The development of animal model for chromosome trisomy-syndrome by microcell-mediated chromosome transfer

在本研究中，通过微细胞介导的染色体转移(MMCT)将hChr.21导入小鼠胚胎干细胞，并由此产生了可存活的嵌合体小鼠。我们对这些小鼠进行了如下分析。用荧光原位杂交技术(FISH)检测了4只嵌合小鼠不同组织的中期分裂相，以评价hChr.21在体细胞中的稳定性。含有hChr.21的价差百分比显示为50%-100%。对其中一只小鼠的RT-PCR分析表明，hChr.21上的几个基因以适当的组织特异性方式表达。最后，我们确定嵌合小鼠可以通过生殖系将hChr.21片段(hChr.21f)传递给后代。对11只围产期死亡的嵌合小鼠进行解剖和组织学观察，发现它们均出现胸骨发育不全和生殖细胞显著减少，心、肝、肾等脏器零星出现不同程度的组织学异常。作为对照，对4只含有免疫球蛋白基因的嵌合小鼠进行了解剖学和组织学研究。大多数患者颈椎椎体延迟骨化，胸骨发育不全和前肢多指畸形，散在出现HERT、肝、肾肥大和各种组织学异常。HChr.21嵌合小鼠生殖细胞显著减少和hChr.2f嵌合小鼠多指畸形很可能与人类染色体上引入的基因(S)有关。

In present study, hChr.21 was introduced into mouse embryonic stem (ES) cells via microcell-mediated chromosome transfer (MMCT), and viable chimeric mice were produced from them. We analyzed theses mice as followings. Metaphase spreads of various tissues from four chimeric mice were examined by Fluorescence in situ hybridization (FISH) to evaluate the stability of hChr.21 in somatic cells. The percentage of the spreads containing the hChr.21 showed 50-100%. RT-PCR analysis of one of these mice showed that several genes on hChr.21 were expressed in a proper tissue-specific manner. Finally, we have determined that chimeric mice could transmit hChr.21 fragment (hChr.21f) to their offspring through germline. FISH analysis of various tissues in these germline mice showed that the retention of hChr.21f of them were lower than that of chimeric mice.In anatomical and histological observation of 11 chimeric mice dead in perinatal period, it was found that aplasia of the sternum and remarkable decrease of germ cell occurred in all of them, and various histological abnormality occurred sporadically in heart, liver and kidney. As a control, four chimeric mice induced hChr.2f (containing immunoglobulin genes) were anatomically and histologically studied. In almost of them delayed ossification of the cervical vertebra centrum, aplasia of the sternum and polydactyly of the forelimb were observed, and hypertrophy and histologically various abnormality in hert, liver and kidney occurred sporadically. It is highly possible that remarkable decrease of germ cell in the hChr.21-chimeric mice and polydactyly in the hChr.2f-chimeric mice are related to the gene(s) on the human chromosome introduced.