The Spatiotemporal Expression Pattern Of Two Types Of Somatostatin Receptors In Zebrafish Embryos

The somatostatin (SS) signal pathway plays an important role in the growth, development and many other physiological processes of different organisms. The SS can serve as a neurotransmitter to participate the activities of brain, such as sensation, cognition and autonomic regulation functions and inhibit the release of many hormones produced by the nervous system, such as growth hormone. It also can modulate the action of organisms as a endocrine substance. Of all this, the somatostatin receptor (SSTR) possesses the critical position in mediating the signal pathway induced by SS. SSTR is a kind of protein with seven transmembranes segments. The mammals always owns five kinds of SSTRs which are encoded by five different genes located in five different chromosomes, and some types have several subtypes generated by alternative splicing of the genes. There have been reached a great progress in studying SSTR of mammals, while there have little researches about SSTRs in lower vertebrate animals and little attention was payed to that areas, especially the function of SSTRs signal pathway in development was still elusive.In order to elucidate the spatiotemporal expression pattern of SSTRs of the embryos in the early development stages, we used zebrafish as our model animal and utilized RT-PCR, in situ hybridization analysis methods to study the two kinds of somatostatin receptors(sstr1b,sstr2) cDNA. There are four kinds of types of sstr (sstrl,2,3,5), several of which produce alternative splicers. Utilizing RT-PCR technology, we cloned the partial segments of the above two sstr subtypes and linked them to PMD-19T vector. Then the segments were sent to company to be sequenced. After the results were feedback to us, we subcloned the segments into pCR-bluntâ…¡-topo vector for in situ hybridization experiments and resequenced in order to ensure the fidelity of the results. Then we synthesized the sense and anti-sense probes with in vitro transcription system. It was necessary to test the purity and integrality of the probes. The results are listed below:In the zebrafish ebmbryos, the sstr1b mRNA was first detected at about 24hpf (hours postfertilization) mainly in some nerve clusters of telencephalon, and the contents and levels of sstrlb mRNA were rather stable in the following developmental stages. The sstr2 gene owns a more extensive expression patterns including the whole neuraxis, namely some nerve clusters of hypothalamic position, the most parts of hindbrain and the whole spinal chord neuron. In our research, we found that sstr2 mRNA appeared at about 22hpf, or earlier. And at about 24hpf, the sstr2 mRNA positive signals also appeared at some parts of telencephalon. All this results serve as the basis for the further research of our study of the development function of SSTR signal pathway in the development of zebrafish.