A Computational Approach to Estimating Nondisjunction Frequency in Saccharomyces cerevisiae.
A Computational Approach to Estimating Nondisjunction Frequency in Saccharomyces cerevisiae.
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DOI：
10.1534/g3.115.024380
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发表时间：
2016-01-08
期刊：
影响因子：
--
通讯作者：
Burgess SM
中科院分区：
文献类型：
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作者：
Chu DB;Burgess SM
减数分裂过程中同源染色体分离错误会导致非整倍体配子，是导致人类出生缺陷和自然流产的最大因素。酿酒酵母长期以来一直作为研究支持正常染色体分离的基因网络的模式生物。测量同源不分离频率是费力的，并且涉及解剖数千个四分体以检测单独标记的染色体的错误分离。在这里，我们描述了一种计算方法（TetFit）来估计减数分裂 I 不分离和随机孢子死亡对野生型和突变株中孢子不存活的相对贡献。这些值基于找到 4、3、2、1 和 0 个活孢子四分体与观察到的分布的最佳拟合分布。使用 TetFit，我们发现减数分裂 I 不分离是野生型菌株中孢子不存活的内在组成部分。我们证明了原理证明，由 TetFit 确定的计算出的平均减数分裂 I 不分离频率与突变株中根据经验确定的值非常匹配。利用这些已发表的数据集，TetFit 发现了两类突变体：A 类突变体倾向于增加非分离死亡，并包括那些在建立同源染色体配对、重组和/或突触方面具有已知缺陷的突变体。 B 类突变体倾向于随机孢子死亡，包括那些姐妹染色单体凝聚力和着丝粒功能有缺陷的突变体。使用 TetFit 进行上位分析是由于比较不同突变体背景中对孢子死亡的贡献所需的四分体数量较少（少至 200 个）。 TetFit 分析不需要任何特殊的应变构建，并且可以应用于之前观察到的四分体分布。
Errors segregating homologous chromosomes during meiosis result in aneuploid gametes and are the largest contributing factor to birth defects and spontaneous abortions in humans. Saccharomyces cerevisiae has long served as a model organism for studying the gene network supporting normal chromosome segregation. Measuring homolog nondisjunction frequencies is laborious, and involves dissecting thousands of tetrads to detect missegregation of individually marked chromosomes. Here we describe a computational method (TetFit) to estimate the relative contributions of meiosis I nondisjunction and random-spore death to spore inviability in wild type and mutant strains. These values are based on finding the best-fit distribution of 4, 3, 2, 1, and 0 viable-spore tetrads to an observed distribution. Using TetFit, we found that meiosis I nondisjunction is an intrinsic component of spore inviability in wild-type strains. We show proof-of-principle that the calculated average meiosis I nondisjunction frequency determined by TetFit closely matches empirically determined values in mutant strains. Using these published data sets, TetFit uncovered two classes of mutants: Class A mutants skew toward increased nondisjunction death, and include those with known defects in establishing pairing, recombination, and/or synapsis of homologous chromosomes. Class B mutants skew toward random spore death, and include those with defects in sister-chromatid cohesion and centromere function. Epistasis analysis using TetFit is facilitated by the low numbers of tetrads (as few as 200) required to compare the contributions to spore death in different mutant backgrounds. TetFit analysis does not require any special strain construction, and can be applied to previously observed tetrad distributions.