The hypothalamic–neurohypophysial system: genomes, genes and genetics

Abstract

This issue of Experimental Physiology contains symposium papers on Genomes, genes and genetics featured at the 10th World Congress on Neurohypophysial Hormones, held on the 15-19 July 2013 in Bristol, which covered the broader theme of Old hormones -new insights. The hypothalamic-neurohypophysial system integrates information about hydromineral balance and cardiovascular homeostasis and plays a vital role in lactation and parturition. It comprises the large, vasopressin (VP) and oxytocin (OT) magnocellular neurones of the hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei that project through the median eminence to terminate in the posterior pituitary gland, from where the peptides are released into the bloodstream. These neurones are a cornerstone of neuroendocrine research, providing excellent physiological models that have yielded important insights into how neuropeptides/neurotransmitters (and their receptors) function at the molecular and cellular level.In the first report, Laurence Amar and co-workers (Baroin-Tourancheau et al. 2014) describe the use of high-throughput (Illumina) sequencing to identify short, non-coding microRNAs (miRNAs) in hypothalamic arcuate nuclei. In general terms, miRNAs interact with the 3 untranslated regions of target mRNAs in a sequence-specific manner, resulting in mRNA degradation and/or repression of protein translation. The arcuate nucleus is an attractive target for miRNA-led post-transcriptional regulation because it is a hypothalamic hotspot for the control of whole-body energy homeostasis via a complex interplay between a number of orexigenic and anorexigenic genes and by providing integrated signals to the hypothalamic PVN. MicroRNA profiling by Illumina sequencing represents the 'deepest' miRNA sampling to date and has the potential to reveal novel miRNAs. Amar and co-workers (Baroin-Tourancheau et al. 2014) argue the merits of sampling individual (microdissected) brain regions for miRNA expression profiling, rather than pooled nuclei from a number of animals, to facilitate the detection of possible genetic or epigenetic differences between individuals. They describe the basic steps in cDNA library construction for establishing miRNA expression profiles using Illumina sequencing. The sequences from seven individual arcuate nuclei were then analysed with the miRanalyzer Web server to identify known and/or unannotated miRNAs. The challenge will be to identify the major targets of these miRNAs; that some targets are undoubtedly important is evidenced by the fact that deletion of an enzyme, Dicer, essential for producing the mature form of miRNAs, in arcuate nuclei pro-opiomelanocortin neurones leads to obesity (Schneeberger et al. 2013). It will also be interesting to see how hypothalamic nuclei miRNA expression profiles alter in response to changes in water or nutrient balance, which can be performed in parallel to compiling the expression profiles of coding mRNAs from the same cDNA library.Hiroshi Arima et al. (2014) shift our attention to their findings on ...

Neuropeptidome of the Hypothalamus and Pituitary Gland of Indicine × Taurine Heifers: Evidence of Differential Neuropeptide Processing in the Pituitary Gland before and after Puberty

“…It is important to note, however, that in this study the pituitary gland contained both anterior pituitary gland and posterior pituitary gland (neurohypophysis), so the tissue extract could have contained peptides that entered the pituitary gland through neurons that extended from the hypothalamus. 38,64,65 In this study, we have established several striking examples of altered levels of individual peptide products in the PRE-and POST-pubertal hypothalamus and pituitary gland, despite similar levels of transcription of their precursors. These examples invoke both differential processing and translocation as possible control mechanisms.…”

“…Many of the peptides detected in the pituitary gland could have been synthesized in the hypothalamus and entered the pituitary gland through the hypothalamic–hypophyseal portal veins. It is important to note, however, that in this study the pituitary gland contained both anterior pituitary gland and posterior pituitary gland (neurohypophysis), so the tissue extract could have contained peptides that entered the pituitary gland through neurons that extended from the hypothalamus. ,, …”

“…The POMC neurons in the arcuate nucleus of the hypothalamus appear to be part of a metabolic sensing pathway for the reproductive neuroendocrine axis. ,, Peptide products of POMC were detected in both the hypothalamus and pituitary gland (Tables and ), yet there were varied responses observed among the PRE and POST heifer tissues. Specifically, CLIP was detected as a 10-fold increase in the POST pituitary gland and the mature JP [106–129] was equally abundant, but the processed JP [109–129] was observed as a 30-fold decrease; however, the biological role of these peptides remains to be elucidated.…”