Hox genes encode transcription factors that play important roles in patterning the anterior-posterior (A-P) body axis. In vertebrates, up to 14 Hox genes are physically linked in 4-13 chromosomal clusters. Their expression patterns obey spatial and temporal collinearity. Genes located at the 3' end of the clusters are expressed earlier and more anteriorly than those at the 5' end. To investigate how the expression of Hox genes has evolved after very recent ( approximately 25-100 Mya) and relatively recent ( approximately 320-350 Mya) genome duplications, we focused on three paralogous groups of salmon anterior Hox genes, in which gene duplicates have been retained. RNA-RNA whole mount in situ hybridization with gene-specific probes at early development stages showed essentially conserved expression patterns for most genes when compared to mouse and zebrafish orthologs. However, changes in spatial expression were observed for the ancient fish gene duplicate HoxB3b, while recently duplicated genes showed divergence in their expression levels.

中文翻译：

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大西洋鲑（Salmo salar）中Hox基因的时空表达模式。

Hox基因编码的转录因子在构图前后（AP）体轴中起重要作用。在脊椎动物中，多达14个Hox基因在4-13个染色体簇中物理连接。它们的表达方式服从空间和时间共线性。位于簇3'端的基因比5'端的基因更早，更早地表达。为了研究在最近（大约25-100 Mya）和相对最近（大约320-350 Mya）基因组重复后Hox基因的表达如何演变，我们集中研究了鲑鱼前Hox基因的三个同源群，其中基因重复被保留。与小鼠和斑马鱼直系同源物相比，在早期发育阶段与基因特异性探针的RNA-RNA整体原位杂交显示了大多数基因的基本保守表达模式。但是，观察到古代鱼类基因复制品HoxB3b的空间表达发生了变化，而最近复制的基因显示出它们表达水平的差异。