Alibardi Lorenzo
Comparative Histolab and Department of Biology, University of Bologna, Bologna, Italy.
J Exp Zool B Mol Dev Evol. 2014 Jan;322(1):54-63. doi: 10.1002/jez.b.22548. Epub 2013 Nov 19.
The corneous layer of the epidermis in hard-shelled turtles largely derives from the accumulation of beta-proteins as indicated by microscopic, in situ hybridization, and immunocytochemical and Western blotting analysis. The expression of mRNAs of one of the most common type of beta-proteins shows higher expression in upper spinosus and pre-corneous keratinocytes of growing scutes. Two beta-proteins of 14-16 kDa, indicated as Tu2 and Tu17 and representing two subtypes of beta-proteins co-accumulate in the thick corneous layer of the epidermis in hard-shelled turtle. The two beta-proteins apparently mix in differentiating and mature corneocytes although Tu2 appears more prevalent than Tu17. The specific role of the different subtypes in the formation of the hard corneous material of the carapace and plastron is not clear. It is hypothesized that the relative amount of beta-proteins belonging to the two subclasses in relation to the alpha-keratin meshwork present in keratinocytes contributes to the formation of a variably resistant and inflexible corneous layer. Tu17 may have a more globular structure than Tu2 and is likely present in denser areas of the corneous layer containing also alpha-keratin. The increase of cysteine-glycine-rich beta-proteins in the matrix located among alpha-keratin filaments may allow the formation of a hard corneous material, probably through increase of cross-bridge formation and hydrophobicity.
硬壳龟表皮的角质层主要源于β-蛋白的积累，微观、原位杂交、免疫细胞化学和蛋白质印迹分析均表明了这一点。最常见的一种β-蛋白的mRNA表达在生长盾片的上棘状细胞和角质前角质形成细胞中较高。两种分子量为14 - 16 kDa的β-蛋白，分别标记为Tu2和Tu17，代表β-蛋白的两种亚型，它们在硬壳龟表皮的厚角质层中共积累。这两种β-蛋白在分化和成熟的角质形成细胞中明显混合，尽管Tu2似乎比Tu17更普遍。不同亚型在背甲和腹甲硬角质材料形成中的具体作用尚不清楚。据推测，与角质形成细胞中存在的α-角蛋白网络相关的两个亚类β-蛋白的相对含量有助于形成具有不同抗性和柔韧性的角质层。Tu17可能比Tu2具有更球状的结构，并且可能存在于也含有α-角蛋白的角质层较致密区域。富含半胱氨酸-甘氨酸的β-蛋白在α-角蛋白丝之间的基质中的增加可能允许形成硬角质材料，可能是通过增加交联形成和疏水性。
