Bilirubin arrests the cell cycle in the cerebellum of developing hyperbilirubinemic Gunn rat

M. CELESTE ROBERT; SILVIA GAZZIN; CLAUDIO TIRIBELLI

Torino

Congreso; 36th FEBS congress Biochemistry for Tomorrow's Medicine; 2011

Federation of European Biochemical Societies (FEBS), Italian Society of Biochemistry and Molecular Biology (SIB), University of Torino (UNITO)

Bilirubin arrests the cell cycle in the cerebellum of developing hyperbilirubinemic Gunn rat Robert, M.Celeste; Gazzin, Silvia; Tiribelli, Claudio. Fondazione Italiana Fegato- Area Science Park Basovizza and department of ACADEM University of Trieste, Trieste, Italy. celeste.robert@csf.units.it Keywords: Bilirubin- Cell cycle- cerebella hypoplasia- Gunn rat- Crigler-Najjar type I Syndrome Neonatal hyperbilirubinemia in jj Gunn rat results from a deficiency of the hepatic bilirubin conjugating enzyme UDP-glucuronosyl transferase 1A1, homologous to human patients with Crigler Najjar type I Syndrome and analogous to the reduced enzyme activity seen in neonates during the first days of life. The high levels of unconjugated bilirubin (UCB) in plasma can lead to the accumulation of bilirubin in the brain. The hyperbilirubinemic jj Gunn rat develop a marked cerebellar hypoplasia, with the greatest damage occurring in brain areas that mature postnatally. Recently, an effect of UCB on cell cycle progression has been described with cell cycle arrest in the late G1 phase. The aim of this study was to investigate the role of cell cycle arrest in the cerebellar hypoplasia in hyperbilirubinemic jj Gunn rat. The cerebellum from hyperbilirubinemic (jj) and normal (JJ) Gunn rat at 9 days after birth was dissected and divided in two parts. The first was used to evaluated the mRNA relative expression of Cyclin A, D1, E, and Cdk2 genes using Real Time q-PCR (n=11); and the other one to determinate the protein levels of Cdk2 and Cyclin A by quantitative Western Blot (n=9 and n=7 respectively). At the mRNA level, we observed a slight reduction in Cyclin D1 expression in jj rats (JJ 1.00 ± 0.18 vs. jj 0.80 ± 0.30 NS) and a significant increase in the Cyclin E expression (JJ 1.00 ± 0.34 vs. jj 1.44 ± 0.26, p < 0.01). The mRNA expression of Cyclin A and Cdk2 was unchanged. The protein relative expression of Cdk2 and Cyclin A was significantly reduced in jj animals (1.12 ± 0.11 vs. 0.84 ± 0.07 p