Natural or "wild-type" embryo. All the embryos shown are between 24 and 36 hours old.

Chordino mutants develop enlarged tail at the expense of head and trunk. In these mutants abnormal embryonic coordinates cause cells to migrate towards the tail instead of converging toward the embryo’s midline and contributing to the development of the head and trunk.

Myers, D.C., Sepich, D.S. and Solnica-Krezel, L. (2002) BMP activity gradient regulates convergence and extension movements during zebrafish gastrulation. Developmental Biology, 243, 81-98.

Cyclopic mutants in zebrafish feature only a single eye or partially fused eyes. These conditions have been traced to three genes – schmalspur (narrow rail in German), cyclops and one-eyed pinhead genes – that produce proteins that act as components of a signaling pathway called Nodal. The zebrafish studies showed for the first time that this pathway is required for formation of two separate eyes in vertebrate embryos, including humans.

Sampath, K., Rubinstein, A.L., Cheng, A.M.S., Liang, J.O., Fekany, K., Solnica-Krezel, L., Korzh, V., Halpern, M., Wright, C.V.E. (1998) Induction of the zebrafish ventral brain and floor plate requires Cyclops/Nodal signaling. Nature, 395, 185-189.

Pogoda, H.-S., Solnica-Krezel, L., Driever, W. and Meyer, D. (2000) Zebrafish Fast1/FoxH1 is a modulator of Nodal signaling required for organizer formation. Current Biology, 10, 1041-1049.

Trilobite mutants have a shortened and broadened embryonic axis because it does not produce a key protein required for orienting the long axis of cells in the direction of movement during the migration that elongates the embryo from head to tail and narrows it from back to underside. This impedes cell movement. In addition, lack of this protein inhibits the migration of specific sets of neurons from one portion of the trilobite brain to another.

Jessen, J.R., Topczewski, J., Bingham, S., Sepich, D.S., Marlow, F., Chandrasekhar, A. and Solnica-Krezel, L. (2002) Zebrafish trilobite reveals new roles for Strabismus in gastrulation and neuronal movements. Nature Cell Biology 4, 610-5.

The knypek (stands for "shorty" in Polish) mutant acts in a fashion similarly to trilobite. The embryos growth from head to tail is shortened due to defective cell movements. Knypek produces a protein decorated with sugars that scientists think collaborates with signals that orient moving cells.

Topczewski, J., Sepich, D.S., Myers, D.C., Walker, C., Amores, A., Lele, Z., Hammerschmidt, M., Postlethwait, J., and Solnica-Krezel, L. (2001) The zebrafish glypican Knypek controls cell polarity during gastrulation movements of convergent extension. Developmental Cell 1, 251-264.

This morphant mutant fails to form somites, segmented structures of early vertebrate embryos that give rise to musculature, skeleton and part of the skin. In such morphant embryos, gene function is disrupted not by a heritable mutation, but rather through injection of a short nucleotide sequence that blocks protein synthesis by a specific gene. Blockage of other genes causes other types of disruptions in embryo development.

Topczewska, J. M., Topczewski, J., Kume, T., Solnica-Krezel, L. and Hogan, B.L.M. (2001) The winged helix transcription factor Foxc1a is essential for somitogenesis in zebrafish. Genes & Development 15, 2483-2493.