Zhdanova Natalia S, Minina Julia M, Karamisheva Tatjana V, Draskovic Irena, Rubtsov Nikolai B, Londoño-Vallejo Jose-Arturo
Institute of Cytology and Genetics of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia.
Chromosome Res. 2007;15(7):881-90. doi: 10.1007/s10577-007-1170-x. Epub 2007 Oct 1.
Two closely related shrew species, Sorex granarius and Sorex araneus, in which Robertsonian rearrangements have played a primary role in karyotype evolution, present very distinct telomere length patterns. S. granarius displays hyperlong telomeres specifically associated with the short arms of acrocentrics, whereas telomere lengths in S. araneus are rather short and homogenous. Using a combined approach of chromosome and fibre FISH, modified Q-FISH, 3D-FISH, Ag-NOR staining and TRF analysis, we carried out a comparative analysis of telomeric repeats and rDNA distribution on chromosome ends of Sorex granarius. Our results show that rDNA sequences forming active nuclear organizing regions are interspersed with the long telomere tracts of all short arms of acrocentrics. These observations suggest that the major rearrangements that gave rise to today's karyotype in S. granarius were accompanied by a profound reorganization of chromosome ends, which comprised extensive amplification of telomeric and rDNA repeats on the short arms of acrocentrics and finally contributed to the stabilization of telomeres. This is the first time that such telomeric structures have been observed in any mammalian species.
两种亲缘关系密切的鼩鼱物种，即谷物鼩鼱（Sorex granarius）和普通鼩鼱（Sorex araneus），罗伯逊重排在其核型进化中起主要作用，它们呈现出非常不同的端粒长度模式。谷物鼩鼱表现出超长端粒，这些端粒与近端着丝粒染色体的短臂特异性相关，而普通鼩鼱的端粒长度相当短且均匀。我们采用染色体和纤维荧光原位杂交、改良的Q-荧光原位杂交、3D-荧光原位杂交、银染核仁组织区染色和端粒限制性片段分析相结合的方法，对谷物鼩鼱染色体末端的端粒重复序列和核糖体DNA（rDNA）分布进行了比较分析。我们的结果表明，形成活跃核组织区的rDNA序列散布在近端着丝粒染色体所有短臂的长端粒区域中。这些观察结果表明，导致现今谷物鼩鼱核型的主要重排伴随着染色体末端的深刻重组，其中包括近端着丝粒染色体短臂上的端粒和rDNA重复序列的广泛扩增，最终有助于端粒的稳定。这是首次在任何哺乳动物物种中观察到这种端粒结构。
