Left/Right Determination Factor 1 (LEFTY1)

Vertebrates exhibit numerous left-right (L-R) asymmetries, such as the position of the heart and spleen on the left side. L-R polarity is determined early during development, around the presomite stage in mammals. Several genes have been shown to be expressed asymmetrically relative to the L-R axis. Meno et al. (1996, 1997) identified 2 transforming growth factor-beta-related genes, Lefty1 and Lefty2, that are expressed on the left side of developing mouse embryos.Kosaki et al. (1999) characterized 2 homologs of the murine Lefty1 and Lefty2 genes, which they designated LEFTY B and LEFTY A, respectively. Both genes encode proteins with 366 amino acids. The deduced amino acid sequences of LEFTY B and LEFTY A are more similar to each other than to mouse Lefty1 or Lefty2.