Bailey Kimberly J, Maslov Alexander Y, Pruitt Steven C
Department of Molecular and Cellular Biology, Roswell Park Cancer Institute, Buffalo, NY 14263, USA.
Aging Cell. 2004 Dec;3(6):391-7. doi: 10.1111/j.1474-9728.2004.00128.x.
Genomic instability within somatic stem cells may lead to the accumulation of mutations and contribute to cancer or other age-related phenotypes. However, determining the frequency of mutations that differ among individual stem cells is difficult from whole tissue samples because each event is diluted in the total population of both stem cells and differentiated tissue. Here the ability to expand neural stem/progenitor cells clonally permitted measurement of genomic alterations derived from a single initial cell. C57Bl/6 x DBA/2 hybrid mice were used and PCR analysis with strain-specific primers was performed to detect loss of heterozygosity on nine different chromosomes for each neurosphere. The frequency with which changes occurred in neurospheres derived from 2-month- and 2-year-old mice was compared. In 15 neurospheres derived from young animals both parental chromosomes were present for all nine chromosome pairs. In contrast, 16/17 neurospheres from old animals demonstrated loss of heterozygosity (LOH) on one or more chromosomes and seven exhibited a complete deletion of at least one chromosomal region. For chromosomes 9 and 19 there is a significant bias in the allele that is lost where in each case the C57Bl/6 allele is retained in 6/6 neurospheres exhibiting LOH. These data suggest that aging leads to a substantial mutational load within the neural stem cell compartment which can be expected to affect the normal function of these cells. Furthermore, the retention of specific alleles for chromosomes 9 and 19 suggests that a subset of mutational events lead to an allele-specific survival advantage within the neural stem cell compartment.
体细胞干细胞内的基因组不稳定可能导致突变积累，并促成癌症或其他与年龄相关的表型。然而，从整个组织样本中很难确定单个干细胞之间不同的突变频率，因为每个事件在干细胞和分化组织的总体中都会被稀释。在这里，克隆扩增神经干细胞/祖细胞的能力使得对源自单个初始细胞的基因组改变进行测量成为可能。使用C57Bl/6×DBA/2杂交小鼠，并使用菌株特异性引物进行PCR分析，以检测每个神经球在九条不同染色体上的杂合性缺失。比较了来自2个月和2岁小鼠的神经球中发生变化的频率。在来自幼龄动物的15个神经球中，所有九对染色体的双亲染色体均存在。相比之下，来自老龄动物的16/17个神经球在一条或多条染色体上表现出杂合性缺失（LOH），七个神经球表现出至少一个染色体区域的完全缺失。对于9号和19号染色体，在发生杂合性缺失的6/6个神经球中，C57Bl/6等位基因在每种情况下均保留，在丢失的等位基因上存在显著偏差。这些数据表明，衰老导致神经干细胞区室中存在大量的突变负荷，预计这会影响这些细胞的正常功能。此外，9号和19号染色体特定等位基因的保留表明，一部分突变事件导致神经干细胞区室中存在等位基因特异性的生存优势。
