Microcytosis in ank/ank mice and the role of ANKH in promoting erythroid differentiation.
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.
Wang
John
J
Genetics and Development Division, Toronto Western Research Institute, Toronto, Ontario, Canada.
Wang
Chen
C
Tsui
Hing Wo
HW
Las Heras
Facundo
F
Cheng
Emily Y
EY
Iscove
Norman N
NN
Chiu
Basil
B
Inman
Robert D
RD
Pritzker
Kenneth P H
KP
Tsui
Florence W L
FW
D000818:Animals; D019898:Autocrine Communication; D002454:Cell Differentiation; D015536:Down-Regulation; D004705:Endocytosis; D004912:Erythrocytes / Q000166:cytology / Q000378:metabolism; D041905:Erythroid Cells / Q000166:cytology*; D015672:Erythroid Precursor Cells / Q000166:cytology / Q000378:metabolism; D004921:Erythropoietin / Q000097:blood; D005786:Gene Expression Regulation; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D020014:K562 Cells; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008817:Mice, Mutant Strains; D028061:Phosphate Transport Proteins / Q000235:genetics / Q000378:metabolism*; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6 / Q000235:genetics / Q000378:metabolism; D017467:Receptors, Erythropoietin / Q000378:metabolism; D014162:Transfection
C498770:ANKH protein, human; D008565:Membrane Proteins; D028061:Phosphate Transport Proteins; D017467:Receptors, Erythropoietin; C410982:ank protein, mouse; D004921:Erythropoietin; D007334:Insulin-Like Growth Factor I; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6