Mutant skin won’t hold water according to a report in Nature Science Update 29 March 2002. Shoichiro Tsukita and colleagues from Kyoto University, Japan set out to study a protein named Claudin-1 that forms part of a structure called a tight junction. Tight junctions hold cells together in body organs such as the liver and kidneys and help control the movement of water and dissolved ions across layers of cells. The Japanese scientists bred mice that were lacking the protein and were surprised when the mice died of dehydration from water loss through the skin within a day of being born. Tsukito then looked for tight junctions in skin of normal mice and found them. It seems no one had bothered to look for them before because it was assumed that skin was waterproof because of the way the cells were layered on one one another, along with proteins and oils between the cells. Dysfunctional tight junctions are known to cause several human diseases such as inflammatory bowel disease. This new discovery may help scientist find the cause of some skin problems.
Editorial Comment: If lack of Claudin-1 causes mice to die of dehydration the day they are born, this protein did not evolve naturally over many generations. Neither could any of the other proteins needed to make tight junctions. There is another lesson to be learnt from this experience – don’t assume something does not exist just because no-one has found it before. As in this case, it may be that no-one has looked for it. (Ref. Claudin-1, skin, mutation)