What Tells Tissues When and Where to Grow: The Signaling Centers SHH, BMP, FGF
Take the reading one piece at a time. For each piece: read it once, underline the sentence that says what happens, then look up any word in the list. Tap a word to see its definition.
Piece 1 of 2
A signaling molecule is a chemical message a cell releases that changes the behavior of nearby cells, and the cells that release it are a signaling center, like a small broadcast tower. In the palate the two tissue layers talk constantly, the epithelium (surface lining) and the mesenchyme (growing inner tissue), a back-and-forth called epithelial-mesenchymal cross-talk. SHH (Sonic hedgehog) is released from the oral epithelium and tells the shelf mesenchyme to proliferate; it is the central player in shelf growth. FGF10 from the mesenchyme keeps SHH switched on, so the two layers keep each other going in a loop. BMP drives growth especially in the front (anterior) of the palate and is dose-sensitive, since too little or too much both cause problems.
Piece 2 of 2
Now remove a signal and watch the shelf. Block the mesenchyme's ability to receive Hedgehog (delete the transducer Smo) and the secondary palate does not form at all (complete agenesis): no SHH signal, no growth, no shelf. Disrupt the FGF10-to-receptor conversation and the shelf grows poorly and sticks to wrong surfaces (palate to tongue, palate to jaw), giving a cleft. Lose BMP signaling and the shelf grows too little, especially in front, and may fail to elevate or fuse. The pattern: each signal is an instruction; remove it and the shelf grows too little, mis-grows, or never forms, and a shelf that grew too little cannot reach the midline to fuse.
Reading the Research
- Skim the title and abstract first to get the gist.
- Circle the one sentence that states the main claim.
- Box the evidence the authors give for that claim.
- Mark one sentence that confuses you, and move on.
Now put it together: In one or two sentences, say what this whole reading is telling you about Mateo. Then go back to the lesson and fill in the guided notes.