The human osmoregulatory Na+/myo-inositol cotransporter gene (SLC5A3): molecular cloning and localization to chromosome 21

Genomics. 1995 Jan 20;25(2):507-13. doi: 10.1016/0888-7543(95)80052-n.


A human Na+/myo-inositol cotransporter (SLC5A3) gene was cloned; sequencing revealed a single intron-free open reading frame of 2157 nucleotides. Containing 718 amino acid residues, the predicted protein is highly homologous to the product of the canine osmoregulatory SLC5A3 gene. The SLC5A3 protein is number 3 of the solute carrier family 5 and was previously designated SMIT. Using fluorescence in situ hybridization, the human SLC5A3 gene was localized to band q22 on chromosome 21. Many tissues including brain demonstrate gene expression. The inability of a trisomic 21 cell to downregulate expression of three copies of this osmoregulatory gene could result in increased flux of both myo-inositol and Na+ across the plasma membrane. The potential consequences include perturbations in the cell membrane potential and tissue osmolyte levels. The SLC5A3 gene may play a role in the pathogenesis of Down syndrome.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Carrier Proteins / genetics*
  • Chromosome Mapping
  • Chromosomes, Human, Pair 21*
  • Cloning, Molecular
  • Dogs / genetics
  • Genes*
  • Heat-Shock Proteins / genetics*
  • Humans
  • In Situ Hybridization, Fluorescence
  • Membrane Proteins*
  • Molecular Sequence Data
  • Open Reading Frames
  • Organ Specificity
  • Symporters*


  • Carrier Proteins
  • Heat-Shock Proteins
  • Membrane Proteins
  • Symporters
  • SLC5A3 protein, human

Associated data

  • GENBANK/L38500