The mouse and human genomes each contain two homeo box genes, En-1 and En-2, closely related to the Drosophila segmentation gene engrailed (en). These genes, which presumably arose by gene duplication, have diverged from each other, and from Drosophila en, in both sequence and regulation. Human homeo box containing genes En-1 and En-2 located in chr.2 and chr.7 correspondingly. In mouse embryo expression of these genes was first detected at 8 day in overlapping bands of the anterior neural folds. By 12 day the genes were expressed in a similar ring of cells in the central nervous system at midbrain/hindbrain junction. En-1 was also expressed de novo in two lateral stripes extending the length of the hindbrain and spinal cord in the developing vertebral column and in the tail and limb buds. These data are consistent with En-1 and En-2 genes playing a role early in development in defining spatial domains in the CNS. Later in development the En genes may have an additional function in neurogenesis. En-1 expression in the developing perichordal tube suggests that it may also be involved in vertebrae assembly.
[Joyner AL; Martin GR En-1 and En-2, two mouse genes with sequence
homology to the Drosophila engrailed gene: expression during embryogenesis
Genes Dev 1: 29-38 (1987)]
Antisense oligonucleotide targeting of engrailed-1 (En-1) in early mouse embryos resulted in reduced En protein levels and produced abnormalities of the brain, face, and heart and shortening of the embryonic axis (caudal dysgenesis). Thus, in addition to participating in the signaling pathway for brain and limb development, En-1 appears to play a role in patterning the embryonic axis.
[Sadler TW; Liu ET; Augustine KA Antisense targeting of engrailed-1 causes abnormal axis formation in mouse embryos. Teratology 51: 292-9 (1995)]