Virus DNA in human genome (evolution by infection)

If it wasn't for virus DNA in human genome, humans would NOT exist. The evolution of the mammalian placenta has happened because of endogenous retroviruses. The viruses in human genome have come from infections millions of years ago that have stayed around in our DNA.

The human endogenous retroviruses are on longer functional viruses capable of infecting. Instead, what's left in the human genome are parts of these viruses, specific important genes. These are the critical genes for placental evolution. Placental mammals have adopted these genes in a wonderful way, and turned a tool used by viruses to infect cells into a tool for creating the placenta.

The evolution of the mammalian placenta is not a rare, one time event. Instead, the evolution of the mammalian placenta has occurred over and over. What's even more astounding is that the placenta has evolved in non-mammalian species as well.

We humans need retrovirus genes for our development. We descend from viruses.

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Resources

The original article finding the viral origins of human syncytins
https://www.ncbi.nlm.nih.gov/pubmed/10693809

A review article on the placentation and captured env-genes
https://doi.org/10.1016/j.placenta.2012.05.005

OPEN - Another thorough review of placentation and retroviruses
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3758191/

OPEN – A concise review of retroviruses and the evolution of the placenta
https://www.pnas.org/content/pnas/109/7/2184.full.pdf

OPEN - A general review of retroviruses
https://www.ncbi.nlm.nih.gov/books/NBK19382/

A general review on endogenous retroviruses, retroviruses that are part of our genome
https://www.ncbi.nlm.nih.gov/pubmed/18694346

OPEN - Description of the membrane protein recognized by env
https://www.pnas.org/content/pnas/105/45/17532.full.pdf

Description of the workings of the placenta
https://www.ncbi.nlm.nih.gov/pubmed/15507270

An article describing a hyena env-gene. Also fresh source for the timeline of syncytin captures. Here Heidmann and colleagues also talk about their model for placental formation.
https://www.ncbi.nlm.nih.gov/pubmed/30463979

OPEN - Finding of Syncytin-Car1, a syncytin functional in the whole Carnivora order
https://www.pnas.org/content/pnas/109/7/E432.full.pdf

OPEN – Blocking mice syncytin disrupts the formation of their placenta
https://www.ncbi.nlm.nih.gov/pubmed/19564597

OPEN - Description of the envV syncytin.
https://www.ncbi.nlm.nih.gov/pubmed/23555306

OPEN – The Mabuya syncytin
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5754801/pdf/pnas.201714590.pdf
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Credits

Graph of the family tree of mammals and times of Syncytin domestication based on a graph from this hyena env article: https://www.ncbi.nlm.nih.gov/pubmed/30463979

3D-model of Syncytin 2 adopted from
https://www.ncbi.nlm.nih.gov/pubmed/16140326

Cell video - Toshiyuki Hatano, Greenfield Sluder (2011) CIL:34849, Homo sapiens, retinal pigment epithelium. CIL. Dataset. https://doi.org/doi:10.7295/W9CIL34849

Chromosomes adopted from an image by National Human Genome Research Institute

HIV- virion - CDC/ Maureen Metcalfe, Tom Hodge

HIV close up image - CDC/ A. Harrison; Dr. P. Feorino

HIV -budding-out - CDC

Tab V, fetus with umbilical cord and placenta - Wellcome Collection. Creative Commons Attribution [CC BY 4.0 (https://creativecommons.org/licenses/by/4.0)] https://wellcomecollection.org/works/pnbunkzq

human embryo - Ed Uthman - [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0/
)] https://www.flickr.com/photos/euthman/548063929

Staphylococcus - NIAID - Attribution 2.0 Generic [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0/)] https://upload.wikimedia.org/wikipedia/commons/2/2e/Staphylococcus_epidermidis_Bacteria_%285613984108%29.jpg

Eosinophils in Peripheral Blood Smear - Ed Uthman - Attribution 2.0 Generic [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0/)] https://www.flickr.com/photos/euthman/4746281402

Lizards:
Mabuya - Izalete Tavares - Attribution 2.0 Generic [CC BY 2.0(https://creativecommons.org/licenses/by/2.0/)]
https://flic.kr/p/pjjBQU

Long-tailed_Skink_(Mabuya_longicaudata)_長尾南蜥2 - Thomas Brown [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)]
Mabuya mabouya - Mark Stevens - Attribution 2.0 Generic [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0/)] https://www.flickr.com/photos/46679531@N02/4288472733

Bronze_Grass_Skink_(Mabuya_macularia)_W_IMG_2753 - J.M.Garg - J.M.Garg [CC BY 3.0 (https://creativecommons.org/licenses/by/3.0)]
https://upload.wikimedia.org/wikipedia/commons/4/46/Bronze_Grass_Skink_%28Mabuya_macularia%29_W_IMG_2753.jpg

File:Bronze Grass Skink (Mabuya macularia) W IMG 9977 - J.M.Garg - J.M.Garg [CC BY 3.0 (https://creativecommons.org/licenses/by/3.0)]
https://upload.wikimedia.org/wikipedia/commons/6/6f/Bronze_Grass_Skink_%28Mabuya_macularia%29_W_IMG_9977.jpg

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