My Web Markups - Kev Peng
In the BAM model, phage adhere to mucus protecting the metazoan host against invading, potentially pathogenic bacteria.
Viruses and the origin of microbiome selection and immunity - ProQuest
but you do need to be giving it some serious thought, in the context of the questions that are in that weekly writing assignment.
Mail - Peng, Kevin - Outlook
The most striking example, though, relates to the evolution of the mammalian placenta and the timing of gene expression in human pregnancy. Evidence indicates that we owe our ability to have live births to a bit of genetic code that was co-opted from ancient retroviruses that infected our ancestors more than 130 million years ago.
In 2018, for example, two research teams independently made a fascinating discovery. A gene of viral origin encodes for a protein that plays a key role in long-term memory formation by moving information between cells in the nervous system.
Ultimately, though, the more we learn about all viruses, not just the pathogens, the better equipped we will be to harness certain viruses for good and to develop defenses against others that could lead to the next pandemic.
Why the world needs viruses to function - BBC Future
Syncytin originated from a retroviral gene encoding a protein that is embedded in the outer surface of a virus. This protein mediates the fusion of the virions with the host cell membrane, thereby facilitating viral infection. In a remarkable turn of events, the human body has repurposed the viral protein's cell-fusing activities to promote the formation of the layer of cells that merge the placenta and the uterus.
When viruses infect us, they can embed small chunks of their genetic material in our DNA. Although infrequent, the incorporation of this material into the human genome has been occurring for millions of years. As a result of this ongoing process, viral genetic material comprises nearly 10 percent of the modern human genome.
Our complicated relationship with viruses -- ScienceDaily
At first, endogenous retroviruses coax cells to make more retroviruses that can infect other cells. But over the generations, the viral DNA mutates, and endogenous retroviruses eventually lose the ability to infect new cells.
If a retrovirus happens to infect an egg or sperm, its DNA can potentially be passed to the next generation and the generation after that.
Placentas make viral proteins, and scientists have found that some types, known as syncytins, fuse together placental cells, a crucial step in fetal development.“My speculation is that without syncytins, mammal evolution would have looked very different,” Dr. Coffin said.
But in certain cases, Dr. Coffin said, we have domesticated our viruses. We make proteins from endogenous retroviruses to carry out functions we depend on.
Ancient Viruses Are Buried in Your DNA - The New York Times
Phylogenetic analyses showed that mammalian Arc is derived from an ancient retrotransposon of the Ty3/ gypsy family and contains homology to the retroviral Gag polyproteins
Recent studies made the surprising observation that the neuronal gene Arc forms virus-like protein capsids that can transfer RNA between neurons to mediate a novel intercellular communication pathway.
Viruses and transposable elements are major drivers of evolution and make up over half the sequences in the human genome
Intercellular Communication in the Nervous System Goes Viral: Trends in Neurosciences
Evolutionary analysis indicates that Arc is derived from a vertebrate lineage of Ty3/gypsy retrotransposons, which are also ancestors to retroviruses.
Ty3/gypsy retrotransposons are ancient mobile elements that are widely distributed and often abundant in eukaryotic genomes and are considered ancestral to modern retroviruses (Malik et al., 2000). There is evidence that coding sequences derived from Ty3/gypsy and other retroviral-like elements have been repurposed for cellular functions repeatedly during evolution (Feschotte and Gilbert, 2012).
The Neuronal Gene Arc Encodes a Repurposed Retrotransposon Gag Protein that Mediates Intercellular RNA Transfer - ScienceDirect
fuse cells into a wall — the placenta
Once a viral protein, the virus essentially morphed or evolved into what we now know as syncytin.
we get this viral DNA that lets us make a protein that fuses things.
When evolutionary biologists like Chuong mapped the genomes of these cells, they found that the protein that allowed these cells to fuse into a wall, called syncytin, didn’t look like it came from human DNA. It looked more like HIV. According to Chuong, this protein actually came from an ancient retrovirus,
evolved about 150 million to 200 million years ago. Before that, if you wanted to reproduce, you had to lay eggs.
Because half of the fetus is maternal, but the other half is paternal, and yet the pregnancy can go on for nine months without the mom’s body destroying it,” Barroeta said. “And that, from an immune standpoint, is fascinating, because if you were to receive a piece of someone else and insert that under your skin, that would not last there for three days, your body will actively reject it.”
it’s the baby’s lung, it’s a waste-disposal system, and it’s a nutrition source.”
How the placenta evolved from an ancient virus — WHYY
noncoding regulatory elements
mediating cell–cell fusion to form a multinucleate barrier, suppressing maternal immunity, and protecting the fetus from exogenous viruses
These findings have led to speculation that the co-option of unrelated ERVs in different species was a driving force underlying the evolutionary diversification of the placenta
Most ERVs are considered fossilized relics that can no longer replicate or encode functional viruses, but the occasional insertion may prove beneficial for the host and become co-opted for a cellular role.
Genome-sequencing projects of many species have revealed that ERVs have a ubiquitous presence in vertebrate genomes, constituting over 8% of the human genome
A key step in the retrovirus lifecycle is retrotransposition, in which the RNA-based virus genome is reverse transcribed and integrated into the DNA of the host cell.
The placenta goes viral: Retroviruses control gene expression in pregnancy
Unexpectedly, syncytin-B null embryos are viable, with only limited late-onset growth retardation and reduced neonate number.
A pair of co-opted retroviral envelope syncytin genes is required for formation of the two-layered murine placental syncytiotrophoblast - ProQuest
from egg-laying to placental mammals.
tolerance of the fetus by the maternal immune system
Knocking out one or both mouse syncytin-A and -B genes provided evidence that they indeed play a critical role in placentation.
such events must have occurred repeatedly during the course of millions of years of evolution.
From ancestral infectious retroviruses to bona fide cellular genes: Role of the captured syncytins in placentation - ScienceDirect
Then there’s the fact that Arc has been implicated in a variety of neurological diseases and conditions, ranging from Fragile X syndrome to Alzheimer’s disease. The Arc study will be an invaluable corner piece for those puzzles.
rather than simply asking the other side of the synapse to turn up the gain, Arc packages the raw genetic material to do so, and then visits the other side of the synapse in person. Effectively, Arc ‘infects’ other neurons with the raw materials of memory.
Arc still seems to act like a virus.
which contains stretches that look eerily similar to those found in ancient viruses.
One of these genes, known as Arc, is so critical to these processes that it has often been called a ‘master-regulator’ of synaptic plasticity.
This ‘synaptic plasticity’, is fundamental to the ability of animals to learn, and without it we would no more be able to tie our shoes than to remember our own names.
Prehistoric Viruses and the Function of the Brain - Scientific American
BEST source. Search these 3 databases at the same time; a good way to start searching for primary literature about almost any topic in Biology.
Identify - Biology - LibGuides at Grinnell College Libraries
AirTags: Everything We Know So Far - MacRumors
your last name, followed by a space with a page number
In the upper left-hand corner of the first page, list your name, your instructor's name, the course, and the date.
Do not make a title page
1 inch on all sides
Create a header that numbers all pages consecutively
Indent the first line of each paragraph
a legible font (e.g. Times New Roman).
white 8.5 x 11-inch paper.
General Format // Purdue Writing Lab
When placed in a darkened box, normal mice will stay away from a dish of bobcat urine, but will happily wander near a dish of rabbit urine. But when infected by Toxo—any strain of Toxo—they’ll blithely wander near the bobcat pee too.
turned it into a Trojan rodent
Mind-Bending Parasite Permanently Quells Cat Fear in Mice