Presence of acid phosphatase in the epidermis of the regenerating tail of the lizard (<i>Podarcis muralis</i>) and its possible role in the process of shedding and keratinization

2001

Journal of Morphology

The morphogenesis and ultrastructure of the epidermis of snake embryos were studied at progressive stages of development through hatching to determine the time and modality of differentiation of the shedding complex. Scales form as symmetric epidermal bumps that become slanted and eventually very overlapped. During the asymmetrization of the bumps, the basal cells of the forming outer surface of the scale become columnar, as in an epidermal placode, and accumulate glycogen. Small dermal condensations are sometimes seen and probably represent primordia of the axial dense dermis of the growing tip of scales. Deep, dense, and superficial loose dermal regions are formed when the epidermis is bilayered (periderm and basal epidermis) and undifferentiated. Glycogen and lipids decrease from basal cells to differentiating suprabasal cells. On the outer scale surface, beneath the peridermis, a layer containing dense granules and sparse 25-30-nm thick coarse filaments is formed. The underlying clear layer does not contain keratohyalin-like granules but has a rich cytoskeleton of intermediate filaments. Small denticles are formed and they interdigitate with the oberhautchen spinulae formed underneath. On the inner scale surface the clear layer contains dense granules, coarse filaments, and does not form denticles with the aspinulated oberhautchen. On the inner side surface the oberhautchen only forms occasional spinulae. The sloughing of the periderm and embryonic epidermis takes place in ovo 5-6 days before hatching. There follow beta-, mesos-, and alpha-layers, not yet mature before hatching. No resting period is present but a new generation is immediately produced so that at 6-10 h posthatching an inner generation and a new shedding complex are forming beneath the outer generation. The first shedding complex differentiates 10-11 days before hatching. In hatchlings 6-10 h old, tritiated histidine is taken up in the epidermis 4 h after injection and is found mainly in the shedding complex, especially in the apposed membranes of the clear layer and oberhautchen cells. This indicates that a histidine-rich protein is produced in preparation for shedding, as previously seen in lizard epidermis. The second shedding (first posthatching) takes place at 7-9 days posthatching. It is suggested that the shedding complex in lepidosaurian reptiles has evolved after the production of a histidine-rich protein and of a beta-keratin layer beneath the former alpha-layer.

Section: Shedding Complex Formation and Histidine In Lepidosauriansmentioning

confidence: 59%

“…26). Formation of such bundles had already occurred in the flat suprabasal cells, which also contained pale vacuoles or lipid droplets, a characteristic of differentiating alpha-and lacunar cells (Alexander, 1970;Landmann, 1986;Alibardi, 1998b).…”

Section: Ultrastructural Analysis: Epidermal Differentiationmentioning

confidence: 99%

Ultrastructure of the embryonic snake skin and putative role of histidine in the differentiation of the shedding complex

2001

Journal of Morphology

“…The presence of an enzymatic mechanism for the degradation of cell junctions in the corneus layer is probably widespread in vertebrate epidermis (Spearman, 1966;Budz & Larsen, 1975;Menon et al, 1992), including reptiles (Goslar, 1964;Landmann, 1979;Alibardi, 1998). When an alpha-layer was separated from a syncitial beta-layer, the degradation of the cell junctions joining the two layers also determined the separation of an entire sequence of alpha-cells (the alpha-layer) from the beta-layer.…”

Section: Speculations On the Evolution Of The Shedding Complex In Lepmentioning

confidence: 99%

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

2002

Journal of Zoology

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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.

“…After tail amputation, most lizards regenerate numerous tissues from those of the tail stump, and they are organized into a new although anatomically simplified tail (Alibardi, 1998(Alibardi, , 2014(Alibardi, , 2017aBellairs & Bryant, 1985;Delorme, Lungu, & Vickaryous, 2012;Fisher et al, 2012;Gilbert, Delorme, & Vickaryous, 2015;Lozito & Tuan, 2016;McLean & Vickaryous, 2011). Conversely, the amputated limb heals more slowly and, later, gives rise to an outgrowth that generally forms a short scaling scar (Alibardi, 2016a(Alibardi, , 2016b.…”

Section: Introductionmentioning

confidence: 99%

“…During the traumatic phase of the initial 1-7 days post-amputation of the tail, a number of signalling factors, including c-myc, p63 and telomerase, are activated (Alibardi, 2015(Alibardi, , 2016a(Alibardi, , 2016b(Alibardi, , 2016c(Alibardi, , 2017b(Alibardi, , 2017c. | 125 ALIBARDI During this phase, an intense tissue remodelling occurs in the tail stump (Alibardi, 1998(Alibardi, , 2014Delorme et al, 2012;McLean & Vickaryous, 2011;Nambiar et al, 2008) and in the stump of the limb (Alibardi, 2014(Alibardi, , 2016a, in which proteases are called into action to degrade dying cells and damaged extracellular matrix molecules. Also, a process of de-differentiation may occur through the activity of proteases, among which those containing zinc ions in their catalitic site that are needed for their function, and indicated as "Matrix Metalloproteinases" (MMPs, Lee & Murphy, 2004;Caley, Martins, & O'Toole, 2014) and as "A Disintegrins and Metalloproteases" (ADAMs, Seals & Courtneidge, 2003).…”

Section: Introductionmentioning

confidence: 99%

Immunolocalization of Matrix Metalloproteinases in regenerating lizard tail suggests that an intense remodelling activity allows for apical tail growth

2018

Acta Zoologica

Regeneration of the tail in lizards suggests that a continuous remodelling process is active in the developing tissues. The present immunological study has detected Matrix Metalloproteinases (MMPs), previously indicated from a transcriptome study, in the lizard Podarcis muralis. Immunoblots show a main labelled band for MMPs around 68 kDa, possibly a MMP16‐like. Immunofluorescence shows that MMPs are mainly present in the central apical region of the mesenchymal blastema, in the ependyma of regenerating spinal cord, and in the basal layer and basement membrane‐region of the apical wound epidermis. The immune‐labelling decreases or disappears in differentiating tissues present in proximal regions of the regenerating tail such as the epidermis and dermis, muscles, inner connective tissues and in the axial cartilaginous tube. The prevalent localization of MMPs in the central mesenchyme of the blastema indicates a continuous remodelling of the extracellular matrix that actively contributes to the progressive distal growth of the apical blastema into a new tail. The study stresses that in regenerating organs of amniotes, a massive growth can only occur where connective tissues are maintained loose by the continuous action of extracellular matrix proteases in concert with the high production of hyaluronate and consequent tissue hydration.