1 Morphology, biology and biochemistry of cobalamin- and folate-deficient bone marrow cells

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Summary

B12- or folate-deficient haemopoietic cells display abnormalities in their morphology under both the light and electron microscope, their cell kinetics and their capacity to synthesize protein. These abnormalities are maximal in the last dividing cell class and in non-dividing cells, presumably because B12 and folate uptake is largely confined to the most immature erythroid and granulocyte precursors. In patients with moderate or severe anaemia due to B12 or folate deficiency, erythropoiesis is markedly ineffective; intramedullary cell death occurs mainly in the early and late polychromatic megaloblasts. The damaged erythroblasts appear to display neoantigens or normally-hidden antigens at their cell surface and these react with naturally occurring antibodies. The opsonised erythroblasts are then recognised by macrophages via their IgG-Fc receptors and phagocytosed.

Marrow cells from B12- or folate-deficient patients show a subnormal suppression of 3H-thymidine incorporation after pre-incubation with non-radioactive deoxyuridine, suggesting that such cells suffer from an impairment of the 5,10-methylene-THF-dependent methylation of deoxyuridylate to thymidylate. However, the exact mechanism by which B12 deficiency causes a reduced supply of this folate coenzyme is uncertain. Methylcobalamin is required for the 5-methyl-THF-dependent methylation of homocysteine to methionine and an impairment of this reaction will result in both reduced conversion of 5-methyl-THF to THF and in reduced methionine synthesis. There is controversy as to whether the reduced supply of THF or methionine is responsible for the reduced availability of 5,10-methylene-THF. Currently, the balance of evidence favours the hypothesis that the reduced supply of methionine leads to reduced synthesis of formyl-THF and, eventually, of 5,10-methylene-THF.

Despite the evidence for impaired thymidylate synthesis, the duration of the S phase of megaloblasts appears to be normal or only modestly increased. Data on rates of DNA strand elongation are inconsistent, with subnormal rates reported in PHA-stimulated B12- or folate-deficient lymphocytes and normal rates in B12- or folate-deficient bone marrow cells. Recent studies have shown that HL60 cells grown in B12- or folate-deficient medium and B12- or folate-deficient megaloblastic bone marrow cells misincorporate uracil in lieu of thymine into DNA. Excision of misincorporated uracil without repair and, possibly, slowing of the movement of DNA replication forks may lead to an arrest in the progress of cells through the cell cycle. Recent in vitro data suggest that some of the arrested cells may suffer apoptosis.

The biochemical basis of the characteristic stippled appearance of nuclei in B12 or folate deficiency remains speculative.

References (70)

  • MenziesRC et al.

    Cytogenetic and cytochemical studies on marrow cells in B12 and folate deficiency

    Blood

    (1966)
  • PainterRB et al.

    Rate of synthesis along replicons of different kinds of mammalian cells

    Journal of Molecular Biology

    (1969)
  • SirotnakFM et al.

    Alteration of folate analogue transport following induced maturation of HL60 leukemia cells. Early decline in mediated influx, relationship to commitment, and functional dissociation of entry and exit routes

    Journal of Biological Chemistry

    (1986)
  • WickramasingheSN et al.

    Bone marrow cells from vitamin B12- and folate-deficient patients misincorporate uracil into DNA

    Blood

    (1994)
  • WickramasingheSN et al.

    Deoxyuridine suppression: biochemical basis and diagnostic applications

    Blood Reviews

    (1988)
  • WickramasingheSN et al.

    A study of erythropoiesis by combined morphologic, quantitative cytochemical and autoradiographic methods. Normal human bone marrow, vitamin B12 deficiency and iron deficiency anemia

    Blood

    (1968)
  • YoshidaY et al.

    Proliferation of megaloblasts in pernicious anemia as observed from nucleic acid metabolism

    Blood

    (1968)
  • BeckWS

    The metabolic basis of megaloblastic erythropoiesis

    Medicine (Baltimore)

    (1964)
  • BondAN et al.

    DNA chain elongation rates in marrow cells from vitamin B12- deficient patients and methotrexate-treated mice

    British Journal of Haematology

    (1982)
  • ChanarinI et al.

    Vitamin B12 regulates folate metabolism by the supply of formate

    Lancet

    (1980)
  • ChanarinI et al.

    Cobalamin and folate: recent developments

    Journal of Clinical Pathology

    (1992)
  • CichowiczDJ et al.

    Mammalian folyl-γ-glutamate synthetase. 2. Substrate specificity and kinetic properties

    Biochemistry

    (1987)
  • DörmerP

    Kinetics of erythropoietic cell proliferation in normal and anaemic man. A new approach using quantitative 14C-autoradiography

    Progress in Histochemistry and Cytochemistry

    (1973)
  • EastmanA et al.

    The origins of DNA breaks: a consequence of DNA damage, DNA repair, or apoptosis?

    Cancer Investigation

    (1992)
  • GerschensonLE et al.

    Apoptosis: a different type of cell death

    The FASEB Journal

    (1992)
  • GillDS et al.

    Changes in the uptake of 57Co-cyanocobalamin during dimethylsulphoxide-induced differentiation of HL60 cells to neutrophils

    Clinical and Laboratory Haematology

    (1985)
  • GoodmanJR et al.

    The ultrastructure of bone marrow histiocytes in megaloblastic anaemia and the anaemia of infection

    British Journal of Haematology

    (1968)
  • GoulianM et al.

    Methotrexate-induced misincorporation of uracil into DNA

  • GreenR et al.

    The methylation status of DNA is not altered in patients with untreated megaloblastic anemia or in methotrexate-treated cultured human leukemic cells

    Blood

    (1992)
  • HerbertV et al.

    Interrelation of vitamin B12 and folic acid metabolism: folic acid clearance studies

    Journal of Clinical Investigation

    (1962)
  • HoffbrandAV et al.

    Correction of the DNA synthesis defect in vitamin B12 deficiency by tetrahydrofolate: evidence in favour of the methyl-folate trap hypothesis as the cause of megaloblastic anaemia in vitamin B12 deficiency

    British Journal of Haematology

    (1993)
  • HoffbrandAV et al.

    Thymidylate concentration in megaloblastic anaemia

    Nature

    (1974)
  • KillmannS-A

    Effect of deoxyuridine on incorporation of tritiated thymidine: difference between normoblasts and megaloblasts

    Acta Medica Scandinavica

    (1964)
  • KillmannS-A

    Cell classification and kinetic aspects of normoblastic and megaloblastic erythropoiesis

    Cell and Tissue Kinetics

    (1970)
  • KouryMJ et al.

    Apoptosis mediates and thymidine prevents erythroblast destruction in folate deficiency anemia

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