Knezevic V, De Santo R, Mackem S
Laboratory of Pathology, NCI, NIH, Bethesda, MD 20892, USA.
Development. 1997 Jan;124(2):411-9. doi: 10.1242/dev.124.2.411.
The mouse Brachyury (T) gene plays critical roles in the genesis of normal mesoderm during gastrulation and in the maintenance of a functioning notochord. Abrogation of Brachyury (T) expression within the chordamesoderm of homozygous null mutants nevertheless spares anterior axis formation. An intriguing possibility to explain the preservation of anterior axis formation in these mutants would be the existence of other genes compensating for the loss of Brachyury. This compensation and the recent demonstration that Brachyury is the prototype for an evolutionarily conserved family, prompted a search for other T-box genes participating in axis formation. The chick Brachyury orthologue and two related chick T-box genes that are expressed at the onset of gastrulation have been isolated. One of these novel genes (Ch-TbxT) becomes restricted to the axial mesoderm lineage and is a potential candidate for complementing or extending Brachyury function in the anterior axis (formation of the head process, prechordal plate). The other gene (Ch-Tbx6L), together with chick T, appears to mark primitive streak progenitors before gastrulation. As cells leave the primitive streak, Ch-Tbx6L becomes restricted to the early paraxial mesoderm lineage and could play a role in regulating somitogenesis.
小鼠短尾（T）基因在原肠胚形成过程中正常中胚层的发生以及有功能的脊索的维持中起着关键作用。然而，纯合无效突变体的脊索中胚层内短尾（T）表达的缺失并不影响前轴的形成。解释这些突变体中前轴形成得以保留的一个有趣可能性是存在其他基因来补偿短尾的缺失。这种补偿作用以及最近关于短尾是一个进化上保守家族的原型的证明，促使人们寻找其他参与轴形成的T盒基因。已分离出鸡的短尾直系同源基因以及在原肠胚形成开始时表达的两个相关鸡T盒基因。这些新基因之一（Ch-TbxT）局限于轴中胚层谱系，是在前轴（头突、前索板的形成）中补充或扩展短尾功能的潜在候选基因。另一个基因（Ch-Tbx6L）与鸡的T基因一起，似乎在原肠胚形成前标记原条祖细胞。随着细胞离开原条，Ch-Tbx6L局限于早期近轴中胚层谱系，并可能在调节体节发生中起作用。
