Model of tooth morphogenesis predicts carabelli cusp expression, size, and symmetry in humans.
Model of tooth morphogenesis predicts carabelli cusp expression, size, and symmetry in humans.
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DOI：
10.1371/journal.pone.0011844
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发表时间：
2010-07-29
期刊：
影响因子：
3.7
通讯作者：
Betsinger TK
中科院分区：
文献类型：
--
作者：
Hunter JP;Guatelli-Steinberg D;Weston TC;Durner R;Betsinger TK
牙齿形态发生的模式级联模型通过少量基因的相互作用来解释形状的发育。在该模型中，基因表达既指导发育，又受发育中牙齿的形状控制。牙釉质结（非增殖上皮区）标记了牙尖的未来位置。为了形成，一个新的釉质结必须逃脱抑制领域周围的其他釉质结前冠组件成为空间固定的形态发生停止。由于牙尖位置在一个完全形成的牙齿反映釉质结的位置和牙齿的大小是有限的形态发生的停止，该模型预测，牙尖表达随牙尖间距相对于牙齿大小。虽然以前在人类中的研究支持该模型的影响，在这里，我们直接测试该模型的预测的表达，大小和对称性的Carabelli尖，在许多人群中存在的变化。在上第一磨牙（M1）（187权利，189左，和185对对）的牙模样本，我们测量牙齿面积和牙尖间距离与Hirox数字显微镜。我们评估了Carabelli表达定量作为一个区域的子样本和定性使用两个类型学计划在整个样本。如预测的那样，使用定性或定量测量，在右侧和左侧样本中，低相对尖间距离与Carabelli表达相关。此外，Carabelli区的不对称性与相对牙尖间距的不对称性相关。这些发现支持了该模型对个体间和个体内Carabelli尖表达的预测。通过比较同一个体的左右对，我们的数据表明，小的变化，在发育时间或间距的釉质结可以影响牙尖模式独立的基因型。我们的研究结果表明，在进化过程中，新的牙尖可能首先出现作为一个小的变化，在相对于冠大小的釉质结的间距。
The patterning cascade model of tooth morphogenesis accounts for shape development through the interaction of a small number of genes. In the model, gene expression both directs development and is controlled by the shape of developing teeth. Enamel knots (zones of nonproliferating epithelium) mark the future sites of cusps. In order to form, a new enamel knot must escape the inhibitory fields surrounding other enamel knots before crown components become spatially fixed as morphogenesis ceases. Because cusp location on a fully formed tooth reflects enamel knot placement and tooth size is limited by the cessation of morphogenesis, the model predicts that cusp expression varies with intercusp spacing relative to tooth size. Although previous studies in humans have supported the model's implications, here we directly test the model's predictions for the expression, size, and symmetry of Carabelli cusp, a variation present in many human populations. In a dental cast sample of upper first molars (M1s) (187 rights, 189 lefts, and 185 antimeric pairs), we measured tooth area and intercusp distances with a Hirox digital microscope. We assessed Carabelli expression quantitatively as an area in a subsample and qualitatively using two typological schemes in the full sample. As predicted, low relative intercusp distance is associated with Carabelli expression in both right and left samples using either qualitative or quantitative measures. Furthermore, asymmetry in Carabelli area is associated with asymmetry in relative intercusp spacing. These findings support the model's predictions for Carabelli cusp expression both across and within individuals. By comparing right-left pairs of the same individual, our data show that small variations in developmental timing or spacing of enamel knots can influence cusp pattern independently of genotype. Our findings suggest that during evolution new cusps may first appear as a result of small changes in the spacing of enamel knots relative to crown size.
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