Turilova Victoria I, Goryachaya Tatyana S, Yakovleva Tatiana K
Laboratory of Cell Morphology, Institute of Cytology, Russian Academy of Sciences, Tikhoretsky ave., 4, St Petersburg, Russia, 194064.
Centre of Cell Technologies, Institute of Cytology, Russian Academy of Sciences, Tikhoretsky ave., 4, St Petersburg, Russia, 194064.
Mol Cytogenet. 2021 Feb 17;14(1):11. doi: 10.1186/s13039-021-00528-3.
Chinese hamster ovary cell lines, also known as CHO cells, represent a large family of related, yet quite different, cell lines which are metabolic mutants derived from the original cell line, CHO-ori. Dihydrofolate reductase-deficient DXB-11 cell line, one of the first CHO derivatives, serves as the host cell line for the production of therapeutic proteins. It is generally assumed that DXB-11 is identical to DUKX or CHO-DUK cell lines, but, to our knowledge, DXB-11 karyotype has not been described yet.
Using differential staining approaches (G-, C-banding and Ag-staining), we presented DXB-11 karyotype and revealed that karyotypes of DXB-11 and CHO-DUK cells have a number of differences. Although the number of chromosomes is equal-20 in each cell line-DXB-11 has normal chromosomes of the 1st and 5th pairs as well as an intact chromosome 8. Besides, in DXB-11 line, chromosome der(Z9) includes the material of chromosomes X and 6, whereas in CHO-DUK it results from the translocation of chromosomes 1 and 6. Ag-positive nucleolar organizer regions were revealed in the long arms of chromosome del(4)(q11q12) and both chromosome 5 homologues, as well as in the short arms of chromosomes 8 and add(8)(q11). Only 19 from 112 (16.96%) DXB-11 cells display identical chromosome complement accepted as the main structural variant of karyotype. The karyotype heterogeneity of all the rest of cells (93, 83.04%) occurs due to clonal and nonclonal additional structural rearrangements of chromosomes. Estimation of the frequency of chromosome involvement in these rearrangements allowed us to reveal that chromosomes 9, der(X)t(X;3;4), del(2)(p21p23), del(2)(q11q22) /Z2, der(4) /Z7, add(6)(p11) /Z8 are the most stable, whereas mar2, probably der(10), is the most unstable chromosome. A comparative analysis of our own and literary data on CHO karyotypes allowed to designate conservative chromosomes, both normal and rearranged, that remain unchanged in different CHO cell lines, as well as variable chromosomes that determine the individuality of karyotypes of CHO derivatives.
DXB-11and CHO-DUK cell lines differ in karyotypes. The revealed differential instability of DXB-11 chromosomes is likely not incidental and results in karyotype heterogeneity of cell population.
中国仓鼠卵巢细胞系，也称为CHO细胞系，代表了一大类相关但又有很大差异的细胞系，它们是源自原始细胞系CHO-ori的代谢突变体。二氢叶酸还原酶缺陷型DXB-11细胞系是最早的CHO衍生物之一，用作生产治疗性蛋白质的宿主细胞系。一般认为DXB-11与DUKX或CHO-DUK细胞系相同，但据我们所知，DXB-11的核型尚未见报道。
使用差异染色方法（G显带、C显带和银染），我们展示了DXB-11的核型，并揭示DXB-11和CHO-DUK细胞的核型存在许多差异。尽管每个细胞系的染色体数目均为20条，但DXB-11具有第1和第5对正常染色体以及完整的8号染色体。此外，在DXB-11细胞系中，der(Z9)染色体包含X和6号染色体的物质，而在CHO-DUK细胞系中，它是由1号和6号染色体的易位导致的。在del(4)(q11q12)染色体长臂、两条5号同源染色体以及8号和add(8)(q11)染色体短臂上发现了银染阳性的核仁组织区。在112个DXB-11细胞中，只有19个(16.96%)显示出被认为是核型主要结构变异的相同染色体组成。其余所有细胞(93个，83.04%)的核型异质性是由于染色体的克隆性和非克隆性额外结构重排所致。对这些重排中涉及的染色体频率进行估计，使我们能够揭示9号染色体、der(X)t(X;3;4)、del(2)(p21p23)、del(2)(q11q22)/Z2、der(4)/Z7、add(6)(p11)/Z8是最稳定的，而mar2，可能是der(10)，是最不稳定的染色体。对我们自己以及关于CHO核型的文献数据进行比较分析，可以确定保守染色体，包括正常的和重排的，它们在不同的CHO细胞系中保持不变，以及可变染色体，它们决定了CHO衍生物核型的个体性。
DXB-11和CHO-DUK细胞系的核型不同。DXB-11染色体显示出的差异不稳定性可能并非偶然，导致了细胞群体的核型异质性。
