COVID and smell loss: answers begin to emerge | Nature | 09.06.22
▻https://www.nature.com/articles/d41586-022-01589-z
Columbia University in New York City examined people who had died from COVID-19 and found that, although their neurons were intact, they had fewer membrane-embedded receptors for detecting odour molecules than usual. This was because the neurons’ nuclei had been scrambled. Normally, the chromosomes in these nuclei are organized into two compartments — a structure that enables the neurons to express specific odour receptors at high levels. But when the team looked at the autopsied neurons, “the nuclear architecture was unrecognizable,” Lomvardas says.
Other studies suggest why only some people experience long-term smell loss. In January, a research team reported finding a genetic mutation in people that was associated with a greater propensity for smell or taste loss. The mutation — a change to a single ‘letter’, or base, of DNA — was found in two overlapping genes, called UGT2A1 and UGT2A2. Both encode proteins that remove odour molecules from the nostrils after they have been detected. But it’s not yet clear how SARS-CoV-2 interacts with these genes.
There is also evidence of lasting changes to the brain for people with smell loss. [...] “When we cut off input from the nose, the brain atrophies,” says Danielle Reed, a geneticist also at Monell. “It’s one of the clearest things we know about taste and smell.”