Alibardi Lorenzo, Jaeger Karin, Dalla Valle Luisa, Eckhart Leopold
Dipartimento di Biologia, University of Bologna, via Selmi 3, 40126, Bologna, Italy.
J Morphol. 2011 Mar;272(3):363-70. doi: 10.1002/jmor.10920. Epub 2010 Dec 15.
The claw of lizards is largely composed of beta-keratins, also referred to as keratin-associated beta-proteins. Recently, we have reported that the genome of the lizard Anolis carolinensis contains alpha keratin genes homologous to hair keratins typical of hairs and claws of mammals. Molecular and immunohistochemical studies demonstrated that two hair keratin homologs named hard acid keratin 1 (HA1) and hard basic keratin 1 (HB1) are expressed in keratinocytes forming the claws of A. carolinensis. Here, we extended the immunocytochemical localization of the novel reptilian keratins to the ultrastructural level. After sectioning, claws were subjected to immunogold labeling using antibodies against HA1, HB1, and, for comparison, beta-keratins. Electron microscopy showed that the randomly organized network of tonofilaments in basal and suprabasal keratinocytes becomes organized in long and parallel bundles of keratin in precorneous layers, resembling cortical cells of hairs. Entering the cornified part of the claw, the elongated corneous cells fuse and accumulate corneous material. HA1 and HB1 are absent in the basal layer and lower spinosus layers of the claw and are expressed in the upper and precorneous layers, including the elongating corneocytes. The labeling for alpha-keratin was loosely associated with filament structures forming the fibrous framework of the claws. The ultrastructural distribution pattern of hard alpha-keratins resembled that of beta-keratins, which is compatible with the hypothesis of an interaction during claw morphogenesis. The data on the ultrastructural localization of hair keratin homologs facilitate a comparison of lizard claws and mammalian hard epidermal appendages containing hair keratins.
蜥蜴的爪子主要由β -角蛋白组成，也被称为角蛋白相关β -蛋白。最近，我们报道了绿安乐蜥的基因组中含有与哺乳动物毛发和爪子中典型的毛发角蛋白同源的α -角蛋白基因。分子和免疫组织化学研究表明，两种名为硬酸性角蛋白1（HA1）和硬碱性角蛋白1（HB1）的毛发角蛋白同源物在形成绿安乐蜥爪子的角质形成细胞中表达。在这里，我们将这种新型爬行动物角蛋白的免疫细胞化学定位扩展到了超微结构水平。切片后，使用针对HA1、HB1以及作为对照的β -角蛋白的抗体对爪子进行免疫金标记。电子显微镜显示，基底和基底上层角质形成细胞中随机排列的张力丝网络在角质前层中形成了长而平行的角蛋白束，类似于毛发的皮质细胞。进入爪子的角质化部分，细长的角质细胞融合并积累角质物质。HA1和HB1在爪子的基底层和下棘层中不存在，而在上层和角质前层中表达，包括伸长的角质形成细胞。α -角蛋白的标记与形成爪子纤维框架的丝状结构松散相关。硬α -角蛋白的超微结构分布模式与β -角蛋白相似，这与爪子形态发生过程中相互作用的假设相符。毛发角蛋白同源物的超微结构定位数据有助于比较蜥蜴爪子和含有毛发角蛋白的哺乳动物硬表皮附属器。
