CHORDIN AND NOGGIN

Tavishi

Biologists are infamous for stupid names. To be fair, if you discover a gene crucial to our understanding of developmental biology, you should be allowed to give it a stupid name.

I, for one, am a huge fan of dumb names. I once named a praying mantis Galapagos Sea Lion.

Some of these stupid names include: the Sonic hedgehog gene, Lunatic fringe, scramblase (this does exactly what you think it does), and Makes Caterpillars Floppy gene (known as MCF).

It seems, however, that silly names are concentrated in the field of embryology, as I discovered when I realized that two of the antagonists for BMP4 are named chordin and noggin...

BMP stands for bone morphogenic protein, and it's a class of proteins generally used during embryonic development. There are several different types, with each protein serving its own function. But ultimately, they all serve the purpose of being a growth factor, or something that stimulates further cell proliferation.

There are two pathways by which BMPs stimulate cell stuff to happen: the canonical and noncanonical pathways. In cell biology, canonical just means the more common/well known pathway, whereas noncanonical is just the opposite.

The canonical BMP pathway involves the BMPR protein, which is a cell surface receptor protein. Essetially, BMP binds to BMPR, setting off a chain reaction of stuff inside the cell. There are two types of BMPR proteins: BMPR I and BMPR II. When the BMP binds to the receptor complex, BMPR II is activated and phosphorylates (adds a phosphate group) to BMPR I.

MPQLYIYIRLLGAYLFIISRVQGQNLDSMLHGTGMKSDSDQKKSENGVTLAPEDTLPFLKCYCSGHCPDDAINNTCITNGHCFAIIEEDDQGETTLASGCMKYEGSDFQCKDSPKAQLRRTIECCRTNLCNQYLQPTLPPVVIGPFFDGSIRWLVLLISMAVCIIAMIIFSSCFCYKHYCKSISSRRRYNRDLEQDEAFIPVGESLKDLIDQSQSSGSGSGLPLLVQRTIAKQIQMVRQVGKGRYGEVWMGKWRGEKVAVKVFFTTEEASWFRETEIYQTVLMRHENILGFIAADIKGTGSWTQLYLITDYHENGSLYDFLKCATLDTRALLKLAYSAACGLCHLHTEIYGTQGKPAIAHRDLKSKNILIKKNGSCCIADLGLAVKFNSDTNEVDVPLNTRVGTKRYMAPEVLDESLNKNHFQPYIMADIYSFGLIIWEMARRCITGGIVEEYQLPYYNMVPSDPSYEDMREVVCVKRLRPIVSNRWNSDECLRAVLKLMSECWAHNPASRLTALRIKKTLAKMVESQDVKI (otherwise known as the amino acid sequence for BMPR 1A)

BMPR is a serine-threonine kinase, meaning that it adds a phosphate group to serine or threonine amino acid residues in a protein. (Adds a little tag on a specific part of the protein allowing it to do other things in the cell). BMPR I, as part of this receptor complex, does the phosphorylating of the Smad proteins.

aside: this creature inspired the name for SMAD proteins; it's a homolog of MAD proteins, or mothers against decapentaplagic, which are proteins discovered in drosophila melanogaster!

Smad proteins set off the events within the cell itself. There are several types of Smads used in signal transduction; in this case, it's R-smad, or receptor Smad. Anyways, Smad goes on to do silly little things inside the cell, including messing with the DNA to turn off and on genes. Smad gets a little buddy, a co-Smad so that it might successfully mess with DNA. Wheeee, gene expression! Gene expression is where the real magic happens, because that's what actually controls things happening inside the cell.

For example, BMP4 signaling is so crucial to the successful formation of a child. Without a functioning BMP4, a baby can fail to form a mesoderm, which is the germ layer that forms bones among other things.

Two important roles of BMP4 is to form the dorsal-ventral axis in an embryo and the formation of the neural tube. In these cases, it's the absence of BMP4 that promotes this development, bringing us back to the title of this post.

Chordin and noggin are two inhibitors of BMP4. Chordin inhibits BMP4 from binding to BMPR, allowing for the neural cells to develop more, in turn promoting dorsalization of the infant. Noggin also inactivates BMP4, allowing for babies to, uh, get a head. More specifically, Noggin helps pattern how the neural tube forms, influencing both the fate of the peripheral and central nervous systems.

noggin

As a former baby who has a head, I am very qualified to speak about such subjects.