Don't you mean "Sonic The Hedgehog"? The blue critter on Sega?

No. If you were hoping for a node about that particular blue hedgehog that functioned as Sega's mascot/ flagship/icon in the very early 1990's, you will be disappointed. If you were of a certain age to remember him, good for you. I, however, was not of that era, and when I became a man, I put away such childish things. If only that were actually true.

The sonic hedgehog I am talking about is of a different nature. Not blue, without character, but fundamentally important to life as we know it.

Sonic hedgehog (SHH) is a protein that plays an integral part in vertebrate neural tube differentiation. The gene was first identified using homology cloning. Researchers identified similarities between the Sonic hedgehog gene, Shh, and its Drosophila counterpart hedgehog (hh). They had already worked out that hedgehog is involved in cell-cell signalling during segmentation and limb development in flies.

Sonic hedgehog is the protein responsible for the induction of floor plate cells and motor neurons in vertebrate neural tubes. It is one of three homologues found in vertebrates, the hedgehog family. The hedgehog family of proteins consists of sonic hedgehog (shh), desert hedgehog (dhh), and Indian hedgehog (ihh). Since Shh is the most commonly found of the three proteins, most of the hedgehog research has been focused on it.

The protein has a number of functions throughout the vertebrate life cycle in which it is expressed, however embryonic development is the most important. Shh is made in the notochord of developing embryos, which influences the formation and differentiation of the neural tube by acting as a signal protein. The notochord secretes a number of proteins including shh. Shh is very important, as different types of cells are created in the neural tube by different concentrations of shh, in developing embryos, anyway. Shh also forms a gradient as it is secreted from the notochord. Remember all this, class, it is necessary for comprehenshion.

Shh is secreted from notochord cells via cholesterol-mediated cleavage. The notochord cells produce a precursor, which udergoes cleavage before leaving the cell. A cholesterol molecule is attached to the carboxyl end of the protein. After secretion, they induce the formation of the neural tube floor plate from medial hinge cells.

Shh is also capable of regulating transcription. It binds with a trancription repressing protein in cell membranes. This allows other proteins to enter the cells and activate transcription

There is also evidence that shh is actively involved in:- optical development, cerebral development, something important sounding called left-right axis patterning pathways, the growth of cutaneous appendages (hair, feathers or scales), the specification of the mesoderm in gut formation, limb development, and motor neuron development

Its repression is also involved in pancreatic development.

On a trivial note, I bet you're wondering how the protein got its name. Of couse you are, you can't help yourself, can you? Well, blame the mutants. You should always blame the mutants. They're responsible for everything, including many of the important contributions to modern biology in recent decades.

Well, a mutant form of the protein was found. It made embryos look like, well, a hedgehog. Presumably, the researchers were of an age where they remembered old Sonic, and said "Gee, doesn't that look like... Sonic the Hedgehog!"

WEEELLLL! It makes a good story anyway.

More facts about Shh

According to the single letter amino acid code, the protein is "LLLTAAHLLFVAPHNDSATGEPEASSGSGPPSGGALGPR"

This is only 8.4% of the original protein precursor, which looks like this: -

"MLLLARCLLL VLVSSLLVCS GLACGPGRGF GKRRHPKKLT PLAYKQFIPN VAEKTLGASG RYEGKISRNS ERFKELTPNY NPDIIFKDEE NTGADRLMTQ RCKDKLNALA ISVMNQWPGV KLRVTEGWDE DGHHSEESLH YEGRAVDITT SDRDRSKYGM LARLAVEAGF DWVYYESKAH IHCSVKAENS VAAKSGGCFP GSATVHLEQG GTKLVKDLSP GDRVLAADDQ GRLLYSDFLT FLDRDDGAKK VFYVIETREP RERLLLTAAH LLFVAPHNDS ATGEPEASSG SGPPSGGALG PRALFASRVR PGQRVYVVAE RDGDRRLLPA AVHSVTLSEE AAGAYAPLTA QGTILINRVL ASCYAVIEEH SWAHRAFAPF RLAHALLAAL APARTDRGGD SGGGDRGGGG GRVALTAPGA ADAPGAGATA GIHWYSQLLY QIGTWLLDSE ALHPLGMAVK SS"

Makes you want to hide in a hole just looking at it, doesn't it?

Additional information from PeptideAtlas