A spatio-temporal model to reveal oscillator phenotypes in molecular clocks: Parameter estimation elucidates circadian gene transcription dynamics in single-cells

Expression of the Circadian Clock Gene ARNTL associated with DNA repair gene and prognosis of patient with osteosarcoma

PURPOSE

The study objects were to explore the correlation between the biological role of clock genes and clinical indicators in patients with osteosarcoma (OS).

METHODS

We acquired the clinical information and RNA sequencing data of OS samples from the TARGET database. The protein-protein interaction (PPI) network and expression correlation analysis of clock genes were performed. Then, the functional enrichment analysis of clock genes was analyzed. The survival analysis of clock genes in patients of OS was carried out by univariate cox regression, Kaplan-Meier (KM) curve and multivariate cox regression methods. Moreover, the spearmen correlation analysis was performed to explore the correlation between clock genes and DNA repair genes in patients with OS.

RESULTS

The PPI network and expression correlation analysis of clock genes indicated that the clock genes were highly correlated with each other. The survival analysis of clock genes found that clock gene ARNTL is a protective factor for the prognosis of patients with OS. We found that ARNTL was positively related to DNA repair genes and was involved in the biological process of DNA damage repair in patients with OS.

CONCLUSIONS

ARNTL may affect the prognosis and chemotherapy response of patients with OS by regulating DNA repair pathways.

Deciphering clock cell network morphology within the biological master clock, suprachiasmatic nucleus: From the perspective of circadian wave dynamics

The biological master clock, suprachiasmatic nucleus (of rat and mouse), is composed of ~10,000 clock cells which are heterogeneous with respect to their circadian periods. Despite this inhomogeneity, an intact SCN maintains a very good degree of circadian phase (time) coherence which is vital for sustaining various circadian rhythmic activities, and it is supposedly achieved by not just one but a few different cell-to-cell coupling mechanisms, among which action potential (AP)-mediated connectivity is known to be essential. But, due to technical difficulties and limitations in experiments, so far very little information is available about the morphology of the connectivity at a cellular scale. Building upon this limited amount of information, here we exhaustively and systematically explore a large pool (~25,000) of various network morphologies to come up with some plausible network features of SCN networks. All candidates under consideration reflect an experimentally obtained ‘indegree distribution’ as well as a ‘physical range distribution of afferent clock cells.’ Then, importantly, with a set of multitude criteria based on the properties of SCN circadian phase waves in extrinsically perturbed as well as in their natural states, we select out appropriate model networks: Some important measures are, 1) level of phase dispersal and direction of wave propagation, 2) phase-resetting ability of the model networks subject to external circadian forcing, and 3) decay rate of perturbation induced “phase-singularities.” The successful, realistic networks have several common features: 1) “indegree” and “outdegree” should have a positive correlation; 2) the cells in the SCN ventrolateral region (core) have a much larger total degree than that of the dorsal medial region (shell); 3) The number of intra-core edges is about 7.5 times that of intra-shell edges; and 4) the distance probability density function for the afferent connections fits well to a beta function. We believe that these newly identified network features would be a useful guide for future explorations on the very much unknown AP-mediated clock cell connectome within the SCN.