RESUMEN
BACKGROUND: KCNQx genes encode slowly activating-inactivating K+ channels, are linked to physiological signal transduction pathways, and mutations in them underlie diseases such as long QT syndrome (KCNQ1), epilepsy in adults (KCNQ2/3), benign familial neonatal convulsions in children (KCNQ3), and hearing loss or tinnitus in humans (KCNQ4, but not KCNQ5). Identification of kcnqx potassium channel transcripts in zebrafish (Danio rerio) remains to be fully characterized although some genes have been mapped to the genome. Using zebrafish genome resources as the source of putative kcnq sequences, we investigated the expression of kcnq1-5 in heart, brain and ear tissues. RESULTS: Overall expression of the kcnqx channel transcripts is similar to that found in mammals. We found that kcnq1 expression was highest in the heart, and also present in the ear and brain. kcnq2 was lowest in the heart, while kcnq3 was highly expressed in the brain, heart and ear. kcnq5 expression was highest in the ear. We analyzed zebrafish genomic clones containing putative kcnq4 sequences to identify transcripts and protein for this highly conserved member of the Kcnq channel family. The zebrafish appears to have two kcnq4 genes that produce distinct mRNA species in brain, ear, and heart tissues. CONCLUSIONS: We conclude that the zebrafish is an attractive model for the study of the KCNQ (Kv7) superfamily of genes, and are important to processes involved in neuronal excitability, cardiac anomalies, epileptic seizures, and hearing loss or tinnitus.
Asunto(s)
Canales de Potasio KCNQ/metabolismo , Proteínas de Pez Cebra/metabolismo , Pez Cebra/metabolismo , Secuencia de Aminoácidos , Animales , Canales de Potasio KCNQ/química , Canales de Potasio KCNQ/genética , Datos de Secuencia Molecular , Pez Cebra/genética , Proteínas de Pez Cebra/química , Proteínas de Pez Cebra/genéticaRESUMEN
Head and neck squamous cell carcinomas (HNSCC) are associated with poor morbidity and mortality. Current treatment strategies are highly toxic and do not benefit over 50% of patients. There is therefore a crucial need for predictive and/or prognostic biomarkers to allow treatment stratification for individual patients. One class of biomarkers that has recently gained importance are microRNA (miRNA). MiRNA are small, noncoding molecules which regulate gene expression post-transcriptionally. We performed miRNA expression profiling of a cohort of head and neck tumours with known clinical outcomes. The results showed miR-9 to be significantly downregulated in patients with poor treatment outcome, indicating its role as a potential biomarker in HNSCC. Overexpression of miR-9 in HNSCC cell lines significantly decreased cellular proliferation and inhibited colony formation in soft agar. Conversely, miR-9 knockdown significantly increased both these features. Importantly, endogenous CXCR4 expression levels, a known target of miR-9, inversely correlated with miR-9 expression in a panel of HNSCC cell lines tested. Induced overexpression of CXCR4 in low expressing cells increased proliferation, colony formation and cell cycle progression. Moreover, CXCR4-specific ligand, CXCL12, enhanced cellular proliferation, migration, colony formation and invasion in CXCR4-overexpressing and similarly in miR-9 knockdown cells. CXCR4-specific inhibitor plerixafor abrogated the oncogenic phenotype of CXCR4 overexpression as well as miR-9 knockdown. Our data demonstrate a clear role for miR-9 as a tumour suppressor microRNA in HNSCC, and its role seems to be mediated through CXCR4 suppression. MiR-9 knockdown, similar to CXCR4 overexpression, significantly promoted aggressive HNSCC tumour cell characteristics. Our results suggest CXCR4-specific inhibitor plerixafor as a potential therapeutic agent, and miR-9 as a possible predictive biomarker of treatment response in HNSCC.
Asunto(s)
Antineoplásicos/farmacología , Neoplasias de Cabeza y Cuello/tratamiento farmacológico , Neoplasias de Cabeza y Cuello/genética , Compuestos Heterocíclicos/farmacología , MicroARNs/genética , Receptores CXCR4/genética , Bencilaminas , Ciclo Celular/efectos de los fármacos , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Ciclamas , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Neoplasias de Cabeza y Cuello/diagnóstico , Neoplasias de Cabeza y Cuello/patología , Humanos , Invasividad Neoplásica/diagnóstico , Invasividad Neoplásica/genética , Invasividad Neoplásica/patología , Invasividad Neoplásica/prevención & control , Pronóstico , Receptores CXCR4/antagonistas & inhibidores , Resultado del TratamientoRESUMEN
Cell division is a process by which a mother cell divides into genetically identical sister cells, although sister cells often display considerable diversity. In this report, over 350 sister embryonic stem cells (ESCs) were isolated through a microdissection method, and then expression levels of 48 key genes were examined for each sister cell. Our system revealed considerable diversities between sister ESCs at both pluripotent and differentiated states, whereas the similarity between sister ESCs was significantly elevated in a 2i (MEK and GSK3b inhibitors) condition, which is believed to mimic the ground state of pluripotency. DNA methyltransferase 3a/3b were downregulated in 2i-grown ESCs, and the loss of DNA methyltransferases was sufficient to generate nearly identical sister cells. These results suggest that DNA methylation is a major cause of the diversity between sister cells at the pluripotent states, and thus demethylation per se plays an important role in promoting ESC's self-renewal.