Something I've been meaning to cover is that Japanese scientists recently reported that they had developed a strain of lab mice in which the gene for filaggrin had been "knocked out."
That is, these mice, which are inbred for genetic purity, are missing the filaggrin gene. Their skin contains no filaggrin.
Filaggrin is a giant protein that consists of a chain of repeated components. It helps create the flattened structure of upper skin cells, and then breaks down into smaller, acidic molecules that form a natural moisturizing factor and probably help combat infection.
This will be a valuable experimental tool going forward. Paradoxically, a
mouse model without filaggrin can teach you a lot about what filaggrin
does--because it will be absent in those mice.
Using these new mice, researchers can focus on specific aspects of the skin, including various molecular pathways, and by comparing the knockout mice to regular mice, they can see what roles filaggrin plays.
Not surprisingly, the knockout mice have "dry, scaly skin" that lets more antigens through. Despite the skin's obvious fragility, the scientists find that the upper layers are normally hydrated, and show no increased tendency to lose water to the air.
The research was led by Masayuki Amagai at Keio University in Tokyo.