Translational efficiency in patients with Diamond-Blackfan anemia.
OBJECTIVE
Diamond-Blackfan anemia (DBA) is a rare congenital pure red cell aplasia characterized by normochromic macrocytic anemia, reticulocytopenia, and normocellular bone marrow with a selective deficiency of erythroid precursors. Ribosomal protein S19 (RPS19), currently the only gene associated with DBA, is mutated in 25% of DBA patients, but its role in erythropoiesis is unknown. We attempted to elucidate the importance of RPS19 in translation in relation to the pathogenesis of DBA.


METHODS
We measured translation and proliferation rates in unstimulated and phytohemagglutinin (PHA)-stimulated lymphocytes isolated from DBA patients, as well as in K562 cells expressing several RPS19 mutants to directly test the effect of RPS19 mutations on translation. The effect of leucine on overall translation was also studied.


RESULTS
We found that the level of translation was on average 48-73% of controls in both unstimulated and PHA-activated DBA lymphocytes irrespective of mutations in RPS19. The addition of leucine increased the translational level in RPS19-non-mutated DBA cells, but not in cells with an RPS19 mutation. In unstimulated DBA cells, proliferation was significantly impaired in both RPS19-mutated and non-mutated cells, but in both groups could be efficiently activated by PHA. Studies on K562 cells showed that RPS19 mutations affecting RPS19 conserved arginines R56Q and R62Q could significantly inhibit the rate of protein synthesis, indicating the importance of RPS19 in translation.


CONCLUSIONS
Our results indicate that inefficient translation may be the main cause of DBA, and administration of leucine may be beneficial for at least some DBA patients.
Cmejlova
Jana
J
Department of Cell Physiology, Institute of Hematology and Blood Transfusion, U Nemocnice 1, 128 20, Prague, Czech Republic. cmejla@uhkt.cz
Dolezalova
Ludmila
L
Pospisilova
Dagmar
D
Petrtylova
Kvetoslava
K
Petrak
Jiri
J
Cmejla
Radek
R
D029503:Anemia, Diamond-Blackfan / Q000097:blood* / Q000235:genetics* / Q000473:pathology; D001120:Arginine / Q000235:genetics; D001798:Blood Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D020014:K562 Cells; D008214:Lymphocytes / Q000378:metabolism / Q000473:pathology; D008297:Male; D009154:Mutation; D014176:Protein Biosynthesis; D012269:Ribosomal Proteins / Q000096:biosynthesis / Q000097:blood / Q000235:genetics
D001798:Blood Proteins; D012269:Ribosomal Proteins; C040343:ribosomal protein S19; D001120:Arginine