Heterozygous variants in SIX3 and POU1F1 cause pituitary hormone deficiency in mouse and man.

Congenital hypopituitarism is a genetically heterogeneous condition that is part of a spectrum disorder that can include holoprosencephaly. Heterozygous mutations in SIX3 cause variable holoprosencephaly in humans and mice. We identified two children with neonatal hypopituitarism and thin pituitary stalk who were doubly heterozygous for rare, likely deleterious variants in the transcription factors SIX3 and POU1F1. We used genetically engineered mice to understand the disease pathophysiology. Pou1f1 loss-of-function heterozygotes are unaffected; Six3 heterozygotes have pituitary gland dysmorphology and incompletely ossified palate; and the Six3+/-; Pou1f1+/dw double heterozygote mice have a pronounced phenotype, including pituitary growth through the palate. The interaction of Pou1f1 and Six3 in mice supports the possibility of digenic pituitary disease in children. Disruption of Six3 expression in the oral ectoderm completely ablated anterior pituitary development, and deletion of Six3 in the neural ectoderm blocked the development of the pituitary stalk and both anterior and posterior pituitary lobes. Six3 is required in both oral and neural ectodermal tissues for the activation of signaling pathways and transcription factors necessary for pituitary cell fate. These studies clarify the mechanism of SIX3 action in pituitary development and provide support for a digenic basis for hypopituitarism.

High-throughput splicing assays identify missense and silent splice-disruptive POU1F1 variants underlying pituitary hormone deficiency.

Pituitary hormone deficiency occurs in ∼1:4,000 live births. Approximately 3% of the cases are due to mutations in the alpha isoform of POU1F1, a pituitary-specific transcriptional activator. We found four separate heterozygous missense variants in unrelated individuals with hypopituitarism that were predicted to affect a minor isoform, POU1F1 beta, which can act as a transcriptional repressor. These variants retain repressor activity, but they shift splicing to favor the expression of the beta isoform, resulting in dominant-negative loss of function. Using a high-throughput splicing reporter assay, we tested 1,070 single-nucleotide variants in POU1F1. We identified 96 splice-disruptive variants, including 14 synonymous variants. In separate cohorts, we found two additional synonymous variants nominated by this screen that co-segregate with hypopituitarism. This study underlines the importance of evaluating the impact of variants on splicing and provides a catalog for interpretation of variants of unknown significance in POU1F1.

Genetic Characterization of Myf5 and POU1F1 Genes in Different Egyptian Local Rabbit Breeds and Their Association with Growth Traits.

Genetic characterization and its association with quantitative traits in local breeds are important tools for the genetic improvement and sustainable management of animal genetic resources. Myogenic regulatory factor 5 (MYf5) and POU class 1 homeobox 1 (POU1F1) are candidate genes which play important roles in growth and development of mammals. The present study aims to detect the genetic diversity of the MYf5 and POU1F1 genes in four local Egyptian rabbit breeds and their association with growth traits, using PCR-restriction enzyme (PCR-RFLP), PCR-single-strand conformational polymorphism (PCR-SSCP), and direct sequencing techniques. The results showed that MYF5 exon 1 was observed with two genotypes in Baladi Black (BB), Gabali (GB) and New Zealand White (NZW) breeds while APRI-line (APRI) presented one genotype. The genetic diversity of Myf5 exon 2 between breeds showed two genotypes in APRI compared to three in NZW and four genotypes in BB and GB breeds. The genetic diversity of the POU1F1 gene (intron 5 and partial cds) in different rabbit breeds was two genotypes in NZW and three genotypes in BB, GB, and APRI breeds with different frequencies for each genotype. Based on the statistically significant difference between genes genotypes and growth weight, the results suggested that the genotypes of Myf5 exon 2 (1 and 2) of the BB breed, Myf5 exon 2 genotype 2 of the APRI breed, and genotype 1 of Myf5 exon 1 and genotype 1 of POU1F1 of the NZW breed compared to genotypes for each gene can be considered candidate molecular markers associated with the improvement of growth traits in these breeds.

The effect of miR-23b-3p on regulating GH by targeting POU1F1 in Yanbian yellow cattle.

This study aimed to evaluate the effect of miR-23b-3p on growth hormone (GH) in pituitary cells of Yanbian yellow cattle. The mRNA and protein levels of GH and miR-23b-3p target genes were measured by real time fluorescence quantitative PCR (qPCR) and Western blot, respectively. The target relationship of miR-23b-3p was validated by double luciferase reporter gene system. The results showed that GH mRNA and protein levels in pituitary cells of Yanbian yellow cattle were significantly lower in the miR-23b-3p-mi group than in the NC group (P<0.01), while GH mRNA and protein levels were higher in the miR-23b-3p-in group than in the iNC group (P<0.05). The result of bioinformatics analysis and double luciferase reporter gene system validation proved that miR-23b-3p targeted 3'UTR of pituitary specific transcription factor 1 (POU1F1). POU1F1 mRNA and protein levels were lower miR-23b-3p-mi group than in the NC group (P<0.01), while POU1F1 mRNA and protein levels were higher in the miR-23b-3p-in group than in the iNC group (P<0.01). These results demonstrated that miR-23b-3p could regulate GH expression in pituitary cells by regulating POU1F1 gene.

Determination of the relationship between Anatolian black cattle growth properties and myostatin, GHR and Pit-1 gene.

The aim of this study is to determine the relationship between some growth and development characteristics in Anatolian Black cattle from birth to twelve months of age with the Pit-1, GHR and Myostatin genes. PCR-RFLP method was used to detect the polymorphism. Genotype and allele frequencies were found to be AA/AB/BB: 0.096/0.519/0.385 and A/B: 0.356/0.644; AA/AG/GG: 0.346/0.385/0.269 and A/G: 0.538/0.462 in the Pit-1 and GHR genes respectively. Myostatin gene was found to be also monomorphic in all genotypes. Although the chi-square χ2 test in the Pit-1 gene showed an agreement to Hardy-Weinberg equilibrium (p > 0.05), in the GHR gene did not showed an agreement (p < 0.05). The results of the statistical analysis indicated an association between Pit-1 and GHR genes polymorphism and growth traits at different stage ages in Anatolian Black cattle. But Pit-1/HinfI gene and GHR/Alul polymorphisms were not found statistically significant in the specified periods, at all characters. On the other hand, since the MSTN/BstF5I gene was found to be monomorphic, no association analysis was performed between the measured values and this gene. In conclusion, mutation of these genes is difficult to suggest as a potential marker in a herd selection regarding the growth and development characteristics.

Uraemic extracellular vesicles augment osteogenic transdifferentiation of vascular smooth muscle cells via enhanced AKT signalling and PiT-1 expression.

Extracellular vesicles (EV) function as messengers between endothelial cells (EC) and vascular smooth muscle cells (VSMC). Since chronic kidney disease (CKD) increases the risk for vascular calcifications, we investigated whether EV derived from uraemic milieu-stimulated EC and derived from uraemic rats impact the osteogenic transdifferentiation/calcification of VSMC. For that purpose, human EC were treated with urea and indoxyl sulphate or left untreated. Experimental uraemia in rats was induced by adenine feeding. 'Uraemic' and control EV (EVUR ; EVCTRL ) were isolated from supernatants and plasma by using an exosome isolation reagent. Rat VSMC were treated with a pro-calcifying medium (CM) with or without EV supplementation. Gene expressions, miRNA contents and protein expressions were determined by qPCR and Western blots, respectively. Calcifications were determined by colorimetric assays. Delivery of miRNA inhibitors/mimics to EV and siRNA to VSMC was achieved via transfection. EVCTRL and EVUR differed in size and miRNA contents. Contrary to EVCTRL , EC- and plasma-derived EVUR significantly increased the pro-calcifying effects of CM, including altered gene expressions of osterix, runx2, osteocalcin and SM22α. Further, EVUR enhanced the protein expression of the phosphate transporter PiT-1 in VSMC and induced a phosphorylation of AKT and ERK. Knock down of PiT-1 and individual inhibition of AKT and ERK signalling in VSMC blocked the pro-calcifying effects of EVUR . Similar effects were achieved by inhibition of miR-221/-222 and mimicking of miR-143/-145 in EVUR . In conclusion, EVUR might represent an additional puzzle piece of the complex pathophysiology of vascular calcifications in CKD.

Intronic variant in POU1F1 associated with canine pituitary dwarfism.

The anterior pituitary gland secretes several endocrine hormones, essential for growth, reproduction and other basic physiological functions. Abnormal development or function of the pituitary gland leads to isolated or combined pituitary hormone deficiency (CPHD). At least 30 genes have been associated with human CPHD, including many transcription factors, such as POU1F1. CPHD occurs spontaneously also in mice and dogs. Two affected breeds have been reported in dogs: German Shepherds with a splice defect in the LHX3 gene and Karelian Bear Dogs (KBD) with an unknown genetic cause. We obtained samples from five KBDs presenting dwarfism and abnormal coats. A combined analysis of genome-wide association and next-generation sequencing mapped the disease to a region in chromosome 31 and identified a homozygous intronic variant in the fourth exon of the POU1F1 gene in the affected dogs. The identified variant, c.605-3C>A, resided in the splice region and was predicted to affect splicing. The variant's screening in three new prospective cases, related breeds, and ~ 8000 dogs from 207 breeds indicated complete segregation in KBDs with a carrier frequency of 8%, and high breed-specificity as carriers were found at a low frequency only in Lapponian Herders, a related breed. Our study establishes a novel canine model for CPHD with a candidate POU1F1 defect.

Protective effects of spironolactone on vascular calcification in chronic kidney disease.

BACKGROUND: Vascular calcification is common in chronic kidney disease (CKD) and associated with increased cardiovascular mortality. Aldosterone has been implicated as an augmenting factor in the progression of vascular calcification. The present study further explored putative beneficial effects of aldosterone inhibition by the mineralocorticoid receptor antagonist spironolactone on vascular calcification in CKD. METHODS: Serum calcification propensity was determined in serum samples from the MiREnDa trial, a prospective, randomized controlled clinical trial to investigate efficacy and safety of spironolactone in maintenance hemodialysis patients. Experiments were conducted in mice with subtotal nephrectomy and cholecalciferol treatment, and in calcifying primary human aortic smooth muscle cells (HAoSMCs). RESULTS: Serum calcification propensity was improved by spironolactone treatment in patients on hemodialysis from the MiREnDa trial. In mouse models and HAoSMCs, spironolactone treatment ameliorated vascular calcification and expression of osteogenic markers. CONCLUSIONS: These observations support a putative benefit of spironolactone treatment in CKD-associated vascular calcification. Further research is required to investigate possible improvements in cardiovascular outcomes by spironolactone and whether the benefits outweigh the risks in patients with CKD.

A novel POU1F1 pathogenic variant: Two familial case reports with phenotype expansion.

Up: A schematic-diagram of POU1F1-gene. Down right: an electrophoretogram of the detected novel pathogenic-variant in comparison with wild-type POU1F1 exon-6 sequence. Down left: Family pedigree of the two-siblings reported.

Evidence of an intestinal phosphate transporter alternative to type IIb sodium-dependent phosphate transporter in rats with chronic kidney disease.

BACKGROUND: Phosphate is absorbed in the small intestine via passive flow and active transport.NaPi-IIb, a type II sodium-dependent phosphate transporter, is considered to mediate active phosphate transport in rodents. To study the regulation of intestinal phosphate transport in chronic kidney disease (CKD), we analyzed the expression levels of NaPi-IIb, pituitary-specific transcription factor 1 (PiT-1) and PiT-2 and the kinetics of intestinal phosphate transport using two CKD models. METHODS: CKD was induced in rats via adenine orThy1 antibody injection. Phosphate uptake by intestinal brush border membrane vesicles (BBMV) and the messenger RNA (mRNA) expression of NaPi-IIb, PiT-1 and PiT-2 were analyzed. The protein expression level of NaPi-IIb was measured by mass spectrometry (e.g. liquid chromatography tandem mass spectrometry). RESULTS: In normal rats, phosphate uptake into BBMV consisted of a single saturable component and its Michaelis constant (Km) was comparable to that of NaPi-IIb. The maximum velocity (Vmax) correlated with mRNA and protein levels of NaPi-IIb. In the CKD models, intestinal phosphate uptake consisted of two saturable components. The Vmax of the higher-affinity transport, which is thought to be responsible for NaPi-IIb, significantly decreased and the decrease correlated with reduced NaPi-IIb expression. The Km of the lower-affinity transport was comparable to that of PiT-1 and -2. PiT-1 mRNA expression was much higher than that of PiT-2, suggesting that PiT-1 was mostly responsible for phosphate transport. CONCLUSIONS: This study suggests that the contribution of NaPi-IIb to intestinal phosphate absorption dramatically decreases in rats with CKD and that a low-affinity alternative to NaPi-IIb, in particular PiT-1, is upregulated in a compensatory manner in CKD.

POU1F1 mutations in combined pituitary hormone deficiency: differing spectrum of mutations in a Western-Indian cohort and systematic analysis of world literature.

CONTEXT: POU1F1 mutations are prevalent in Indian CPHD cohorts. Genotype-phenotype correlation is not well-studied. AIM: To describe phenotypic and genotypic spectrum of POU1F1 mutations in our CPHD cohort and present systematic review as well as genotype-phenotype analysis of all mutation-positive cases reported in world literature. METHODS: Retrospective study of POU1F1 mutation-positive patients from a western-Indian center. PRISMA guidelines based pubmed search of published literature of all mutation-positive patients. RESULTS: Our cohort had 15 POU1F1 mutation-positive patients (9 index, 6 relatives). All had severe GH, TSH and prolactin deficiencies (GHD, TSHD and PD). TSHD was diagnosed earliest followed by GHD (median ages: TSHD-6 months, GHD-3 years), while PD was more variable. Two sisters had central precocious puberty at 7 years of age. Pubic hair was deficient in all post-pubertal patients (females: P1-P2, males: P3-P4). Splice-site/intronic/frameshift mutations were most common, while missense/nonsense mutations were less frequent (33%). Review of world literature yielded 114 patients (82 index patients) from 58 studies. GHD was present in all patients. TSHD was spared in 12.5% and PD in 4.4% patients. Missense/nonsense mutations accounted for 75% of spectrum. Phenotype-genotype analysis revealed higher mean peak-GH levels (1.1 vs 0.2 ng/ml, p = 0.008) and lower prevalence of anterior-pituitary hypoplasia (63.6% vs 86.3%, p = 0.03) in patients with heterozygous than homozygous and compound heterozygous mutations. CONCLUSIONS: We present largest series of POU1F1 mutation-positive patients. Precocious puberty and defective pubarche are lesser-appreciated phenotypic features. Our mutation spectrum is different from that of world literature. Patients with heterozygous mutations have milder phenotype.

POU1F1 transcription factor promotes breast cancer metastasis via recruitment and polarization of macrophages.

Cancer progression requires cells surrounding tumors be reeducated and activated to support tumor growth. Oncogenic signals from malignant cells directly influence stromal composition and activation, but the factors mediating this communication are still not well understood. We have previously shown that the transcription factor POU class 1 homeobox 1 (POU1F1), also known as Pit-1, induces profound changes on neoplastic cell-autonomous processes favoring metastasis in human breast cancer. Here we describe for the first time Pit-1-mediated paracrine actions on macrophages in the tumor microenvironment by using cell lines in vitro, zebrafish and mouse models in vivo, and samples from human breast cancer patients. Through the release of CXCL12, Pit-1 in tumor cells was found to mediate the recruitment and polarization of macrophages into tumor-associated macrophages (TAMs). In turn, TAMs collaborated with tumor cells to increase tumor growth, angiogenesis, extravasation and metastasis to lung. Our data reveal a new mechanism of cooperation between tumor cells and macrophages favoring metastasis and poor clinical outcome in human breast cancer, which suggests that Pit-1 and CXCL12 should be further studied as potential prognostic and therapeutic indicators. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Required enhancer-matrin-3 network interactions for a homeodomain transcription program.

Homeodomain proteins, described 30 years ago, exert essential roles in development as regulators of target gene expression; however, the molecular mechanisms underlying transcriptional activity of homeodomain factors remain poorly understood. Here investigation of a developmentally required POU-homeodomain transcription factor, Pit1 (also known as Pou1f1), has revealed that, unexpectedly, binding of Pit1-occupied enhancers to a nuclear matrin-3-rich network/architecture is a key event in effective activation of the Pit1-regulated enhancer/coding gene transcriptional program. Pit1 association with Satb1 (ref. 8) and ß-catenin is required for this tethering event. A naturally occurring, dominant negative, point mutation in human PIT1(R271W), causing combined pituitary hormone deficiency, results in loss of Pit1 association with ß-catenin and Satb1 and therefore the matrin-3-rich network, blocking Pit1-dependent enhancer/coding target gene activation. This defective activation can be rescued by artificial tethering of the mutant R271W Pit1 protein to the matrin-3 network, bypassing the pre-requisite association with ß-catenin and Satb1 otherwise required. The matrin-3 network-tethered R271W Pit1 mutant, but not the untethered protein, restores Pit1-dependent activation of the enhancers and recruitment of co-activators, exemplified by p300, causing both enhancer RNA transcription and target gene activation. These studies have thus revealed an unanticipated homeodomain factor/ß-catenin/Satb1-dependent localization of target gene regulatory enhancer regions to a subnuclear architectural structure that serves as an underlying mechanism by which an enhancer-bound homeodomain factor effectively activates developmental gene transcriptional programs.

Biochemical and structural characterization of a novel cooperative binding mode by Pit-1 with CATT repeats in the macrophage migration inhibitory factor promoter.

Overexpression of the proinflammatory cytokine macrophage migration inhibitory factor (MIF) is linked to a number of autoimmune diseases and cancer. MIF production has been correlated to the number of CATT repeats in a microsatellite region upstream of the MIF gene. We have characterized the interaction of pituitary-specific positive transcription factor 1 (Pit-1) with a portion of the MIF promoter region flanking a microsatellite polymorphism (-794 CATT5-8). Using fluorescence anisotropy, we quantified tight complex formation between Pit-1 and an oligonucleotide consisting of eight consecutive CATT repeats (8xCATT) with an apparent Kd of 35 nM. Using competition experiments we found a 23 base pair oligonucleotide with 4xCATT repeats to be the minimum DNA sequence necessary for high affinity interaction with Pit-1. The stoichiometry of the Pit-1 DNA interaction was determined to be 2:1 and binding is cooperative in nature. We subsequently structurally characterized the complex and discovered a completely novel binding mode for Pit-1 in contrast to previously described Pit-1 complex structures. The affinity of Pit-1 for the CATT target sequence was found to be highly dependent on cooperativity. This work lays the groundwork for understanding transcriptional regulation of MIF and pursuing Pit-1 as a therapeutic target to treat MIF-mediated inflammatory disorders.

MSH6/2 and PD-L1 Expressions Are Associated with Tumor Growth and Invasiveness in Silent Pituitary Adenoma Subtypes.

Mismatch repair genes mutS homologs 6/2 (MSH6/2) expressions are involved in tumor growth and programmed cell death 1 ligand 1 (PD-L1) expression in tumor immunity, but the direct association with pituitary adenomas (PAs) is not well understood. We aimed to clarify the effects of MSH6/2 and PD-L1 expression on tumor proliferation and invasiveness in nonfunctioning (NF) PAs. We performed immunohistochemistry to classify the NFPAs into gonadotroph adenoma (GAs), silent corticotroph adenomas (SCAs), null cell adenoma (NCAs), and pituitary transcription factor 1 (PIT1) lineage PAs. We evaluated MSH6/2 and PD-L1 mRNA expressions in NFPAs by real-time PCR (n = 73), and statistically analyzed the expressions and clinicopathological factors. We also investigated the effect of MSH6 knockout on PD-L1 expression in AtT-20ins and GH3. MSH6/2 expressions were significantly lower in invasive NFPAs than in non-invasive NFPAs, and lower in SCAs and NCAs than in GAs. MSH6/2 expressions were positively associated with PD-L1 expression. PD-L1 expression was significantly lower in invasive NFPAs than in non-invasive NFPAs, and lower in SCAs and NCAs than in GAs. Although MSH6/2 expressions also tended to be lower in PIT1 lineage PAs than in GAs, PIT1 lineage PAs expressed PD-L1 equivalently to GA, which was unlike SCAs and NCAs. MSH6 knockout in AtT-20ins and GH3 significantly decreased PD-L1 expression (75% and 34% reduction, respectively) with cell proliferation promotion. In conclusion, differences in MSH6/2 and PD-L1 expressions of SCAs, NCAs, and PIT1-lineage PAs from those of GAs appear to contribute to their clinically aggressive characteristics, such as more proliferation and invasiveness.

[Clinical and genetic analysis of an infant with combined pituitary hormone deficiency due to POU1F1 gene variants].

OBJECTIVE: To explore the clinical characteristics and genetic basis for an infant featuring combined pituitary hormone deficiency. METHODS: Clinical data and results of DNA sequencing of the child were analyzed. RESULTS: The 10-month-old male infant presented with recurrent hypoglycemia, extremely poor appetite and constipation, and severe growth retardation from 2 months on, in addition with pituitary hormone deficiency involving growth hormone, thyroid stimulating hormone, and prolactin. Next generation sequencing revealed a novel heterozygous c.767-769del (p.Glu256del) variant of the POU1F1 gene in the patient. CONCLUSION: The patient was diagnosed with combined pituitary hormone deficiency due to the POU1F1 gene variant, for which replacement therapy including thyroxine and growth hormone was provided. Hypoglycemia is unusual in patients carrying POU1F1 gene variants and requires close attention in clinical practice. For children with multiple pituitary hormone deficiency, genetic testing should be recommended to determine the cause.

Intestinal Response to Acute Intragastric and Intravenous Administration of Phosphate in Rats.

BACKGROUND/AIMS: Phosphate (Pi) homeostasis is controlled by the intestine and kidneys whose capacities to transport Pi are under endocrine control. Several studies point to intestinal absorption as a therapeutic target to modulate Pi homeostasis. The small intestine is responsible for almost all Pi absorption in the gut, a process involving Na+-dependent and independent mechanisms. Three Na+-dependent Pi cotransporters have been described in the gastrointestinal tract: NaPi-IIb (a SLC34 member) and Pit-1 and Pit-2 (SLC20 transporters). We recently analysed the acute hormonal and renal response to intragastric (i.g) and intravenous (i.v) Pi-loading. This study demonstrated that the kidney quickly adapts to Pi-loading, with changes manifesting earlier in the i.v than i.g intervention. The aim of this work was to extend the previous studies in order to investigate the acute adaptation of intestinal transport of Pi and expression of intestinal Na+/Pi-cotransporters in response to acute Pi-loading. METHODS: Duodenal and jejunal mucosa was collected 40 minutes and/or 4 hours after administration (i.g and i.v) of either NaCl or Pi to anaesthetized rats. Uptakes of Pi and protein expression of Na+/Pi cotransporters were measured in brush border membrane vesicles (BBMV); the cotransporters' mRNA abundance was quantified by real-time PCR in total RNA extracted from whole mucosa. RESULTS: Pi-loading did not modify transport of Pi in duodenal and jejunal BBMV 4 hours after treatment. Administration of Pi did not alter either the intestinal expression of NaPi-IIb and Pit-2 mRNAs, whereas Pit-1 mRNA expression was only regulated (diminished) in duodenum collected 4 hours after i.g Pi-loading. NaPi-IIb protein expression was decreased in duodenum 4 hours upon i.v Pi infusion, whereas the duodenal and jejunal abundance of the cotransporter was unaffected by i.g administration of Pi. CONCLUSION: Together, these data suggest that the intestine responds acutely to Pi-loading, though this response seems slower than the renal adaptation.

Characterization of a Novel POU1F1 Mutation Identified on Screening 160 Growth Hormone Deficiency Patients.

The objective of the study is the functional characterization of a novel POU1F1 c.605delC mutation in combined pituitary hormone deficiency (CPHD) and to report the clinical and genetic details of 160 growth hormone deficiency patients. Screening of GH1, GHRHR, POU1F1, PROP1, and HESX1 genes by Sanger sequencing was carried out in 160 trios and 100 controls followed by characterization of the POU1F1 c.605delC mutation by expression studies including site directed mutagenesis, co-transfection, protein degradation, and luciferase assays to compare the wild type and mutant POU1F1. In vitro studies showed that the POU1F1 c.605delC mutation codes for a truncated protein with reduced transactivation capacity on its downstream effectors, viz., growth hormone (GH) and prolactin (PRL) causing severe CPHD. Experiments using different protease inhibitors reveal rescue of the protein upon blockage of the lysosomal pathway that might be useful in novel drug designing using targeted approach thereby maintaining the milieu and preventing/delaying the disease. The study provides an insight into the disease causing mechanism of POU1F1 c.605delC mutation identified in a CPHD child with severe short stature and failure to thrive. It also shows mutation effect on the expression, function and turnover of protein and highlights mechanistic details by which these potent regulators may operate.

Receptor for advanced glycation end products: a key molecule in the genesis of chronic kidney disease vascular calcification and a potential modulator of sodium phosphate co-transporter PIT-1 expression.

BACKGROUND: Chronic kidney disease (CKD) is associated with increased cardiovascular mortality, frequent vascular calcification (VC) and accumulation of uraemic toxins. Advanced glycation end products and S100 proteins interact with the receptor for advanced glycation end products (RAGE). In the present work, we aimed to investigate the role(s) of RAGE in the CKD-VC process. METHODS: Apoe-/- or Apoe-/-Ager (RAGE)-/- male mice were assigned to CKD or sham-operated groups. A high-phosphate diet was given to a subgroup of Apoe-/-and Apoe-/-Ager-/- CKD mice. Primary cultures of Ager+/+ and Ager-/- vascular smooth muscle cells (VSMCs) were established and stimulated with either vehicle, inorganic phosphate (Pi) or RAGE ligands (S100A12; 20 µM). RESULTS: After 12 weeks of CKD we observed a significant increase in RAGE ligand (AGE and S100 proteins) concentrations in the serum of CKD Apoe-/- mice. Ager messenger RNA (mRNA) levels were 4-fold higher in CKD vessels of Apoe-/- mice. CKD Apoe-/- but not CKD Apoe-/- or Ager-/- mice displayed a marked increase in the VC surface area. Similar trends were found in the high-phosphate diet condition. mRNA levels of Runx2 significantly increased in the Apoe-/- CKD group. In vitro, stimulation of Ager+/+VSMCs with Pi or S100A12 induced mineralization and osteoblast transformation, and this was inhibited by phosphonoformic acid (Pi co-transporters inhibitor) and Ager deletion. In vivo and in vitro RAGE was necessary for regulation of the expression of Pit-1, at least in part through production of reactive oxygen species. CONCLUSION: RAGE, through the modulation of Pit-1 expression, is a key molecule in the genesis of VC.

Functional characterization of a human POU1F1 mutation associated with isolated growth hormone deficiency: a novel etiology for IGHD.

POU1F1, a pituitary-specific POU-homeo domain transcription factor, plays an essential role in the specification of the somatotroph, lactotroph and thyrotroph lineages and in the activation of GH1, PRL and TSHß transcription. Individuals with mutations in POU1F1 present with combined deficiency of GH, PRL and TSH. Here, we identified a heterozygous missense mutation with evidence of pathogenicity, at the POU1F1 locus, in a large family in which an isolated growth hormone deficiency segregates as an autosomal dominant trait. The corresponding p.Pro76Leu mutation maps to a conserved site within the POU1F1 transactivation domain. Bandshift assays revealed that the mutation alters wild-type POU1F1 binding to cognate sites within the hGH-LCR and hGH1 promoter, but not to sites within the PRL promoter, and it selectively increases binding affinity to sites within the hGH-LCR. Co-immunoprecipitation studies reveal that this substitution enhances interactions of POU1F1 with three of its cofactors, PITX1, LHX3a and ELK1, and that residue 76 plays a critical role in these interactions. The insertion of the mutation at the mouse Pou1f1 locus results in a dramatic loss of protein expression despite normal mRNA concentrations. Mice heterozygous for the p.Pro76Leu mutation were phenotypically normal while homozygotes demonstrated a dwarf phenotype. Overall, this study unveils the involvement of POU1F1 in dominantly inherited isolated GH deficiency and demonstrates a significant impact of the Pro76Leu mutation on DNA-binding activities, alterations in transactivating functions and interactions with cofactors. Our data further highlight difficulties in modeling human genetic disorders in the mouse despite apparent conservation of gene expression pathways and physiologic functions.