Cardoso Adauto Lima, Fantinatti Bruno Evaristo de Almeida, Venturelli Natália Bortholazzi, Carmello Bianca de Oliveira, de Oliveira Rogério Antonio, Martins Cesar
Integrative Genomics Laboratory, Department of Morphology, Institute of Biosciences, São Paulo State University - Universidade Estadual Paulista, Botucatu, Brazil.
Department of Biostatistics, Institute of Biosciences, São Paulo State University - Universidade Estadual Paulista, Botucatu, Brazil.
Front Genet. 2019 Apr 12;10:324. doi: 10.3389/fgene.2019.00324. eCollection 2019.
Supernumerary B chromosomes are dispensable elements found in several groups of eukaryotes, and their impacts in host organisms are not clear. The cichlid fish presents one or two large metacentric B chromosomes. These elements affect the transcription of several classes of RNAs. Here, we evaluated the epigenetic DNA modification status of B chromosomes using immunocytogenetics and assessed the impact of B chromosome presence on the global contents of 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) and the molecular mechanisms underlying these variations. We found that the B chromosome of has an active pattern of DNA epimarks, and its presence promotes the loss of 5mC in gonads of females with B chromosome (FB+) and promotes the loss of 5hmC in the muscle of males with the B element (MB+). Based on the transcriptional quantification of DNA modification genes (, and ) and their candidate regulators ( genes, microRNAs, and long non-coding RNAs) and on RNA-protein interaction prediction, we suggest the occurrence of passive demethylation in gonads of FB+ and 5hmC loss by Tet inhibition or by 5hmC oxidation in MB+ muscle. We suggest that these results can also explain the previously reported variations in the transcription levels of several classes of RNA depending on B chromosome presence. The DNA modifications detected here are also influenced by sex. Although the correlation between B chromosomes and sex has been previously reported, it remains unexplained. The B chromosome of seems to be active and impacts cell physiology in a very complex way, including at the epigenetic level.
超数B染色体是在几类真核生物中发现的可有可无的元件，它们对宿主生物体的影响尚不清楚。丽鱼科鱼类存在一两条大型中着丝粒B染色体。这些元件会影响几类RNA的转录。在这里，我们使用免疫细胞遗传学评估了B染色体的表观遗传DNA修饰状态，并评估了B染色体的存在对5-甲基胞嘧啶（5mC）和5-羟甲基胞嘧啶（5hmC）整体含量的影响以及这些变化背后的分子机制。我们发现，[具体丽鱼科鱼类名称未给出]的B染色体具有活跃的DNA表观标记模式，其存在促进了带有B染色体的雌性（FB+）性腺中5mC的丢失，并促进了带有B元件的雄性（MB+）肌肉中5hmC的丢失。基于DNA修饰基因（[具体基因名称未给出]）及其候选调节因子（[具体基因名称未给出]基因、微小RNA和长链非编码RNA）的转录定量以及RNA-蛋白质相互作用预测，我们认为在FB+的性腺中发生了被动去甲基化，而在MB+的肌肉中5hmC的丢失是由于Tet抑制或5hmC氧化。我们认为这些结果也可以解释先前报道的几类RNA转录水平因B染色体的存在而发生的变化。这里检测到的DNA修饰也受性别影响。尽管先前已经报道了B染色体与性别的相关性，但仍未得到解释。[具体丽鱼科鱼类名称未给出]的B染色体似乎是活跃的，并以非常复杂的方式影响细胞生理，包括在表观遗传水平。
