Leibniz Institute for Age Research-Fritz Lipmann Institute, Genome Analysis, Beutenbergstr. 11, Jena, Germany.
Gene. 2010 May 1;455(1-2):1-7. doi: 10.1016/j.gene.2010.01.005. Epub 2010 Feb 4.
The paralogous genes RABL2A (chr2) and RABL2B (chr22) emerged by duplication of a single gene in the human-chimpanzee ancestor and share a high degree of sequence similarity. In Phelan-McDermid-Syndrome microdeletions of 22q13 often also affecting RABL2B are of clinical importance but their incidence is still unknown. We analyzed a German population (190 individuals) for such aneuploidies and the paralogs' expression in cell lines by RABL2 paralogous sequence quantification. For determination of the genomic and transcriptional ratios of RABL2A and RABL2B a Pyrosequencing protocol was introduced as a high-throughput method. During PCR the 3' end of the biotinylated strand is engineered by a backfolding oligonucleotide to hybridize in the Pyrosequencing reaction to an internal site near the sequence to be analyzed. In human samples no deviations of the euploid genomic state could be detected indicating that 22q13 microdeletions involving RABL2B are rare. However, despite equal gene dosage a preferential expression of RABL2B in human tissues and lymphoblastoid cell lines was detected which is most pronounced in brain and placenta. This renders a complete functional complementation of one paralog by the respective other unlikely and hints to a functional and clinical importance, in particular with respect to the 22q13 chromosomal deletion syndrome. Remarkably and in contrast to human, expression levels of the two paralogs in a chimpanzee cell line are equal. This finding is discussed in view of the relocation of RABL2A from its ancestral telomeric to its pericentromeric location in human.
RABL2A（2 号染色体）和 RABL2B（22 号染色体）这两个基因是人类和黑猩猩的祖先通过单一基因复制产生的，具有高度的序列相似性。在 22q13 微缺失综合征中，经常涉及 RABL2B 的缺失，这具有重要的临床意义，但它们的发生率仍不清楚。我们通过 RABL2 基因同源序列定量分析，研究了一个德国人群（190 例个体）是否存在这种非整倍体和基因的细胞系表达情况。为了确定 RABL2A 和 RABL2B 的基因组和转录比值，我们引入了焦磷酸测序方案作为高通量方法。在 PCR 过程中，通过反向折叠寡核苷酸工程化修饰生物素化链的 3' 末端，使其在焦磷酸测序反应中与靠近待分析序列的内部位点杂交。在人类样本中，未检测到染色体 22q13 微缺失导致的常染色体基因组状态的偏差，这表明涉及 RABL2B 的微缺失是罕见的。然而，尽管基因剂量相等，但在人类组织和淋巴母细胞系中检测到 RABL2B 的表达偏好，在大脑和胎盘组织中最为明显。这表明一个基因的功能不可能完全由另一个基因的拷贝来补偿，这暗示着 RABL2B 具有功能和临床重要性，特别是考虑到 22q13 染色体缺失综合征。值得注意的是，与人类不同的是，在黑猩猩细胞系中，两个基因的表达水平是相等的。这一发现考虑到了 RABL2A 从其祖先的端粒位置到人类的着丝粒位置的重新定位。
