title: TNAP activity is localized at critical sites of retinal neurotransmission across various vertebrate species.
abstract: Evidence is emerging with regard to the role of tissue non-specific alkaline phosphatase (TNAP) in neural functions. As an ectophosphatase, this enzyme might influence neural activity and synaptic transmission in diverse ways. The localization of the enzyme in known neural circuits, such as the retina, might significantly advance an understanding of its role in normal and pathological functioning. However, the presence of TNAP in the retina is scarcely investigated. Our multispecies comparative study (zebrafish, cichlid, frog, chicken, mouse, rat, golden hamster, guinea pig, rabbit, sheep, cat, dog, ferret, squirrel monkey, human) using enzyme histochemistry and Western blots has shown the presence of TNAP activity in the retina of several mammalian species, including humans. Although the TNAP activity pattern varies across species, we have observed the following trends: (1) in all investigated species (except golden hamster), retinal vessels display TNAP activity; (2) TNAP activity consistently occurs in the photoreceptor layer; (3) in majority of the investigated species, marked TNAP activity is present in the outer and inner plexiform layers. In zebrafish, frog, chicken, guinea pig, and rat, TNAP histochemistry has revealed several sublayers of the inner plexiform layer. Frog, golden hamster, guinea pig, mouse, and human retinas possess a subpopulation of amacrine cells positively staining for TNAP activity. The expression of TNAP in critical sites of retinal signal transmission across a wide range of species suggests its fundamental, evolutionally conserved role in vision.
authors.affiliation: Department of Anatomy, Histology and Embryology, Semmelweis University, Tűzoltó u. 58, Budapest, 1094, Hungary, kantororsi@googlemail.com.
authors.forename: Orsolya
authors.initials: O
authors.lastname: Kántor
authors.forename: Alexandra
authors.initials: A
authors.lastname: Varga
authors.forename: Tamás
authors.initials: T
authors.lastname: Kovács-Öller
authors.forename: Anna
authors.initials: A
authors.lastname: Énzsöly
authors.forename: Lajos
authors.initials: L
authors.lastname: Balogh
authors.forename: Gábor
authors.initials: G
authors.lastname: Baksa
authors.forename: Zsuzsanna
authors.initials: Z
authors.lastname: Szepessy
authors.forename: Caroline
authors.initials: C
authors.lastname: Fonta
authors.forename: Anna Wang
authors.initials: AW
authors.lastname: Roe
authors.forename: Roland
authors.initials: R
authors.lastname: Nitschke
authors.forename: Ágoston
authors.initials: Á
authors.lastname: Szél
authors.forename: László
authors.initials: L
authors.lastname: Négyessy
authors.forename: Béla
authors.initials: B
authors.lastname: Völgyi
authors.forename: Ákos
authors.initials: Á
authors.lastname: Lukáts
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism*; D000818:Animals; D002415:Cats; D006224:Cricetinae; D004285:Dogs; D005289:Ferrets; D006168:Guinea Pigs; D006801:Humans; D008647:Mesocricetus; D051379:Mice; D011817:Rabbits; D051381:Rats; D055351:Retinal Neurons / Q000201:enzymology*; D012453:Saimiri; D012756:Sheep; D013045:Species Specificity; D009435:Synaptic Transmission / Q000502:physiology*; D015027:Zebrafish
chemical_list: C510878:ALPL protein, mouse; D000469:Alkaline Phosphatase