Human testicles produce nearly a thousand unique proteins — more than the brain's 318 unique proteins, according to the latest version of the Human Protein Atlas.
"What's going on in the testes is unique, as sperm must survive with half the chromosomes and outside the human body," Mathias Uhlén from the Swedish Royal Institute of Technology tells the New Scientist. Uhlén led the decade-long effort to examine the proteins produced in various tissues of the human body.
Starting in 2005, he and his colleagues began to analyze tissues from 360 healthy people. As the Economist reports, the researchers developed antibodies to some 17,000 proteins and then applied these antibodies, bound to staining molecules, to thin tissue slices to see which proteins were present there. The project's new webpage may be found here.
"The result will be of great value to researchers trying to understand how tissues differ at the molecular level," the Economist says. "Most biological functions depend on proteins, so it is the mix of proteins within a cell which defines what that cell is."
Although Uhlén and his team identified 3,500 human genes that encode proteins that are only found in one or two tissues, their atlas is not yet complete as there are some 20,000 protein-coding genes in the human genome, the Economist adds.