| Dictyostelium discoideum is a social amoeba. The individual cells grow and multiply by equal mitotic division when the food is enough. Exhaustion of the food source triggers a development programme. Despite the multicellular development process is relatively simple, the regulatory signaling pathways are as complex as those in metazoan development, the homologous signal proteins can also be finded during metazoan development. So Dictyostelium discoideum has been used as a model organism for researching regulation of signaling molecules during multicellular development and cell apoptosis.gp150 is encoded by lagC gene, and it is a membrane glycoprotein. High concentrations of gp150 are present at cell-cell contacts, they regulate cell-cell adhesion by heterophilic interactions. gp150 is expressed on cells in the early post-aggregation stage, it can be detected in the wild type KAx-3 cells but not in the mutant type AK127 cells by Western blot. The mutant type strain AK127, as a result of absence of gp150, can't complete multicellular development and the development is arrested at the loose aggregate stage. The obtained data suggested gp150 proteins play an important part in Dictyostelium discoideum development, it may take part in the signaling pathway for regulating cell differentiation and cell apoptosis. So far, our knowledge of the signaling pathway is still very limited. So we are tried to find the differential display genes between the KAx-3 cells and AK127 cells (developed for 14 hours), so that we can know more about the signaling path controlled by gp150.Total RNAs from KAx-3 cells and AK127 cells(developed for 14h) were isolated. After the reverse transcription and PCR reaction, two distinct differential fragments were acquired., fragment A was from KAx-3 cells and fragment C was from AK127 cells. After retriving and reamplifying the differentially expressed fragments, white-blue plaqueselection, the fragments were purified. Northern blot proved that fragment A was from KAx-3 cells and fragment C was from AK127 cells. The results of sequencing and researching for NCBI database have been showed: part sequence of fragment A shows 91% similarity to the gene encoding DhkA, 92% similarity to the gene encoding DhkF, 91% similarity to the gene encoding STATc, 97% similarity to the homoeobox gene encoding protein. These genes play important part in controlling cell differentiation and cell proportion in Dictyostelium discoideum. Fragment C shows 99% similarity to 635bp of Dictyostelium discoideum mitochondrion DNA, it contains most part of nad3 gene and genes encoding tRNA-Cys and tRNA-Asn. The product of nad3 is NADH dehydrogenase subunit 3, NADH is a coenzyme needed for cell energy metabolism, transferring electrons in biological process and it is an important part of hydrogen transferring in respiratory chain. Metabolin pass hydrogen to NAD~+, and then NADH dehydrogenase pass hydrogen to FAD or FMN, at last, hydrogen is combined with oxygen, release energy. The ratio of NAD~+/NADH not only play an important part in controlling redox in cells , but also is considered as a metabolic guideline and related with metabolism, rhythm, caducity, pathological changes and death of cells. NADH dehydrogenase regulates NAD~+/NADH, and thus it is important for cell metabolism and apoptosis. These genes may be involved in the signaling pathway controlled by gp150, they play important parts in controlling cell differentiation and proportion, gp150 may exert the influence on the development of Dictyostelium discoideum by affecting the expression of these genes. This research can provide some data for constructing vectors to express these genes, researching the moleculer location in the organism and related functions.
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