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

本研究中，hChr。21通过微细胞介导的染色体转移（microcell-mediated chromosome transfer， MMCT）转染到小鼠胚胎干细胞（ES）中，获得了可存活的嵌合小鼠。我们对这些小鼠进行了如下分析。采用荧光原位杂交（Fluorescence in situ hybridization， FISH）检测了4只嵌合小鼠的中期组织扩散情况，以评价hChr的稳定性。体细胞中有21个。包含hChr的传播的百分比。21例为50-100%。对其中一只小鼠的RT-PCR分析显示，hChr上有几个基因。21个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传播hChr。21片段（hhr .21f）通过生殖系传给后代。对这些种系小鼠各种组织的FISH分析表明，hChr的保留。其中21个低于嵌合小鼠。对11只围生期死亡的嵌合小鼠进行解剖和组织学观察，发现所有小鼠胸骨发育不全，生殖细胞明显减少，心脏、肝脏和肾脏零星出现各种组织学异常。作为对照，4只嵌合小鼠诱导hChr。2f（含免疫球蛋白基因）进行了解剖和组织学研究。几乎均出现颈椎椎体迟发性骨化、胸骨发育不全、前肢多指畸形，偶见心、肝、肾组织肥大及各种组织学异常。生殖细胞极有可能在hChr中显著减少。21-嵌合小鼠和多指畸形。2f嵌合小鼠与引入的人类染色体上的基因有关。

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.