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Rat race: illustrations from an eighteenth-century Japanese treatise on breeding rodents for colour. Credit: NATIONAL DIET LIBRARY, JAPAN

As passionate rat researchers we were delighted to see the rat on the cover of the 1 April 2004 issue of Nature. It is little known that Japan has a long history of rat research, including studies on coat-colour inheritance that date back to the eighteenth century. Chingansodategusa, a Japanese guidebook on the breeding of fancy rats and mice, was published in 1787, during the Edo period, when Japan's civilization was isolated from the rest of the world. Japan is still an island but, we hope, is not so isolated today.

Your News Feature “The Renaissance rat” (Nature 428, 464–466; 2004) hailed a remarkable rodent, but it did not mention a modern Japanese contribution to its research: the National Bio Resource Project for the Rat (http://www.anim.med.kyoto-u.ac.jp/nbr). This rat-strain repository, one of the largest in the world, currently has more than 200 rat strains, which are freely distributed — at no cost except shipping — to any interested rat researcher worldwide.

In addition, we also provide a database for more than 100 different phenotype parameters of the rat strains. This allows for strain ranking, a method by which the parameters are sorted and unexpected abnormal values in reference strains can be revealed. This project already covers almost 50 rat strains and will finally comprise 200. This sort of phenotype ranking has the potential to save rat researchers all over the world valuable time, money and animals.