Autonomous control of terminal erythropoiesis via physical interactions among erythroid cells

AbstractIn vitro erythropoiesis has been studied extensively for its application in the manufacture of transfusable erythrocytes. Unfortunately, culture conditions have not been as effective as in vivo growth conditions, where bone marrow macrophages are known to be a key regulator of erythropoiesis. This study focused on the fact that some erythroblasts are detached from macrophages and only contact other erythroblasts. We hypothesized that additional factors regulate erythroblasts, likely through either physical contact or secreted factors. To further elucidate these critical factors, human erythroblasts derived from cord blood were cultured at high density to mimic marrow conditions. This growth condition resulted in a significantly increased erythroid enucleation rate and viability. We found several novel contact-related signals in erythroblasts: intercellular adhesion molecule-4 (ICAM-4) and deleted in liver cancer-1 (DLC-1). DLC-1, a Rho-GTPase-activating protein, has not previously been reported in erythroid cells, but its interaction with ICAM-4 was demonstrated here. We further confirmed the presence of a secreted form of human ICAM-4 for the first time. When soluble ICAM-4 was added to media, cell viability and enucleation increased with decreased nuclear dysplasia, suggesting that ICAM-4 is a key factor in contact between cells. These results highlight potential new mechanisms for autonomous control of erythropoiesis. The application of these procedures to erythrocyte manufacturing could enhance in vitro erythrocyte production for clinical use

Eosinophilic gastroenteritis in an 18-year-old male with prolonged nephrotic syndrome

Eosinophilic gastroenteritis is a rare disease characterized by prominent eosinophilic tissue infiltration of the gastrointestinal tract. Here, we report a case of eosinophilic gastroenteritis in an 18-year-old patient with prolonged nephrotic syndrome who presented with abdominal pain and peripheral hypereosinophilia. During the previous 2 years, he had visited local Emergency Department several times because of epigastric pain and nausea. He had been treated with steroid-dependent nephrotic syndrome since 3 years of age. Tests ruled out allergic and parasitic disease etiologies. Gastroduodenoscopy with biopsy revealed marked eosinophilic infiltration in the duodenum. Renal biopsy findings indicated minimal change disease spectrum without eosinophilic infiltration. The oral deflazacort dosage was increased, and the patient was discharged after abdominal pain resolved. To our knowledge, this is the first report of eosinophilic gastroenteritis in a patient with minimal change disease

RBFOX3 regulates Claudin-1 expression in human lung tissue via attenuation of proteasomal degradation

RBFOX3, a nuclear RNA-binding protein, is well known as a regulator of alternative pre-mRNA splicing during neuronal development. However, other functions of RBFOX3 are poorly understood. Here, we investigated the function of RBFOX3 in the cytoplasm with respect to regulation of Claudin-1 expression. In human lung tissue, Claudin-1 is higher in RBFOX3-positive cells than in RBFOX3-negative cells. Immunostaining and mRNA quantification revealed that protein levels, but not mRNA levels, of Claudin-1 are increased by RBFOX3. In addition, cycloheximide treatment of human lung cancer cells revealed that RB-FOX3 increases the stability of Claudin-1 through attenuation of its ubiquitination. Our study provides insights into the molecular mechanisms by which RBFOX3 regulates Claudin-1 expression in human lung tissue