Identification and tissue-specific expression of amphioxus GM2 activator protein gene from amphioxus Branchiostoma belcheri.

An amphioxus cDNA, AmphiGM2AP, encoding GM2 activator protein was isolated from the gut cDNA library of Branchiostoma belcheri. It is 907 bp long, and its longest open reading frame codes for a precursor protein consisting of 242 amino acid residues with a signal peptide of 14 amino acids. The deduced amino acid sequence includes a conserved domain typical of GM2APs between residues 53 and 224, a single N-linked glycosylation site at position 65 and 8 conserved cysteines. Phylogenetic analysis showed that amphiGM2AP forms a club together with invertebrate GM2APs, indicating that AmphiGM2AP is evolutionarily closely related to invertebrate GM2APs rather than vertebrate ones. Both Northern blotting and in situ hybridization histochemistry analyses revealed a tissue-specific expression pattern of AmphiGM2AP in adult amphioxus with the strongest expression in the digestive system, which is in contrast to the widespread expression pattern of human, mouse and sheep GM2AP genes. It is suggested that AmphiGM2AP is possibly involved in the take-in of digested food components like lipid molecules.

Verification, characterization and tissue-specific expression of UreG, a urease accessory protein gene, from the amphioxus Branchiostoma belcheri.

UreG genes have been found in bacteria, fungi and plants but have not yet identified in animals, although a putative UreG-like gene has been documented in sea urchin. In the course of a large-scale sequencing of amphioxus gut cDNA library, we have identified a cDNA with high similarity to UreG genes. Both reverse transcription-polymerase chain reaction and nested polymerase chain reaction, as well as in situ hybridization histochemistry, verified that the cDNA represented an amphioxus UreG gene (AmphiUreG) rather than a microbial contaminant of the cDNA library. This is further supported by the presence of urease activity in amphioxus gut, gill and ovary. AmphiUreG encodes a deduced protein of 200 amino acid residues including a highly conserved P-loop, bearing approximately 46%-49%, 44%-48%, and 29%-37% similarity to fungal, plant and bacterial UreG proteins, respectively. It shows a tissue-specific expression pattern in amphioxus, and is especially abundant in the digestive system. This is the first UreG gene identified in animal species.

[Synergism of c-myc and p16 in oral squamous cell carcinoma].

BACKGROUND & OBJECTIVE: The study on the protein expression of c-myc and p16 in oral squamous cell carcinoma (OSCC) has been reported, and a few researches involved in their gene amplification and mRNA expression in OSCC, however, the synergism of c-myc and p16 in OSCC in multiple levels is still unclear. This study aims to probe the synergism of c-myc and p16 in OSCC in gene amplification, mRNA expression, and protein expression levels. METHODS: The gene amplification, expression of mRNA, and protein of c-myc and p16 in 30 cases of OSCC were determined by in situ hybridization and immunohistochemical techniques. RESULTS: The amplification rate of c-myc was 63.3%, but no amplification of p16 was found in OSCC. The mRNA expression rates of c-myc and p16 were 83.3% and 93.3%, and their protein expression rates were 60.0% and 86.7%, respectively. The correlation analysis showed that there was significant correlativity between p16 and c-myc both in mRNA expression (r=0.676 5, P=4.055 6E-05) and in protein expression (r=0.564 2, P=0.001 2). CONCLUSION: The gene amplification and overexpression of c-myc plays an important role in the tumorigenesis and development of OSCC. There is certain internal relationship between p16 and c-myc expression in OSCC.