CONICET | Buscador de Institutos y Recursos Humanos

Daily variations in the proliferation of progenitor cells are regulated by extracellular nucleotides in the adult zebrafish retina Jimena Ricatti1, Ariadna Battista1, Paula Faillace1,2 1Departamento de Fisiología, Facultad de Medicina, UBA 2IQUIFIB-CONICET Buenos Aires, Argentina Teleost retina can regenerate and grow during the animal's life. Fish retina is endowed with a rim of tissue called margin germinal zone (MGZ) which contains proliferative (PC) and differentiating cells. We have recently described variations in the number of PC during a 24 h light/dark cycle. We found a peak at the middle of the light phase (L-14 h) and a minimum in the first half of the dark phase (from I-21 to I-02 h). On the other hand, we have described the presence of NTPDase enzymes that control extracellular nucleotide levels by immunohistochemistry in the zebrafish retina. Our aim was to study the role of extracellular nucleotides in regulating cell proliferation during a 14/10 h light/dark cycle. Zebrafish (Danio rerio) were separated in 2 groups. Group I was maintained under a light/dark cycle with an inverted phase respect to Group L. Three different treatments were performed by intravitreal injections of either apyrase (an enzyme that hydrolyzes nucleotides), MRS2179 (an antagonist of P2Y1 receptor), or ARL67156 (an NTPDase inhibitor). Saline or inactivated-apyrase were injected to control eyes. 20 h post-treatment, at L-14, I-21 and I-02 h, eyes were treated with 5-bromo-2-deoxiuridine (BrdU) for 2 h. BrdU-labeled cells in the MGZ were quantified in 15 µm slices. NTPDases mRNA from retinal homogenates was assessed by RT-PCR. We found that at L-14 h apyrase-, MRS2179- or ARL67156-treatment significantly inhibited light-induced PC numbers increase. At I-21 and I-02 h apyrase-treatment also significantly decreased PC counts. Moreover, we described the presence of NTPDase1, 2 and 3 by RT-PCR. Our results suggest that nucleotides in the extracellular environment regulate daily variations of PC numbers in the MGZ of the zebrafish retina.