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Here's a thought. Perhaps viruses are picking up DNA from host organisms and transmitting them to new hosts as they pass from one to the next. Viruses that tran

Here's a thought. Perhaps viruses are picking up DNA from host organisms and transmitting them to new hosts as they pass from one to the next. Viruses that transmit advantageous DNA will survive in our genome. Viral DNA can be particularly useful when it has an impact on the morphological development of an organism, i.e. as it is developing from an embryo. If this is true it is not surprising that we find a lot of activation of retro viruses during embryonic development. This also provides us a clue about how cancer develops. These retro viruses are associated with the changing of form and function of the cell within which they are contained, since they impact this within the development of the embryo. When they are activated within adult cells they drive similar functional changes. Which might be why many cancers, seem, to me, to look like distinct entities, like the tissue has suddenly switched to a different functional mode. It's not just one characteristic of the tissue that has changed to make it dangerous, but a whole constellation of changes that together seem to form a unified whole. I.e. we are looking at groups of changes transported into the genome by a virus that has propagated because those changes are advantageous to the host organism. These changes do not suddenly arise within the body due selection pressures on the tissue, but are activated and mediated by the virus. This kind of cross species transportation of DNA, could well be analogous to what we see at the microbial level, where horizontal gene transfer is an important driver of evolution.

fifnir 8y ago
> activation of retro viruses during embryonic development. Citation on this? As far as I know (am writing a phd thesis on development++), there's nothing like "virus activation". Viral elements (mostly transposons) are big evolutionary players but are usually actively repressed by DNA methylation (in eucaryots). > Which might be why many cancers, seem, to me, to look like distinct entities, like the tissue has suddenly switched to a different functional mode. I don't 100% understand your comments about viruses here, but related to this, we don't need to imagine some virus orchestrating such a thing (besides, as far as I know they are way too simple to drive complex eucaryot gene regulation), but rather gene regulatory networks which if they get unbalanced can lead to significant changes in morphology. <edit> some spelling
- memebox3f 8y ago
  "The early embryo is a hotbed of activity for endogenous retroviruses, recent studies have shown. To understand why embryonic cells make viral proteins, scientists have run experiments to see what happens when viral genes are silenced. These experiments suggest that viral proteins help the embryo develop a variety of tissues. " From the op article. I'm am not an expert in this at all, these are just my thoughts on the matter, take them or leave them. Regarding regulatory networks binding together elements so as to orchestrate changes in morphology - I had not thought about this, of course you are correct. Where you say that the viruses are too simple to drive sufficiently complex changes to the regulatory networks, I would counter by saying that chance mutations are sufficient to drive these changes.
  - cryptonector 8y ago
    Link?
    - memebox3f 8y ago
      "From the op article"
  - fifnir 8y ago
    We have a LOT of "appropriated" viral code in our own DNA: "Reverse-transcribed RNA molecules compose a significant portion of the human genome. Many of these RNA molecules were retrovirus genomes either infecting germline cells or having done so in a previous generation but retaining transcriptional activity. This mechanism itself accounts for a quarter of the genomic sequence information of mammals for which there is data."[1] But that they are now part of us and when they are activated it's not some virus waking up but parts of viruses that we have adapted into doing useful things for out cells. Viruses can cause significant changes in gene networks (for example oncoviruses usually suppress tumor-suppressing proteins [2] which dramatically affects things downstream), but the changes are not as holistic as I think you are describing them. Yes point mutations (and viruses) can derail neural networks and that can have far-reaching consequences, but I think these things are accidental in both cases and not some virus plan as I felt you were arguing. [1] https://www.sciencedirect.com/science/article/pii/S1369527416300170 https://www.sciencedirect.com/science/article/pii/S136952741... [2] https://en.wikipedia.org/wiki/Oncovirus https://en.wikipedia.org/wiki/Oncovirus

fifnir 8y ago

> activation of retro viruses during embryonic development. Citation on this? As far as I know (am writing a phd thesis on development++), there's nothing like "virus activation". Viral elements (mostly transposons) are big evolutionary players but are usually actively repressed by DNA methylation (in eucaryots). > Which might be why many cancers, seem, to me, to look like distinct entities, like the tissue has suddenly switched to a different functional mode. I don't 100% understand your comments about viruses here, but related to this, we don't need to imagine some virus orchestrating such a thing (besides, as far as I know they are way too simple to drive complex eucaryot gene regulation), but rather gene regulatory networks which if they get unbalanced can lead to significant changes in morphology. <edit> some spelling

memebox3f 8y ago
"The early embryo is a hotbed of activity for endogenous retroviruses, recent studies have shown. To understand why embryonic cells make viral proteins, scientists have run experiments to see what happens when viral genes are silenced. These experiments suggest that viral proteins help the embryo develop a variety of tissues. " From the op article. I'm am not an expert in this at all, these are just my thoughts on the matter, take them or leave them. Regarding regulatory networks binding together elements so as to orchestrate changes in morphology - I had not thought about this, of course you are correct. Where you say that the viruses are too simple to drive sufficiently complex changes to the regulatory networks, I would counter by saying that chance mutations are sufficient to drive these changes.
- cryptonector 8y ago
  Link?
  - memebox3f 8y ago
    "From the op article"
- fifnir 8y ago
  We have a LOT of "appropriated" viral code in our own DNA: "Reverse-transcribed RNA molecules compose a significant portion of the human genome. Many of these RNA molecules were retrovirus genomes either infecting germline cells or having done so in a previous generation but retaining transcriptional activity. This mechanism itself accounts for a quarter of the genomic sequence information of mammals for which there is data."[1] But that they are now part of us and when they are activated it's not some virus waking up but parts of viruses that we have adapted into doing useful things for out cells. Viruses can cause significant changes in gene networks (for example oncoviruses usually suppress tumor-suppressing proteins [2] which dramatically affects things downstream), but the changes are not as holistic as I think you are describing them. Yes point mutations (and viruses) can derail neural networks and that can have far-reaching consequences, but I think these things are accidental in both cases and not some virus plan as I felt you were arguing. [1] https://www.sciencedirect.com/science/article/pii/S1369527416300170 https://www.sciencedirect.com/science/article/pii/S136952741... [2] https://en.wikipedia.org/wiki/Oncovirus https://en.wikipedia.org/wiki/Oncovirus