This year's Nobel prize in Physiology or Medicine — awarded to Oliver Smithies, Mario Capecchi and Martin Evans for '...introducing specific gene modifications in mice by the use of embryonic stem cells'— was a well expected and richly deserved announcement. After all, the technique provides a cornerstone of many key findings by allowing them to be validated in a physiological setting. For the same reason, we would like to re-emphasize that new knockout models fall under our policy for the unrestricted distribution of materials and methods (see http://www.nature.com/authors/editorial_policies/availability and May 2006 editorial). It is expensive and legally cumbersome to transport live stock. However, the distribution of ES cells or sperm is certainly feasible and we strongly recommend using public repositories such as the Jackson Laboratory, the Mutant Mouse Regional Resource Centers and the Federation of International Mouse Resources.

It is understandable that scientists want to reap academic credit for their mouse knockouts. However, this must not result in blocking access to published reagents. Authorship on follow-on studies may be appropriate, but again note our explicit policies on authorship (http://www.nature.com/authors/editorial_policies/authorship and March 2005 editorial). If you do encounter a persistent refusal to comply with these guidelines please contact the editors.

Often it is not the researchers themselves but overzealous intellectual property offices that restrict material sharing through prohibitive MTAs. It is therefore important to keep your institutional IPO appraised of journal policies and to link to relevant MTAs from the published paper.

Several consortia are pursuing genome-wide libraries of conditional mutant strains. These tremendous resources should largely alleviate problems with sharing valuable reagents such as mouse knockout strains (see also Nature Cell Biology 9, 993–999; 2007).