The Hedgehog Signaling Pathway in Vertebrates ?

The hedgehog signaling pathway is a mechanism that regulates cell growth and differentiation [4] during embryonic development, called embryogenesis [5], in animals. The hedgehog signaling pathway works both between cells and within individual cells. The hedgehog gene ( hh) was observed in fruit flies (Drosophila melanogaster [6]) in 1980, and later in vertebrates in 1993. Unlike flies, which have one hh gene, vertebrates have several hh genes [7]. The hedgehog signaling pathway controls a wide range of developmental processes in the vertebrate embryo, and researchers found that dysfunction in the hedgehog signaling pathway leads to birth defects [8] including extra digits, cyclopia [9] with one eye and no forebrain [10], and cancers in adults and juveniles.