Expression and function of Bapx1 during chick limb development
Expression and function of Bapx1 during chick limb development
复制标题
DOI：
10.1007/s00429-005-0464-z
复制
发表时间：
2005-07-01
期刊：
影响因子：
--
通讯作者：
Francis-West, P
中科院分区：
文献类型：
--
作者：
Church, V;Yamaguchi, K;Francis-West, P
含有同源框的转录因子Bapx1（也称为Nkx3.2）对中轴骨骼和软骨颅骨的部分发育至关重要。在这里，我们描述了Bapx1在鸡肢体发育过程中的详细表达，并表明，与其在中轴骨骼中的表达相反，Bapx1在软骨形成后表达。Bapx1最初在不同软骨形成层的明显分化之前在整个发育中的骨骼元件中表达。一旦不同的层（增殖，prehypertrophic和肥大）已经形成，Bapx1的表达仅限于增殖的软骨细胞。Bapx1转录本被排除在关节软骨之外。第二个含有同源框的转录因子Barx1在发育中的关节和关节软骨中以互补的方式表达。有趣的是，体外功能分析表明，Bapx1在微团培养物中的过表达增加了基质产生和结节数量，这表明Bapx1足以促进肢体中的软骨形成。相反，Barx 1对结节数量有相反的影响，表明它对软骨形成起始有抑制作用，这与其在发育中的关节中的表达一致。还观察到基质水平略有增加，与其在关节软骨细胞中的表达一致。最后，我们发现Bapx1也在软组织中表达，如发育中的肌腱，肌鞘和周围的间充质，因此可能有额外的尚未表征的肢体形态发生的作用。
The homeobox-containing transcription factor Bapx1 (also known as Nkx3.2) is crucial for development of the axial skeleton and parts of the chondrocranium. Here we describe the detailed expression of Bapx1 during chick limb development and show that in contrast to its expression in the axial skeleton, Bapx1 is expressed after the commitment to chondrogenesis. Bapx1 is initially expressed throughout the developing skeletal elements prior to the overt differentiation of the distinct chondrogenic layers. Once distinct layers (proliferating, prehypertrophic and hypertrophic) have formed, Bapx1 expression is restricted to the proliferating chondrocytes. Bapx1 transcripts are excluded from the articular cartilage. A second homeobox-containing transcription factor, Barx1, is expressed in a complementary fashion in the developing joint and articular cartilage. Interestingly, in vitro functional analyses showed that Bapx1 overexpression in micromass cultures increased both matrix production and nodule number suggesting that Bapx1 is sufficient to promote chondrogenesis in the limb. In contrast, Barx1 had the opposite effect on nodule number suggesting that it has an inhibitory effect on chondrogenic initiation consistent with its expression in the developing joint. A slight increase in matrix levels was also observed consistent with its expression in the articular chondrocytes. Finally, we show that Bapx1 is also expressed in the soft tissues such as the developing tendons, muscle sheaths and surrounding mesenchyme, and therefore may have additional as yet uncharacterized roles in limb morphogenesis.