Grow a segmented spine!


You want to see something awesome? This is a video of human embryonic cells developing in a dish and activating the segmentation clock to build a series of somites.

That embryos do this is pretty neat but not surprising. It’s easy to see that process going on in zebrafish embryos, where a new segmental blob pinches off every 20 minutes. What’s cool is that they’ve pared down the system to just what looks like presomitic mesoderm — no gut endoderm, no nervous system or ectoderm, just those mesodermal cells grouping and organizing to make pre-muscle tissue. At first, I thought, no big deal. We’ve observed vertebrate segmentation in fish and frogs and chicks for many decades, why would we need to look at it in human embryos? They almost certainly use the same molecules and interactions as mice or any other vertebrate. It’s got to be using Notch signaling, after all.

What’s special here, though, is that they’ve reduced the complexity of the system to a remarkable degree. You don’t need a nervous system or a gut or even, it seems, a notochord to assemble segmental organization. They’re even getting colinear expression of HOX genes! That’s the surprise to me, that so little is required to trigger oscillatory expression and patterning. And that’s the point the authors emphasize.

Our bottom-up experimental approach demonstrates that complex developmental events such as somitogenesis, can be deconstructed and dissected into discrete “building blocks” of developmental principles which are usually intricately connected and cannot be easily uncoupled in vivo. Axioloids, a self-organizing in vitro model of human axial development allowed us to individually assess and manipulate such building blocks at the molecular, cellular and morphogenetic level. Axioloids -a surrogate model of the human embryonic tail and forming axis- are capable of recapitulating core features of human somitogenesis, and represent an exciting new platform to investigate axial development and disease in a human context.

Don’t read the YouTube comments. There are people complaining that it’s a human life with a unique genetic code (no, it’s not a person, and these embryonic cultures cannot develop into a person — while scraps of mesoderm might be enough to make somites, it’s not sufficient to build a whole human being) and Stop trying to PLAY GOD!!! (this isn’t god-like, it’s biology).

Comments

  1. bcw bcw says

    I guess if you can build Republican bodies without a spine, it’s not surprising you can build spines without a body.

  2. DanDare says

    That is beautiful. Seeing the complexity of development broken down into discrete patterns that are self sufficient allows a lot of new knowledge to be gained.

  3. drsteve says

    @3 Wouldn’t that defeat the end purpose of creating an army of zombie lab slaves, (but without all the bureaucracy and paperwork of hiring grad students)?

  4. birgerjohansson says

    The politicians on certain parties have gone one step further and segmented their conscience, achieving a surprising flexibility.

  5. nomdeplume says

    @4 Of course it would, silly me, they would also be useful for, oh, I don’t know, storming the Capital to overturn an election their glorious leader lost…

  6. says

    I guess that sinks the “lump of chewed flesh” somite model of the Qur’anic embryologists. What intrigues me is that all the illustrations show a large blob of tissue at one end. Are these undifferentiated cells or perhaps a proto-head?

  7. drsteve says

    @6 For that purpose I think it’s been shown to be more effective to use subjects that already HAVE souls, which they can then be induced to sell off at fire sale prices in service of motivations such as economic libertarianism, Christian white nationalism, pwnership of the left, and so on.

  8. bcw bcw says

    In the video, there is a clear propagation direction and the process thus defines a head and tail. I’m curious what the sequence is in defining head and tail; is this already set before this segmentation or does this segmentation define the direction? I’m guessing that it must have happened first along with a process to create the initial elongated shape before segmenting.

    I guess I should try to struggle through one of PZ’s broadcast classes as this looks vaguely familiar. Unfortunately my brain tends to get full pretty fast with this kind of subject. To really learn it, I’d need to use it in an applied way so I guess I need to go create some life from scratch.

  9. Howard Brazee says

    I figure “playing god” starts off with medicine. If it was our time to die, but we put a compress on our bleeding cut, that’s interfering with nature/God.

    But farming should also qualify, and wearing enough clothes to not feeze.

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