Control of Cell Fate During Vertebrate Neuronal Development 
other investigators, which showed that embry- 
onic control genes identified by mutational analy- 
sis in the fruit fly Drosophila have counterparts 
in the mouse and human that are remarkably con- 
served in their structure. We therefore reasoned 
by analogy that Drosophila genes controlling 
neural development might also be conserved in 
mammals. 
One important set of genes that control neuro- 
nal development in Drosophila are those of the 
achaete-scute complex (AS-C). These scute 
genes encode a group of related proteins that act 
by binding to DNA, thereby controlling the activ- 
ity of other genes. If the function of these genes is 
eliminated by mutation in the fly, certain classes 
of neurons fail to form. We succeeded in isolating 
two scM^e-related genes from the rat chromafiin- 
neuron precursor cell line. The structures of 
these genes are remarkably similar to those of 
their fruit fly counterparts. Moreover, the rat 
scM^e-related genes appear to be expressed specif- 
ically in neuronal precursor cells, like their 
counterparts in the fly. These data indicate that 
there has been a striking parallel conservation of 
gene structure and cell type specificity during 
evolution. They further suggest that the scute- 
related genes may control the development of 
mammalian neurons. This discovery opens up a 
new line of investigation, which will be aimed at 
finding both the precise role of the scute-veldxed 
genes during neuronal development and the 
manner in which these genes are controlled. 
These exciting findings suggest that the molecu- 
lar mechanisms controlling nerve cell develop- 
ment in vertebrate and invertebrate organisms 
may be fundamentally similar. Studies in each 
system will therefore contribute to our under- 
standing of the other, leading to a unified view of 
the basic principles that guide the building of a 
nervous system. 
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