Organogenesis of the liver, thymus and spleen is affected in jumonji mutant mice.

The recessive mutant mouse jumonji (jmj), obtained by a gene trap strategy, shows neural tube defects in approximately half of homozygotes with a Balb/cA and 129/Ola mixed background. Here, we show that no neural tube defects are observed with a Balb/cA background. We also found hypoplasia of the liver, thymus and spleen with full penetrance with a Balb/cA background. In the livers of homozygous embryos we found excessive cell death in the peripheral region. In both the thymus and spleen, the accumulation of hematopoietic cells is affected in mutant embryos. These phenotypes were also observed with C57BL/6J and DBA/2J backgrounds, suggesting that the jmj gene plays an essential role in the organogenesis of these tissues.