CONTROL OF GEM EXPRESSION DURING LYMPHOID DEVELOPMENT - TARGETED GENEDISRUPTION PROVIDES NEW CLUES

The expression of structural genes is thought to be regulated by DNA-b inding factors interacting with cis-acting regulatory elements. These regulatory elements, identified for many lymphopoietic genes, have ser ved in recent years to identify and clone novel transcription factors. The expression of some of these factors is found to be confined to th e lymphoid lineage. This regulated expression in both time and space i s thought to mediate entry into and progression along the correct deve lopmental differentiation programs. In recent years, many laboratories have tried to assess the functional relevance of these DNA-binding fa ctors by making use of gene targeting techniques. A review of the resu lts of such knock-out experiments and the consequences for lymphoid de velopment models appears below.