MESOTOCIN GENE-EXPRESSION IN THE DIENCEPHALON OF DOMESTIC-FOWL - CLONING AND SEQUENCING OF THE MT CDNA AND DISTRIBUTION OF MT GENE EXPRESSING NEURONS IN THE CHICKEN HYPOTHALAMUS

This study focuses on the structure and expression of the mesotocin (M T) gene in the chicken hypothalamus. Using an anchored and nested RT-P CR strategy, combined with circular RACE-PCR, the full length sequence of the chicken MT cDNA was obtained, The cDNA and derived amino acid sequences conformed to the structure of the oxytocin-like gene family. However, unlike most mammalian species, there does not appear to be f requent gene conversion between the MT and AVT cDNA sequences. A singl e specific hybridization signal of 1.2 kb was detected by Southern ana lysis of chicken genomic DNA, indicating only a single gene copy in th e chicken genome, Northern analysis of hypothalamic RNA revealed a sin gle band at approximately 0.6 kb, Using the same probe for in situ hyb ridization histochemistry, MT-mRNA was demonstrated to be predominantl y localized in the parvocellular, magnocellular and periventricular su bgroups of the paraventricular nucleus and, when compared to the distr ibution of neurons containing arginine-vasotocin (AVT)-mRNA in the sam e region, with far fewer neurons expressing the MT gene in the lateral subgroups. Only few and scattered neurons expressing the MT gene were found in the ventral and external subgroups of the supraoptic nucleus in which many neurons contain AVT transcripts, as demonstrated in con secutive sections. In all nuclei investigated, the intensity of AVT an d MT hybridization signals per cell was approximately equal, No specif ic labelling for MT-mRNA was found in the bed nucleus of the stria ter minalis, nor the nucleus accumbens, Using immunocytochemical detection of AVT and in situ hybridization for neurons expressing MT-mRNA, some neurons were found to contain both AVT and MT gene products in the pa raventricular nucleus but not in the supraoptic nucleus.