Extracellular nucleotides regulate proliferation of progenitor cells in the adult zebrafish retina during the light:dark cycle.

RICATTI MJ; BATTISTA AG; FAILLACE MP

San Diego, California, USA.

Congreso; 40th Annual Meeting of the Society for Neuroscience; 2010

Society for Neuroscience

Extracellular nucleotides regulate proliferation of progenitor cells in the adult zebrafish retina during the light:dark cycle   Jimena Ricatti1, Ariadna Battista1, Paula Faillace1,2 1Departamento de Fisiología, Facultad de Medicina, UBA 2IQUIFIB-CONICET Buenos Aires, Argentina   The retina of teleost fish can regenerate and grow cells throughout the animal’s life. Their retina is endowed with a rim of tissue at the periphery called ciliary marginal zone (CMZ), which contains proliferative (PC) and differentiating cells. In this work, we first described variations in the total number of PC in the CMZ during a 14:10 h light:dark cycle with a peak at the middle of the light phase (ZT14) and a minimum at the beginning of the dark phase (ZT21). However, we did not find circadian variations in the number of proliferative cells. We had previously described the presence of NTPDase enzymes, that control extracellular nucleotide levels, in the zebrafish retinal layers by immunohistochemistry. Here we report the presence of mRNA for NTPDases 1, 2 (with three isoforms) and 3 and the purinergic receptor P2Y1 by qRT-PCR in the retina. We found that all NTPDases examined showed around a two fold increase of their mRNA levels during the light phase. Then, we studied the role of extracellular nucleotides in regulating cell proliferation during the light:dark cycle. Different treatments were performed by intravitreal injections of ADPβS, apyrase (an enzyme that hydrolyzes tri- and diphosphate nucleotides), hexokinase (an enzyme that hydrolyzes mainly ATP), ARL67156 (a selective ectoATPase inhibitor) or different antagonists of purinergic receptors. Either saline or inactivated-apyrase or hexokinase were injected to control eyes. 20 h post-treatment, at ZT14 or ZT21, eyes were treated with 5-bromo-2’-deoxiuridine (BrdU) for 2 h. BrdU-labeled cells in the CMZ were quantified in 16 µm slices. At ZT14, we found that apyrase-, MRS2179- (a specific inhibitor of ADP activated P2Y1 receptors) or ARL67156-treatment significantly inhibited light-induced PC number increase. At ZT21, apyrase-treatment also significantly decreased PC counts, whereas we found that ADPβS significantly enhanced cell division at night to the levels observed during the light phase. This study suggests a crucial role for ADP as a paracrine signal in the regulation of the proliferative activity of the CMZ throughout the light-dark cycle during normal retinal growth.