Microcytosis in ank/ank mice and the role of ANKH in promoting erythroid differentiation

• Published in: Experimental cell research Vol. 313; no. 20; pp. 4120 - 4129
• Main Authors: Wang, John, Wang, Chen, Tsui, Hing Wo, Las Heras, Facundo, Cheng, Emily Y., Iscove, Norman N., Chiu, Basil, Inman, Robert D., Pritzker, Kenneth P.H., Tsui, Florence W.L.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 10.12.2007; Elsevier BV
• Subjects: Animals; Ank mice; Autocrine Communication; Autocrine Epo–EpoR signaling; Cell Differentiation; Cellular biology; Down-Regulation; Early erythroid differentiation; Endocytosis; Erythrocytes - cytology; Erythrocytes - metabolism; Erythroid Cells - cytology; Erythroid Precursor Cells - cytology; Erythroid Precursor Cells - metabolism; Erythropoietin - blood; Gene Expression Regulation; Genetics; Humans; Insulin-Like Growth Factor I - metabolism; K562 Cells; K562 transfectants; Membrane Proteins - metabolism; Mice; Mice, Mutant Strains; Microcytosis; Mutation; Phosphate Transport Proteins - genetics; Phosphate Transport Proteins - metabolism; Protein Tyrosine Phosphatase, Non-Receptor Type 6 - genetics; Protein Tyrosine Phosphatase, Non-Receptor Type 6 - metabolism; Receptors, Erythropoietin - metabolism; Rodents; Serum erythropoietin; Signal transduction; Transfection; Microcytosis; Serum erythropoietin; Early erythroid differentiation; Autocrine Epo–EpoR signaling; Ank mice; K562 transfectants
• ISSN: 0014-4827; 1090-2422
• DOI: 10.1016/j.yexcr.2007.09.008

Progressive ankylosis (Ank and the human homolog, ANKH) is a transmembrane protein which regulates transport of inorganic pyrophosphate (PPi). ank/ank mice with a mutated ank gene, have calcification and bone ankylosis of the affected joints. In the course of studying these mutant mice, we found that they have microcytosis. These mutant mice have lower mean red blood cell volume (MCV) and lower hemoglobin content in red cells (mean corpuscular hemoglobin, MCH) than normal mice. Using quantitative real-time PCR analysis, we showed that Ank was expressed in the E/Meg bipotent precursor, BFU-E, CFU-E, but there was no Ank expression in the hemoglobinizing erythroblasts. Stable ANKH transfectants in K562 cells highly expressed two immature erythroid cell markers, E-cadherin and endoglin. Enhanced Erythropoietin (Epo) expression and downregulation of SHP-1 were detected in these transfectants. Consequently, the autocrine Epo–EpoR signaling pathway was activated, as evidenced by higher p-Tyr JAK2, p-Tyr EpoR and p-Tyr STAT5B in the ANKH transfectants. Our results revealed a novel function of ANKH in the promotion of early erythroid differentiation in K562 cells. We also showed that ank/ank mice have lower serum levels of Epo than the normal littermates, and this is the likely cause of microcytosis in these mutant mice.