The -216- to -100-bp Sequence in the 5'-Flanking Region of the Oxytocin Gene Contains a Cell-Type Specific Regulatory Element for its Selective Expression in Oxytocin Magnocellular Neurones

The oxytocin (OXT) gene is abundantly and highly selectively expressed in magnocellular neurones (MCNs) of the hypothalamic-neurohypophysial system. Previous DNA sequence deletion studies in vivo have shown that the -216- to -100-bp sequence in the 5'-flanking region of the oxytocin gene was required for its cell-type specific expression in the rat supraoptic nucleus. In the present study, we test the coupled hypotheses that this -216- to -100-bp sequence is responsible for (i) the selective expression of the OXT gene in OXT-MNCs and (ii) its selective repression in vasopressin (AVP)-MCNs. We show that, consistent with hypothesis 1, removal of the -216- to -100-bp sequence from the OXT gene completely eliminates its expression in OXT-MCNs in vivo but, in contrast to the prediction of hypothesis 2, there was no appearance of OXT gene expression in AVP-MCNs. Taken together, these and other data demonstrate that the -216- to -100-bp sequence in the 5'-flanking region of the oxytocin gene contains only an activator of transcription operating in the OXT-MCNs.