Epigenetic Regulation of Gonadotropin Hormone Beta Subunit Gene Expression

Gonadotropin releasing hormone (GnRH) from the hypothalamus regulates the synthesis and secretion of gonadotropin hormones, luteinizing hormone (LH) and follicle-stimulating hormone (FSH). LH regulates steroidogenesis in both sexes and ovulation in females, while FSH stimulates folliculogenesis in females and spermatogenesis in males. LH and FSH are heterodimers of a common alpha subunit and a unique beta subunit, which provides biological specificity and is the rate limiting factor in hormone synthesis. Immediate early genes, early growth response 1 (Egr1) and fos proto-oncogene (cFos) are critical in the induction of LH-beta and FSH-beta subunits by GnRH, respectfully. However, gaps exist in our understanding of developmental initiation and hormonal regulation of gonadotropin gene expression. Specifically, epigenetic mechanisms that may play a role in beta subunit transcriptional regulation are unknown. The aim of this work was to identify transcriptional cofactors that are recruited to gonadotropin beta-subunit promoters with or without GnRH. Transcription factors interact with cofactors that recruit chromatin remodeling enzymes in order to regulate transcription. Identification of cofactors may explain tight regulation of gonadotropin hormone levels in reproductive physiology. Previous studies identified regions on the beta-subunit promoters that are necessary for GnRH responsiveness. These regions were used to pull down interacting proteins that bind to these response elements using nuclear extracts from the immortalized mature gonadotrope cell line, LβT2. Using a discovery proteomics approach, we identified different transcriptional cofactors that are recruited to beta subunit promoters with or without GnRH. Approximately 1500-2000 proteins were identified per pulldown. As expected, proteins known to interact with beta subunit promoters, such as Egr1, cFos and cJun were identified in the DNA pulldown experiments as positive controls. We identified 63 proteins unique for LH-beta promoter under control conditions and 60 unique for FSH-beta promoter, of which 7 proteins for LH-beta and 8 proteins for FSH-beta may play a role as corepressors. We further identified 97 proteins that were pulled down with the LH-beta promoter following GnRH treatment, of which 9 proteins were also pulled down with Egr1 as potential coactivator candidates. We also identified 72 proteins that were pulled down with the FSH-beta promoter following GnRH treatment, of which 6 proteins were pulled down with cFos as potential coactivator candidates. Functional studies to identify roles of these cofactors in gonadotropin hormone expression are in progress. The identification of epigenetic regulators will allow for better understanding of the transcriptional regulation of gonadotropin beta-subunit gene expression, which is critical for reproductive function.

Influence of Temperature and Sulfate Concentration on the Sulfate/Sulfite Reduction Prokaryotic Communities in the Tibetan Hot Springs

The distribution and diversity of sulfate/sulfite reduction prokaryotic (SRP) communities in hot springs from the Quzhuomu and Daggyai Geothermal Zone of Tibetan, China, was reported for the first time. In hot springs that are naturally hyperthermal and anoxic, the sulfur cycle is one of the most active cycles of the elements. The distribution of SRP in response to temperature is of great importance to the understanding of biogeochemical cycling of sulfur in geothermal features. Little is known about the SRP in geothermal zone. In this study, the diversity of SRP was investigated in the sediments from the Daggyai and Quzhuomu geothermal zone using PCR amplification, cloning and sequencing of the dissimilatory sulfite reductase beta subunit gene (dsrB). The abundance of dsrB and 16S rRNA genes, were determined by quantitative polymerase chain reactions. In addition, correlations of the SRP assemblages with environmental factors were analyzed by the aggregated boosted tree (ABT) statistical analysis. The results showed that SRP populations were diverse, but were mainly composed of Desulfobacterales, Desulfovibrionales, Syntrophobacterales, Clostridia and Nitrospirales, and large fraction (25%) of novel sequences have branched groups in the dsrB phylogenetic tree. In Quzhuomu geothermal zone, sulfate-rich hot springs are characterized by thick bacterial mats that are green or red and the SRP populations mainly appear at mid-temperature (50 °C to 70 °C). In low-sulfate hot springs in the Daggyai geothermal zone, although gray or pink streamers are widely formed at 60 °C to 80 °C, they prefer to inhabit in green mat at lower temperature (30 °C to 50 °C). With increasing temperature, the diversity of the dsrB gene at the OTU level (cutoff 97%) decreased, while its relative abundance increased. This result suggests that temperature played an important role in affecting dsrB gene distribution.

Clinical and genetic analysis of multi-system pseudohypoaldosteronism type 1 caused by a novel splice site mutation of the beta subunit gene of epithelial sodium channel (ENaC)

This article aims to provide a comprehensive review of the clinical features and genetics basis of multi-system pseudohypoaldosteronism type 1 caused by SCNN1B gene mutations.

The analysis of FSH beta-subunit gene genotypes in East Anatolian Red, East Anatolian Red×Holstein, and Zavot bulls

This study aimed to investigate the genotypic distribution and population genetic parameters of the single nucleotide polymorphism (SNP) located on exon 3 at the FSHB gene in East Anatolian Red (EAR), East Anatolian Red×Holstein (EAR×H), and Zavot (Z) bulls. A total of 68 cattle including EAR (n=34), EAR×H (n=20), and Z (n=14) bulls were used. Genomic DNA was isolated from blood samples using the phenol/chloroform method. The genotyping of the SNP was carried out by the PCR-RFLP using the PstI restriction enzyme. Deviation from Hardy–Weinberg equilibrium (HWE) was calculated by using the chi-square goodness-of-fit test. Population genetics evaluation was performed for effective allele numbers, the polymorphism information content, theoretical heterozygosity, the fixation index, level of possible variability realization, and the Shannon-Weaver diversity index. In the present study, the AA and the AB genotypes were predominant in EAR and EAR×H bulls, respectively. Zavot breed was found to be monomorphic. There was a deviation from HWE, concerning the total cattle population. The population genetics evaluation showed that the marker was moderately informative for EAR and the crossbreeds, as well as the total population. Consequently, the polymorphism (rs207774587) within exon 3 of the bovine FSHB can be interpreted as a genetic marker with reliable variability for EAR and the crossbreeds, but not in Zavot cattle.

HDAC inhibitors impair Fshb subunit expression in murine gonadotrope cells

Fertility is dependent on follicle-stimulating hormone (FSH), a product of gonadotrope cells of the anterior pituitary gland. Hypothalamic gonadotropin-releasing hormone (GnRH) and intra-pituitary activins are regarded as the primary drivers of FSH synthesis and secretion. Both stimulate expression of the FSH beta subunit gene (Fshb), although the underlying mechanisms of GnRH action are poorly described relative to those of the activins. There is currently no consensus on how GnRH regulates Fshb transcription, as results vary across species and between in vivo and in vitro approaches. One of the more fully developed models suggests that the murine Fshb promoter is tonically repressed by histone deacetylases (HDACs) and that GnRH relieves this repression, at least in immortalized murine gonadotrope-like cells (LβT2 and αT3-1). In contrast, we observed that the class I/II HDAC inhibitor trichostatin A (TSA) robustly inhibited basal, activin A-, and GnRH-induced Fshb mRNA expression in LβT2 cells and in primary murine pituitary cultures. Similar results were obtained with the class I specific HDAC inhibitor, entinostat, whereas two class II-specific inhibitors, MC1568 and TMP269, had no effects on Fshb expression. Collectively, these data suggest that class I HDACs are positive, not negative, regulators of Fshb expression in vitro and that, contrary to earlier reports, GnRH may not stimulate Fshb by inhibiting HDAC-mediated repression of the gene.

The lysidyl aminoacyl transfer RNA synthetase intron, a new marker for demosponge phylogeographics – case study on Neopetrosia

Suitable genetic markers for population studies in sponges are necessary to further our understanding of biodiversity and dispersal patterns, and contribute to conservation efforts. Due to the slow mitochondrial substitution rates in demosponges, nuclear introns are among the preferable markers for phylogeographic studies, but so far only the second intron of the ATP synthetase beta subunit-gene (ATPSβ) has been successfully established. In the present study, we analyse the intron of the Lysidyl Aminoacyl Transfer RNA Synthetase (LTRS), another potential marker to study demosponge intraspecific relationships, on samples of Neopetrosia chaliniformis from various locations in the Indo-Pacific and compare its variation with a mitochondrial marker (CO2). LTRS recovers several reciprocal monophyletic groups among the Indo-Pacific N. chaliniformis and provides a potential alternative to ATPSβ.