关键词: 中枢神经细胞瘤, 少突胶质细胞瘤, FAC1, mRNA, 差异显示

Abstract: Objective Central neurocytoma(CN) is a rare, benign intraventricular tumor of central nervous system(CNS). Histologically, CN closely resembles oligodendroglioma(OG) in terms of morpholog. According to the WHO new classification of CNS tumors, CN is classified as neuronal and mixed neuronal-lial tumors of neuroepithelial tissue, and OG as oligodendroglial tumors of neuroepithelial tissue. The former is characterized by its high radiosensitivity, but the latter is sensitive to chemotherapy partly. This study aims at investigating the molecular mechanisms underlying the differences between CN and OG, and their pathogeneses. For this purpose, we applied fluorescent DD-CR/DDRT-PCR to identify differentially expressed genes in CN, OG and normal brain tissues. Methods In this study, tissues including 2 case of CN, 4 case of OG, and 2 normal brain tissues obtained during decompression surgery for cerebral trauma as control group. The total RNAs from frozen specimens were compared by fluorescent DDRT-PCR. Differential display bands of interest were chosen. Eight cDNA fragments isolated from DD denaturing gel were extracted and reamplified, cloned into pMD18-T vector and sequenced. Then the sequences of the bands were analyzed for homology with known genes using the BLAST search. Results Significant differences of gene expression were detected among CN, OG and normal brain tissues. Eight bands were selected. In these bands, one(W8) was highly expressed in CN, three(W3, 4, 7) in OG, and 4(W1, 2, 5, 6) in normal brain tissue. BLAST analysis and a GenBank search of these 8 clones showed that 2(W3, 8) represented known genes, namely fetal Alz-50 reactive clone 1(FAC1) located in chromosome 17q24.3 and aspartylglucosaminidase(AGA) in 4q32-q33. The protein encoded by FAC1 is a novel member of the PHD/LAP zinc finger family. Two clones(W1, 2) showed homology to human without known gene sequence. Another four clones(W4, 5, 6, 7) shared sequence homology to Mus musculus or Rattus norvegicus. Conclusion Differentially displayed band W1, a sequence located in chromosome 16, is expressed highly in normal brain tissue but not in CN and OG. It might be a novel gene encoding a protein of transcription factors regulator which contains a zinc finger motif. FAC1 is expressed at low level or not in normal brain tissues but higher in OG. It is supposed that FAC1 may play a role in the development of OG depending on the regulation of gene expression.

Key words: central neurocytoma, oligoden droglioma, FAC1, mRNA, differential display