Figure 4. Zebrafish kugelig Mutants.

The image shows live one-week-old zebrafish embryos. The embryos around the outside are wild-type fish. Those in the middle are a mutant called kugelig and have a homozygous mutation in a gene called cdx4. Loss of the proper functioning of this gene causes the obvious trunk and tail defects but also causes a reduction in the number of haematopoietic stem cells in the embryos, which therefore become severely anaemic. Studies on this mutant might lead to the discovery of molecules that can drive stem cell differentiation, for example, or could help improve understanding of human haematological malignancies. (Image courtesy of Alan Davidson, Harvard Medical School, Boston, Massachusetts, United States.)