Neurogranin expression oscillates on a daily basis in the hippocampus and is modified by a vitamin A-deficient diet

GOLINI RS; PONCE IT; DELGADO SM; ANZULOVICH AC

Huerta Grande, Cordoba

Congreso; I IRCN de la Sociedad Argentina de Investigación en Neurociencias; 2009

Neurogranine (RC3) is a postsynaptic PKC substrate involved in synaptic plasticity and implicated in the maintenance phase of LTP. RC3 and retinoid nuclear receptors, RARá and RXRâ, have been detected in the rat hippocampus. Here, we investigate whether RC3 displays a daily expression pattern in the rat hippocampus, and evaluate to which extent vitamin A deficiency could modify RC3 rhythmicity. Holtzman rats weaned at 21 d of age were immediately assigned to either the experimental diet, devoid of vitamin A (vitamin A-deficient group) or the same diet containing 4000 IU of vitamin A/Kg diet (control group) during 3 months. Hippocampus samples were taken every 4 h from control and vitamin A-deficient rats. Scanning of RC3 gene regulatory region for putative RAREs and clock-responsive E-boxes was carried out using MatInspector software from Genomatix. Total RNA was isolated using Trizol reagent. RARá and RXRâ mRNA levels were quantified by Real-time PCR. Daily RC3, Bmal1, Per1 and Cry1 transcript levels, were determined by RT-PCR. Protein levels were analyzed by immunoblotting. We found three E-boxes and two RAREs within 1550 bp upstream of the translation start codon in the RC3 gene. We observed RC3 expression displays a daily rhythmicity in the rat hippocampus. RXRâ mRNA levels were significantly reduced in the vitamin A-deficient rats. Daily rhythm of RC3 expression was phase shifted in the vitamin A-deficient group following changes in BMAL1 levels, probably by a lower availability of RXRâ. Above observations raise the possibility that nutritional factors might be essential to maintain the daily expression pattern of clock-controlled, learning-related, genes in the hippocampus.