Comparative transcript profiles of cell cycle-related genes in mouse primordial germ cells, embryonic stem cells and embryonic germ cells.

We used cDNA array to compare the relative transcript levels of 96 cell cycle-related genes in mouse primordial germ cells (PGCs), embryonic germ (EG) cells and embryonic stem (ES) cells. Among 38 genes of the G1 phase analysed, Ccnd3 (CyclinD3), Cdkn1c (p57(kip2)), Rb1, and Tceb1l (Skip1-like) were expressed at significantly higher levels in PGCs than in EG and ES cells; Ccnd1 (CyclinD1) was more abundant in EG cells than in PGCs. Except for higher mRNA levels of Ccng (CyclinG1) in EG and ES cells in comparison to PGCs, no difference among 20 genes of the S and 12 genes of G2/M phases was found. Less than half of the 26 genes regarded as DNA damage checkpoint/Trp53/Atm pathway genes showed significant transcript levels in all three cell populations. Among these, the transcript levels of Ube1x and Atm were significantly higher in PGCs than in EG and ES cells while that of Ube3a was higher in these latter. In addition, relatively high mRNA levels of Timp3 characterizes EG cells while transcripts of this gene were very low in PGCs and barely detectable in ES cells. With the exception of Tceb1l, differential transcript levels found in the cDNA array assay were confirmed by real time RT-PCR. Using this method, we also analysed the transcripts of two genes not present in the cDNA array: c-myc, known to be critical for the control of cell cycle in many cell types, and Eras, specifically expressed in ES cells and involved in the control of ES cell proliferation and their tumorigenic properties. While c-myc transcripts were present at similar levels in all three cell types examined, Eras was expressed at high levels in ES cells (10-fold) and even more so in EG cells (almost 40-fold) in comparison to PGCs. Taken together, these results indicate that despite similarities between PGCs and ES or EG cells, their cell cycles are differently regulated. In particular, it appears that PGCs, like most mitotic cells, possess a more regulatable control of G1 phase than EG and ES cells. Moreover, our data provide useful clues for further studies aimed at identifying cell cycle genes critical for PGC growth and their transformation in tumorigenic cells.

Neuroprotective effects of the mGlu5R antagonist MPEP towards quinolinic acid-induced striatal toxicity: involvement of pre- and post-synaptic mechanisms and lack of direct NMDA blocking activity.

The aim of this work was to investigate the potential neuroprotective effects of the metabotropic glutamate receptor 5 (mGlu5R) antagonist 2-Methyl-6-(phenylethynyl)-pyridine (MPEP) towards quinolinic acid (QA)-induced striatal excitoxicity. Intrastriatal MPEP (5 nmol/0.5 micro L) significantly attenuated the body weight loss, the electroencephalographic alterations, the impairment in spatial memory and the striatal damage induced by bilateral striatal injection of QA (210 nmol/0.7 micro L). In a second set of experiments, we aimed to elucidate the mechanisms underlying the neuroprotective effects of MPEP. In microdialysis studies in naive rats MPEP (80-250 micro m through the dialysis probe) significantly reduced the increase in glutamate levels induced by 5 mm QA. In primary cultures of striatal neurons MPEP (50 micro m) reduced the toxicity induced by direct application of glutamate [measured as release of lactate dehydrogenase [LDH]). Finally, we found that 50 micro m MPEP was unable to directly block NMDA-induced effects (namely field potential reduction in corticostriatal slices, as well as LDH release and intracellular calcium increase in striatal neurons). We conclude that: (i) MPEP has neuroprotective effects towards QA-induced striatal excitotoxicity; (ii) both pre- and post-synaptic mechanisms are involved; (iii) the neuroprotective effects of MPEP do not appear to involve a direct blockade of NMDA receptors.