Weiss K M, Ruddle F H, Bollekens J
Graduate Program in Genetics, Penn State University, University Park, Pennsylvania 16802, USA.
Connect Tissue Res. 1995;32(1-4):35-40. doi: 10.3109/03008209509013703.
The dentition is a segmental system whose evolution and morphology bears analogy to the evolution of segmentation in the vertebral column and limb. Combinatorial expression of members of the large "Hox" class of homeobox regulatory genes has been shown to play an important role in positional specification in these skeletal systems. This raises the possibility that homeobox genes are also used for positional specification in the dentition, and several homeobox genes are known to be expressed in developing teeth. To identify additional dentally expressed homeobox genes, cDNA from from murine tooth germs at 9.5, 14.5, and 17.5 days gestational age was amplified by PCR using sets of degenerate primers to the homeodomains of 18 different classes of homeobox genes. Amplification products were cloned and sequenced and compared to known gene sequences. To date this approach has confirmed the presence of Msx1, Msx2, Dlx1, and Dlx2, and identified several other homeobox genes not previously known to be expressed in teeth: Dbx, MHox, and Mox2A, plus an a additional Dlx gene, Dlx7. The Msx and Dlx genes are the best current candidates for a combinatorial mechanism that controls the differentiation of structures within and between teeth, and perhaps also the evolution of those structures.
牙列是一个节段性系统，其进化和形态与脊柱及肢体节段化的进化具有相似性。大型“同源框”（Hox）类同源异型框调控基因成员的组合表达已被证明在这些骨骼系统的位置指定中起重要作用。这就增加了同源异型框基因也用于牙列位置指定的可能性，并且已知有几种同源异型框基因在发育中的牙齿中表达。为了鉴定其他在牙齿中表达的同源异型框基因，使用针对18种不同类型同源异型框基因同源结构域的简并引物对，通过聚合酶链反应（PCR）扩增来自妊娠9.5、14.5和17.5天的小鼠牙胚的互补脱氧核糖核酸（cDNA）。扩增产物被克隆、测序并与已知基因序列进行比较。迄今为止，这种方法已证实Msx1、Msx2、Dlx1和Dlx2的存在，并鉴定出其他几种以前未知在牙齿中表达的同源异型框基因：Dbx、MHox和Mox2A，以及另一个Dlx基因Dlx7。Msx和Dlx基因是目前控制牙齿内部和牙齿之间结构分化以及这些结构进化的组合机制的最佳候选基因。
