Immunolocalization of large corneous beta-proteins in the green anole lizard (Anolis carolinensis) suggests that they form filaments that associate to the smaller beta-proteins in the beta-layer of the epidermis

Abstract

The distribution of large corneous beta-proteins of 18-43 kDa (Ac37, 39, and 40) in the epidermis of the lizard Anolis carolinensis is unknown. This study analyses the localization of these beta-proteins in different body scales during regeneration. Western blot analysis indicates most protein bands at 40-50 kDa suggesting they mix with alpha-keratin of intermediate filament keratin proteins. Ac37 is present in mature alpha-layers of most scales and in beta-cells of the outer scale surface in some scales but is absent in the Oberhäutchen, in the setae and beta-layer of adhesive pads and in mesos cells. In differentiating beta-keratinocytes Ac37 is present over 3-4 nm thick filaments located around the amorphous beta-packets and in alpha-cells, but is scarce in precorneous and corneous layers of the claw. Ac37 forms long filaments and, therefore, resembles alpha-keratins to which it probably associates. Ac39 is seen in the beta-layer of tail and digital scales, in beta-cells of regenerating scales but not in the Oberhäutchen (and adhesive setae) or in beta- and alpha-layers of the other scales. Ac40 is present in the mature beta-layer of most scales and dewlap, in differentiating beta-cells of regenerating scales, but is absent in all the other epidermal layers. The large beta-proteins are accumulated among forming beta-packets of beta-cells and are packed in the beta-corneous material of mature beta-layer. Together alpha-keratins, large beta-proteins form the denser areas of mature beta-layer that may have a different consistence that the electron-paler areas.

Identification and comparative analysis of the epidermal differentiation complex in snakes

“…Previous immunolabeling studies in the green anole lizard have suggested expression of Beta1, also referred to as Li-Ac40, in the beta-layer of scales on different body sites investigated56. The immunolabeling for this large beta-protein was associated with filaments of 3 nm thickness, i.e.…”

Microscopic and immunohistochemical analyses of the claw of the nesting dinosaur, Citipati osmolskae

“…Alternatively, these voids may represent amorphous corneous material, containing glycine-rich beta-keratins, in a poorly stainable, electron-pale matrix ( [10] and references therein).…”

“…We hypothesize that voids may represent structural remnants of original lipid droplets in developing claw sheath tissue [35,36]. Alternatively, these voids may represent amorphous corneous material in a poorly stainable, electron-lucent matrix ( [10] and references therein). (Online version in colour.)…”

“…Alpha-keratins [5] are widely distributed across all vertebrates, consistent with an early evolutionary origin and comprise an alpha-helical central rod, producing a 10 nm intermediate filament [6]. Beta-keratins (or 'corneous beta-proteins' [7][8][9][10]) are insoluble, rigid, fibrous, structural proteins distinct from alpha-keratins in composition and structure. They are expressed only in reptiles and birds (sauropsids) [11][12][13], suggesting that this gene family originated after the divergence of sauropsids from other vertebrates [5,[14][15][16].…”

Current Understanding on Tail Regeneration in Green Anoles (<i>Anolis carolinensis</i>)

“…Beta proteins Ac37, Ac39 and Ac40 found in mature alpha layer, beta layer of tail, and mature layer of most scales and dewlap, respectively. Beta proteins together with alpha keratins form the denser areas of mature beta layer [36]. However, regenerated scales lose the ability of physiological color change due to the lack of melanophores, precisely iridophores [37].…”