一种新的人血管内皮生长因子基因的剪切体(英文)

A probable novel splicing isoform of human vascular endothelial growth factor

目的探索人胚胎肺组织中是否存在一种新的血管内皮生长因子（VEGF）基因可变剪切形式。方法对1例4月龄引产胎儿肺组织的总RNA进行逆转录聚合酶链反应、克隆并测定扩增片段的序列。结果用一对引物（引物5’端-21~7 bp, 3’端554~576 bp）可扩增出3条片段，一条为长度正常的VEGF165 （619 bp）全长序列，另一条为长度正常的VEGF12（1 487 bp）全长序列，第三条为新的VEGF mRNA异常剪切片段。测序检测显示，此扩增片段长度为639 bp，同样为VEGF165全长核苷酸序列，但在VEGF165的第3和第4外显子之间插入了长度为20 bp的碱基片段。序列分析显示此插入序列为滞留的第Ⅲ内含子终末序列，含内含子剪切信号。上述移码突变导致VEGF基因阅读框架发生改变，在第4外显子中游出现终止密码，故仅含VEGF165外显子1~3及4部分序列，在蛋白水平上可能编码含97个氨基酸的新肽链。结论在一引产胎儿的肺组织中发现了新的VEGF mRNA可变剪切形式，其生物学意义有待进一步研究。

Objective To characterize a new alternative splicing isoform of human vascular endothelial growth factor （VEGF） gene. Methods The total RNA was extracted from the lung tissue of a legally aborted 4-month-old fetus and amplified by RT-PCR. The amplified product was cloned into the plasmid pMD18-T and plasmid pcDNA3.1- for sequence analysis. Results Electrophoresis of the RT-PCR products displayed one short band for VEGF121 （487 bp） and a long band. The latter was characterized to contain two fragments： one was normal VEGF165 （619 bp）, and the other （639 bp） had an identical nucleotide sequence to VEGF165 with a 20 bp fragment inserted between exons 3 and 4. Sequence analysis showed that this 20-bp nucleotide was inserted from the 3’ end of the third intron containing a splicing signal, thus causing shift mutation in the reading frame of VEGF gene and early appearance of the stop codon UAG in the middle of exon 4. Conclusion A new alternative splicing isoform of VEGF probably exists in the lung tissue of a legally aborted human fetus, and its biological significance remains to be further investigated.