C-MYC, a transforming oncogene that is frequently overexpressed in many human cancers, regulates a variety of normal functions including cell cycle progression, apoptosis, and maintenance of cell size, morphology, and genomic integrity. Many target genes are modulated by c-Myc, and some can recapitulate a limited number of the above functions. Because most of these have been assessed in cells which also express endogenous c-Myc, however, it is not clear to what extent its proper regulation is also required. We show here that, in c-Myc nullizygous cells, two direct target genes, MT-MC1 and HMG-I, could each recapitulate multiple c-Myc phenotypes. Although these differ somewhat for the two genes, substantial overlap and cooperativity exist. The enforced expression of these two genes was also associated with the differential deregulation of some previously described c-Myc target genes, indicating the presence of a complex molecular circuitry. These observations argue that, despite the great diversity of gene regulation by c-Myc, many, although not all, of its functions can be phenocopied by a small subset of key downstream target genes. The approach described here should permit the identification of other target genes capable of further c-Myc-independent complementation. (Cancer Res 2005; 65(6): 2097-107)

Nucleostemin (NS) encodes a nucleolar GTPase which is highly expressed in stem/progenitor cells and in most cancer cells. However, little is known about the regulation of NS expression. Here we identify NS as a novel direct transcriptional target of the c-Myc oncoprotein. We show that Myc overexpression enhances NS transcription in cultured cells and in pre-neoplastic B-cells from Eμ-myc transgenic mice. Consistent with NS being downstream of Myc, NS expression parallels that of Myc in a large panel of human cancer cell lines. Using chromatin IP we show that c-Myc binds to a well-conserved E-box in the NS promoter. Critically, we show NS haploinsufficiency profoundly delays Myc-induced cancer formation in vivo. NS+/−Eμ-myc transgenics have indeed much slower rates of B cell lymphoma development, with life spans twice that of wild-type littermates. Moreover, we demonstrate that NS is essential for the proliferation of Myc-overexpressing cells both in vitro and in vivo. Impaired lymphoma development was associated with a drastic decrease of c-Myc-induced proliferation of pre-tumoural B-cells. Finally, we provide evidence that NS control cultured cell proliferation independently of p53 and that NS haploinsufficiency significantly delayed lymphomagenesis on a p53-deficient background. Together these data indicate that NS functions, downstream of Myc, as a rate limiting factor for the proliferation and transformation of cells independently from its putative role within the p53 pathway. Targeting NS is therefore expected to compromise early tumour development irrespectively of the p53 status.

Abnormal EEG features are a hallmark of epilepsy, and abnormal frequency and network features are apparent in EEGs from people with idiopathic generalised epilepsy in both ictal and interictal states. Here, we characterise differences in the resting-state EEG of individuals with juvenile myoclonic epilepsy and assess factors influencing the heterogeneity of EEG features. We collected EEG data from 147 participants with juvenile myoclonic epilepsy through the Biology of Juvenile Myoclonic Epilepsy study. 95 control EEGs were acquired from two independent studies (Chowdhury et al. (2014) and EU-AIMS Longitudinal European Autism Project). We extracted frequency and functional network-based features from 10-20 s epochs of resting-state EEG, including relative power spectral density, peak alpha frequency, network topology measures and brain network ictogenicity: a computational measure of the propensity of networks to generate seizure dynamics. We tested for differences between epilepsy and control EEGs using univariate, multivariable and receiver operating curve analysis. Additionally, we explored the heterogeneity of EEG features within and between cohorts by testing for associations with potentially influential factors such as age, sex, epoch length and time, as well as testing for associations with clinical phenotypes including anti-seizure medication, and seizure characteristics in the epilepsy cohort. P-values were corrected for multiple comparisons. Univariate analysis showed significant differences in power spectral density in delta (2-5 Hz) (p = 0.0007, hedges’ g = 0.55) and low-alpha (6-9 Hz) (p = 2.9 × 10−8, g = 0.80) frequency bands, peak alpha frequency (p = 0.000007, g = 0.66), functional network mean degree (p = 0.0006, g = 0.48) and brain network ictogenicity (p = 0.00006, g = 0.56) between epilepsy and controls. Since age (p = 0.009) and epoch length (p = 1.7 × 10−8) differed between the two groups and were potential confounders, we controlled for these covariates in multivariable analysis where disparities in EEG features between epilepsy and controls remained. Receiver operating curve analysis showed low-alpha power spectral density was optimal at distinguishing epilepsy from controls, with an area under the curve of 0.72. Lower average normalized clustering coefficient and shorter average normalized path length were associated with poorer seizure control in epilepsy patients. To conclude, individuals with juvenile myoclonic epilepsy have increased power of neural oscillatory activity at low-alpha frequencies, and increased brain network ictogenicity compared to controls, supporting evidence from studies in other epilepsies with considerable external validity. In addition, the impact of confounders on different frequency-based and network-based EEG features observed in this study highlights the need for careful consideration and control of these factors in future EEG research in idiopathic generalised epilepsy particularly for their use as biomarkers.