Heinzelmann A, Kumar S, Noggle S, Goedegebuur I, Sauer K M, Rath S, Durdik J M
Department of Biological Sciences, University of Arkansas, Fayetteville 72701, USA.
J Immunol. 1998 Jul 15;161(2):666-73.
Fully recombined transgenes are stable in their transmission in the germline of transgenic mice, in common with the endogenous genetic complement of most mammalian somatic tissues, including the genes for lymphoid Ag receptors somatically generated from germline minigenes. There have, however, been isolated reports of unusual low frequency transgene losses in various transgenic mice. Here we show, using Southern blots and PCR-based assays, that plasmablast hybridomas and B cells from three independently derived founder lines of transgenic mice bearing a recombined heavy chain Ig transgene we have been studying show a significant net loss of transgene copies. This loss is more marked in the B cells expressing endogenous heavy chains than in those expressing transgenic heavy chains. We have also examined cells of the B lineage in the bone marrow, and a small degree of deletion is also evident in CD19+ CD23- IgM- immature B-lineage cells. As greater deletion is observed in mature B cells, it is possible that the deletion process either continues into B cell maturity and/or provides a selective advantage. We have investigated the relationship between transgene expression and deletion, and we find that while thymocytes in these mice express the transgene well, T cell hybridomas derived from transgenic thymus do not show any loss of the transgene. Thus, a recombined Ig heavy chain transgene prominently undergoes somatic deletion in B-lineage cells independent of its insertion site or expression. This transgenic instability is significant to the analysis of genomic stability as well as to the design of gene therapy strategies.
与大多数哺乳动物体细胞组织的内源性遗传互补一样，完全重组的转基因在转基因小鼠的种系传递中是稳定的，包括从种系小基因体细胞产生的淋巴样抗原受体基因。然而，已有关于各种转基因小鼠中异常低频转基因丢失的个别报道。在这里，我们使用Southern印迹和基于PCR的检测方法表明，来自我们一直在研究的携带重组重链Ig转基因的三个独立衍生的转基因小鼠创始系的浆母细胞杂交瘤和B细胞显示出转基因拷贝的显著净损失。这种损失在表达内源性重链的B细胞中比在表达转基因重链的B细胞中更明显。我们还检查了骨髓中B谱系的细胞，并且在CD19 + CD23 - IgM - 未成熟B谱系细胞中也明显存在少量缺失。由于在成熟B细胞中观察到更大的缺失，因此缺失过程可能会持续到B细胞成熟和/或提供选择优势。我们研究了转基因表达与缺失之间的关系，发现虽然这些小鼠中的胸腺细胞很好地表达了转基因，但源自转基因胸腺的T细胞杂交瘤并未显示出转基因的任何丢失。因此，重组的Ig重链转基因在B谱系细胞中明显发生体细胞缺失，与其插入位点或表达无关。这种转基因不稳定性对基因组稳定性分析以及基因治疗策略的设计具有重要意义。
