Sep 5, 2022 04:51 AM
https://aeon.co/essays/how-xenobots-resh...f-genetics
INTRO: Where in the embryo does the person reside? Morphogenesis – the formation of the body from an embryo – once seemed so mystifying that scholars presumed the body must somehow already exist in tiny form at conception. In the 17th century, the Dutch microscopist Nicolaas Hartsoeker illustrated this ‘preformationist’ theory by drawing a foetal homunculus tucked into the head of a sperm.
This idea finds modern expression in the notion that the body plan is encoded in our DNA. But the more we come to understand how cells produce shape and form, the more inadequate the idea of a genomic blueprint looks, too. What cells follow is not a blueprint; if they can be considered programmed at all, it’s not with a plan of what to make, but with a set of rules to guide construction. One implication is that humans and other complex organisms are not the unique result of cells’ behaviour, but only one of many possible outcomes.
This view of the cell as a contingent, constructional entity challenges our traditional idea of what a body is, and what it can be. It also opens up some remarkable and even disconcerting possibilities about the prospects of redirecting biology into new shapes and structures. Life suddenly seems more plastic and amenable to being reconfigured by design. Understanding the contingency and malleability of multicellular form also connects us to our deep evolutionary past, when single-celled organisms first discovered the potential benefits of becoming multicellular. ‘The cell may be the focus of evolution, more than genes or even than the organism,’ says Iñaki Ruiz-Trillo of the Institute of Evolutionary Biology in Barcelona. Far from the pinnacle of the tree of life, humans become just one of the many things our cells are capable of doing.
In one of the most dramatic demonstrations to date that cells are capable of more than we had imagined, the biologist Michael Levin of Tufts University in Medford, Massachusetts and his colleagues have shown that frog cells liberated from their normal developmental path can organise themselves in distinctly un-froglike ways. The researchers separated cells from frog embryos that were developing into skin cells, and simply watched what the free cells did.
Culturing cells – growing them in a dish where they are fed the nutrients they need – is a mature technology. In general, such cells will form an expanding colony as they divide. But the frog skin cells had other plans. They clustered into roughly spherical clumps of up to several thousand cells each, and the surface cells developed little hairlike protrusions called cilia (also present on normal frog skin).
The cilia waved in coordinated fashion to propel the clusters through the solution, much like rowing oars. These cell clumps behaved like tiny organisms in their own right, surviving for a week or more – sometimes several months – if supplied with food. The researchers called them xenobots, derived from Xenopus laevis, the Latin name of the African clawed frog from which the cells were taken.
Some of this wasn’t entirely new. Scientists have known for more than a century that a piece of embryonic tissue destined to become skin will, if cut off and cultured, grow cilia. Such a piece of tissue is called the ‘animal cap’, and various studies have shown that Xenopus animal caps can, if given the right biochemical signals, grow into many other tissue types, including neurons, muscle and even beating heart tissue.
But Levin and colleagues now say that some of these structures are not just random blobs of sticky cells: they resemble autonomous organisms. If they are damaged, the cells heal back in the original shape. They can signal to one another by emitting pulses of calcium ions, although the researchers aren’t sure what the message conveys. They move with apparent purpose, sometimes circling one another or sweeping up other individual cells around them into piles.
The cells are like Lego bricks that can be assembled in different ways – except they do the assembly themselves
These xenobots seem to represent an entirely different developmental program, Levin says, that the frog cells can adopt. Having been freed from their usual environment, it’s as if the cells are able to discover a new way of life. What’s baffling is that they are genetically no different to ordinary frog cells. So what does the genome encode, if not a ‘plan for a frog’?
It seems that, instead, the genes are part of a molecular program that gives cells certain tendencies, for example to stick together in particular configurations. The cells are like Lego bricks that can be assembled in different ways – except that the cells do the assembly themselves... (MORE - details)
https://youtu.be/w77_yhkXzzo
https://www.youtube-nocookie.com/embed/w77_yhkXzzo
INTRO: Where in the embryo does the person reside? Morphogenesis – the formation of the body from an embryo – once seemed so mystifying that scholars presumed the body must somehow already exist in tiny form at conception. In the 17th century, the Dutch microscopist Nicolaas Hartsoeker illustrated this ‘preformationist’ theory by drawing a foetal homunculus tucked into the head of a sperm.
This idea finds modern expression in the notion that the body plan is encoded in our DNA. But the more we come to understand how cells produce shape and form, the more inadequate the idea of a genomic blueprint looks, too. What cells follow is not a blueprint; if they can be considered programmed at all, it’s not with a plan of what to make, but with a set of rules to guide construction. One implication is that humans and other complex organisms are not the unique result of cells’ behaviour, but only one of many possible outcomes.
This view of the cell as a contingent, constructional entity challenges our traditional idea of what a body is, and what it can be. It also opens up some remarkable and even disconcerting possibilities about the prospects of redirecting biology into new shapes and structures. Life suddenly seems more plastic and amenable to being reconfigured by design. Understanding the contingency and malleability of multicellular form also connects us to our deep evolutionary past, when single-celled organisms first discovered the potential benefits of becoming multicellular. ‘The cell may be the focus of evolution, more than genes or even than the organism,’ says Iñaki Ruiz-Trillo of the Institute of Evolutionary Biology in Barcelona. Far from the pinnacle of the tree of life, humans become just one of the many things our cells are capable of doing.
In one of the most dramatic demonstrations to date that cells are capable of more than we had imagined, the biologist Michael Levin of Tufts University in Medford, Massachusetts and his colleagues have shown that frog cells liberated from their normal developmental path can organise themselves in distinctly un-froglike ways. The researchers separated cells from frog embryos that were developing into skin cells, and simply watched what the free cells did.
Culturing cells – growing them in a dish where they are fed the nutrients they need – is a mature technology. In general, such cells will form an expanding colony as they divide. But the frog skin cells had other plans. They clustered into roughly spherical clumps of up to several thousand cells each, and the surface cells developed little hairlike protrusions called cilia (also present on normal frog skin).
The cilia waved in coordinated fashion to propel the clusters through the solution, much like rowing oars. These cell clumps behaved like tiny organisms in their own right, surviving for a week or more – sometimes several months – if supplied with food. The researchers called them xenobots, derived from Xenopus laevis, the Latin name of the African clawed frog from which the cells were taken.
Some of this wasn’t entirely new. Scientists have known for more than a century that a piece of embryonic tissue destined to become skin will, if cut off and cultured, grow cilia. Such a piece of tissue is called the ‘animal cap’, and various studies have shown that Xenopus animal caps can, if given the right biochemical signals, grow into many other tissue types, including neurons, muscle and even beating heart tissue.
But Levin and colleagues now say that some of these structures are not just random blobs of sticky cells: they resemble autonomous organisms. If they are damaged, the cells heal back in the original shape. They can signal to one another by emitting pulses of calcium ions, although the researchers aren’t sure what the message conveys. They move with apparent purpose, sometimes circling one another or sweeping up other individual cells around them into piles.
The cells are like Lego bricks that can be assembled in different ways – except they do the assembly themselves
These xenobots seem to represent an entirely different developmental program, Levin says, that the frog cells can adopt. Having been freed from their usual environment, it’s as if the cells are able to discover a new way of life. What’s baffling is that they are genetically no different to ordinary frog cells. So what does the genome encode, if not a ‘plan for a frog’?
It seems that, instead, the genes are part of a molecular program that gives cells certain tendencies, for example to stick together in particular configurations. The cells are like Lego bricks that can be assembled in different ways – except that the cells do the assembly themselves... (MORE - details)
https://youtu.be/w77_yhkXzzo