Big flies, small repeats: the "Thr-Gly" region of the period gene in Diptera

The region of the clock gene period (per) that encodes a repetitive tract of threonine-glycine (Thr-Gly) pairs has been compared between Dipteran species both within and outside the Drosophilidae. All the non- Drosophilidae sequences in this region are short and present a remarkably stable picture compared to the Drosophilidae, in which the region is much larger and extremely variable, both in size and composition. The accelerated evolution in the repetitive region of the Drosophilidae appears to be mainly due to an expansion of two ancestral repeats, one encoding a Thr-Gly dipeptide and the other a pentapeptide rich in serine, glycine, and asparagine or threonine. In some drosophilids the expansion involves a duplication of the pentapeptide sequence, but in Drosophila pseudoobscura both the dipeptide and the pentapeptide repeats are present in larger numbers. In the nondrosophilids, however, the pentapeptide sequence is represented by one copy and the dipeptide by two copies. These observations fulfill some of the predictions of recent theoretical models that have simulated the evolution of repetitive sequences.      

Twenty-Four hour blood pressure profile in subjects with different subtypes of primary aldosteronism

The aim of our study was to evaluate the potential differences in blood pressure (BP) profile in subjects with different forms of primary aldosteronism (PA). Simultaneously, we studied the effects of PA treatment on BP curve. We therefore monitored 24-hour ambulatory blood pressure values in 22 subjects with aldosterone-producing adenoma (APA), 22 subjects with idiopathic hyperaldosteronism (IHA) and 33 subjects with essential hypertension (EH) as controls. We found a significantly attenuated nighttime systolic BP decline in the APA group (P=0.02). Patients with IHA had lower nighttime systolic BP values (P=0.01) and also a diastolic BP decline (P=0.02) during the night in comparison with EH. We did not detect any significant differences in BP profile characteristics between APA and IHA. Specific treatment of primary aldosteronism (adrenalectomy, treatment with spironolactone) led to the normalization of the BP curve with a marked BP decline. Our study thus demonstrates a blunted diurnal BP variability in patients with primary aldosteronism the specific treatment of which normalized previously attenuated nocturnal BP fall.     

Dissection of a metastatic gene expression signature into distinct components

Background

Metastasis, the process whereby cancer cells spread, is in part caused by an incompletely understood interplay between cancer cells and the surrounding stroma. Gene expression studies typically analyze samples containing tumor cells and stroma. Samples with less than 50% tumor cells are generally excluded, thereby reducing the number of patients that can benefit from clinically relevant signatures.

Results

For a head-neck squamous cell carcinoma (HNSCC) primary tumor expression signature that predicts the presence of lymph node metastasis, we first show that reduced proportions of tumor cells results in decreased predictive accuracy. To determine the influence of stroma on the predictive signature and to investigate the interaction between tumor cells and the surrounding microenvironment, we used laser capture microdissection to divide the metastatic signature into six distinct components based on tumor versus stroma expression and on association with the metastatic phenotype. A strikingly skewed distribution of metastasis associated genes is revealed.

Conclusion

Dissection of predictive signatures into different components has implications for design of expression signatures and for our understanding of the metastatic process. Compared to primary tumors that have not formed metastases, primary HNSCC tumors that have metastasized are characterized by predominant down-regulation of tumor cell specific genes and exclusive up-regulation of stromal cell specific genes. The skewed distribution agrees with poor signature performance on samples that contain less than 50% tumor cells. Methods for reducing tumor composition bias that lead to greater predictive accuracy and an increase in the types of samples that can be included are presented.