[1] Univ Calif San Francisco, Howard Hughes Med Inst, San Francisco, CA 94143 USA
[2] Univ Calif San Francisco, Program Dev Biol, San Francisco, CA 94143 USA
[3] Univ Calif San Francisco, Genet Program, San Francisco, CA 94143 USA
[4] Univ Calif San Francisco, Program Neurosci, San Francisco, CA 94143 USA
[5] Univ Calif San Francisco, Dept Anat, San Francisco, CA 94143 USA
[6] Univ Calif San Francisco, Dept Biochem & Biophys, San Francisco, CA 94143 USA
[7] Univ Utah, Dept Biol, Salt Lake City, UT 84112 USA
[8] Oklahoma Med Res Fdn, Oklahoma City, OK 73104 USA