Of all the organs in the human body, there is one that can now be called the most uniquely “human” of all, according to scientists, who based their judgments on new findings on the number of proteins produced by different bodily organs.
A decade ago, the Human Genome Projects finally mapped all of the genes in human cells. But contrary to popular perception, genes alone do not determine human characteristics. What genes do is produce proteins, and those proteins do the work of making you who you are — and of keeping you alive.
The findings of the team of biologists led by Mathia Uhlen of the Swedish Royal Institute of Technology are compiled in The Human Protein Atlas, in which they list the various different proteins produced by the various human organs.
The proteins present in a specific organ determine its function. The presence of different proteins is what makes, for example, the human liver perform different functions from the brain.
“It’s all very well knowing all our genes but at the end of the day, all human disease and biology stem from the proteins – the building blocks of humans,” Uhlén explains. “What we’ve produced is like a Gray’s Anatomy for proteins.”
The most sophisticated, complex organs, it would stand to reason, should contain the greatest number of unique proteins. And that’s why their findings about the most sophisticated organ in the human body is surprising.
The human brain — which would appear to be the most sophisticated organ not only in the human body, but in all of nature — should contain the most different proteins. Right? Well, it doesn’t. The brain contains 318 unique proteins, Uhlen’s team found. That’s an impressive number. But it’s less than one-third the amount of proteins found in another organ. And what organ is that?
The human testicles.
That’s right, it turns out that the male testes are more complex than the human brain, proteomically speaking, that is. Testicles are the protein-making champs, with 999 different proteins that the scientists have so far been able to identify.
So what is it about balls that make them more complicated than brains? For one thing, Uhlen says, testicles are charged with the responsibility — or half of it, anyway — for keeping the human race going. And that’s not easy, because it means producing a certain type of cell that must not only have the ability to survive on its own when separated from the rest of the body, it must survive with only half the DNA of the body’s other cells.
That’s what makes sperm cells remarkable little beings, and testicles have a tough job, churning out hundreds of millions of these sophisticated little machines.
Uhlen added that human ovaries, which produce egg cells, may contain an equally high number of proteins, but because ovaries develop in fetuses, there’s no way to get tissue samples to test the theory.