- A sequence of developmental events transforms neurons from their immature state to their mature, terminally differentiated state. The elav locus is one of the first examples of a gene that is expressed in neurons early during this developmental sequence. This gene has been shown to be required for the proper development of young neurons and for the maintenance of mature neurons. DNA sequence data presented in this report suggest that the elav gene product is an RNA binding protein, based on the presence of RNP (ribonucleoprotein) consensus sequences. This leads to the proposal that this protein is involved in the RNA metabolism of neurons.