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Genomewide scans of red cell indices suggest linkage on chromosome 6q23
  1. A Iliadou1,
  2. D M Evans1,
  3. G Zhu1,
  4. D L Duffy1,
  5. I H Frazer2,
  6. G W Montgomery1,
  7. N G Martin1
  1. 1Queensland Institute of Medical Research, Brisbane, Queensland, Australia
  2. 2Centre for Immunology and Cancer Research, University of Queensland, Princess Alexandra Hospital, Brisbane, Queensland, Australia
  1. Correspondence to:
 Dr D M Evans
 The Welcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK; davide{at}


Background: The red cell indices quantify the size, number and oxygen-carrying ability of erythrocytes. Although the genetic basis of many monogenic forms of anaemia is well understood, comparatively little is known about the genes responsible for variation in the red cell indices among healthy participants.

Objective: To identify quantitative trait loci (QTLs) responsible for normal variation in the red cell indices of 391 pairs of dizygotic twins who were measured longitudinally at 12, 14 and 16 years of age.

Results: Evidence suggesting linkage of red cell indices to haemoglobin concentration (LOD  = 3.03) and haematocrit (LOD  = 2.95) on chromosome 6q23, a region previously identified as possibly harbouring a QTL for haematocrit, was found. Evidence for linkage to several other regions of the genome, including chromosome 4q32 for red cell count and 7q for mean cell volume, was also found. In contrast, there was little evidence of linkage to the chromosomal regions containing the genes for erythropoietin (7q21) and its receptor (19p13.2), nor to the regions containing the genes for the haemoglobin α (16p13.3) and β chains (11p15.5).

Conclusion: Findings provide additional evidence for a QTL affecting haemoglobin and haematocrit on chromosome 6q23. In contrast, polymorphisms in the genes coding for erythropoietin, its receptor and the haemoglobin α and β chains do not appear to contribute substantially to variation in the red cell indices between healthy persons.

  • HCT, haematocrit
  • ibd, identical-by-descent
  • LOD, logarithm of odds ratio
  • MCV, mean corpuscular volume
  • QTL, quantitative trait locus
  • RBC, red blood cell count

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  • Published Online First 1 September 2006

  • Competing interests: None declared.

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