Mampumbu André R, Mello Maria Luiza S
Department of Cell Biology, Institute of Biology, State University of Campinas (UNICAMP), Campinas, Sao Paulo, Brazil.
Cytometry A. 2006 Sep 1;69(9):986-91. doi: 10.1002/cyto.a.20312.
The stingless bee genus Melipona has been divided into two groups, based on their heterochromatin content. Melipona quadrifasciata and Melipona rufiventris have low and high levels of heterochromatin, respectively. Since condensed chromatin may be rich in methylated DNA sequences, M. quadrifasciata and M. rufiventris nuclei may contain different amounts of methylated CpG. These differences could be assessed by comparing Feulgen-DNA values obtained by image analysis of cells treated with the restriction enzymes Msp I and Hpa II that distinguish between methylated and unmethylated DNA. Msp I and Hpa II cleave the sequence -CCGG-, but there is no cleavage by Hpa II if the cytosine of the central CG dinucleotide is methylated.
Malpighian tubules of M. quadrifasciata and M. rufiventris were treated with Msp I and Hpa II prior to the Feulgen reaction, and analyzed by automatic scanning microspectrophotometry.
The Feulgen-DNA values for the heterochromatin of M. rufiventris and for the small heterochromatin and some euchromatin domains of M. quadrifasciata mostly decreased after treatment with Msp I, but were unchanged after treatment with Hpa II.
CpG methylation, although detected in diverse chromatin compartments in different bee species, may induce silencing effects required for the same cell physiology.
无刺蜂属的麦蜂根据其异染色质含量被分为两组。四带麦蜂和红腹麦蜂分别具有低水平和高水平的异染色质。由于浓缩染色质可能富含甲基化DNA序列，四带麦蜂和红腹麦蜂的细胞核可能含有不同量的甲基化CpG。这些差异可以通过比较用区分甲基化和未甲基化DNA的限制性内切酶Msp I和Hpa II处理细胞后通过图像分析获得的福尔根DNA值来评估。Msp I和Hpa II切割序列-CCGG-，但如果中央CG二核苷酸的胞嘧啶被甲基化，则Hpa II不会切割。
在福尔根反应之前，用Msp I和Hpa II处理四带麦蜂和红腹麦蜂的马氏管，并通过自动扫描显微分光光度法进行分析。
用Msp I处理后，红腹麦蜂异染色质以及四带麦蜂小异染色质和一些常染色质区域的福尔根DNA值大多下降，但用Hpa II处理后不变。
尽管在不同蜜蜂物种的不同染色质区域中检测到了CpG甲基化，但它可能诱导相同细胞生理所需的沉默效应。
