Pierpont Syndrome Research Articles

Genetic predisposition to porto-sinusoidal vascular disorder.

Porto-sinusoidal vascular disorder is a rare liver disease. The pathophysiological mechanisms underlying the development of porto-sinusoidal vascular disorder are unknown. Isolated cases of porto-sinusoidal vascular disorder associated with gene mutations have been reported, but no overview is available. Therefore, we performed an extensive literature search to provide a comprehensive overview of gene mutations associated with porto-sinusoidal vascular disorder. We identified 34 genes and one chromosomal abnormality associated with porto-sinusoidal vascular disorder in the literature, and we describe here one additional gene mutation (TBL1XR1 mutation, leading to Pierpont syndrome). These gene mutations are associated either with extrahepatic organ involvement as part of syndromes (Adams Oliver, telomere biology disorders, retinal vasculopathy with cerebral leukoencephalopathy and systemic manifestations, immune deficiencies, cystic fibrosis, cystinosis, Williams Beuren, Turner, Pierpont) or with isolated porto-sinusoidal vascular disorder (KCNN3, DGUOK, FOPV, GIMAP5, FCHSD1, TRMT5, HRG gene mutations). Most of the cases were revealed by signs or complications of portal hypertension. When analysing the cell types in which these genes are expressed, we found that these genes are predominantly expressed in immune cells, suggesting that these cells may play a more important role in the development of porto-sinusoidal vascular disorder than previously thought. In addition, pathway analyses suggested that there may be 2 types of porto-sinusoidal vascular disorder associated with gene mutations: those resulting directly from morphogenetic abnormalities and those secondary to immune changes.

Analysis of genes differentially expressed in the cortex of mice with the Tbl1xr1Y446C/Y446C variant

Transducin β-like 1 X-linked receptor 1 (mouse Tbl1xr1) or TBL1X/Y related 1 (human TBL1XR1), part of the NCoR/SMRT corepressor complex, is involved in nuclear receptor signaling. Variants in TBL1XR1 cause a variety of neurodevelopmental disorders including Pierpont syndrome caused by the p.Tyr446Cys variant. We recently reported a mouse model carrying the Tbl1xr1Y446C/Y446C variant as a model for Pierpont syndrome.To obtain insight into mechanisms involved in altered brain development we studied gene expression patterns in the cortex of mutant and wild type (WT) mice, using RNA-sequencing, differentially expressed gene (DEG) analysis, gene set enrichment analysis (GSEA), weighted gene correlation network analysis (WGCNA) and hub gene analysis. We validated results in mutated mouse cortex, as well as in BV2 and SK-N-AS cell lines, in both of which Tbl1xr1 was knocked down by siRNA.Two DEGs (adj.P. Val < 0.05) were found in the cortex, Mpeg1 (downregulated in mutant mice) and 2900052N01Rik (upregulated in mutant mice). GSEA, WGCNA and hub gene analysis demonstrated changes in genes involved in ion channel function and neuroinflammation in the cortex of the Tbl1xr1Y446C/Y446C mice. The lowered expression of ion channel genes Kcnh3 and Kcnj4 mRNA was validated in the mutant mouse cortex, and increased expression of TRIM9, associated with neuroinflammation, was confirmed in the SK-N-AS cell line.Conclusively, our results show altered expression of genes involved in ion channel function and neuroinflammation in the cortex of the Tbl1xr1Y446C/Y446C mice. These may partly explain the impaired neurodevelopment observed in individuals with Pierpont syndrome and related TBL1XR1-related disorders.

The role of transducin β-like 1 X-linked receptor 1 (TBL1XR1) in thyroid hormone metabolism and action in mice.

Transducin β-like 1 X-linked receptor 1 (TBL1XR1) is a WD40 repeat-containing protein and part of the corepressor complex SMRT/NCoR that binds to the thyroid hormone receptor (TR). We recently described a mutation in TBL1XR1 in patients with Pierpont syndrome. A mouse model bearing this Tbl1xr1 mutation (Tbl1xr1Y446C/Y446C ) displays several aspects of the Pierpont phenotype. Although serum thyroid hormone (TH) concentrations were unremarkable in these mice, tissue TH action might be affected due to the role of TBL1XR1 in the SMRT/NCoR corepressor complex. The aim of the present study was to evaluate tissue TH metabolism and action in a variety of tissues of Tbl1xr1Y446C/Y446C mice. We studied the expression of genes involved in TH metabolism and action in tissues of naïve Tbl1xr1Y446C/Y446C mice and wild type (WT) mice. In addition, we measured deiodinase activity in liver (Dio1 and Dio3), kidney (Dio1 and Dio3) and BAT (Dio2). No striking differences were observed in the liver, hypothalamus, muscle and BAT between Tbl1xr1Y446C/Y446C and WT mice. Pituitary TRα1 mRNA expression was lower in Tbl1xr1Y446C/Y446C mice compared to WT, while the mRNA expression of Tshβ and the positively T3-regulated gene Nmb were significantly increased in mutant mice. Interestingly, Mct8 expression was markedly higher in WAT and kidney of mutants, resulting in (subtle) changes in T3-regulated gene expression in both WAT and kidney. In conclusion, mice harboring a mutation in TBL1XR1 display minor changes in cellular TH metabolism and action. TH transport via MCT8 might be affected as the expression is increased in WAT and kidney. The mechanisms involved need to be clarified.

Novel De Novo TBL1XR1 Variant Causing PIERPONT Syndrome in an Indian Child: A Case Report and Genotype–Phenotype Review of Reported Patients

AbstractThe transducin β-like-1 X-linked-receptor-1 gene (TBL1XR1) encodes for the TBL1XR1 protein which is involved in transcription. Single-nucleotide variants (SNVs) in the TBL1XR1 gene have been reported to be associated with Pierpont's syndrome (PS) which exhibits numerous features including global developmental delay (GDD), intellectual disability (ID), varying neurobehavioral and psychiatric manifestations with/without autism spectrum disorder (ASD), abnormal fat distribution in the distal extremities, short stature (SS), head circumference abnormalities, hearing loss (HL), and facial dysmorphisms. Eight PS patients, having a de novo mutation resulting in p.Tyr446Cys, showed no manifestations of ASD. The three other PS patients, having mutations resulting in p.Tyr446His, p.Cys325Tyr and p.Gly237Asp, respectively, and without the p.Tyr446Cys alteration, were in addition associated with neurobehavioral abnormalities, including ASD, hyperactivity, and self-mutilation tendencies. Here, via trio whole exome sequencing, we describe a 12th PS patient, the first from the Indian subcontinent, reflecting a novel TBL1XR1 p.His348Arg alteration. The proband is a 4.5-year-old male having GDD, speech delay, facial dysmorphisms, abnormal digital fat pads, hypotonia, microcephaly, patent ductus arteriosus, and ASD features. Our report strengthens the hypothesis that TBL1XR1 variants coding for the TBL1XR1 protein other than p.Tyr446Cys might be more commonly associated with a neurobehavioral phenotype and autistic tendencies.

An animal model for Pierpont syndrome: a mouse bearing the Tbl1xr1Y446C/Y446C mutation.

Pierpont syndrome is a rare disorder characterized mainly by global developmental delay, unusual facial features, altered fat distribution in the limbs and hearing loss. A specific mutation (p.Tyr446Cys) in TBL1XR1, encoding a WD40 repeat-containing protein, which is a component of the SMRT/NCoR (silencing mediator retinoid and thyroid hormone receptors/nuclear receptor corepressors), has been reported as the genetic cause of Pierpont syndrome. Here, we used CRISPR-cas9 technology to generate a mutant mouse with the Y446C mutation in Tbl1xr1, which is also present in Pierpont syndrome. Several aspects of the phenotype were studied in the mutant mice: growth, body composition, hearing, motor behavior, thyroid hormone state and lipid and glucose metabolism. The mutant mice (Tbl1xr1Y446C/Y446C) displayed delayed growth, altered body composition with increased relative lean mass and impaired hearing. Expression of several genes involved in fatty acid metabolism differed in white adipose tissue, but not in liver or muscle of mutant mice compared to wild-type mice (Tbl1xr1+/+). No difference in thyroid hormone plasma concentrations was observed. Tbl1xr1Y446C/Y446C mice can be used as a model for distinct features of Pierpont syndrome, which will enable future studies on the pathogenic mechanisms underlying the various phenotypic characteristics.

EP196: Phenotypic and genotypic heterogeneity related to gene defects in TBL1XR1

Genetic causes of common neurologic conditions, such as autism and developmental delay, are increasingly recognized. The widespread availability of genetic testing has led to the identification of numerous monogenic origins of these prevalent disorders. Despite these advances, relatively few causative genes have been studied systematically and fully characterized. The gene TBL1XR1 regulates transcriptional activities as part of the nuclear receptor corepressor (NCoR) complex. TBL1XR1 was first implicated as the genetic basis for Pierpont Syndrome, a rare disorder characterized by developmental delay, epilepsy, and characteristic dysmorphic features including abnormal subcutaneous fat distribution with prominent plantar and digital fat pads and deep palmar and plantar grooves with “pillowing” of the palms and soles, along with microcephaly, midface hypoplasia, other facial anomalies, and short stature.

Pierpont syndrome due to mutation c.1337A>G in TBL1XR1 gene.

Tesarova, Marketaa; Baxova, Aliceb; Hansikova, Hanaa; Lambert, Lukasc; Vondrackova, Alzbetaa; Leiska, Alenac; Zeman, Jiria Author Information

10. New evidence for triplosensitivity of TBL1XR1

Transducin-beta-like 1 receptor 1 (TBL1XR1), encoded on chromosome 3 at q26.32, is a WD40 domain-containing protein with roles in both transcriptional activation and repression. Missense and loss-of-function sequence variants in TBL1XR1 have been identified in individuals with autism, developmental delay, and/or intellectual disability, as well as Pierpont syndrome, characterized by distinctive facial features, global developmental delay, learning disability, and palmer and plantar fat pads. Additionally, microdeletions involving TBL1XR1 are associated with autosomal dominant intellectual disability with nonspecific dysmorphic facial features.

Pierpont syndrome associated with the p.Tyr446Cys missense mutation in TBL1XR1

We present a 7-year old male with severe delays, hypotonia and dysmorphic features who had striking, deep palmar and plantar creases and pillowing of the soft tissues of the palms and soles. His facial features included a high anterior hairline, small eyes with narrowed palpebral fissures, a bulbous nasal tip with a short columella, and a large mouth with a thin upper vermilion, and small chin. He had a submucous cleft palate, bilateral cryptorchidism and hydronephrosis. Cranial imaging demonstrated an Arnold Chiari malformation that was also present in his maternal uncle by report. Exome sequencing revealed a de novo heterozygous sequence variant, p.Tyr446Cys, in TBL1XR1 that has previously been reported in six patients with Pierpont syndrome. This sequence variant occurs in the carboxy-terminal, WD40 domain of the protein. As TBL1XR1 is a critical component of the NCoR/SMRT co-repressor complex and the WD40 repeats are hypothesized to interact with histone H2B and H4, the mutation may impact protein interactions necessary for stabilizing the complex with chromatin. De novo missense and frameshift mutations and deletions involving TBL1XR1 have been described in patients with intellectual disability and autism, but without any of the dysmorphic findings or malformations associated with Pierpont syndrome, implying a mutation-specific mechanism for the pathogenicity of p.Tyr446Cys. Our case is the first individual with this mutation to have a submucous cleft palate and hydronephrosis, although his severe delays, hypotonia, dysmorphic findings and emerging scoliosis appear consistent with previous reports. His distinctive facial and digital features are further evidence that p.Tyr446Cys results in a clinically recognizable, syndromic form of intellectual disability in contrast to other TBL1XR1 mutations.

A heritable microduplication encompassing TBL1XR1 causes a genomic sister-disorder for the 3q26.32 microdeletion syndrome.

Recently, a new syndrome with intellectual disability (ID) and dysmorphic features due to deletions or point mutations within the TBL1XR1 gene located in the chromosomal band 3q26.32 has been described (MRD41, OMIM 616944). One recurrent point mutation in the TBL1XR1 gene has been identified as the cause of Pierpont syndrome (OMIM 602342), a distinct intellectual disability syndrome with plantar lipomatosis. In addition, different de novo point mutations in the TBL1XR1 gene have been found in patients with autism spectrum disorders (ASD) and intellectual disability. Here, we report four patients from two unrelated families in whom array-CGH analysis and real-time quantitative PCR of genomic DNA revealed a TBL1XR1-microduplication. Adjacent genes were not affected. The microduplication occurred as a de novo event in one patient, whereas the other three cases occurred in two generations of a second, unrelated family. We compare and contrast the clinical findings in TBL1XR1 microdeletion, point mutation, and microduplication cases and expand the TBL1XR1-associated phenotypic spectrum. ID, hearing loss, and ASD are common features of TBL1XR1-associated diseases. Our clinical observations add to the increasing evidence of the role of TBL1XR1 in brain development, and they simultaneously demonstrate that different genetic disease mechanisms affecting TBL1XR1 can lead to similar ID phenotypes. The TBL1XR1-microduplication syndrome is an intellectual disability/learning disability syndrome with associated incomplete penetrance ASD, hearing loss, and delay of puberty. Its phenotypic overlap indicates that it is a genomic sister-disorder to the 3q26.32 microdeletion syndrome.

A specific mutation in TBL1XR1 causes Pierpont syndrome

BackgroundThe combination of developmental delay, facial characteristics, hearing loss and abnormal fat distribution in the distal limbs is known as Pierpont syndrome. The aim of the present study was to...

Choroid plexus papilloma and Pierpont syndrome

The authors describe the case of a child who presented with hydrocephalus and phenotypic features characteristic of a multiple congenital anomalies/mental retardation syndrome. Dysmorphic facies, medial plantar lipomatosis, and developmental delay were observed in this case and are identical to documented findings of Pierpont syndrome diagnosed in 3 boys. This is the fourth case reported to date and is the first documented case of an oncological process- an intraventricular atypical choroid plexus papilloma tumor-found in association with Pierpont syndrome. Syndromes associated with choroid plexus papilloma are reviewed.

Pierpont syndrome: A collaborative study

Pierpont syndrome is a multiple congenital anomaly syndrome with learning disability first described in 1998. There are only three patients with Pierpont syndrome who have previously been published in the literature. Details of a series of patients with features of this condition were therefore obtained retrospectively to better characterize its key features. These patients were noted to have distinctive shared facial characteristics, in addition to plantar fat pads and other limb abnormalities. Further individuals with equally striking hand and foot findings were identified whose facies were less characteristic, and hence we considered them unlikely to be affected with the same condition. Despite several patients with possible Pierpont syndrome having had high-resolution array CGH or SNP array, the etiology of this phenotype remains unknown. Whilst it is as yet unclear whether it is a single entity, there appears to be a group of patients in whom Pierpont syndrome may be a recognizable condition, with typical facies, particularly when smiling, and characteristic hand and foot findings. © 2011 Wiley-Liss, Inc.

Further case of microdeletion of 8q24 with phenotype overlapping Langer–Giedion without TRPS1 deletion

Langer-Giedion syndrome results from a microdeletion at 8q24.1 encompassing the EXT1 and the adjacent TRPS1 gene. We report on a boy with an oligo array-cgh characterized small microdeletion involving EXT1 alone but with some features of Langer-Giedion syndrome suggesting a functional disturbance of TRPS1. This boy, in addition to a mild Langer-Giedion like phenotype, also had some unusual features including prominent toe pads and fat pads on the soles of his feet similar to those described in Pierpont syndrome.

Plantar lipomatosis, unusual facies, and developmental delay: Confirmation of Pierpont syndrome

In 1998, Pierpont et al. reported on two unrelated boys with plantar lipomatosis, unusual facial phenotype, and developmental delay as a possible new MR/MCA syndrome. Here we report on a 2-year-old boy with similar manifestations: axial hypotonia in the first few months, prolonged feeding problems, moderate developmental delay, no speech development, deep palmar and plantar grooves, fat pads at the anteromedial aspect of the heels, and a distinct facial phenotype (high forehead, high anterior hairline, mild midfacial hypoplasia, remarkably narrow and upward slanted palpebral fissures, broad nasal ridge and tip, broad philtrum, bowed upper lip, "pouting" lower lip, full cheeks, and flat occiput). Brain MRI and MR spectroscopy studies showed relatively small frontal lobes, some widening of the lateral and third ventricles, and increased choline levels in the frontal white matter. Cytogenetic studies in lymphocytes and skin fibroblasts and whole genome micro-array CGH failed to show abnormalities. The present patient has a phenotype almost identical to that of the earlier reported children (Pierpont et al. [1998]: Am J Med Genet 75:18-21), which thereby validates this as a separate MR/MCA syndrome, appropriately designated Pierpont syndrome. The cause of the entity remains uncertain, the most likely etiologies being X-linked recessive or autosomal dominant genes.