The fastest protein, based on a fictional blue hedgehog...

What is it with geneticists and video games? In his book 'Your Inner Fish', Shubin describes the Zone of Polarising Activity, which is a tissue present in early embryos. It contains signals which instruct developing limb buds to form along an anterior (nearer the front)/posterior (nearer the back) axis, so the thumb and smallest finger are correctly differentiated. An essential gene that must be activated within the ZPA during the 8th week of embryonic development is known as the Sonic Hedgehog gene (insert Pewdiepie Sanic reference). It codes for a protein called, once again, Sonic Hedgehog, which is an essential ligand on the hedgehog signalling pathway. This pathway is vitally important for organogenesis in us vertebrates, the process by which the ectoderm, endoderm and mesoderm primary germ layers on an early embryo develop into working organs, and obviously digit formation, which is why the Sonic Hedgehog gene is needed in the ZPA. The SH protein is also required to organise the brain into its different zones, cortexes and bulbs, and is one the best known examples of a morphogen. Apart from sounding a bit like an evil gelatinous mass bend on destruction, a morphogen is a chemical that causes an organism to develop its shape. The SH protein molecules can diffuse, to create concentration gradients in different tissues of the embryo, and the concentration in the cells of these tissues has a profound effect of what SH's function is. That is why it is able to cause differentiation of the digits when active in the ZPA! And so we have come full circle, and we now know that there is yet another essential protein in our bodies, with nomenclature based on a video game character, who is in Super Smash Bros... So where's the Shulk gene then? *laughs awkwardly*