Bye Bye, Sonic Hedgehog

sonichedgehog.jpgI planned to make a good start for Gene Genie but my first gene related post is about a farewell. Sonic Hedgehog, one of the most famous genes, will lost his name. According to the Discover article:

An international committee of human geneticists recently voted to change the names of a few human genes because the current, sometimes flamboyant names—like Sonic hedgehog—are either offensive or embarrassing… The vote was conducted by the HUGO Gene Nomenclature Committee, which establishes naming protocols for human genes.

The gene map locus is 7q 36 . Sonic Hedgehog regulates vertebrate organogenesis, the growth of digits on limbs and organisation of the nervous system (brain, spinal cord, thalamus, zona limitans interthalamica). Additionally, fruit flies with a mutation in this gene don’t have external genitalia.

The so called hedgehog gene (hh) was first identified in 1978 as a morphogen. Sonic got his weird name after a phenomenon well described in the Wikipedia article: the hh loss of function mutant phenotype causes the embryos to be covered with denticles (small pointy projections), much like a hedgehog.

What kind of disorders is this gene responsible for?

  • Holoprosencephaly type 3: cerebral disorder characterized by the failure of the prosencephalon (forebrain) development in the embryo.
  • Ocular Colobomas: eye related malformations that result from a defect in the fusion of the fetal optic fissure
  • Preaxial Polydactyly II: anatomical variant consisting of more than the usual number of digits on the hands and/or feet.
  • Cleft Lip and/or Palate

shhmap.jpg
Click to enlarge!

1732_fs.jpg
Zebrafish embryo with a stain that shows where the hedgehog protein is acting during development.

References :

Update! One additional sentence from the Wikipedia article: many “[call] it inappropriate that patients with ‘a serious illness or disability are told that they or their child have a mutation in a gene such as Sonic hedgehog.’” (Thank you, Darmok, for the suggestion!)