Expression of synaptic vesicle trafficking proteins in the developing rat pineal gland

Abstract

Adult mammalian pinealocytes contain several synaptic membrane proteins that are probably involved in the regulation of targeting and exocytosis of synaptic-like microvesicles (SLMVs). Immunohistochemical techniques have now demonstrated the spatiotemporal expression pattern of some of these proteins during rat pineal ontogenesis. Various synaptic vesicle trafficking proteins are detectable in proliferating epithelial cells of the pineal anlage even at embryonic day 17.5 (E 17.5), with the exception of syntaxin I (weakly expressed from E 19.5) and dynamin I (whose levels increase markedly during the first postnatal week). Numerous cells exhibiting strong immunoreactivity for synaptobrevin II, SNAP-25, synaptophysin, and munc-18-1 are distributed throughout the increasingly compact gland at E 19.5 and E 20.5; however, their number declines toward the proximal deep part of the organ. Groups of postmitotic cells situated at the surface of the developing gland exhibit marked immunoreactivity for the aforementioned proteins and lie close to the laminin-immunoreactive outer limiting basement membrane or to its remnants in regions of basement membrane dissolution. We also show that synthesis of vimentin and S-antigen seems to begin earlier during pineal development than previously recognized. Thus, synaptic vesicle trafficking proteins are the earliest molecular markers of pinealocyte differentiation known to date, being expressed well before the onset of rhythmic hormone secretion in the pineal gland, where they may play a role in morphogenetic events. Components of the extracellular matrix such as laminin may be critically involved in the upregulation of synaptic membrane protein expression. The dynamin immunostaining pattern indicates that SLMVs of pinealocytes begin to undergo regulated cycles of exo/endocytosis during postnatal week 1.

The expression pattern and assembly profile of synaptic membrane proteins in ribbon synapses of the developing mouse retina

“…In B the immunosignals were semiquantitatively evaluated by fluorescence intensity measurements. Late ontogenetic expression of syntaxin has also been reported in the pineal gland, which is a retina-related tissue (Redecker 2000). In the adult retina, fluorescence intensities of Rab3 and synaptogyrin in the OPL are roughly the same in amplitude as synaptophysin (peaks 2, 5) (oNBL outer neuroblast layer, NBL neuroblast layer, OPL outer plexiform layer, IPL inner plexiform layer).…”

Identification and Analysis of Two Novel Sites of Rat GnRH Receptor Gene Promoter Activity: The Pineal Gland and Retina

“…The onset of gene activity occurs during embryonic life, first in the pineal gland as early as E13.5 and later in the retina, at E17.5. Interestingly, regarding the pineal gland, usual marker genes are not expressed until P1 [42], either clock genes or genes coding for enzymes involved in melatonin synthesis. Indeed, in mammals, mothers provide photoperiodic information to their developing fetuses through circulating melatonin, unlike birds and fishes [43].…”

Mass‐spectrometry analysis of the human pineal proteome during night and day and in autism

“…17,18 The synaptic ribbons are electron-dense structures tethering synaptic vesicles, considered as specific marker structure for the pinealocytes with a unique type of chemical synapse, referred by Jouvet et al (1994) as the ribbon synapse. [19][20][21][22][23] The ribbon synapse is not a classical synapse and its protein composition differs from conventional synapses reflecting different modes of transmitter release. In contrast to other synapses, there is no postsynaptic specialization in apposition to the ribbon and vesicles.…”

“…The main cell type of the mammalian pineal parenchymal is the pinealocyte, (~95%), however, many endothelial and vascular smooth muscle cells, few glia, phagocytic cells, and rarely neurons are present, too 17,18 . The synaptic ribbons are electron‐dense structures tethering synaptic vesicles, considered as specific marker structure for the pinealocytes with a unique type of chemical synapse, referred by Jouvet et al (1994) as the ribbon synapse 19‐23 . The ribbon synapse is not a classical synapse and its protein composition differs from conventional synapses reflecting different modes of transmitter release.…”