Quantitative analysis of thyroid-stimulating hormone messenger RNA and heterogeneous nuclear RNA in hypothyroid rats

Contribution of molecular analysis to the typification of the non-functioning pituitary adenomas

AIM

The WHO Classification of Tumours of Endocrine Organs considers the inmunohistochemical characterization of pituitary adenomas (PA) as mandatory for patient diagnosis. Recent advances in the knowledge of the molecular patterns of these tumours could complement this classification with gene expression profiling.

METHODS

Within the context of the Spanish Molecular Registry of Pituitary Adenomas (REMAH), a multicentre clinical-basic research project, we analysed the molecular phenotype of 142 PAs with complete IHC and clinical information. Gene expression levels of all pituitary hormones, type 1 corticotrophin-releasing hormone receptor, dopamine receptors and arginine vasopressin receptor 1b were measured by quantitative real-time polymerase chain reaction. In addition, we used three housekeeping genes for normalization and a pool of nine healthy pituitary glands from autopsies as calibration reference standard.

RESULTS

Based on the clinically functioning PA (FPA: somatotroph, corticotroph, thyrotroph and lactotroph adenomas), we established the interquartile range of relative expression for all genes studied in each PA subtype. That allowed molecularly the different PA subtypes, including the clinically non-functioning PA (NFPA). Afterwards, we estimated the concordance of the molecular and immunohistochemical classification with clinical diagnosis in FPA and between them in NFPA. The kappa values were higher in molecular than in immunohistochemical classification in FPA and showed a bad concordance in all NFPA subtypes.

CONCLUSIONS

According to these results, the molecular characterization of the PA complements the IHC analysis, allowing a better typification of the NFPA.

Post-transcriptional homeostasis and regulation of MCM2-7 in mammalian cells

The MiniChromosome Maintenance 2-7 (MCM2-7) complex provides essential replicative helicase function. Insufficient MCMs impair the cell cycle and cause genomic instability (GIN), leading to cancer and developmental defects in mice. Remarkably, depletion or mutation of one Mcm can decrease all Mcm levels. Here, we use mice and cells bearing a GIN-causing hypomophic allele of Mcm4 (Chaos3), in conjunction with disruption alleles of other Mcms, to reveal two new mechanisms that regulate MCM protein levels and pre-RC formation. First, the Mcm4^Chaos3 allele, which disrupts MCM4:MCM6 interaction, triggers a Dicer1 and Drosha-dependent ∼40% reduction in Mcm2–7 mRNAs. The decreases in Mcm mRNAs coincide with up-regulation of the miR-34 family of microRNAs, which is known to be Trp53-regulated and target Mcms. Second, MCM3 acts as a negative regulator of the MCM2–7 helicase in vivo by complexing with MCM5 in a manner dependent upon a nuclear-export signal-like domain, blocking the recruitment of MCMs onto chromatin. Therefore, the stoichiometry of MCM components and their localization is controlled post-transcriptionally at both the mRNA and protein levels. Alterations to these pathways cause significant defects in cell growth reflected by disease phenotypes in mice.

Molt-inhibiting hormone stimulates vitellogenesis at advanced ovarian developmental stages in the female blue crab, Callinectes sapidus 1: an ovarian stage dependent involvement

To understand the hormonal coordination of the antagonism between molting and reproduction in crustaceans, the terminally anecdysial mature female Callinectes sapidus was used as a model. The regulatory roles of crustacean hyperglycemic hormone (CHH) and molt-inhibiting hormone (MIH) in vitellogenesis were examined. A competitive specific RIA was used to measure the levels of MIH and CHH in the hemolymphs of mature females at pre- and mid- vitellogenic stages, and their effects on vitellogenesis at early (early 2, E2) and mid vitellogenesis (3) stages were determined in vitro. A hepatopancreas fragments incubation system was developed and the levels of vitellogenin (VtG), as well as VtG mRNA and heterogeneous nuclear (hn)VtG RNA were determined using RIA or QPCR, respectively. MIH titers were four times higher at mid-vitellogenesis than at pre-vitellogenesis, while CHH levels in the hemolymph were constant. In the in vitro incubation experiments, MIH increased both VtG mRNA levels and secretion at ovarian stage 3. At stage E2, however, MIH resulted in a mixed response: downregulation of VtG mRNA and upregulation of hnVtG RNA. CHH had no effect on any of the parameters. Actinomycin D blocked the stimulatory effects of MIH in stage 3 animals on VtG mRNA and VtG, while cycloheximide attenuated only VtG levels, confirming the MIH stimulatory effect at this stage. MIH is a key endocrine regulator in the coordination of molting and reproduction in the mature female C. sapidus, which simultaneously inhibits molt and stimulates vitellogenesis.