Construction Of CDNA Library And EST Analysis From The Nervous System Of The Polyclad

Planarian is the typical species in the Turbellaria of Platyhelminthes.The characteristicsof three embryonic layers and primary bilateral symmetry make great significance to theevolution of animals. As well as，it is the important models for the development andregeneration research, the origin of the metazoan evolutionary biology.There is a small butterfly-shaped brain in polyclad flatworm, and it has a surroundingsheath which separates the neurons from the tissues.The central of the brain is mainlycomposed by neural fiber network, and the neurons cell bodies mainly distribute in neuralsection close to the sheath, also cell body partition is very clear. Nine main pairs of nervetrunks extend from the margins of the brain, with transverse nerves connected to the network,spreading all over the body.In this study, the Notoplana humilis is firstly used the experimental material inconstructing the cDNA library of the nervous systems of polyclad flatworm representatively.The study makes important significance on studying the mechanisms of regeneration anddevelopment of the planarian. The result showed that the capacity of the library was1.1×105clones with recombination rate about95%and the insertion size are mainly concentratedbetween500bp and3000bp with a average length of980bp. This cDNA library will sufficefor the follow-up experiments.Through sequence determination and EST analysis of the cDNA library，we got anumber of specific genes of planarian nervous systems, such as FMRFamide neuropeptideprecursor homologous gene, protein tyrosine phosphatease homologous gene, olfactory braincDNA homologous gene and putative Neuroendocrine protein7B2homologous gene. Also afew genes after blast were not found their homologous genes, and we speculated that theymay be the specific genes of the planarian.In situ hybridization histochemistry(ISHH) is now widely applied in current molecularbiology research.Through in situ hybridization，eight planarian specific genes were located inthe nervous system. Observing the distribution of these genes were contributed to furtherunderstanding of the function of the planarian nervous system, and it is crucial significant inanalyzing the development and regeneration of specificity expression. The ISHH resultshowed that: most of these specific gene-positive hybridization signals were located in the brain of the nervous system; because of different division of different genes on different levelsof the brain, we speculated functions division began to emerge in the planarian; consideringsome positive reaction cells were near the nerve trunk, we speculated they affected the nerveconduction; some positive reaction appeared in the oocytes, we speculated these genes playedimportant roles in early embryos development. In order to study the genes more clearly, wecan do further work by genes knockout or RNA interference technology to study the functionof the genes in neural development and regeneration.