Uncoupling of chondrocyte differentiation and perichondrial mineralization underlies the skeletal dysplasia in tricho-rhino-phalangeal syndrome

Analysis of the function, mechanism and clinical application prospect of TRPS1, a new marker for breast cancer

It has been discovered that Trichorhinophalangeal Syndrome-1 (TRPS1), a novel member of the GATA transcription factor family, participates in both normal physiological processes and the development of numerous diseases. Recently, TRPS1 has been identified as a new biomarker to aid in cancer diagnosis and is very common in breast cancer (BC), especially in triple-negative breast cancer (TNBC). In this review, we discussed the structure and function of TRPS1 in various normal cells, focused on its role in tumorigenesis and tumor development, and summarize the research status of TRPS1 in the occurrence and development of BC. We also analyzed the potential use of TRPS1 in guiding clinically personalized precision treatment and the development of targeted drugs.

Deficiency of Trps1 in Cementoblasts Impairs Cementogenesis and Tooth Root Formation

Cementum is the least studied of all mineralized tissues and little is known about mechanisms regulating its formation. Therefore, the goal of this study was to provide new insights into the transcriptional regulation of cementum formation by determining the consequences of the deficiency of the Trps1 transcription factor in cementoblasts. We used Trps1Col1a1 cKO (2.3Co1a1-CreERT2;Trps1fl/fl) mice, in which Trps1 is deleted in cementoblasts. Micro-computed tomography analyses of molars of 4-week-old males and females demonstrated significantly shorter roots with thinner mineralized tissues (root dentin and cementum) in Trps1Col1a1 cKO compared to WT mice. Semi-quantitative histological analyses revealed a significantly reduced area of cellular cementum and localized deficiencies of acellular cementum in Trps1Col1a1 cKO mice. Immunohistochemical analyses revealed clustering of cementoblasts at the apex of roots, and intermittent absence of cementoblasts on Trps1Col1a1 cKO cementum surfaces. Fewer Osterix-positive cells adjacent to cellular cementum were also detected in Trps1Col1a1 cKO compared to WT mice. Decreased levels of tissue-nonspecific alkaline phosphatase (TNAP), an enzyme required for proper cementogenesis, were apparent in cementum, periodontal ligament, and alveolar bone of Trps1Col1a1 cKO. There were no apparent differences in levels of bone sialoprotein (Bsp) in cementum. Quantitative analyses of picrosirius red-stained periodontal ligament revealed shorter and disorganized collagen fibers in Trps1Col1a1 cKO mice demonstrating impaired periodontal structure. In conclusion, this study has identified Trps1 transcription factor as one of the important regulators of cellular and acellular cementum formation. Furthermore, this study suggests that Trps1 supports the function of cementoblasts by upregulating expression of the major proteins required for cementogenesis, such as Osterix and TNAP.

Deletion of Trps1 regulatory elements recapitulates postnatal hip joint abnormalities and growth retardation of Trichorhinophalangeal syndrome in mice

Trichorhinophalangeal syndrome (TRPS) is a genetic disorder caused by point mutations or deletions in the gene-encoding transcription factor TRPS1. TRPS patients display a range of skeletal dysplasias, including reduced jaw size, short stature, and a cone-shaped digit epiphysis. Certain TRPS patients experience early onset coxarthrosis that leads to a devastating drop in their daily activities. The etiologies of congenital skeletal abnormalities of TRPS were revealed through the analysis of Trps1 mutant mouse strains. However, early postnatal lethality in Trps1 knockout mice has hampered the study of postnatal TRPS pathology. Here, through epigenomic analysis we identified two previously uncharacterized candidate gene regulatory regions in the first intron of Trps1. We deleted these regions, either individually or simultaneously, and examined their effects on skeletal morphogenesis. Animals that were deleted individually for either region displayed only modest phenotypes. In contrast, the Trps1Δint/Δint mouse strain with simultaneous deletion of both genomic regions exhibit postnatal growth retardation. This strain displayed delayed secondary ossification center formation in the long bones and misshaped hip joint development that resulted in acetabular dysplasia. Reducing one allele of the Trps1 gene in Trps1Δint mice resulted in medial patellar dislocation that has been observed in some patients with TRPS. Our novel Trps1 hypomorphic strain recapitulates many postnatal pathologies observed in human TRPS patients, thus positioning this strain as a useful animal model to study postnatal TRPS pathogenesis. Our observations also suggest that Trps1 gene expression is regulated through several regulatory elements, thus guaranteeing robust expression maintenance in skeletal cells.

Cis-regulatory control of mammalian Trps1 gene expression

TRPS1 serves as the causative gene for tricho-rhino phalangeal syndrome, known for its craniofacial and skeletal abnormalities. The Trps1 gene encodes a protein that represses Wnt signaling through strong interactions with Wnt signaling inhibitors. The identification of genomic cis-acting regulatory sequences governing Trps1 expression is crucial for understanding its role in embryogenesis. Nevertheless, to date, no investigations have been conducted concerning these aspects of Trps1. To identify deeply conserved noncoding elements (CNEs) within the Trps1 locus, we employed a comparative genomics approach, utilizing slowly evolving fish such as coelacanth and spotted gar. These analyses resulted in the identification of eight CNEs in the intronic region of the Trps1 gene. Functional characterization of these CNEs in zebrafish revealed their regulatory potential in various tissues, including pectoral fins, heart, and pharyngeal arches. RNA in-situ hybridization experiments revealed concordance between the reporter expression pattern induced by the identified set of CNEs and the spatial expression pattern of the trps1 gene in zebrafish. Comparative in vivo data from zebrafish and mice for CNE7/hs919 revealed conserved functions of these enhancers. Each of these eight CNEs was further investigated in cell line-based reporter assays, revealing their repressive potential. Taken together, in vivo and in vitro assays suggest a context-dependent dual functionality for the identified set of Trps1-associated CNE enhancers. This functionally characterized set of CNE-enhancers will contribute to a more comprehensive understanding of the developmental roles of Trps1 and can aid in the identification of noncoding DNA variants associated with human diseases.

Comprehensive analysis of the proximity-dependent nuclear interactome for the oncoprotein NOTCH1 in live cells

Notch signaling plays a critical role in cell fate decisions in all cell types. Furthermore, gain-of-function mutations in NOTCH1 have been uncovered in many human cancers. Disruption of Notch signaling has recently emerged as an attractive disease treatment strategy. However, the nuclear interaction landscape of the oncoprotein NOTCH1 remains largely unexplored. We therefore employed here a proximity-dependent biotin identification approach to identify in vivo protein associations with the nuclear Notch1 intracellular domain in live cells. We identified a large set of previously reported and unreported proteins that associate with NOTCH1, including general transcription and elongation factors, DNA repair and replication factors, coactivators, corepressors, and components of the NuRD and SWI/SNF chromatin remodeling complexes. We also found that Notch1 intracellular domain associates with protein modifiers and components of other signaling pathways that may influence Notch signal transduction and protein stability such as USP7. We further validated the interaction of NOTCH1 with histone deacetylase 1 or GATAD2B using protein network analysis, proximity-based ligation, in vivo cross-linking and coimmunoprecipitation assays in several Notch-addicted cancer cell lines. Through data mining, we also revealed potential drug targets for the inhibition of Notch signaling. Collectively, these results provide a valuable resource to uncover the mechanisms that fine-tune Notch signaling in tumorigenesis and inform therapeutic targets for Notch-addicted tumors.

A dysfunctional miR-1-TRPS1-MYOG axis drives ERMS by suppressing terminal myogenic differentiation

Rhabdomyosarcoma is the most common pediatric soft tissue tumor, comprising two major subtypes: the PAX3/7-FOXO1 fusion-negative embryonal and the PAX3/7-FOXO1 fusion-positive alveolar subtype. Here, we demonstrate that the expression levels of the transcriptional repressor TRPS1 are specifically enhanced in the embryonal subtype, resulting in impaired terminal myogenic differentiation and tumor growth. During normal myogenesis, expression levels of TRPS1 have to decrease to allow myogenic progression, as demonstrated by overexpression of TRPS1 in myoblasts impairing myotube formation. Consequentially, myogenic differentiation in embryonal rhabdomyosarcoma in vitro as well as in vivo can be achieved by reducing TRPS1 levels. Furthermore, we show that TRPS1 levels in RD cells, the bona fide model cell line for embryonal rhabdomyosarcoma, are regulated by miR-1 and that TRPS1 and MYOD1 share common genomic binding sites. The myogenin (MYOG) promoter is one of the critical targets of TRPS1 and MYOD1; we demonstrate that TRPS1 restricts MYOG expression and thereby inhibits terminal myogenic differentiation. Therefore, reduction of TRPS1 levels in embryonal rhabdomyosarcoma might be a therapeutic approach to drive embryonal rhabdomyosarcoma cells into myogenic differentiation, thereby generating postmitotic myotubes.

Modeling human skeletal development using human pluripotent stem cells

Chondrocytes and osteoblasts differentiated from induced pluripotent stem cells (iPSCs) will provide insights into skeletal development and genetic skeletal disorders and will generate cells for regenerative medicine applications. Here, we describe a method that directs iPSC-derived sclerotome to chondroprogenitors in 3D pellet culture then to articular chondrocytes or, alternatively, along the growth plate cartilage pathway to become hypertrophic chondrocytes that can transition to osteoblasts. Osteogenic organoids deposit and mineralize a collagen I extracellular matrix (ECM), mirroring in vivo endochondral bone formation. We have identified gene expression signatures at key developmental stages including chondrocyte maturation, hypertrophy, and transition to osteoblasts and show that this system can be used to model genetic cartilage and bone disorders.

Molecular Genetic Analysis and Growth Hormone Treatment in a Three-Generation Chinese Family with Tricho-Rhino-Phalangeal Syndrome I

INTRODUCTION

Tricho-rhino-phalangeal syndrome (TRPS) is a rare genetic disorder characterized by craniofacial and skeletal abnormalities, which is caused by variants in the TRPS1 gene.

METHODS

Clinical information and follow-up data were collected. Whole-exome sequencing (WES) was performed for variants and validated by Sanger sequencing. Bioinformatic analysis was performed to predict the pathogenicity of the identified variant. Moreover, wild-type and mutated TRPS1 vectors were constructed and transfected into human embryonic kidney (HEK) 293T cells. Immunofluorescence experiments were performed to assess the localization and expression of the mutated protein. Western blot analysis and RT-qPCR were used to detect the expression of downstream genes.

RESULTS

The affected family members had typical craniofacial phenotype including sparse lateral eyebrows, pear-shaped nasal tip, and large prominent ears, plus skeletal abnormalities including short stature and brachydactyly. WES and Sanger sequencing identified the TRPS1 c.880_882delAAG variant in affected family members. In vitro functional studies showed that the TRPS1 variant did not affect the cellular localization and the expression of TRPS1, but the transcriptional repression effect of the TRPS1 on the RUNX2 and STAT3 was disturbed. The proband and his brother have been treated with growth hormone (GH) for 2 years until now, and we have observed the improvement of the linear growth in both.

CONCLUSIONS

The variant of c.880_882delAAG in TRPS1 was responsible for the pathogenesis of the Chinese family with TRPS I. The treatment of GH could be beneficial for the height outcome in TRPS I patients, and earlier initiation and longer duration of the therapy in prepubertal or early pubertal stage could be associated with better height outcomes.

Increased PHOSPHO1 and alkaline phosphatase expression during the anabolic bone response to intermittent parathyroid hormone delivery

The administration of intermittent parathyroid hormone (iPTH) is anabolic to the skeleton. Recent studies with cultured osteoblasts have revealed that the expression of PHOSPHO1, a bone-specific phosphatase essential for the initiation of mineralisation, is regulated by PTH. Therefore, this study sought to determine whether the bone anabolic response to iPTH involves modulation of expression of Phospho1 and of other enzymes critical for bone matrix mineralisation. To mimic iPTH treatment, primary murine osteoblasts were challenged with 50 nM PTH for 6 h in every 48 h period for 8 days (4 cycles), 14 days (7 cycles) and 20 days (10 cycles) in total. The expression of both Phospho1 and Smpd3 was almost completely inhibited after 4 cycles, whereas 10 cycles were required to stimulate a similar response in Alpl expression. To explore the in vivo role of PHOSPHO1 in PTH-mediated osteogenesis, the effects of 14- and 28-day iPTH (80 µg/kg/day) administration was assessed in male wild-type (WT) and Phospho1-/- mice. The expression of Phospho1, Alpl, Smpd3, Enpp1, Runx2 and Trps1 expression was enhanced in the femora of WT mice following iPTH administration but remained unchanged in the femora of Phospho1-/- mice. After 28 days of iPTH administration, the anabolic response in the femora of WT was greater than that noted in Phospho1-/- mice. Specifically, cortical and trabecular bone volume/total volume, as well as cortical thickness, were increased in femora of iPTH-treated WT but not in iPTH-treated Phospho1-/- mice. Trabecular bone osteoblast number was also increased in iPTH-treated WT mice but not in iPTH-treated Phospho1-/-  mice. The increased levels of Phospho1, Alpl, Enpp1 and Smpd3 in WT mice in response to iPTH administration is consistent with their contribution to the potent anabolic properties of iPTH in bone. Furthermore, as the anabolic response to iPTH was attenuated in mice deficient in PHOSPHO1, this suggests that the osteoanabolic effects of iPTH are at least partly mediated via bone mineralisation processes.

Characterization of a Novel Frameshift Mutation Within the TRPS1 Gene Causing Trichorhinophalangeal Syndrome Type 1 in a Kindred Cypriot Family

Trichorhinophalangeal syndrome (TRPS) is an extremely rare autosomal dominant multisystem disorder characterized by craniofacial and skeletal abnormalities. Three subtypes of TRPS have been described: TRPS type I, TRPS type II, and TRPS type III. Mutations in the TRPS1 gene can cause both TRPS type I and TRPS type III. Therefore, the genotype-phenotype correlation is crucial to determine the subtype. The current family study from Cyprus involves affected patients from 4 generations who presented with alopecia, unoperated umbilical hernia, caput quadratum, long philtrum, depressed nasal bridge, frontal bossing, pes planus, beaked nose, and some deformities in hands and feet. Sequence analysis of the TRPS1 gene revealed a novel c.2854_2858del (p.Asn952ArgfsTer2) frameshift variant leading to a premature stop codon. To the best of our knowledge, we report here the first case of a Turkish Cypriot family of 4 generations with a novel frameshift mutation leading to truncated protein in the TRPS1 gene causing TRPS type I clinical phenotype. Overall, as the genotype and phenotype correlation in TRPSI is still uncertain and complex, the present outcome can enhance our knowledge of this complicated, rare, and severe genetic disorder.

Recombinant Human Growth Hormone Therapy for Childhood Trichorhinophalangeal Syndrome Type I: A Case Report

Trichorhinophalangeal syndrome type I (TRPS I; MIM 190350) is a rare autosomal dominant disorder of congenital malformations due to variants of the gene TRPS1. We reported on an 11-year-old Chinese boy with TRPS I. He had typical clinical findings, including sparse hair, a bulbous nose, a long philtrum, a thin upper lip, and skeletal abnormalities including cone-shaped epiphyses, shortening of the phalanges, and short stature. Trio whole exome sequencing identified a likely pathogenic heterozygous variant c.1957C > T (p.Q653*) in exon 4 of TRPS1, which has not been previously reported. He had been treated with rhGH therapy at a dose of 0.34 mg/(kg/week) at age 11, and a follow-up was conducted for one year. The rhGH therapy led to an increase in growth with a mean growth velocity of 1.12 cm/month (+1.1 SDS/year), and insulin-like growth factor 1 (IGF-1) concentration increased within normal range in our case. Moreover, we summarize 12 cases with TRPS I, including TRPS1 gene variants, growth hormone (GH) axis evaluation, IGF-1 concentration, and treatment in each analyzed case. Eight cases with TRPS I show a good response to rhGH therapy, and five of them have elevated IGF-1. Classic GH deficiency is not common among patients with TRPS I. The presence or absence of GH deficiency is not an absolute criterion for determining whether rhGH therapy should be used in TRPS I. It proves that rhGH therapy improves height outcomes before puberty in TRPS I in the short term. Effects on final adult height will need a longer follow-up and more adult-height data. The rise in IGF-1 could correlate with an increase in short-term height. Measuring IGF-1 levels is recommended as part of the assessment during the follow-up of patients with TRPS I.

Functional mechanisms of TRPS1 in disease progression and its potential role in personalized medicine

The gene of transcriptional repressor GATA binding 1 (TRPS1), as an atypical GATA transcription factor, has received considerable attention in a plethora of physiological and pathological processes, and may become a promising biomarker for targeted therapies in diseases and tumors. However, there still lacks a comprehensive exploration of its functions and promising clinical applications. Herein, relevant researches published in English from 2000 to 2022 were retrieved from PubMed, Google Scholar and MEDLINE, concerning the roles of TRPS1 in organ differentiation and tumorigenesis. This systematic review predominantly focused on summarizing the structural characteristics and biological mechanisms of TRPS1, its involvement in tricho-rhino-phalangeal syndrome (TRPS), its participation in the development of multiple tissues, the recent advances of its vital features in metabolic disorders as well as malignant tumors, in order to prospect its potential applications in disease detection and cancer targeted therapy. From the clinical perspective, the deeply and thoroughly understanding of the complicated context-dependent and cell-lineage-specific mechanisms of TRPS1 would not only gain novel insights into the complex etiology of diseases, but also provide the fundamental basis for the development of therapeutic drugs targeting both TRPS1 and its critical cofactors, which would facilitate individualized treatment.

Deficiency of Mineralization-Regulating Transcription Factor Trps1 Compromises Quality of Dental Tissues and Increases Susceptibility to Dental Caries

Dental caries is the most common chronic disease in children and adults worldwide. The complex etiology of dental caries includes environmental factors as well as host genetics, which together contribute to inter-individual variation in susceptibility. The goal of this study was to provide insights into the molecular pathology underlying increased predisposition to dental caries in trichorhinophalangeal syndrome (TRPS). This rare inherited skeletal dysplasia is caused by mutations in the TRPS1 gene coding for the TRPS1 transcription factor. Considering Trps1 expression in odontoblasts, where Trps1 supports expression of multiple mineralization-related genes, we focused on determining the consequences of odontoblast-specific Trps1 deficiency on the quality of dental tissues. We generated a conditional Trps1Col1a1 knockout mouse, in which Trps1 is deleted in differentiated odontoblasts using 2.3kbCol1a1-CreERT2 driver. Mandibular first molars of 4wk old male and female mice were analyzed by micro-computed tomography (μCT) and histology. Mechanical properties of dentin and enamel were analyzed by Vickers microhardness test. The susceptibility to acid demineralization was compared between WT and Trps1Col1a1cKO molars using an ex vivo artificial caries procedure. μCT analyses demonstrated that odontoblast-specific deletion of Trps1 results in decreased dentin volume in male and female mice, while no significant differences were detected in dentin mineral density. However, histology revealed a wider predentin layer and the presence of globular dentin, which are indicative of disturbed mineralization. The secondary effect on enamel was also detected, with both dentin and enamel of Trps1Col1a1cKO mice being more susceptible to demineralization than WT tissues. The quality of dental tissues was particularly impaired in molar pits, which are sites highly susceptible to dental caries in human teeth. Interestingly, Trps1Col1a1cKO males demonstrated a stronger phenotype than females, which calls for attention to genetically-driven sex differences in predisposition to dental caries. In conclusion, the analyses of Trps1Col1a1cKO mice suggest that compromised quality of dental tissues contributes to the high prevalence of dental caries in TRPS patients. Furthermore, our results suggest that TRPS patients will benefit particularly from improved dental caries prevention strategies tailored for individuals genetically predisposed due to developmental defects in tooth mineralization.

Minimal Critical Region and Genes for a Typical Presentation of Langer-Giedion Syndrome

Langer-Giedion syndrome (LGS) is caused by a contiguous deletion at 8q23q24, characterized by exostoses, facial, ectodermal, and skeletal anomalies, and, occasionally, intellectual disability. LGS patients have been diagnosed clinically or by routine cytogenetic techniques, hampering the definition of an accurate genotype-phenotype correlation for the syndrome. We report two unrelated patients with 8q23q24 deletions, characterized by cytogenomic techniques, with one of them, to our knowledge, carrying the smallest deletion reported in classic LGS cases. We assessed the pathogenicity of the deletion of genes within the 8q23q24 region and reviewed other molecularly confirmed cases from the literature. Our findings suggest a 3.2-Mb critical region for a typical presentation of the syndrome, emphasizing the contribution of the TRPS1, RAD21, and EXT1 genes' haploinsufficiency, and facial dysmorphisms as well as bone anomalies as the most frequent features among patients with LGS. We also suggest a possible role for the CSMD3 gene, whose deletion seems to contribute to central nervous system anomalies. Since studies performing such correlation for LGS patients are limited, our data contribute to improving the ge-notype-phenotype characterization for LGS patients.

Divergent Expression of SPARC, SPARC-L, and SCPP Genes During Jawed Vertebrate Cartilage Mineralization

While cartilage is an ancient tissue found both in protostomes and deuterostomes, its mineralization evolved more recently, within the vertebrate lineage. SPARC, SPARC-L, and the SCPP members (Secretory Calcium-binding PhosphoProtein genes which evolved from SPARC-L) are major players of dentine and bone mineralization, but their involvement in the emergence of the vertebrate mineralized cartilage remains unclear. We performed in situ hybridization on mineralizing cartilaginous skeletal elements of the frog Xenopus tropicalis (Xt) and the shark Scyliorhinus canicula (Sc) to examine the expression of SPARC (present in both species), SPARC-L (present in Sc only) and the SCPP members (present in Xt only). We show that while mineralizing cartilage expresses SPARC (but not SPARC-L) in Sc, it expresses the SCPP genes (but not SPARC) in Xt, and propose two possible evolutionary scenarios to explain these opposite expression patterns. In spite of these genetic divergences, our data draw the attention on an overlooked and evolutionarily conserved peripheral cartilage subdomain expressing SPARC or the SCPP genes and exhibiting a high propensity to mineralize.

Molecular genetic analysis and growth hormone response in patients with syndromic short stature

BACKGROUND

Syndromic short stature is a genetic and phenotypic heterogeneous disorder with multiple causes. This study aims to identify genetic causes in patients with syndromic short stature of unknown cause and evaluate the efficacy of the growth hormone response.

METHODS

Trio-whole-exome sequencing was applied to identify pathogenic gene mutations in seven patents with short stature, multiple malformations, and/or intellectual disability. Whole-genome low-coverage sequencing was also performed to identify copy number variants in three patients with concurrent intellectual disability. Recombinant human growth hormone was administered to improve height in patients with an identified cause of syndromic short stature.

RESULTS

Of the seven patients, three pathogenic/likely pathogenic gene mutations, including one FGFR3 mutation (c.1620C>A p.N540K), one novel GNAS mutation (c.2288C>T p.A763V), and one novel TRPS1 mutation (c.2527_c.2528dupTA p.S843fsX72), were identified in three patients. No copy number variants were identified in the three patients with concurrent intellectual disability. The proband with an FGFR3 mutation, a female 4 and 3/12 years of age, was diagnosed with hypochondroplasia. Long-acting growth hormone improved her height from 85.8 cm [- 5.05 standard deviation (SD)] to 100.4 cm (- 4.02 SD), and her increased height SD score (SDS) was 1.03 after 25 months of treatment. The proband with a GNAS mutation, a female 12 and 9/12 years of age, was diagnosed with pseudohypoparathyroidism Ia. After 14 months of treatment with short-acting growth hormone, her height improved from 139.3 cm (- 2.69 SD) to 145.0 cm (- 2.36 SD), and her increased height SDS was 0.33.

CONCLUSIONS

Trio-whole-exome sequencing was an important approach to confirm genetic disorders in patients with syndromic short stature of unknown etiology. Short-term growth hormone was effective in improving height in patients with hypochondroplasia and pseudohypoparathyroidism Ia.

Trps1 transcription factor represses phosphate-induced expression of SerpinB2 in osteogenic cells

Serine protease inhibitor SerpinB2 is one of the most upregulated proteins following cellular stress. This multifunctional serpin has been attributed a number of pleiotropic activities, including roles in cell survival, proliferation, differentiation, immunity and extracellular matrix (ECM) remodeling. Studies of cancer cells demonstrated that expression of SerpinB2 is directly repressed by the Trps1 transcription factor, which is a regulator of skeletal and dental tissues mineralization. In our previous studies, we identified SerpinB2 as one of the novel genes highly upregulated by phosphate (P_i) at the initiation of the mineralization process, however SerpinB2 has never been implicated in formation nor homeostasis of mineralized tissues. The aim of this study was to establish, if SerpinB2 is involved in function of cells producing mineralized ECM and to determine the interplay between P_i signaling and Trps1 in the regulation of SerpinB2 expression specifically in cells producing mineralized ECM. Analyses of the SerpinB2 expression pattern in mouse skeletal and dental tissues detected high SerpinB2 protein levels specifically in cells producing mineralized ECM. qRT-PCR and Western blot analyses demonstrated that SerpinB2 expression is activated by elevated P_i specifically in osteogenic cells. However, the P_i-induced SerpinB2 expression was diminished by overexpression of Trps1. Decreased SerpinB2 levels were also detected in osteoblasts and odontoblasts of 2.3Col1a1-Trps1 transgenic mice. Chromatin immunoprecipitation assay (ChIP) revealed that the occupancy of Trps1 on regulatory elements in the SerpinB2 gene changes in response to P_i. In vitro functional assessment of the consequences of SerpinB2 deficiency in cells producing mineralized ECM detected impaired mineralization in SerpinB2-deficient cells in comparison with controls. In conclusion, high and specific expression of SerpinB2 in cells producing mineralized ECM, the impaired mineralization of SerpinB2-deficient cells and regulation of SerpinB2 expression by two molecules regulating formation of mineralized tissues suggest involvement of SerpinB2 in physiological mineralization.

TRPS1 mutation detection in Chinese patients with Tricho-rhino-phalangeal syndrome and identification of four novel mutations

Background

Tricho‐rhino‐phalangeal syndrome (TRPS) is a rare autosomal dominant disorder characterized by craniofacial and skeletal malformations including short stature, thin scalp hair, sparse lateral eyebrows, a pear‐shaped nose, and cone‐shaped epiphyses. This condition is caused by haploinsufficiency or dominant‐negative effect of the TRPS1 gene.

Methods

In this study, we analyzed the clinical and genetic data of five unrelated TRPS patients. They were suspected of having TRPS on the basis of clinical and radiological features including typical hair and facial features, as well as varying degrees of skeletal abnormalities. Next‐generation sequencing was performed to identify variants of the TRPS1 gene in the five patients.

Results

In patient 1, we found a novel mutation at c.1338C>A (p.Tyr446*) (de novo). Patient 2 had a novel phenotype of hydrocephaly and Arnold–Chiari syndrome and we also found a maternally inherited novel mutation at c.2657C>A (p.Ser886*). Patient 3 had a de novo novel mutation at c.2726G>C (p.Cys909Ser) leading to more severe phenotypes. Patient 4 had a paternally inherited known mutation at c.2762G>A (p.Arg921Gln). Patient 5 with a novel phenotype of hepatopathy had a novel deletion at [GRCh37] del(8)(q23.3‐q24.11) chr8:g.116,420,724‐119,124,058 (over 2,700 kb). In addition, the patient 3 who harboring missense variants in the GATA binding domain of TRPS1 showed more severe craniofacial and skeletal phenotypes.

Conclusions

We describe four novel mutations and two novel phenotypes in five patients. The mutational and phenotypic spectrum of TRPS is broadened by our study on TRPS mutations. Our results reveal the significance of molecular analysis of TRPS1 for improving the clinical diagnosis of TRPS.

Transcriptional, epigenetic and microRNA regulation of growth plate

Endochondral ossification is a critical event in bone formation, particularly in long shaft bones. Many cellular differentiation processes work in concert to facilitate the generation of cartilage primordium to formation of trabecular structures, all of which occur within the growth plate. Previous studies have revealed that the growth plate is tightly regulated by various transcription factors, epigenetic systems, and microRNAs. Hence, understanding these mechanisms that regulate the growth plate is crucial to furthering the current understanding on skeletal diseases, and in formulating effective treatment strategies. In this review, we focus on describing the function and mechanisms of the transcription factors, epigenetic systems, and microRNAs known to regulate the growth plate.

Impaired dentin mineralization, supernumerary teeth, hypoplastic mandibular condyles with long condylar necks, and a TRPS1 mutation

Tricho-rhino-phalangeal syndrome type I, an autosomal dominant condition, is caused by heterozygous pathogenic variants in a zinc finger transcription factor, TRPS1, which has important roles in development of endochondral bones, teeth, and hair. Clinical manifestations of the patients include short stature, sparse, fine and slow-growing scalp hair, bulbous nose, supernumerary teeth, hip dysplasia, brachydactyly, and cone-shaped epiphyses of the phalangeal bones.

OBJECTIVE

To clinically, radiographically, and molecular genetically investigate a patient with tricho-rhino-phalangeal syndrome type I.

MATERIALS AND METHODS

Clinical and radiographic examination and mutation analysis of TRPS1 were performed.

RESULTS

Clinical and radiographic examination indicated the patient had tricho-rhino-phalangeal syndrome type I. Sequencing of the TRPS1 gene revealed a heterozygous pathogenic variant (c.2762G>A; p.Arg921Gln). Oral examination showed supernumerary teeth, large dental pulp spaces, dental pulp stones, microdontia of the maxillary permanent lateral incisors, absence of the mandibular left second premolar and short root of the maxillary right second premolar, and hypoplastic mandibular condyles with long condylar necks.

CONCLUSION

TRPS1 has an important function in regulating bone and dentin mineralization. Having large dental pulp spaces suggests that impaired dentin mineralization was the result of the TRPS1 pathogenic variant. This is the first patient with a TRPS1 pathogenic variant who had impaired dentin mineralization. This is also the third report showing the association between TRPS1 pathogenic variants and the presence of supernumerary teeth.

An intragenic duplication of TRPS1 leading to abnormal transcripts and causing trichorhinophalangeal syndrome type I

Trichorhinophalangeal syndrome type I (TRPSI) is a rare disorder that causes distinctive ectodermal, facial, and skeletal features affecting the hair (tricho-), nose (rhino-), and fingers and toes (phalangeal) and is inherited in an autosomal dominant pattern. TRPSI is caused by loss of function variants in TRPS1, involved in the regulation of chondrocyte and perichondrium development. Pathogenic variants in TRPS1 include missense mutations and deletions with variable breakpoints, with only a single instance of an intragenic duplication reported to date. Here we report an affected individual presenting with a classic TRPSI phenotype who is heterozygous for a de novo intragenic ∼36.3-kbp duplication affecting exons 2–4 of TRPS1. Molecular analysis revealed the duplication to be in direct tandem orientation affecting the splicing of TRPS1. The aberrant transcripts are predicted to produce a truncated TRPS1 missing the nuclear localization signal and the GATA and IKAROS-like zinc-finger domains resulting in functional TRPS1 haploinsufficiency. Our study identifies a novel intragenic tandem duplication of TRPS1 and highlights the importance of molecular characterization of intragenic duplications.

TRPS1 Is a Lineage-Specific Transcriptional Dependency in Breast Cancer

Perturbed epigenomic programs play key roles in tumorigenesis, and chromatin modulators are candidate therapeutic targets in various human cancer types. To define singular and shared dependencies on DNA and histone modifiers and transcription factors in poorly differentiated adult and pediatric cancers, we conducted a targeted shRNA screen across 59 cell lines of 6 cancer types. Here, we describe the TRPS1 transcription factor as a strong breast cancer-specific hit, owing largely to lineage-restricted expression. Knockdown of TRPS1 resulted in perturbed mitosis, apoptosis, and reduced tumor growth. Integrated analysis of TRPS1 transcriptional targets, chromatin binding, and protein interactions revealed that TRPS1 is associated with the NuRD repressor complex. These findings uncover a transcriptional network that is essential for breast cancer cell survival and propagation.

Witwicki et al. use a targeted shRNA screening strategy to identify transcriptional and epigenomic dependencies in poorly differentiated human cancers. TRPS1 is a lineage-specific transcription factor that is required for mitosis in breast cancer cells. TRPS1 is associated with the NuRD complex, and it regulates cell adhesion, cytoskeleton, and G2-M phase-related genes.

MicroRNA-221 silencing attenuates the degenerated phenotype of intervertebral disc cells

The aim of this study was to investigate the role of an antichondrogenic factor, MIR221 (miR-221), in intervertebral disc degeneration (IDD), and provide basic information for the development of a therapeutic strategy for the disc repair based on specific nucleic acid based drugs, such as miR-221 silencing. We established a relatively quick protocol to minimize artifacts from extended in vitro culture, without selecting the different types of cells from intervertebral disc (IVD) or completely disrupting extracellular matrix (ECM), but by using the whole cell population with a part of resident ECM. During the de-differentiation process miR-221 expression significantly increased. We demonstrated the effectiveness of miR-221 silencing in driving the cells towards chondrogenic lineage. AntagomiR-221 treated cells showed in fact a significant increase of expression of typical chondrogenic markers including COL2A1, ACAN and SOX9, whose loss is associated with IDD. Moreover, antagomiR-221 treatment restored FOXO3 expression and increased TRPS1 expression levels attenuating the severity grade of degeneration, and demonstrating in a context of tissue degeneration and inflammation not investigated before, that FOXO3 is target of miR-221. Data of present study are promising in the definition of new molecules useful as potential intradiscal injectable biological agents.

How To Build a Bone: PHOSPHO1, Biomineralization, and Beyond

Since its characterization two decades ago, the phosphatase PHOSPHO1 has been the subject of an increasing focus of research. This work has elucidated PHOSPHO1's central role in the biomineralization of bone and other hard tissues, but has also implicated the enzyme in other biological processes in health and disease. During mineralization PHOSPHO1 liberates inorganic phosphate (P_i) to be incorporated into the mineral phase through hydrolysis of its substrates phosphocholine (PCho) and phosphoethanolamine (PEA). Localization of PHOSPHO1 within matrix vesicles allows accumulation of P_i within a protected environment where mineral crystals may nucleate and subsequently invade the organic collagenous scaffold. Here, we examine the evidence for this process, first discussing the discovery and characterization of PHOSPHO1, before considering experimental evidence for its canonical role in matrix vesicle–mediated biomineralization. We also contemplate roles for PHOSPHO1 in disorders of dysregulated mineralization such as vascular calcification, along with emerging evidence of its activity in other systems including choline synthesis and homeostasis, and energy metabolism. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Trps1 Regulates Development of Craniofacial Skeleton and Is Required for the Initiation of Palatal Shelves Fusion

Trichorhinophalangeal syndrome (TRPS) is an autosomal dominant disorder resulting from heterozygous mutations of the TRPS1 gene. Common craniofacial abnormalities in TRPS patients include micrognathia, hypoplastic zygomatic arch, high-arched palate, and, occasionally, cleft palate. Studies have demonstrated that mice with a heterozygous Trps1 mutation (Trps1+/- mice) have similar features to patients with TRPS, including high-arched palates. However, mice with a homozygous Trps1 mutation (Trps1-/- mice) exhibit similar but more severe abnormalities, including cleft palate. Our study aimed to characterize the craniofacial phenotype to understand the role of Trps1 in craniofacial development and gain insight on the cleft palate pathogenesis in Trps1 deficiency. Whole-mount skeletal staining revealed hypoplastic skeletal and cartilaginous elements, steep nasal slope, and missing presphenoid in Trps1-/- mice. Although several craniofacial skeleton elements were abnormal in Trps1-/- mice, the Trps1 deficiency did not appear to disrupt cranial vault development. All Trps1-/- mice presented with cleft palate. Analyses of Trps1 expression during palatogenesis detected Trps1 mRNA and protein in palatal mesenchyme and in specific regions of palatal epithelium, which suggested that Trps1 is involved in palatal fusion. Ex vivo culture experiments demonstrated that Trps1-/- palatal shelves were unable to initiate the fusion process. On the molecular level, Trps1 deficiency resulted in decreased epithelial expression of proteins involved in palatal fusion, including chondroitin sulfate proteoglycan, transforming growth factor-beta 3, Twist1, and beta-catenin. Mesenchymal expression of chondroitin sulfate proteoglycan expression was unaffected, indicating a cell type-specific mechanism of Trps1 regulation on chondroitin sulfate proteoglycan. In conclusion, we demonstrated that Trps1 is involved in the development of craniofacial skeletal elements and in the initiation of the palatal shelves fusion. Furthermore, our studies uncovered that Trps1 is required for epithelial expression of several proteins involved in the palatal shelves fusion.

Trps1 transcription factor regulates mineralization of dental tissues and proliferation of tooth organ cells

Mutations of the TRPS1 gene cause trichorhinophalangeal syndrome (TRPS), a skeletal dysplasia with dental abnormalities. TRPS dental phenotypes suggest that TRPS1 regulates multiple aspects of odontogenesis, including the tooth number and size. Previous studies delineating Trps1 expression throughout embryonic tooth development in mice detected strong Trps1 expression in dental mesenchyme, preodontoblasts, and dental follicles, suggesting that TRPS dental phenotypes result from abnormalities in early developmental processes. In this study, Trps1^+/- and Trps1^-/- mice were analyzed to determine consequences of Trps1 deficiency on odontogenesis. We focused on the aspects of tooth formation that are disturbed in TRPS and on potential molecular abnormalities underlying TRPS dental phenotypes. Microcomputed tomography analyses of molars were used to determine tooth size, crown shape, and mineralization of dental tissues. These analyses uncovered that disruption of one Trps1 allele is sufficient to impair mineralization of dentin in both male and female mice. Enamel mineral density was decreased only in males, while mineralization of the root dental tissues was decreased only in females. In addition, significantly smaller teeth were detected in Trps1^+/- females. Histomorphometric analyses of tooth organs showed reduced anterior-posterior diameter in Trps1^-/- mice. BrdU-incorporation assay detected reduced proliferation of mesenchymal and epithelial cells in Trps1^-/- tooth organs. Immunohistochemistry for Runx2 and Osx osteogenic transcription factors revealed changes in their spatial distribution in Trps1^-/- tooth organs and uncovered cell-type specific requirements of Trps1 for Osx expression. In conclusion, this study has demonstrated that Trps1 is a positive regulator of cell proliferation in both dental mesenchyme and epithelium, suggesting that the microdontia in TRPS is likely due to decreased cell proliferation in developing tooth organs. Furthermore, the reduced mineralization observed in Trps1^+/- mice may provide some explanation for the extensive dental caries reported in TRPS patients.

Gain-of-function mutation of microRNA-140 in human skeletal dysplasia

MicroRNAs (miRNAs) are post-transcriptional regulators of gene expression. Heterozygous loss-of-function point mutations of miRNA genes are associated with several human congenital disorders^1-5, but neomorphic (gain-of-new-function) mutations in miRNAs due to nucleotide substitutions have not been reported. Here we describe a neomorphic seed region mutation in the chondrocyte-specific, super-enhancer-associated MIR140 gene encoding microRNA-140 (miR-140) in a novel autosomal dominant human skeletal dysplasia. Mice with the corresponding single nucleotide substitution show skeletal abnormalities similar to those of the patients but distinct from those of miR-140-null mice⁶. This mutant miRNA gene yields abundant mutant miR-140-5p expression without miRNA-processing defects. In chondrocytes, the mutation causes widespread derepression of wild-type miR-140-5p targets and repression of mutant miR-140-5p targets, indicating that the mutation produces both loss-of-function and gain-of-function effects. Furthermore, the mutant miR-140-5p seed competes with the conserved RNA-binding protein Ybx1 for overlapping binding sites. This finding may explain the potent target repression and robust in vivo effect by this mutant miRNA even in the absence of evolutionary selection of miRNA-target RNA interactions, which contributes to the strong regulatory effects of conserved miRNAs^7,8. Our study presents the first case of a pathogenic gain-of-function miRNA mutation and provides molecular insight into neomorphic actions of emerging and/or mutant miRNAs.

Trps1 is associated with the multidrug resistance of lung cancer cell by regulating MGMT gene expression

Multidrug resistance (MDR) often leads to chemotherapy failure of lung cancer and has been linking to the cellular expression of several DNA transcription- and repair-related genes such as Trps1 and MGMT. However, their roles in the formation of MDR are largely unknown. In this study, overexpression/knockdown, luciferase assay and ChIP assay were performed to study the relationship between Trps1 and MGMT, as well as their roles in MDR formation. Our results demonstrated that Trps1 and MGMT expression both increased in drug-resistant lung cancer cell line (H446/CDDP). Silencing of Trps1 resulted in downregulation of MGMT expression and decrease in the multidrug sensitivity of H446/CDDP cells, while Trps1 overexpression exhibited the opposite effects in H446 cells. Ectopic expression of MGMT had no effect on Trps1 expression, but enhanced the IC50 values of H446 cells or rescued the IC50 values of Trps1-silenced H446/CDDP cells in treatment of multidrug. Our data further showed that, mechanistically, Trps1 acted as a transcription activator that directly induced MGMT transcription by binding to the MGMT promoter. Taken together, we consider that upregulation of Trps1 induces MGMT transcription contributing to the formation of MDR in lung cancer cells. Our findings proved potential targets for reversing MDR in clinical chemotherapy of lung cancer.

A novel TRPS1 mutation in a Moroccan family with Tricho-rhino-phalangeal syndrome type III: case report

BACKGROUND

Tricho-rhino-phalangeal syndrome (TRPS) is an autosomal dominant disorder characterized by craniofacial and skeletal malformations including short stature, thin scalp hair, sparse lateral eyebrows, pear-shaped nose and cone shaped epiphyses. This condition is caused by haploinsufficiency of the TRPS1 gene. Previous genotype-phenotype studies have correlated exon 6 missense mutations with TRPS type III, a severe form of type I with pronounced, facial characteristics, short stature and brachydactyly and differing from type II by the absence of exostoses and mental retardation.

CASE PRESENTATION

We report the first case of a Moroccan family, a father and his three children, in which the diagnosis of type III TRPS was suspected based on severe clinical and radiological features. Molecular analysis of the TRPS1 gene revealed a novel missense mutation in exon 6, (p.Ala932Ser), located in the GATA-type DNA-binding zinc finger domain.

CONCLUSION

Our observations in this kindred support the previous genotype-phenotype results suggesting that patients with more pronounced facial characteristics and more severe shortening of hands and feet are more likely to have mutation in exon 6 of TRPS1.

Exome sequencing identifies de novo pathogenic variants in FBN1 and TRPS1 in a patient with a complex connective tissue phenotype

Here we describe a patient who presented with a history of congenital diaphragmatic hernia, inguinal hernia, and recurrent umbilical hernia. She also has joint laxity, hypotonia, and dysmorphic features. A unifying diagnosis was not identified based on her clinical phenotype. As part of her evaluation through the Undiagnosed Diseases Network, trio whole-exome sequencing was performed. Pathogenic variants in FBN1 and TRPS1 were identified as causing two distinct autosomal dominant conditions, each with de novo inheritance. Fibrillin 1 (FBN1) mutations are associated with Marfan syndrome and a spectrum of similar phenotypes. TRPS1 mutations are associated with trichorhinophalangeal syndrome types I and III. Features of both conditions are evident in the patient reported here. Discrepant features of the conditions (e.g., stature) and the young age of the patient may have made a clinical diagnosis more difficult in the absence of exome-wide genetic testing.

Transcriptional control of chondrocyte specification and differentiation

A milestone in the evolutionary emergence of vertebrates was the invention of cartilage, a tissue that has key roles in modeling, protecting and complementing the bony skeleton. Cartilage is elaborated and maintained by chondrocytes. These cells derive from multipotent skeletal progenitors and they perform highly specialized functions as they proceed through sequential lineage commitment and differentiation steps. They form cartilage primordia, the primary skeleton of the embryo. They then transform these primordia either into cartilage growth plates, temporary drivers of skeletal elongation and endochondral ossification, or into permanent tissues, namely articular cartilage. Chondrocyte fate decisions and differentiated activities are controlled by numerous extrinsic and intrinsic cues, and they are implemented at the gene expression level by transcription factors. The latter are the focus of this review. Meritorious efforts from many research groups have led over the last two decades to the identification of dozens of key chondrogenic transcription factors. These regulators belong to all types of transcription factor families. Some have master roles at one or several differentiation steps. They include SOX9 and RUNX2/3. Others decisively assist or antagonize the activities of these masters. They include TWIST1, SOX5/6, and MEF2C/D. Many more have tissue-patterning roles and regulate cell survival, proliferation and the pace of cell differentiation. They include, but are not limited to, homeodomain-containing proteins and growth factor signaling mediators. We here review current knowledge of all these factors, one superclass, class, and family at a time. We then compile all knowledge into transcriptional networks. We also identify remaining gaps in knowledge and directions for future research to fill these gaps and thereby provide novel insights into cartilage disease mechanisms and treatment options.

Fate mapping of Trps1 daughter cells during cardiac development using novel Trps1-Cre mice

Tricho-rhino-phalangeal syndrome (TRPS) is a rare congenital disorder that is characterized by abnormal hair growth and skeletal deformities. These result in sparse hair, short stature, and early onset of joint problems. Recent reports have shown that a relatively high proportion of patients with TRPS exhibit a broad range of congenital heart defects. To determine the regulation of Trps1 transcription in vivo, we generated novel transgenic mice, which expressed Cre recombinase under the murine Trps1 proximal promoter sequence (Trps1-Cre). We crossed these mice with Cre reporter mice to identify Trps1 daughter cells. Labeled cells were observed in the appendicular joint tissue, dermal papilla of the hair follicles, cardiac valves, aortic sinus, atrial walls, and the interventricular septum. In situ analysis showed restricted Trps1 expression, which was observed in endocardial cushions of the outflow tract, and in leaflets of all mature cardiac valves. These results suggest that the Trps1 proximal promoter sequence contains some of the tissue-specific Trps1 regulatory region. Further, our findings partially explain why patients with TRPS show a broad range of congenital cardiac defects, although Trps1 expression is observed in a more restricted fashion. genesis 54:379-388, 2016. © 2016 Wiley Periodicals, Inc.

The potential function of microRNA in chordomas

Little is known about the molecular biology of chordomas, which are rare, chemoresistant tumors with no well-established treatment. miRNAs regulate gene networks and pathways. We aimed to evaluate the effects of dysregulated miRNA in chordomas would help reveal the underlying mechanisms of chordoma initiation and progression. In this study, miR-31, anti-miR-140-3p, anti-miR148a, and miR-222 were transiently transfected to chordoma cell lines and an MTS assay, apoptosis assay, and cell-cycle analysis were conducted to evaluate the effects. The mRNA level of predicted and confirmed targets of each miRNA, as well as the EMT and MET markers of U-CH1 and MUG-Chor1, were assessed with real-time polymerase chain reaction. Transient transfection of miRNA mimics was achieved, as each mimic increased or decreased the level of its corresponding miRNA. miR-31 decreased cell viability in MUG-Chor1 and U-CH2 after 72h, which is consistent with previous findings for U-CH1. Both miR-31 and anti-miR-148a induced apoptosis in all three cell lines. Although each miRNA had a similar pattern, miR-31 had the most effective S-phase arrest in all three cell lines. RDX, MET, DNMT1, DNMT3B, TRPS1, BIRC5, and KIT were found to be targeted by the selected miRNAs. The level of miR-222 in chordoma cell lines U-CH1 and MUG-Chor1 correlated positively with EMT markers and negatively with MET markers. This study uncovered the potential of miR-31, miR-140-3p, miR-148a, and miR-222-3p to be key molecules in the cell viability, cell cycle, and apoptosis in chordomas, as well as initiation, differentiation, and progression.

Genetic Influences on Temporomandibular Joint Development and Growth

The temporomandibular joint (TMJ) is a small synovial joint at which the mandible articulates with the skull during movements involved in speaking and mastication. However, the secondary cartilage lining its joint surfaces is indicative of a very different developmental history than limb cartilages. This review summarizes our current knowledge of genes that regulate the formation of primary components of the TMJ, as well as genes that regulate postnatal growth of the TMJ. Although the TMJ is regulated by some of the same genes that are important in limb joints, others appear unique to the TMJ or have different actions. Runx2, Sox9, and members of the TGF-β/BMP family are critical drivers of chondrogenesis during condylar cartilage morphogenesis, and Indian hedgehog (Ihh) is important for formation of the articular disc and cavitation. Osterix (Osx) is a critical regulator of endochondral bone formation during postnatal TMJ growth.

A central role for TRPS1 in the control of cell cycle and cancer development

The eukaryotic cell cycle is controlled by a complex regulatory network, which is still poorly understood. Here we demonstrate that TRPS1, an atypical GATA factor, modulates cell proliferation and controls cell cycle progression. Silencing TRPS1 had a differential effect on the expression of nine key cell cycle-related genes. Eight of these genes are known to be involved in the regulation of the G2 phase and the G2/M transition of the cell cycle. Using cell synchronization studies, we confirmed that TRPS1 plays an important role in the control of cells in these phases of the cell cycle. We also show that silencing TRPS1 controls the expression of 53BP1, but not TP53. TRPS1 silencing also decreases the expression of two histone deacetylases, HDAC2 and HDAC4, as well as the overall HDAC activity in the cells, and leads to the subsequent increase in the acetylation of histone4 K16 but not of histone3 K9 or K18. Finally, we demonstrate that TRPS1 expression is elevated in luminal breast cancer cells and luminal breast cancer tissues as compared with other breast cancer subtypes. Overall, our study proposes that TRPS1 acts as a central hub in the control of cell cycle and proliferation during cancer development.

Losartan increases bone mass and accelerates chondrocyte hypertrophy in developing skeleton

Angiotensin receptor blockers (ARBs) are a group of anti-hypertensive drugs that are widely used to treat pediatric hypertension. Recent application of ARBs to treat diseases such as Marfan syndrome or Alport syndrome has shown positive outcomes in animal and human studies, suggesting a broader therapeutic potential for this class of drugs. Multiple studies have reported a benefit of ARBs on adult bone homeostasis; however, its effect on the growing skeleton in children is unknown. We investigated the effect of Losartan, an ARB, in regulating bone mass and cartilage during development in mice. Wild type mice were treated with Losartan from birth until 6 weeks of age, after which bones were collected for microCT and histomorphometric analyses. Losartan increased trabecular bone volume vs. tissue volume (a 98% increase) and cortical thickness (a 9% increase) in 6-weeks old wild type mice. The bone changes were attributed to decreased osteoclastogenesis as demonstrated by reduced osteoclast number per bone surface in vivo and suppressed osteoclast differentiation in vitro. At the molecular level, Angiotensin II-induced ERK1/2 phosphorylation in RAW cells was attenuated by Losartan. Similarly, RANKL-induced ERK1/2 phosphorylation was suppressed by Losartan, suggesting a convergence of RANKL and angiotensin signaling at the level of ERK1/2 regulation. To assess the effect of Losartan on cartilage development, we examined the cartilage phenotype of wild type mice treated with Losartan in utero from conception to 1 day of age. Growth plates of these mice showed an elongated hypertrophic chondrocyte zone and increased Col10a1 expression level, with minimal changes in chondrocyte proliferation. Altogether, inhibition of the angiotensin pathway by Losartan increases bone mass and accelerates chondrocyte hypertrophy in growth plate during skeletal development.

A novel TRPS1 mutation in a family with tricho-rhino-phalangeal syndrome type 1

Tricho-rhino-phalangeal syndrome (TRPS) is an autosomal-dominant disease characterized by sparse and slow-growing scalp hair and craniofacial and skeletal abnormalities. We report here the case of two girls and their father who had TRPS type 1 and received a diagnosis of a new mutation of TRPS1 based on their clinical symptoms. Moreover, histological studies on skin samples obtained from one of the patients showed enhanced signal transducers and activator of transcription (STAT) 3 expression in the outer root sheath. However, TRPS1 protein expression was not reduced in the patient's follicles. These findings indicate that truncated TRPS1 protein from the mutant allele may be stably expressed in the patient's follicles and that enhanced STAT3 expression may be involved in the development of sparse and thin scalp hair in TRPS.

Trichorhinophalangeal syndrome type I: a novel mutation and Perthes-like changes of the hip in a family with 4 cases over 3 generations

The trichorhinophalangeal syndrome is a rare genetic syndrome with characteristic craniofacial and skeletal abnormalities including hip pathology in variable manifestation. We describe hip involvement with Perthes-like changes and a novel mutation of the TRPSI gene in a family with 4 affected individuals. This case series underlines the clinical significance of rare genetic disorders such as TRPS that among other differential diagnoses should be kept in mind when children present with Perthes-like changes of the hip joint.

A novel TRPS1 gene mutation causing trichorhinophalangeal syndrome with growth hormone responsive short stature: a case report and review of the literature

The role of growth hormone (GH) and its therapeutic supplementation in the trichorhinophalangeal syndrome type I (TRPS I) is not well delineated. TRPS I is a rare congenital syndrome, characterized by craniofacial and skeletal malformations including short stature, sparse, thin scalp hair and lateral eyebrows, pear-shaped nose, cone shaped epiphyses and hip dysplasia. It is inherited in an autosomal dominant manner and caused by haploinsufficiency of the TRPS1 gene. We report a family (Mother and 3 of her 4 children) with a novel mutation in the TRPS1 gene. The diagnosis was suspected only after meeting all family members and comparing affected and unaffected siblings since the features of this syndrome might be subtle. The eldest sibling, who had neither GH deficiency nor insensitivity, improved his growth velocity and height SDS after 2 years of treatment with exogenous GH. No change in growth velocity was observed in the untreated siblings during this same period. This report emphasizes the importance of examining all family members when suspecting a genetic syndrome. It also demonstrates the therapeutic effect of GH treatment in TRPS I despite normal GH-IGF1 axis. A review of the literature is included to address whether TRPS I is associated with: a) GH deficiency, b) GH resistance, or c) GH-responsive short stature. More studies are needed before recommending GH treatment for TRPS I but a trial should be considered on an individual basis.

Dual role of the Trps1 transcription factor in dentin mineralization

TRPS1 (tricho-rhino-phalangeal syndrome) is a unique GATA-type transcription factor that acts as a transcriptional repressor. TRPS1 deficiency and dysregulated TRPS1 expression result in skeletal and dental abnormalities implicating TRPS1 in endochondral bone formation and tooth development. Moreover, patients with tricho-rhino-phalangeal syndrome frequently present with low bone mass indicating TRPS1 involvement in bone homeostasis. In addition, our previous data demonstrated accelerated mineralization of the perichondrium in Trps1 mutant mice and impaired dentin mineralization in Col1a1-Trps1 transgenic mice, implicating Trps1 in the mineralization process. To understand the role of Trps1 in the differentiation and function of cells producing mineralized matrix, we used a preodontoblastic cell line as a model of dentin mineralization. We generated both Trps1-deficient and Trps1-overexpressing stable cell lines and analyzed the progression of mineralization by alkaline phosphatase and alizarin red staining. As predicted, based on our previous in vivo data, delayed and decreased mineralization of Trps1-overexpressing odontoblastic cells was observed when compared with control cells. This was associated with down-regulation of genes regulating phosphate homeostasis. Interestingly, Trps1-deficient cells lost the ability to mineralize and demonstrated decreased expression of several genes critical for initiating the mineralization process, including Alpl and Phospho1. Based on these data, we have concluded that Trps1 serves two critical and context-dependent functions in odontoblast-regulated mineralization as follows: 1) Trps1 is required for odontoblast maturation by supporting expression of genes crucial for initiating the mineralization process, and 2) Trps1 represses the function of mature cells and, consequently, restricts the extent of extracellular matrix mineralization.

Association of TRPS1 gene with different EMT markers in ERα-positive and ERα-negative breast cancer

Background

Breast cancer is a heterogeneous disease consisting of different subtypes. Trichorhinophalangeal syndrome type 1 (TRPS1) gene, a GATA-type transcription factor, has been found to be highly expressed in breast cancer. Epithelial-to-mesenchymal transition (EMT) is known to play an important role in tumour invasion and metastasis. Our objective was to elucidate the different roles and clinical relevance of TRPS1 in different estrogen receptor (ER) expression subtypes of breast cancer.

Methods

An immunohistochemical study was performed. The correlation between clinicopathological features and other biomarker profiles were analysed statistically.

Result

TRPS1 expression was correlated with the patients’ age (P = 0.017). It was positively related with ERα (P < 0.001), progesterone receptor (PR) (P < 0.001) and ERβ (P = 0.001) status, but negatively associated with Ki67 (P = 0.002) and HER2 (P = 0.025) status. In ERα-positive breast cancer, TRPS1 expression was positively associated with the expression of E-cadherin (P < 0.001), β-catenin(P = 0.001), ERβ (P = 0.03), and p53 (P = 0.002) status, while in ERα-negative breast cancer, TRPS1 expression was correlated with slug (P = 0.004), vimentin (P = 0.003), smooth muscle actin (SMA) (P = 0.031), and IMP3 (P = 0.005) expression.

Conclusions

Based on our findings, we conclude that TRPS1 is positively associated with E-cadherin and β-catenin status in ERα-positive breast cancer cells, while it is also significantly associated with mesenchymal markers of EMT in ERα-negative breast cancer cells. TRPS1 can be a prognostic marker depending on the type of breast cancer.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/8686515681264281

The multi zinc-finger protein Trps1 acts as a regulator of histone deacetylation during mitosis

TRPS1, the gene mutated in human "Tricho-Rhino-Phalangeal syndrome," encodes a multi zinc-finger nuclear regulator of chondrocyte proliferation and differentiation. Here, we have identified a new function of Trps1 in controlling mitotic progression in chondrocytes. Loss of Trps1 in mice leads to an increased proportion of cells arrested in mitosis and, subsequently, to chromosome segregation defects. Searching for the molecular basis of the defect, we found that Trps1 acts as regulator of histone deacetylation. Trps1 interacts with two histone deacetylases, Hdac1 and Hdac4, thereby increasing their activity. Loss of Trps1 results in histone H3 hyperacetylation, which is maintained during mitosis. Consequently, chromatin condensation and binding of HP1 is impaired, and Trps1-deficient chondrocytes accumulate in prometaphase. Overexpression of Hdac4 rescues the mitotic defect of Trps1-deficient chondrocytes, identifying Trps1 as an important regulator of chromatin deacetylation during mitosis in chondrocytes. Our data provide the first evidence that the control of mitosis can be linked to the regulation of chondrocyte differentiation by epigenetic consequences of altered Hdac activity.