Vitali Valerio, Rothering Rebecca, Catania Francesco
Institute for Evolution and Biodiversity, University of Münster, 48149 Münster, Germany.
Microorganisms. 2021 Sep 17;9(9):1979. doi: 10.3390/microorganisms9091979.
Amitosis is a widespread form of unbalanced nuclear division whose biomedical and evolutionary significance remain unclear. Traditionally, insights into the genetics of amitosis have been gleaned by assessing the rate of phenotypic assortment. Though powerful, this experimental approach relies on the availability of phenotypic markers. Leveraging , a unicellular eukaryote with nuclear dualism and a highly polyploid somatic nucleus, we probe the limits of single-cell whole-genome sequencing to study the consequences of amitosis. To this end, we first evaluate the suitability of single-cell sequencing to study the AT-rich genome of , focusing on common sources of genome representation bias. We then asked: can alternative rearrangements of a given locus eventually assort after a number of amitotic divisions? To address this question, we track somatic assortment of developmentally acquired Internal Eliminated Sequences (IESs) up to 50 amitotic divisions post self-fertilization. To further strengthen our observations, we contrast empirical estimates of IES retention levels with in silico predictions obtained through mathematical modeling. In agreement with theoretical expectations, our empirical findings are consistent with a mild increase in variation of IES retention levels across successive amitotic divisions of the macronucleus. The modest levels of somatic assortment in suggest that IESs retention levels are largely sculpted at the time of macronuclear development, and remain fairly stable during vegetative growth. In forgoing the requirement for phenotypic assortment, our approach can be applied to a wide variety of amitotic species and could facilitate the identification of environmental and genetic factors affecting amitosis.
无丝分裂是一种广泛存在的不平衡核分裂形式，其生物医学和进化意义仍不清楚。传统上，对无丝分裂遗传学的认识是通过评估表型分离率来获得的。尽管这种实验方法很强大，但它依赖于表型标记的可用性。利用具有核二元性和高度多倍体体细胞核的单细胞真核生物，我们探索单细胞全基因组测序的极限，以研究无丝分裂的后果。为此，我们首先评估单细胞测序对研究其富含AT的基因组的适用性，重点关注基因组代表性偏差的常见来源。然后我们提出问题：给定基因座的替代重排在多次无丝分裂后最终能否分离？为了解决这个问题，我们追踪了自受精后多达50次无丝分裂中发育获得的内部消除序列（IESs）的体细胞分离情况。为了进一步加强我们的观察，我们将IES保留水平的经验估计与通过数学建模获得的计算机预测进行了对比。与理论预期一致，我们的经验发现与大核连续无丝分裂过程中IES保留水平的变化略有增加相一致。中体细胞分离的适度水平表明，IES保留水平在大核发育时基本形成，并在营养生长期间保持相当稳定。由于我们的方法不需要表型分离，它可以应用于多种无丝分裂物种，并有助于识别影响无丝分裂的环境和遗传因素。
