title: Molecular genetics of the blood group I system and the regulation of I antigen expression during erythropoiesis and granulopoiesis.
abstract: OBJECTIVE
  The molecular genetics of the blood group I system and the regulation mechanism for I antigen expression in postnatal red blood cells are intriguing. This review summarizes their elucidation and recent findings.
  
  
  RESULTS
  Accumulating data from the molecular analysis of individuals with the adult i phenotype supports the proposed molecular genetic mechanism for the partial association of the adult i phenotype with congenital cataracts. Recent investigations have shown that the regulation of I antigen formation during erythropoiesis is determined by transcription factor CCAAT/enhancer binding protein-α (C/EBPα) and the phosphorylation status of C/EBPα Ser-21 residue.
  
  
  CONCLUSIONS
  The human I locus is organized such that it has an uncommon genetic architecture and expresses three different I transcript forms. The results obtained from molecular analysis of two adult i groups, with and without congenital cataracts, demonstrate that the molecular background accounts for the partial association between these two traits and suggest that an I gene defect may lead directly to the development of congenital cataracts. Analysis of the regulation for I antigen expression shows that the regulation during erythropoiesis and granulopoiesis share a common mechanism, with dephosphorylation of the Ser-21 residue on C/EBPα playing the critical role.
authors.affiliation: Institute of Biochemical Sciences, College of Life Science, National Taiwan University, Taipei, Taiwan. yulc@ntu.edu.tw
authors.forename: Lung-Chih
authors.initials: LC
authors.lastname: Yu
authors.forename: Marie
authors.initials: M
authors.lastname: Lin
mesh_terms: D002386:Cataract / Q000151:congenital / Q000276:immunology; D004912:Erythrocytes / Q000378:metabolism; D004920:Erythropoiesis / Q000235:genetics / Q000502:physiology*; D006028:Glycosphingolipids / Q000378:metabolism*; D006801:Humans; D007048:I Blood-Group System / Q000235:genetics* / Q000276:immunology*; D019891:Leukopoiesis / Q000235:genetics / Q000502:physiology*
chemical_list: D006028:Glycosphingolipids; D007048:I Blood-Group System; C078965:I-antigen