Reid Alasdair I, Gaunt Stephen J
Department of Developmental Genetics and Imprinting, The Babraham Institute, Cambridge, UK.
Int J Dev Biol. 2002 Mar;46(2):209-15. doi: 10.1387/ijdb.011495.
Hox genes are usually expressed temporally and spatially in a colinear manner with respect to their positions in the Hox complex. We found that these characteristics apply to several Hox genes expressed in developing chick skin (Hoxb-4, Hoxa-7 and Hoxc-8), and we classed this group of genes as regionally restricted. To our surprise, we found that most of the Hox genes we examined are regionally unrestricted in their expression in the embryonic chick skin. This second group includes the Hoxd genes, Hoxd-4 to Hoxd-13, Hoxa-11 and Hoxc-6. Temporally, the expression of the regionally restricted genes can be observed by E5 within the epidermis, whereas the spatially unrestricted genes are not expressed in the epidermis until E6.25. Unexpectedly, we found that all the unrestricted genes are expressed concomitantly and therefore do not conform to temporal colinearity. Moreover, the dermal expression for both groups occurs later, but maintains the same anteroposterior patterning to that seen previously in the epidermis. During embryonic day 7-8, expression for all genes is up-regulated within the dense dermis whilst being reduced within the inter-bud regions. Later expression within the bud mesenchyme is down-regulated whilst high levels of transcriptional activity are detectable within the epidermal sheath of each feather bud. These results indicate that the transcriptional activity of Hox genes in the developing chick skin could be important during embryonic skin patterning both by providing regionally restricted positional cues, and also by imparting generic signals necessary for feather morphology.
Hox基因通常在时间和空间上以与其在Hox复合体中的位置呈共线性的方式表达。我们发现这些特征适用于在发育中的鸡皮肤中表达的几个Hox基因（Hoxb - 4、Hoxa - 7和Hoxc - 8），我们将这组基因归类为区域受限型。令我们惊讶的是，我们发现我们检测的大多数Hox基因在胚胎鸡皮肤中的表达是不受区域限制的。第二组包括Hoxd基因，即Hoxd - 4至Hoxd - 13、Hoxa - 11和Hoxc - 6。在时间上，区域受限基因的表达在E5时可在表皮中观察到，而空间不受限基因直到E6.25才在表皮中表达。出乎意料的是，我们发现所有不受限基因都是同时表达的，因此不符合时间共线性。此外，两组基因在真皮中的表达都较晚，但保持与之前在表皮中所见相同的前后模式。在胚胎第7 - 8天，所有基因在致密真皮中的表达上调，而在芽间区域的表达减少。后来在芽间充质中的表达下调，而在每个羽毛芽的表皮鞘中可检测到高水平的转录活性。这些结果表明，Hox基因在发育中的鸡皮肤中的转录活性在胚胎皮肤模式形成过程中可能很重要，这既通过提供区域受限的位置线索，也通过赋予羽毛形态所需的通用信号来实现。
