Correction

DEVELOPMENTAL BIOLOGY. For the article “Targeted disruption of the Walker–Warburg syndrome gene Pomt1 in mouse results in embryonic lethality,” by Tobias Willer, Belén Prados, Juan Manuel Falcón-Pérez, Ingrid Renner-Müller, Gerhard K. H. Przemeck, Mark Lommel, Antonio Coloma, M. Carmen Valero, Martin Hrabé de Angelis, Widmar Tanner, Eckhard Wolf, Sabine Strahl, and Jesús Cruces, which appeared in issue 39, September 28, 2004, of Proc. Natl. Acad. Sci. USA (101, 14126–14131; first published September 21, 2004; 10.1073/pnas.0405899101), due to a printer's error, the first sentence of the fourth paragraph on page 14127 incorrectly reads, “The targeting construct was linearized and electroporated into embryonic day (E)14.1 embryonic stem (ES) cells.” This sentence should be changed to read, “The targeting construct was linearized and electroporated into E14.1 embryonic stem (ES) cells.”