Immunocytochemical analysis of the process of keratinization of the epidermis of snakes

Abstract

The epidermis of snakes produces two types of keratinocytes containing an alpha (soft) and a beta (hard) form of keratin. During epidermal renewal, which allows body growth, six types of epidermal layers are produced before moulting: oberhautchen, beta-, mesos, alpha-, lacunar, and clear. The precise layers in which beta-keratin, alpha-keratin and matrix proteins (loricrin and ®laggrin) are produced, have been studied by light and ultrastructural immunocytochemistry. An antibody against chick scale beta-keratin recognizes also snake beta-keratin only in the oberhautchen and beta-layer. This con®rms the phylogenetic relationships between avian and reptilian hard (beta) keratins. Beta-keratin rapidly disappears in mesoscells, where little beta-keratin is present. Antibodies that recognize alpha-keratins (AE1, AE2, AE3) show that acidic keratins (AE1 positive) mainly localize in the most basal layers and basic keratins (AE3 positive) in all layers but disappear in those layers that are keratinized, especially in the beta-layer. The AE2 immunolabelling (a marker of keratinization in mammalian epidermis) is localized in the compact alphalayer. This pattern is similar to that for loricrin and ®laggrin, although in the latter the reaction is less intense and located mainly in the hinge regions among scales. Alpha-keratins and associated proteins disappear in the oberhautchen and beta-cells where beta-keratin is produced instead. This study suggests that the shedding mechanism in snakes evolved after the hard beta-keratin was compartmentalized beneath the soft alpha-keratin to create an intra-epidermal weakness region. The study also suggests that some common mechanism of alpha-keratinization is present in snakes, and the other amniotes in general.

Formation of the corneous layer in the epidermis of the tuatara (Sphenodon punctatus, Sphenodontida, Lepidosauria, Reptilia)

“…The immunolocalization of alphakeratinins with AE1, AE2, and AE3 antibodies resembles that observed in lizards and snakes (Alibardi 2003). The yellow, non-specific labeling of the beta-layer is also seen in the stratum corneum of lizard and snake (Alibardi 2002c) as well as in mammalian epidermis (Sun et al 1983). This may be due to an intrinsic fluorescence or to the presence of fluorescent melanin granules within the beta-layer.…”

Immunolocalization and characterization of cornification proteins in snake epidermis

“…Previous immunocytochemical studies (Alibardi, 2002c) have shown that, when present, loricrin‐like immunoreactivity is associated with α‐keratin bundles of lacunar and α‐cells, but is not localized along the cornified cell envelope as in corneocytes of mammalian epidermis (Steven et al, 1990; Ishida‐Yamamoto et al, 2000; Kalinin et al, 2002). Similarly, in the cornified cell envelope, transglutaminase substrates (loricrin, filaggrin, etc.)…”

“…Immunocytochemistry on snake epidermis has shown that α‐keratins react weakly with the AE3 antibody for mammalian basic keratins (Alibardi, 2002c). Apart from β‐keratins, all the remaining immunoreactivities observed in gels are associated with α‐keratin layers, suggesting that loricrin‐, sciellin‐, filaggrin/AE2‐positive keratins and transglutaminase‐like proteins are present in the epidermis of snakes.…”

Developmental mechanisms of longitudinal stripes in the Japanese four‐lined snake

“…This is the first study to examine quantitatively the color pattern formation during embryonic development in snakes, although skin differentiation has been studied for lizards and snakes (Alibardi, 2002a, 2002b, 2011, 2012; Dujsebayeva, ; Maderson, ; Swadzba, Maslak, & Rupik, ). Our results provide insights into color pattern formation during embryonic development and ontogeny after hatching by referring to studies of pigment cells from newly hatched juveniles (Murakami et al, ) to adults (Kuriyama et al, ).…”

“…This is the first study to examine quantitatively the color pattern formation during embryonic development in snakes, although skin differentiation has been studied for lizards and snakes (Alibardi, 2002a(Alibardi, , 2002b(Alibardi, , 2011(Alibardi, , 2012Dujsebayeva, 2008;Maderson, 1965; Swadzba, by referring to studies of pigment cells from newly hatched juveniles (Murakami et al, 2016) to adults (Kuriyama et al, 2013).…”