose level and improved glucose tolerance, and no change in body weight between EPO and saline treatment. The similar responses observed in young wild type and TgEpoR mice suggest that the EPO stimulated increase in glucose metabolism is associated with increased erythropoiesis rather than a direct EPO response in non-hematopoietic tissue. TgEpoR mice exhibit an age dependent increase in fat mass even greater than that observed in wild type mice, and by 8 months TgEpoR mice are obese, glucose intolerant and insulin resistant compared with wild type mice. At 8 months, TgEpoR mice treated with EPO show the increase in hematocrit and, despite the increase in fat mass, there is only a minimal decrease in body weight compared with wild type mice. These data provide evidence that in addition to the age dependent association of EPO stimulated decrease in body weight and fat mass, this decrease in body weight is due largely to EPO response related to EpoR expression in non-hematopoietic tissue. Interestingly, young male mice with targeted deletion of EpoR in adipose tissue placed on a high fat diet and treated with EPO show the increase in hematocrit and improvement in glucose tolerance, and at 8 months, the increase in hematocrit with EPO treatment is accompanied by minimal change in body weight. The similar metabolic response of these mice with targeted deletion of EpoR in adipose tissue to TgEpoR mice indicate the contribution of EpoR expression in adipose tissue to the loss of body weight and fat mass. Therefore, the metabolic burden associated with EPO stimulated erythropoiesis appears to be reflected in improved glucose metabolism and glucose tolerance with minimal or no effect on body weight, is evident in young, lean mice, and is independent of EpoR expression in non-hematopoietic tissue. In older mice, non-hematopoietic metabolic EPO response is more readily apparent as reflected in loss of body weight/fat mass, which overshadows the erythropoietic metabolic response. In combination, the metabolic response to EPO treatment results from EPO stimulated increased erythropoiesis, improved glucose metabolism and glucose tolerance, and an age dependent decrease in body weight and fat mass associated with EpoR expression in non-hematopoietic tissue, particularly in white adipose tissue. Disclosures No relevant conflicts of interest to declare.

IGF2BP3 Moderately Increases Fetal Hemoglobin Levels in Human Adult Erythroblasts

Recent studies demonstrated that IGF2BP1 over-expression (IGF2BP1-OE) in adult erythroblasts has robust effects on fetal hemoglobin (HbF; >65% of the total globin levels), accompanied by reversal of the beta-like globin expression patterns to a fetal-like phenotype. Here we investigated if another member of the insulin-like growth factor 2 mRNA-binding protein family, IGF2BP3, also has potential for HbF regulation that may be useful for therapeutic application among patients with beta-hemoglobin disorders.The developmental pattern and expression levels for IGF2BP3 were initially determined in cord blood versus adult blood CD34(+) samples cultivated ex vivo in erythropoietin-supplemented serum-free media for 21 days. RNA samples were collected at culture day 14 and expression levels were measured by qRT-PCR. IGF2BP3 showed a developmentally regulated expression pattern similar to IGF2BP1 (IGF2BP1: cord blood: 1.3.E+03 ± 4.3.E+02 and adult blood: below detection limits; IGF2BP3: cord blood: 5.8.E+02 ± 2.4.E+02 and adult blood: below detection limits). These results were confirmed in vivo by comparing human fetal liver to adult bone marrow samples (IGF2BP1: fetal liver: 3.5.E+02 ± 5.7.E+01, adult bone marrow: below detection limits and IGF2BP3: fetal liver: 2.0.E+01 ± 2.7.E+00, adult bone marrow: below detection limits). To investigate the effects of IGF2BP3 upon erythropoiesis and globin expression, a lentiviral construct was designed for expression of IGF2BP3 driven by the erythroid-specific gene promoter region of the human SPTA1 gene (IGF2BP3-OE), with a matched empty vector control. Transductions were performed in CD34(+) cells from four adult healthy volunteers cultivated ex vivo in erythropoietin-supplemented serum-free media for 21 days. Over-expression of IGF2BP3 was confirmedby qRT-PCR and Western blot analyses at culture day 14. IGF2BP3-OE cells maintained their ability to differentiate and enucleate ex vivo compared to donor-matched controls. The expression levels of globin genes were evaluated at culture day 14 by qRT-PCR and showed that IGF2BP3-OE caused significantly increased gamma-globin expression levels compared to control transductions (control: 7.7.E+05 ± 1.7.E+05; IGF2BP3-OE: 8.4.E+06 ± 3.2.E+06; p=0.018). Consistent with increased gamma-globin, HbF rose to moderately high levels upon IGF2BP3-OE (control: 4.0 ± 2.1%; IGF2BP3-OE: 18.6 ± 1.0%; p=0.0021). In addition, the expression pattern of the erythroid transcription factor BCL11A was investigated by qRT-PCR at culture day 14 and no significant changes were observed (control: 5.6.E+02 ± 2.7.E+02; IGF2BP3-OE: 6.7.E+02 ± 3.5.E+02; p=0.694). However, minor decreases in BCL11A protein levels were detected by Western analysis.These results demonstrate that IGF2BP3 is developmentally regulated in human erythroid tissues with silencing during the fetal-to-adult transition. However, the effects of IGF2BP3-OE on HbF levels were less robust when compared to IGF2BP1-OE in cultured adult erythroblasts. DisclosuresNo relevant conflicts of interest to declare.

Stable Blood Group Chimerism in Recipients of ABO Incompatible Allogeneic Stem Cell Transplantation

Background: The ability to express the ABH antigens in oral mucosa and saliva is present in about 80% of the general population (hence called secretors) and is regulated by the Sec gene on chromosome 19q13.3, which encodes for the enzyme fut2 (α(1,2)Fucosyltransferase), resulting in the expression of blood types in body fluids, including saliva. The gene encoding for the ABH antigens that determines ABO blood type, is located on chromosome 9q34, and transcribes to the enzyme fut1. While fut1 is mainly expressed in erythroid tissue, fut2is expressed in secretory cells. The aim of the present study was to evaluate the ABO type in saliva and red blood cells of patients undergoing allogeneic SCT from ABO mismatched donorsMethods: Secretion status and ABO type in saliva and blood were analyzed in patients with different hematological malignancies undergoing alloSCT from ABO incompatible donors and from healthy donors serving as controls. All study participants signed informed consent. For the determination of ABO type in saliva, following mouth rinse, 5 cc of saliva were collected from each participant into fresh tube and immediately frozen at -800C. Saliva ABH antigens were extracted and enzymes were inactivated. Secretor status and ABO type in patients’ saliva were determined by inhibition test. Agglutination of diluted A, B or O typed donor red cells was tested macroscopically in the presence or absent of the extracted ABH antigens pre-incubated with anti-A, anti-B or anti-H, respectively. ABO blood type was routinely determined in patients at least every 2 weeks and time to ABO type conversion was recorded as along with all transplant-related clinical dataResults: The study cohort included 30 patients (16 males and 14 females; median age 54.2, 18.8-68.5), who underwent alloSCT between Dec 2009 and Feb 2014 from an ABO incompatible donor and were available for routine follow-up. Median follow-up time from transplant to last ABO determination in saliva was 613 days (153-2789).Donors were matched related in 11, matched unrelated in 16 and mismatched unrelated in 3 cases. All grafts were from mobilized peripheral blood. Transplant from major, minor and bidirectional ABO incompatible donors was present in 9, 16 and 5 recipients, respectively. All patients engrafted. Chimerism analysis at day 30 and 100 post transplant by PCR for STR was 100% in 24/25 and 23/25 of tested patients, respectively. Median days to ABO type conversion were 64 (21-290). Of 30 patients, 26 were found to be secretors (87%).In the secretor group, 29/30(96.6%) retained original blood group in the saliva, while one patient originally typed as AB and transplanted from an A type donor, did not retain his original AB blood type in the saliva. It is not clear whether the lack of B-antigen is attributed to the acute mucosal GvHD or to a true conversion of the ABH antigen expression in the salivaConclusion: To the best of our knowledge, this is the first report of stable chimerism of the ABO blood groups post ABO-incompatible allogeneic transplantation, such that the majority of recipients (96.6%) retained the recipient ABO group in the saliva, while expressing the donor ABO group in the blood. The significance of these findings and correlation with long-term outcome need to be further studied in larger patient cohort DisclosuresNo relevant conflicts of interest to declare.

Alternative splicing of EKLF/KLF1 in murine primary erythroid tissues

Alternative splicing has emerged as a vital way to expand the functional repertoire of a set number of mammalian genes. For example, such changes can dramatically alter the function and cellular localization of transcription factors. With this in mind, we addressed whether EKLF/KLF1 mRNA, coding for a transcription factor that plays a critical role in erythropoietic gene regulation, is alternatively spliced. We find that EKLF mRNA undergoes exon skipping only in primary tissues and that this splice variant (SV) remains at a very low level in both embryonic and adult erythroid cells, as well as during terminal differentiation. The resultant protein is truncated and partially encodes a non-erythroid Krüppel-like factor amino acid sequence. Its overexpression can alter full-length erythroid Krüppel-like factor function at selected promoters. We discuss these results in the context of stress and with respect to recent global studies on the role of alternative splicing during terminal erythroid differentiation.

Study of Excretory Organ (Kidney) in Post Flexion to Fingerling Stages of Schizothorax plagiostomus (Heckel)

The present study describes the development of excretory organ (kidney) in post flexion to fingerling stages of the Himalayan snowtrout Schizothorax plagiostomus (Heckel). In observation Schizothorax plagiostomus larvae having a pair of elongated kidney lies above the alimentary canal close to the vertebral column, which is divided into two parts i.e. head kidney and the trunk kidney. In post-flexion to fingerling larvae, the pronephric nephrons and tubules form immediately after the pronephric duct, which connect with the anterior most tips of pronephric duct. Pronephric tubules were convoluted in anterior side and there is a small amount of erythroid and lymphoid tissue associated with this region. At the same time caudal portion of the pronephric duct (near cloaca) starts to become broad in comparison to other parts in 2.0-4.0 cm larvae. On fingerling stage obvious tubules were found in kidney with large blast like cells (Columnar epithelial cells) between the nephric tubules.