The core question addressed is whether neurons communicate with oligodendrocyte precursor cells (OPCs) through direct contact or by releasing a diffusible chemical signal into their surroundings. Researchers tested this using a conditioned medium experiment: they expressed the RETSAT yak mutation in neurons, collected the liquid medium those neurons had been growing in, and transferred it onto separate, unexposed wild-type OPCs. Those OPCs began maturing and myelinating in response, showing that the neurons were secreting a signal into their environment rather than sending it through direct cell-to-cell contact, confirming a paracrine signaling mechanism.
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The experiment is described as establishing that the OPCs themselves were already present and not missing in the diseased state, the open question was instead what was failing to trigger them to mature.
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The transcript introduces the next step in the pathway: the RETSAT gene converts retinal (vitamin A) into a compound called ATDR (13,14-dihydroretinal) through a non-classical branch of retinoid metabolism, distinct from the classical retinal-to-retinoic-acid pathway.
1,010 words · auto-generated from the episode video
1:09:09>> is where the degradation is actually problematic. >> And it's in the source that needs the protection, which is the neuron. >> Exactly. Yeah. And so now we're honing in on this signaling, right? Perhaps it's something called paracrine signaling. It's simply like a chemical message or some kind of raw material that the neuron is producing. It's being secreted into the local neighborhood and then the the oligodendrittes are catching it and being like, "Oh, this guy needs help. I need to go get there." They did they performed, you know, cuz even now what is the mechanism of this signaling? Right. >> Is the signaling neuron to illegal dendrite straight up or is it something more general where the neuron just like
1:09:50puts out a PSA on Twitter? >> Yeah. >> And then and then those who are interested come and help him, right? Is it a DM or is it a full >> tweet or is there an intermediary? Yeah. >> That is a secret is a is it a back channel? >> Yes. Yeah. These are all the possibilities, right? And we need to we need to figure that out. So, how did they how did they figure out what which is what? >> How do we know? >> How do we know? Here's what they did. They took something called a conditioned medium, which is a liquid bath that surrounds the cultured cells. So here's what you do. You express the mutation, the red start mutation, the yak mutation in the neurons. Presumably, the neurons are going to secrete something and then that's going to go to the oligodendritty. How do we know that it's
1:10:31not a DM and just a just a uh something that I'm secretreting into the environment? That's sweet. >> Right. What I can do is I can take the medium. the cells have like some you know the the medium that they grow in and if the neurons are really just secretreting into the environment and it's not a direct signal then I can extract that medium and I can now put it into another >> wild type control >> and it would >> and the the precursors should see this signal >> this signal and start mileating >> because if it was a tweet to everybody it would be >> it would be in the environment >> in the in the Yes. It would be >> and that's exactly what we see. >> Oh my goodness.
1:11:11>> It's it's a nice like it's a nice progressive kind of ah we're getting somewhere >> right. The story is very cool. Um from one figure to the next. And so here on the on the bottom we're seeing the the medium >> and you're seeing a lot more green dots. >> Mhm. >> Yep. >> And that's from and that's from this this um these neurons. So this is so interesting. So we've now identified that the the challenge with uh the the degradation of myelin uh which we initially thought might have been because it wasn't going from baby OPC to these illegalodendrites that were the thing that created and fixed
1:11:53>> myin sheath as things happen. >> Yeah. >> So we thought maybe there's something in the maturity process of that that's problematic. It ended up not being true. We looked at this evolutionary, you know, reference point from high altitude Tibetan animals. We found something that works for hypoxia that seemed like it was connected. We established that uh with the rest, >> it definitely was connected somehow. >> It definitely is connected somehow, but we didn't quite know how. And back to where we started at the beginning, it wasn't clear that the problem was that cuz the OPC's were present in MS patients. And so it wasn't that they weren't there anymore. >> It seemed to be that the the trigger to
1:12:34do the job >> Yeah. >> was breaking down. >> Exactly. >> But we didn't know where the trigger was being triggered from. >> Yes. >> Who's the captain that's giving orders? >> Yes. >> Through this process that the team in this team in Shanghai did, we've now found that the neuron is the captain. >> Exactly. that is triggering the instruction for the OPC's to get the proper instruction to mature to then go to the process to recreate the myelin sheath >> and it's sending those instructions not in a discrete way like a DM it's just literally blasting the signal out >> yeah it's like I need help >> and so what makes sense is uh there's a what the neuron is the source of the
1:13:15problem and it's not tweeting and it's private messaging itself or just it's it set its account on private and no one can see its tweets as a crude annoying analogy >> and that's that that's the the the functional. So now and we know because when we when we took the tweet from one environment and put it around things that were not exposed to the tweet initially it started to do the >> started to do the thing. >> So we know that that's true. >> We know that that's true. And now we just need to hone in on what the tweet is. >> What is the tweet? >> What is the compound that is doing this? Because if we could make this compound, >> right? >> Right. >> Then maybe we could maybe we could solve this problem >> very Yes. Okay. >> So now we've established that there is
1:13:56something in that medium in that cultured medium that we can transfer from one to the other >> and it works. >> And it works. >> That's that's lowkey crazy. >> Yeah. It's it's I I think it's it's really cool just the the story of this whole thing. So now what could that signal be? Well, we've got retinol which is vitamin A and that enters cells and
Evolutionary BiologyNeurobiologyPharmacologyRegenerative Medicine