#cytoskeleton

[bpod-bpod]

Calm in ER

Within a cell there's a world full of organelles (the cell's 'organs' each with a specialised role) and protein scaffolding (the cytoskeleton which includes actin, that shapes the cell and organises to move it). This study of proteins located around (spatial proteomics) the endoplasmic reticulum (ER shown in blue; the organelle key to protein production and transporting them to the right place) reveals that a protein called calmin (in green) tethers the ER with actin (in magenta) to co-ordinate cell adhesion to the substrate, regulating migration

Read the published research article here

Video (repeated) from work by Holly Merta and colleagues

Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX, USA

Video originally published with a Creative Commons Attribution – NonCommercial – NoDerivs (CC BY-NC-ND 4.0)

Published in Cell Reports, April 2025

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[ghostoflostsplendor]

Yes I strongly suspect it's related to the extracellular matrix and cytoskeleton! Very important in connective tissues as well as in synapse formation. While working on my Bachelor's degree I actually came across a research paper linking a cytoskeleton protein to troubles with behavioral flexibility and autism risk genes. It's on fruit flies tho, so we will see if it translates to humans. That same protein activates an enzyme which breaks down collagen.

Alternatively/additionally, I wonder if it could be related to mast cells. MCAS is a common comorbidity with hypermobility, and mast cells are in our brains as well as in connective tissues. They could definitely explain the GI issues, those are common in allergies and MCAS after all.

comorbid disorders are either like "yeah ok, makes sense" or "what the fuck"

adhd and autism having a high comorbidity rate? yeah checks out

adhd and autism both having high rates of comorbidity with hypermobility and GI issues? thats an evil curse

[tired-and-unjellied]

Do someone happen to have a density value for cytoskeletons?

I don't mind if it's an exact value or an average. If it needs to be about a specific species, then humans.

I want to compare how heavy would be a "macro-cytoskeleton" replacing a human skeleton (possibly the whole muscuskeletar system)

[cassiocantdrink]

the pictures are worth it though

[maisha-online]

The Essential Role of Cylicins in Sperm Development and Fertility

Sperm development, known as spermiogenesis, is a complex process involving various stages and intricate structural changes. Recent research has shed light on the crucial role of Cylicins in spermiogenesis and male fertility in both mice and humans. Cylicins, specifically Cylicin 1 (Cylc1) and Cylicin 2 (Cylc2), are essential components of the perinuclear theca (PT), a critical part of the sperm…

[humancelltournament]

Human Cell Tournament Round 2

Propaganda!

Adipocytes, also known as lipocytes and fat cells, are the cells that primarily compose adipose tissue, specialized in storing energy as fat. Adipocytes are derived from mesenchymal stem cells which give rise to adipocytes through adipogenesis. In cell culture, adipocyte progenitors can also form osteoblasts, myocytes and other cell types. There are two types of adipose tissue, white adipose tissue (WAT) and brown adipose tissue (BAT), which are also known as white and brown fat, respectively, and comprise two types of fat cells.

The cytoskeleton is a complex, dynamic network of interlinking protein filaments present in the cytoplasm of all cells, including those of bacteria and archaea. In eukaryotes, it extends from the cell nucleus to the cell membrane and is composed of similar proteins in the various organisms. It is composed of three main components: microfilaments, intermediate filaments, and microtubules, and these are all capable of rapid growth or disassembly depending on the cell's requirements.

[adventuresinchemistry]

The weird thing about leaving academia for a completely different field is that you end up with so much random knowledge that is of no use to anyone, including yourself

[vickysaurus-art]

Prisoner playing the piano, since it is quite prominent in her part of the soundtrack. Also an excellent excuse to draw dapper Prisoner.

[unopenablebox]

i’m drunk at conference. everyone on earth loves me due to my talents

[tisiphoness]

belatedly angry about being spoken to in a condescending way by a second-year student during my practice prelim

[bpod-bpod]

Indirect Influence

A criminal kingpin might orchestrate a whole network of mischief, but only directly instruct a small circle of trusted henchmen. New research on a protein in the cell cytoskeleton – the structural web within cells – reveals a similar pattern of influence. PFN1 is well known to be involved in the assembly of actin (filaments that play a key structural role in the cytoskeleton), but there were also signs of its involvement in microtubules – another cytoskeleton component. Silencing PFN1 caused changes in microtubule abundance and structure (pink and blue, right) compared to normal (left). Reducing actin activity had similar effects, and if actin was restored the microtubule changes reversed, suggesting that PFN1 is acting on microtubules predominantly via actin, rather than directly. Some of the microtubule changes that arose with PFN1 depleted match characteristics of neurodegenerative conditions such as Alzheimer’s disease, so unpicking the lines of power could present new treatment options.

Written by Anthony Lewis

Image from work by Bruno A. Cisterna and colleagues

Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, GA, USA

Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in Journal of Cell Biology, May 2024

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[o-craven-canto]

Filters in the way of technologically advanced life in the universe and how likely I think they are

1. Abiogenesis (4.4-3-8 billion years ago): Total mystery. The fact that it happened so quickly on Earth (possibly as soon as there was abundant liquid water) is a tiny bit of evidence for it being easy. Amino acids and polycyclic hydrocarbons are very common in space, but nucleotides aren't, and all hypothetic models I've seen require very specific conditions and a precise sequence of steps. (It would be funny if the dozen different mechanisms proposed for abiogenesis were all happening independently somewhere.)

2. Oxygenic photosynthesis (3.5 billion years ago) (to fuel abundant biomass, and provide oxygen or some other oxidizer for fast metabolism): Not so sure. Photosynthesis is just good business sense -- sunlight is right there -- and appeared several times among bacteria. But the specific type of ultra-energetic photosynthesis that cracks water and releases oxygen appeared only once, in Cyanobacteria. That required merging two different photosynthetic apparati in a rather complex way; and all later adoptions of oxygenic photosynthesis involved incorporating Cyanobacteria by endosymbiosis. For all that it's so useful, I don't know if I'd expect to see it on every living planet.

3. Eukaryotic cell (2.4 billion years ago?): Probably the narrowest bottleneck on the list. Segregated mitochondria with their own genes and a nucleus protecting the main genome are extremely useful both for energy production (decentralized control to maximize production without overloading) and for genetic storage (less DNA damage due to reactive metabolic waste). But there's a chicken-and-egg problem in which incorporating mitochondria to make energy requires an adjustable cytoskeleton, but that consumes so much energy it would require mitochondria already in place. Current models have found solutions that involve a very specific series of events. Or maybe not? Metabolic symbiosis, per se, is common, and there may have been other ways to gene-energy segregation. Besides, after the origin of eukaryotes, endosymbiosis occurred at least nine more times, and even some bacteria can incorporate smaller cells.

4. Sexual reproduction (by 1.2 billion years ago): Without meiotic sex (combining mutations from different lineages, decoupling useful traits from harmful ones, translating a gene in multiple way), the evolution of complex beings is going to be painfully slow. Bacteria already swap genes to an extent, and sexual recombination is bundled in with the origin of eukaryotes so I probably shouldn't count it separately (meiosis is just as energy-intensive as any other use of the cytoskeleton). Once you have recombination, life cycles with spores or gametes and sex differentiation probably follow almost inevitably.

5. Multicellularity (800 million years ago?): Quite common, actually. Happens all the time among eukaryotes, and once in a very limited form even among bacteria. Now we'd want complex organized bodies with geometry-defining genes, but even that happened thrice: in plants, fungi, and animals. As far as I know, various groups of yeasts are the only regressions to unicellularity.

6. Brains and sense organs (600 million years ago): Nerve cells arose either once or twice, depending on whether Ctenophora (comb-jellies) and Eumetazoa (all other animals except sponges) form a single clade or not. Some form of cellular sensing and communication is universal in life, though, so a tissue specialized for signal transmission is probably near inevitable once you have multicellular organisms whose lifestyle depends on moving and interacting with the environment. Sense organs that work at a distance are also needed, but image-forming eyes evolved in six phyla, so no danger there (and there's so many other potential forms of communication!). Just to be safe, you'll also want muscles and maybe mineralized skeletons on the list, but I don't think either is particularly problematic. An articulated skeleton is probably better than a rigid shell, but we still have multiple examples of that (polyplacophorans, brittle stars, arthropods, vertebrates).

7. Life on land (400 million years ago): (Adding this because air has a lot more oxygen to fuel brains than water (the most intelligent aquatic beings are air-breathers), and technology in water has the issue of fire.) You're going to need a waterproof integument, some kind of rigid support system, and kidneys to regulate water balance. Plenty of animal lineages moved on land: vertebrates, insects, millipedes, spiders, scorpions, multiple types of crabs, snails, earthworms, etc. Note that most of those are arthropods: this step seems to favor exoskeletons, which help a great deal in retaining water. Of course this depends on plants getting on land first, which on Earth happened only once, and required the invention of spores and cuticles. (Actually there are polar environments where all photosynthesis occurs in water, but they are recently settled and hardly the most productive.)

8. Human-like intelligence (a few million years ago?): There seems to a be a general trend in which the max intelligence attainable by animals on Earth has increased over time. There's quite a lot of animals today that approach or rival apes in intelligence: elephants, toothed cetaceans, various carnivorans, corvids, parrots, octopodes, and there's even intriguing data about jumping spiders. Birds seem to have developed neocortex-like brain structures independently. Of course humans got much farther, but the fact that even other human species are gone suggests that a planet is not big enough for more than one sophont, so the uniqueness of humans might not necessarily imply low probability. (We seem to exist about halfway through the habitability span of Earth land, FWIW.) The evolution of sociality should probably be lumped here: we'll want a species that can teach skills to its offspring and cooperate on tasks. But sociality is also a common and useful adaptation: many species on our list (octopodes are a glaring exception) are intensely social and care for their offspring. I mentioned above that the land-step favors exoskeletal beings, which in turns favors small size; but the size ranges of large land arthropods and very intelligent birds overlap, so that's not disqualifying.

9. Agriculture and urban civilization (11,000 years ago): Agriculture arrived quite late in the history of our species, but when it arrived -- i.e. at the end of the Wurm glaciation -- it arrived independently in four to eight different places around the world, in different biogeographic realms and climates, so I must assume that at least some climate regimes are great for it (glacial cycles are a minority of Earth's history; but did agriculture need to come after glaciations? Maybe a shock of seasonality did the trick). And once you have agriculture, complex urbanized societies follow most of the time, just a few millennia later. Even writing arose at least three times (Near East, China, and Mexico), and then spread quickly.

10. Scientific method and industrialization (300 years ago): We're getting too far from my expertise here, but whatever. The Eurasian Axial Age suggests that all civilizations with a certain degree of wealth, literacy, and interconnection will spawn a variety of philosophies. Philosophical schools that focus on material causes and effects like the Ionians or Charvaka have appeared sometimes, but often didn't win over more supernaturalist schools. Perhaps in pre-industrial times pure materialism isn't as useful! You may need to thread a needle between interconnected enough to exchange and combine ideas, and also decentralized enough that the intellectual elite can't quash heterodoxy. As for industrialization, that too happened only once, though that's another case in which the first achiever would snuff out any other. I hear Song China is a popular contender for alternative Industrial Revolutions (with coal-powered steelworks!); Imperial Rome and the Abbasid Caliphate are less convincing ones. For whatever reason, it didn't take until 18th century Britain.

11. Not dying randomly along the way: Mass extinctions killing off a majority of species happened over and over -- the Permian Great Dying, the Chicxulub impact, the early Oxygen Crisis -- but life has always rebounded fairly quickly and effectively. It's hard enough to sterilize an agar plate, let alone a planet. Disasters on this scale are also unlikely to happen in the lifespan of planet-bound civilizations, unless of course the civilizations are causing them. A civilization might still face catastrophic climate change, mega-pandemics, and nuclear war, not to mention lesser setbacks like culture-wide stagnation or collapse, and I couldn't begin to estimate how common, or ruinous, they would actually be.

****

I have no idea how common the origin of life is, but the vast majority of planets with life will only have bacterial mats and stromatolites. Of the tiny sliver that evolved complex cells, a good chunk will have their equivalents of plants and animals, most of which may have intelligent life at least on primate- or cetacean-level at some later point. At any given time, a tiny fraction of those will have agricultural civilizations, at an even tinier fraction of that will have post-industrial science and technology. Let's say maybe 1 planet with industrial technology out of 100 with agriculture, 100,000 with hominid-level intelligence, 10 million with animal-like organisms, 100 millions with complex cells, and 10 billions with life at all?

[mleprae]

Q'wilqilth growth chart

I've talked about leprosy plague angels (LPA) before and slightly touched upon their life stages, LPAs use the nervous system to spawn, where their offspring are born inside neural coils, a species of slime mold that lives in the neuron trees, this proccess is important for the development of the oubain whip, which is their main weapon against threats and helps them stabilize themselves (electrically speaking)

Q'wilqilth wasn't raised by LPAs, and he may be the last one of them, he was raised by tuberculosis plague angels (TBA) which live in the lungs, this means that Q'wilqilth didn't have the chance to develop his Oubain whip, making him have this weird stubble instead of a tail

(an healthier LPA adult; the tail is much thinner and larger)

I've also briefly mentioned that LPAs cannot metabolize carbohydrates, their main source of food is lipids be it animal fat or vegetal oils, anything that is lipid, Q'wilqilth grew lacking access to proper nutrients and developed a very rocky relationship with food in general, his cytoskeleton developed poorly, he had awful food intolerances and other issues; when he cut himself from his family his relationship with it grew worse, preferring to starve himself than go through to it again, after all he never properly learned what food he should eat and now that he was an adult, he grew far too used to what is essentially junk food to him

And last but not least; socialization,

LPAs are similar to locusts / grasshoppers, they can live solitarily by themselves but they have a different form when they're at this stage, when they spawn, they spawn far away from one another and its only when they reach walking/gliding stage that they might bump into others, solitary LPAs are much smaller, thinner and have darker colors, when they have prolonged contacts with other individuals they morph into their 'socialized' forms, where they grow their iconic green/blue pseudofeathers

Once an individual is socialized they cannot return to their original form; the proccess of socialization reshapes their entire being, it physically changes their metabolism, reproduction, "brain", organs and other things to account for sharing resources with other individuals as well as a complete reform on their psychology, socialized individuals are less rational/more emotional but this means that they are strongly chauvinistic and form stronger bonds with one another, once a fully socialized individual becomes solitary; they develop many psychological illnesses, similarly to humans in complete solitude

Q'wiqilth grew with TBAs, who have similar chemical signalling to LPAs, his receptors pretty much took his adoptive family as his 'biological' one, meaning that they were able to trigger his socialization proccess from a very young age, LPAs are meant to only undergo socialization in adulthood so this proccess was extremely mentally and energetically taxing on Q'wilqilth's body, as he became more socialized, his demands for specific signallings were not being met which led to his erratic and paranoid traits in adulthood

I haven't made a species sheet for SPAs (Syphilis plague angels) yet, but they are known as mimics for being able to copy chemical signalling of other species perfectly, its part of why O'sentrael and Q'wilqilth are so close; O'sentrael being able to mimic the same scent and chemicals of an LPA can fill his void, though one must wonder if he loves her for her or its just that her smell is tricking him

[tanadrin]

Lane's thesis around the emergence of eukaryotes (and why it was necessary for complex life) seems to be this:

Bacteria (both kinds, archaea and eubacteria) have pretty strict energy limits in terms of growth. One big constraint here is genome size: the more genes you have, the more energy that gets spent on protein synthesis. But the smaller your genome, the faster you replicate, which is important given how quickly bacterial generations turn over; replicating fast is a big advantage. You can pick up any new genes you need from the environment, thanks to lateral gene transfer. This is why bacteria don't have a lot of junk DNA.

You could try to scale up the size of the cell to increase the size of the membrane, which would allow you to produce more energy. But the volume of the cell scales with the cube of its size and the surface area with the square; and, for obscure reasons, it seems like there is a strong evolutionary pressure to keep the genome near the energy-producing membrane. So what you effectively get is a big dead area inside the cell (a vacuole, in some species of huge bacteria), lots of extra copies of the genome, and no extra energy for your trouble (each copy of the genome is a copy of every gene, which requires more energy to support).

Compare chloroplasts, which often have complicated, folded up membranes to facilitate photosynthesis--and also lots of copies of their genome floating around.

You could imagine breaking the genome up into plasmids, rather than copying every gene, and only putting extra copies of the genes needed for respiration near the cell membrane. But then you need complex transport systems (which require energy), and there's no evolutionary pressure for size for its own sake that would encourage you to develop such a complex transport system to support a large bacterial cell, in aid of maybe in the future developing an ATP surplus.

Eukaryotes didn't evolve to produce extra ATP, they evolved to get a consistent source of hydrogen, for cell growth. The endosymbiont provides the host cell with all the hydrogen it needs, and in return the host cell provides a stable environment for the endosymbiont.

In this safe environment, the endosymbiont's genome is free to shrink without limit, down to the absolute minimum number of genes needed to support respiration. Many genes will move to the nucleus of the host cell; others will simply be lost. But this produces an ATP surplus! All of this ATP needs to be used--if the whole pool of ADP gets converted to ATP, respiration stops (bad!), and free radicals accumulate which fuck up proteins and DNA and can kill the cell. So this excess of ATP encourages the host cell to find uses for it--like a cytoskeleton and internal transport mechanisms and new organelles.

Unlike the plasmid scenario, every step of this evolutionary process confers some benefit on both the host cell and the endosymbiont.

You might wonder, given the benefits, why this only happened once with mitochondria! This is sort of related to the fact that all apparent intermediate cells, like the archaezoa, are actually subsequent, reduced forms of the true eukaryote rather than being offshoots of the process of eukaryote development: the early eukaryote would have been genetically unstable, and small in population size. There was strong selection pressure to quickly converge on a single form (the eukaryote LUCA), and intermediate forms would have been quickly outcompeted and driven to extinction. Likewise, this was a feat not soon to be repeated: eukaryotes got lucky.

Endosymbiosis dumped a ton of introns--self-replicating genetic parasites--into the host cell. Some of these could have been from endosymbionts that failed to thrive in the host cell, and when they died dumped their genetic material into the host. We still sometimes see mitochondrial DNA segments invading and disrupting nuclear DNA.

The eukaryotic genome was able to tolerate the invasion of bacterial introns because of the benefit the endosymbionts provided; but initially, the result was a genetically unstable cell. The nucleus evolved to separate the nuclear DNA from ribosomes, giving time and space for spliceosomes to remove introns from transcribed RNA. Excess lipid synthesis from having both bacterial and archaeal enzymes for membrane formation helped promote the creation of the nucleus (and other membrane-bound organelles).

Because of the intron situation and overall genetic instability, the mutation rate of early eukaryotes was high, selection pressure was immense, and there was a lot of variation in the population--just the circumstances which, in mathematical models, favors the emergence of sexual reproduction.

Lateral gene transfer is of limited use as genomes get bigger, and sexual reproduction, with the genetic recombination that occurs during meiosis, makes individual genes much more salient to evolution, as opposed to just whole genomes.

The individual steps for the evolution of sexual reproduction are not so clear, but the mechanical precursors of both the segregation of genetic material and the fusion of cells are attested in prokaryotes. Various effects arising from natural selection also tend to favor two sexes, anisogamy, and the inheritance of mitochondria from only one parent. Handling mutations and the specialization of tissue, and the separation of cells into somatic cells and germ line cells, also led to the evolution of senescence.

the evolution of sex, incidentally, also favors moving as many mitochondrial genes to the nucleus as possible, so more beneficial versions can be selected for. there's no way to repair the mutational load of genes which remain in the mitochondria, and do not recombine.

[faedastudies]

02.07.2024

.

currently studying: cell biology (mitochondria + cytoskeleton)

I changed the “paper” layout to Cornell notes rather than grid paper and I like it more. I’m taking a study break because my Apple Pencil died.

I still haven’t received my forensics results ( and my gpa for last semester has already been updated so I don’t know if they’re gonna update it when I do get my results back )

[wrong-answers-only-polls]

What's your favourite organ?

Nucleus

Chloroplast

Rough endoplasmic reticulum

Soft endoplasmic reticulum

Cytoskeleton

Ribosome

Lysosome

Phospholipid bilayer

Nucleolus

Cytoplasm

Vesicle

Golgi apparatus

(I'm not adding mitochondria because I feel like a lot of people would pick that and that would be boring)