No abstract

Mantle-cell lymphoma (MCL) is genetically characterized by the translocation t(11;14)(q13;q32) and a high number of secondary chromosomal abnormalities. To identify genes inactivated in this lymphoma, we examined 5 MCL cell lines following a strategy previously described in tumors with microsatellite instability that is based on the combined inhibition of the nonsense-mediated mRNA decay pathway and gene-expression profiling. This approach, together with the design of a conservative algorithm for analysis of the results, allowed the identification of 3 genes carrying premature stop codons. These genes were p53 with a mutation previously described in JEKO-1, the leukocyte-derived arginine aminopeptidase (LRAP) gene in REC-1 that showed a new splicing isoform generating a premature stop codon, and RB1 in UPN-1 that contained an intragenic homozygous deletion resulting in a truncated transcript and total loss of protein expression. The new LRAP isoform was detected also in 2 primary MCLs, whereas inactivating intragenic deletions of RB1 were found in the primary tumor from which UPN-1 was derived and 1 additional blastoid MCL. These tumors carried a concomitant inactivation of p53, whereas p16INK4a was wild type. These results indicate for the first time that RB1 may be inactivated in aggressive MCL by intragenic deletions. IntroductionMantle-cell lymphoma (MCL) is as a distinct type of B-cell non-Hodgkin lymphoma genetically characterized by the t(11; 14)(q13;q32) translocation that leads to the dysregulation of cyclin D1. 1 In addition to the constitutive overexpression of cyclin D1, MCL shows frequent alterations of genes involved in the DNA damage response pathway and in the G1/S-phase checkpoint. 2 The dysregulation of the DNA damage response pathway may facilitate the chromosomal instability observed in these tumors. In that sense, inactivation of the tumor-suppressor genes (TSGs) p53 or ATM has been frequently observed in MCL with high number of chromosome abnormalities. [3][4][5] Oncogenic alterations in the cell cycle machinery include the inactivation of INK4a/ARF and the amplification of potential oncogenes such as BMI-1 or CDK4. [6][7][8] All these alterations play an important pathogenetic role in MCL, probably deregulating the cell cycle control by overcoming the suppressor effect that retinoblastoma 1 (RB1) performs in the G1/S-phase transition. In addition to these molecular oncogenic events, conventional cytogenetic and comparative genomic hybridization (CGH) studies have revealed a high number of secondary chromosomal abnormalities in MCL. However, only a few target genes of these genetic alterations have been identified. 9,10 The nonsense-mediated mRNA decay (NMD) pathway is an eukaryotic cellular mRNA surveillance mechanism that rapidly degrades mRNA transcripts containing premature termination codons (PTCs). 11,12 This mechanism of control prevents the accumulation of truncated proteins generated by translation of mRNAs that carry PTCs due to nonsense mutations, splicing errors, or inaccuracie...

The aim of this study was to develop a rabbit neurosphere culture to characterize differences in basic processes of neurogenesis induced by intrauterine growth restriction (IUGR). A novel in vitro neurosphere culture has been established using fresh or frozen neural progenitor cells from newborn (PND0) rabbit brains. After surgical IUGR induction in pregnant rabbits and cesarean section 5 days later, neural progenitor cells from both control and IUGR groups were isolated and directly cultured or frozen at −80 C. These neural progenitor cells spontaneously formed neurospheres after 7 days in culture. The ability of control and IUGR neurospheres to migrate, proliferate, differentiate to neurons, astrocytes, or oligodendrocytes was compared and the possibility to modulate their responses was tested by exposure to several positive and negative controls. Neurospheres obtained from IUGR brains have a significant impairment in oligodendrocyte differentiation, whereas no significant differences are observed in other basic processes of neurogenesis. This impairment can be reverted by in vitro exposure of IUGR neurospheres to thyroid hormone, which is known to play an essential role in white matter maturation in vivo. Our new rabbit neurosphere model and the results of this study open the possibility to test several substances in vitro as neuroprotective candidates against IUGR induced neurodevelopmental damage while decreasing the number of animals and resources and allowing a more mechanistic approach at a cellular functional level.