He found that a gene called "complement component 4" -- it's called "C4" for short -- comes in dozens of different forms in different people's genomes, and these different forms make different amounts of C4 protein in our brains.
Vio que un gen llamado  "componente 4 del complemento", o C4 en su forma abreviada, se manifiesta de varias maneras distintas en el genoma de diferentes personas, y estas maneras distintas  fabrican distintas cantidades de proteínas C4 en el cerebro.