Department of Developmental Biology, Washington University School of Medicine, Saint Louis, MO, USA.|Program in Bioinformatics & Computational Biology, Saint Louis University, Saint Louis, MO, USA.|Department of Developmental Biology, Washington University School of Medicine, Saint Louis, MO, USA.|Department of Developmental Biology, Washington University School of Medicine, Saint Louis, MO, USA.|Department of Neuroscience, Washington University School of Medicine, Saint Louis, MO, USA.|Department of Mathematics & Statistics, Saint Louis University, Saint Louis, MO, USA.|Department of Developmental Biology, Washington University School of Medicine, Saint Louis, MO, USA.|Program in Bioinformatics & Computational Biology, Saint Louis University, Saint Louis, MO, USA.