Hao Limin, Johnsen Robert, Lauter Gilbert, Baillie David, Bürglin Thomas R
Department of Biosciences and Nutrition, and Center for Genomics and Bioinformatics, Karolinska Institutet, SE-141 57 Huddinge, Sweden.
BMC Genomics. 2006 Oct 31;7:280. doi: 10.1186/1471-2164-7-280.
The Caenorhabditis elegans genome encodes ten proteins that share sequence similarity with the Hedgehog signaling molecule through their C-terminal autoprocessing Hint/Hog domain. These proteins contain novel N-terminal domains, and C. elegans encodes dozens of additional proteins containing only these N-terminal domains. These gene families are called warthog, groundhog, ground-like and quahog, collectively called hedgehog (hh)-related genes. Previously, the expression pattern of seventeen genes was examined, which showed that they are primarily expressed in the ectoderm.
With the completion of the C. elegans genome sequence in November 2002, we reexamined and identified 61 hh-related ORFs. Further, we identified 49 hh-related ORFs in C. briggsae. ORF analysis revealed that 30% of the genes still had errors in their predictions and we improved these predictions here. We performed a comprehensive expression analysis using GFP fusions of the putative intergenic regulatory sequence with one or two transgenic lines for most genes. The hh-related genes are expressed in one or a few of the following tissues: hypodermis, seam cells, excretory duct and pore cells, vulval epithelial cells, rectal epithelial cells, pharyngeal muscle or marginal cells, arcade cells, support cells of sensory organs, and neuronal cells. Using time-lapse recordings, we discovered that some hh-related genes are expressed in a cyclical fashion in phase with molting during larval development. We also generated several translational GFP fusions, but they did not show any subcellular localization. In addition, we also studied the expression patterns of two genes with similarity to Drosophila frizzled, T23D8.1 and F27E11.3A, and the ortholog of the Drosophila gene dally-like, gpn-1, which is a heparan sulfate proteoglycan. The two frizzled homologs are expressed in a few neurons in the head, and gpn-1 is expressed in the pharynx. Finally, we compare the efficacy of our GFP expression effort with EST, OST and SAGE data.
No bona-fide Hh signaling pathway is present in C. elegans. Given that the hh-related gene products have a predicted signal peptide for secretion, it is possible that they constitute components of the extracellular matrix (ECM). They might be associated with the cuticle or be present in soluble form in the body cavity. They might interact with the Patched or the Patched-related proteins in a manner similar to the interaction of Hedgehog with its receptor Patched.
秀丽隐杆线虫基因组编码十种蛋白质，这些蛋白质通过其C端自加工Hint/Hog结构域与刺猬信号分子具有序列相似性。这些蛋白质含有新的N端结构域，并且秀丽隐杆线虫还编码数十种仅含有这些N端结构域的其他蛋白质。这些基因家族被称为疣猪、土拨鼠、土拨鼠样和圆蛤，统称为刺猬（hh）相关基因。此前，研究了17个基因的表达模式，结果表明它们主要在外胚层表达。
随着2002年11月秀丽隐杆线虫基因组序列的完成，我们重新检查并鉴定了61个hh相关的开放阅读框（ORF）。此外，我们在briggsae线虫中鉴定出49个hh相关的ORF。ORF分析表明，30%的基因预测仍有错误，我们在此对这些预测进行了改进。我们使用推定的基因间调控序列与大多数基因的一两个转基因系的绿色荧光蛋白（GFP）融合进行了全面的表达分析。hh相关基因在以下一种或几种组织中表达：皮下组织、接缝细胞、排泄管和孔细胞、外阴上皮细胞、直肠上皮细胞、咽肌或边缘细胞、拱廊细胞、感觉器官的支持细胞和神经细胞。通过延时记录，我们发现一些hh相关基因在幼虫发育期间与蜕皮同步以周期性方式表达。我们还构建了几个翻译型GFP融合体，但它们未显示任何亚细胞定位。此外，我们还研究了与果蝇卷曲蛋白相似的两个基因T23D8.1和F27E11.3A以及果蝇基因dally样的直系同源基因gpn-1（一种硫酸乙酰肝素蛋白聚糖）的表达模式。这两个卷曲蛋白同源物在头部的少数神经元中表达，而gpn-1在咽部表达。最后，我们将我们的GFP表达效果与EST、OST和SAGE数据进行了比较。
秀丽隐杆线虫中不存在真正的Hh信号通路。鉴于hh相关基因产物具有预测的分泌信号肽，它们有可能构成细胞外基质（ECM）的成分。它们可能与角质层相关，或以可溶形式存在于体腔中。它们可能以类似于刺猬与其受体Patched相互作用的方式与Patched或Patched相关蛋白相互作用。
