Oral Development and Orthodontics, Research Unit of Oral Health Sciences, Medical Faculty, University of Oulu, Oulu, Finland.
Medical Research Center Oulu, Oulu University Hospital, Oulu, Finland.
PLoS One. 2018 Nov 15;13(11):e0207070. doi: 10.1371/journal.pone.0207070. eCollection 2018.
Although genes on the human X chromosome reportedly influence tooth crown morphology, little is known about X chromosome activation or inactivation systems relevant to morphological variations. We assessed the relationships between tooth crown size and crown morphological traits in females with Turner syndrome, the variants of which include complete absence of one X chromosome, lack of the short arm (Xp), or duplication of the long arms (Xq), and then estimated the functions of Xp and Xq in the process of unilateral X chromosome inactivation during tooth crown development. The mesiodistal and buccolingual diameters in the maxillary first (M1) and second (M2) permanent molars were compared among X chromosome karyotypes by multiple regression analyses, and their relationships with the development of Carabelli's cusp and the distolingual cusp were analyzed using logistic regression analysis. The crown sizes increased in the order of the 46,X,i(Xq) karyotype, 45,X and 45,X/46,XX karyotypes, and control group. A lower frequency of Carabelli's cusp and higher frequency of a reduced distolingual cusp in M1 were characteristics of Turner syndrome. The overall M1 and M2 crown sizes differed among the X chromosome karyotypes, whereas a smaller crown size was associated with a reduced distolingual cusp but not with Carabelli's cusp. Considering the differences in chromosome arrangement among females with Turner syndrome and the process of unilateral X chromosome inactivation, the observed results can be considered in terms of quantity or number of promoters/inhibitors during tooth crown development. The X chromosome karyotypes have a strong influence on the overall crown sizes of the M1 and M2 molars because those karyotypes with variable numbers of active gene regions directly influence tooth germ development in an early stage of human odontogenesis. The later forming cusps, such as the distolingual cusp and Carabelli's cusp, may be affected by this developmental prerequisite.
虽然据报道人类 X 染色体上的基因会影响牙冠形态，但对于与形态变异相关的 X 染色体激活或失活系统知之甚少。我们评估了特纳综合征女性的牙冠大小与牙冠形态特征之间的关系，特纳综合征的变异包括一条 X 染色体完全缺失、短臂缺失（Xp）或长臂重复（Xq），然后估计 Xp 和 Xq 在牙冠发育过程中单侧 X 染色体失活过程中的作用。通过多元回归分析比较了 X 染色体核型中上颌第一（M1）和第二（M2）恒磨牙的近远中径和颊舌径，并使用逻辑回归分析分析了它们与 Carabelli 尖的发育和远中尖的关系。牙冠大小的增加顺序为 46，X，i（Xq）核型、45，X 和 45，X/46，XX 核型和对照组。M1 中 Carabelli 尖的频率较低，远中尖的频率较低是特纳综合征的特征。X 染色体核型的整体 M1 和 M2 牙冠大小不同，而较小的牙冠大小与远中尖的减小有关，但与 Carabelli 尖无关。考虑到特纳综合征女性染色体排列的差异和单侧 X 染色体失活的过程，观察到的结果可以从牙冠发育过程中启动子/抑制剂的数量或数量来考虑。X 染色体核型对 M1 和 M2 磨牙的整体牙冠大小有很强的影响，因为那些具有可变数量的活性基因区域的核型直接影响人类牙发生早期的牙胚发育。后来形成的尖，如远中尖和 Carabelli 尖，可能受到这种发育前提的影响。
