Glial fibrillary acidic protein and vimentin immunoreactivity of astroglial cells in the central nervous system of adult Podarcis sicula (Squamata, Lacertidae)

Abstract

The present immunoperoxidase cytochemical study describes the distribution of glial intermediate filament molecular markers, glial fibrillary acidic protein (GFAP) and vimentin, in the brain and spinal cord of the adult lizard, Podarcis sicula. GFAP immunoreactivity is abundant and the positive structures are mainly represented by fibres of different lengths which are arranged in a rather regular radial pattern throughout the CNS. They emerge from generally immunopositive radial ependymoglia and are directed from the ventricular wall towards the meningeal surface. The glial fibres give origin to endfeet which are apposed to the blood vessel walls and subpial surface where they form the continous perivascular and subpial glia envelopes, respectively. In the optic tectum and spinal cord, star-shaped astrocytes coexist with radial glia. In the spinal cord, cell bodies of immunopositive radial glia are displaced from the ependyma. While vimentin immunoreactive elements are almost completely absent in the brain except for a few diencephalic radial fibres, the spinal cord ependyma exhibits a clearly vimentin positivity and no GFAP staining. In the Podarcis CNS the immunocytochemical response of the astroglial intermediate filaments appears typical of mature astroglia cell lineage since it fundamentally expresses GFAP immunoreactivity. Moreover, this immunocytochemical study shows that the Podarcis fibre pattern with predominant radial glial cells is morphologically more immature than in avians and mammalians, a condition suggesting that reptiles represent a fundamental step in the phylogenetic evolution of vertebrate astroglial cells.

Evolutionary Changes of Astroglia in Elasmobranchii Comparing to Amniotes: A Study Based on Three Immunohistochemical Markers (GFAP, S-100, and Glutamine Synthetase)

“…In different species with 'elaborated' brains either radial ependymoglia ('tanycytes'), or astrocytes might be predominant. The same pattern is found in Amniotes when comparing the 'tanycytic' brains of reptiles, with only scarce astrocytes (if at all), to the 'astrocytic' brains of birds and mammals Hajós and Kálmán, 1989;Monzon-Mayor et al, 1990;Yanes et al, 1990;Lazzari and Franceschini, 2001;Kálmán and Pritz, 2001]. Among the ray-finned fishes (Actinopterygii), Teleostei have 'elaborated' brains [Butler and Hodos, 2005], but they have only a few astrocyte-like elements, and these are confined to restricted areas [Kálmán, 1998, also for review].…”

Characterization of adult neurogenesis in lizardPhrynocephalus vlangalii(Agamidae: Reptilia)

“…With the advancement of immunocytochemistry, in addition to fibrous or protoplasmic astrocytes, GFAP was detected also in radial structures including tanycytes and radial glial cells, ependymocytes, and Bergmann glia in vertebrate (Wasowicz et al 1994;Lazzari & Franceschini 2001;Ahboucha et al 2003;Lazzari & Franceschini 2004;Huang et al 2005), indicating that GFAP is of considerable stability in its molecular and antigenic features, and conserved throughout vertebrate phylogenesis.…”

“…In P. vlangalii, GFAP immunoreactivity was abundant almost throughout the entire brain: telencephalon, diencephalon and mesencephalon. The general pattern of GFAP immunocytochemistry in P. vlangalii brain revealed several positive elements, including radial glial cells, ependymocytes, and astrocytes, yet fundamentally represented by tanycytes characteristic of somata located in the ependymal lining with a unique radial process extending for variable distances in the neuropil (Lazzari & Franceschini 2001).…”

Glial cells of the central nervous system of Bothrops jararaca (Reptilia, Ofidae): an ultrastructural study

“…Radial glia is generated before neurogenesis and guide neuronal migration in the developing brain. In mammals, radial glial cells disappear or become astrocytes within days to weeks after birth, but in non-mammals they persist into adulthood as radial glia (Lazzari & Franceschini 2001, Weissman et al 2003.…”