A novel erythroid anion exchange variant (Gly796Arg) of hereditary stomatocytosis associated with dyserythropoiesis.
BACKGROUND
Stomatocytoses are a group of inherited autosomal dominant hemolytic anemias and include overhydrated hereditary stomatocytosis, dehydrated hereditary stomatocytosis, hereditary cryohydrocytosis and familial pseudohyperkalemia.


METHODS
We report a novel variant of hereditary stomatocytosis due to a de novo band 3 mutation (p. G796R-band3 CEINGE) associated with a dyserythropoietic phenotype. Band 3 genomic analysis, measurement at of hematologic parameters and red cell indices and morphological analysis of bone marrow were carried out. We then evaluated the red cell membrane permeability and ion transport systems by functional studies of the patient's erythrocytes and Xenopus oocytes transfected with mutated band 3. We analyzed the red cell membrane tyrosine phosphorylation profile and the membrane association of the tyrosine kinases Syk and Lyn from the Src-family-kinase group, since the activity of the membrane cation transport pathways is related to cyclic phosphorylation-dephosphorylation events.


RESULTS
The patient showed mild hemolytic anemia with circulating stomatocytes together with signs of dyserythropoiesis. Her red cells displayed increased Na(+) content with decreased K(+)content and abnormal membrane cation transport activities. Functional characterization of band 3 CEINGE in Xenopus oocytes showed that the mutated band 3 is converted from being an anion exchanger (Cl(-), HCO(3)(-)) to being a cation pathway for Na(+) and K(+). Increased tyrosine phosphorylation of some red cell membrane proteins was observed in diseased erythrocytes. Syk and Lyn membrane association was increased in the patient's red cells compared to in normal controls, indicating perturbation of phospho-signaling pathways involved in cell volume regulation events.


CONCLUSIONS
Band 3 CEINGE alters function from that of anion exchange to cation transport, affects the membrane tyrosine phosphorylation profile, in particular of band 3 and stomatin, and its presence during red cell development likely contributes to dyserythropiesis.
Iolascon
Achille
A
Department of Biochemistry and Medical Biotechnologies, University Federico II, Naples, Italy. iolascon@ceinge.unina.it
De Falco
Luigia
L
Borgese
Franck
F
Esposito
Maria Rosaria
MR
Avvisati
Rosa Anna
RA
Izzo
Pietro
P
Piscopo
Carmelo
C
Guizouarn
Helene
H
Biondani
Andrea
A
Pantaleo
Antonella
A
De Franceschi
Lucia
L
D000328:Adult; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000742:Anemia, Dyserythropoietic, Congenital / Q000150:complications*; D000745:Anemia, Hemolytic, Congenital / Q000150:complications / Q000235:genetics* / Q000503:physiopathology; D000818:Animals; D001457:Anion Exchange Protein 1, Erythrocyte / Q000235:genetics* / Q000502:physiology; D015153:Blotting, Western; D004912:Erythrocytes / Q000378:metabolism; D005192:Family Health; D005260:Female; D006801:Humans; D017136:Ion Transport; D008297:Male; D008565:Membrane Proteins / Q000032:analysis / Q000378:metabolism; D009154:Mutation; D009865:Oocytes / Q000378:metabolism; D010375:Pedigree; D014981:Xenopus
D001457:Anion Exchange Protein 1, Erythrocyte; D008565:Membrane Proteins