Fetal phenotype of Rubinstein-Taybi syndrome caused by CREBBP mutations

Diagnosis and management in Rubinstein-Taybi syndrome: first international consensus statement

Rubinstein-Taybi syndrome (RTS) is an archetypical genetic syndrome that is characterised by intellectual disability, well-defined facial features, distal limb anomalies and atypical growth, among numerous other signs and symptoms. It is caused by variants in either of two genes (CREBBP, EP300) which encode for the proteins CBP and p300, which both have a function in transcription regulation and histone acetylation. As a group of international experts and national support groups dedicated to the syndrome, we realised that marked heterogeneity currently exists in clinical and molecular diagnostic approaches and care practices in various parts of the world. Here, we outline a series of recommendations that document the consensus of a group of international experts on clinical diagnostic criteria for types of RTS (RTS1: CREBBP; RTS2: EP300), molecular investigations, long-term management of various particular physical and behavioural issues and care planning. The recommendations as presented here will need to be evaluated for improvements to allow for continued optimisation of diagnostics and care.

CBP-HSF2 structural and functional interplay in Rubinstein-Taybi neurodevelopmental disorder

Patients carrying autosomal dominant mutations in the histone/lysine acetyl transferases CBP or EP300 develop a neurodevelopmental disorder: Rubinstein-Taybi syndrome (RSTS). The biological pathways underlying these neurodevelopmental defects remain elusive. Here, we unravel the contribution of a stress-responsive pathway to RSTS. We characterize the structural and functional interaction between CBP/EP300 and heat-shock factor 2 (HSF2), a tuner of brain cortical development and major player in prenatal stress responses in the neocortex: CBP/EP300 acetylates HSF2, leading to the stabilization of the HSF2 protein. Consequently, RSTS patient-derived primary cells show decreased levels of HSF2 and HSF2-dependent alteration in their repertoire of molecular chaperones and stress response. Moreover, we unravel a CBP/EP300-HSF2-N-cadherin cascade that is also active in neurodevelopmental contexts, and show that its deregulation disturbs neuroepithelial integrity in 2D and 3D organoid models of cerebral development, generated from RSTS patient-derived iPSC cells, providing a molecular reading key for this complex pathology.

Rubinstein-Taybi Syndrome: Presentation in the First Month of Life

This web-based survey of 311 respondents from 25 countries provides additional information about the early presentation of Rubinstein-Taybi syndrome. Most (86%) infants present during the neonatal period, with 69% of these within 24 hours of life. Prolonged hospital stay is common (61%).

Rubinstein-Taybi Syndrome: A Model of Epigenetic Disorder

The Rubinstein-Taybi syndrome (RSTS) is a rare congenital developmental disorder characterized by a typical facial dysmorphism, distal limb abnormalities, intellectual disability, and many additional phenotypical features. It occurs at between 1/100,000 and 1/125,000 births. Two genes are currently known to cause RSTS, CREBBP and EP300, mutated in around 55% and 8% of clinically diagnosed cases, respectively. To date, 500 pathogenic variants have been reported for the CREBBP gene and 118 for EP300. These two genes encode paralogs acting as lysine acetyltransferase involved in transcriptional regulation and chromatin remodeling with a key role in neuronal plasticity and cognition. Because of the clinical heterogeneity of this syndrome ranging from the typical clinical diagnosis to features overlapping with other Mendelian disorders of the epigenetic machinery, phenotype/genotype correlations remain difficult to establish. In this context, the deciphering of the patho-physiological process underlying these diseases and the definition of a specific episignature will likely improve the diagnostic efficiency but also open novel therapeutic perspectives. This review summarizes the current clinical and molecular knowledge and highlights the epigenetic regulation of RSTS as a model of chromatinopathy.

Introduction of a de novo Creb-binding protein gene mutation in sperm to produce a Rubinstein-Taybi syndrome model using inbred C57BL/6 mice

Neurodevelopmental disorders, including intellectual disability and autism spectrum disorder, are often caused by de novo autosomal dominant mutations. While mouse models are frequently used to investigate these disorders, the genetic background sometimes affects the appearance or severity of mutant phenotypes. In a previous report, we developed a system to produce de novo heterozygous mutant mice using the Cre-LoxP system without the need to maintain the heterozygous mutant line itself (Takagi et al. 2015). To further verify the applicability of the de novo mutation system in sperm, we used this system to produce a mouse model for Rubinstein-Taybi syndrome, using a Cbp heterozygous mutant, which has been reported to be difficult to maintain on a C57BL/6 background. Here, we show that de novo Cbp- loss-of-function heterozygous mutant mice with a C57BL/6 background, present with a clear craniofacial phenotype and reduced locomotor activity in the open field test, which was not observed in the loss-of-function of Cbp heterozygous mutant line mice with a mixed genetic background, but was observed in the dominant negative Cbp heterozygous mutant line with a mixed genetic background. Meanwhile, the de novo heterozygous Cbp mutant mice still showed great variability in survival rates despite their inbred background. These results further confirmed that the de novo mutation system used in germ cells is effective for stable production and analysis of an autosomal dominant disorder mouse model, which is often difficult to maintain as a mutant mouse line.

Ultrasound 2-D and 3-D diagnosis of Rubinstein-Taybi syndrome in a 21-week-old fetus

Rubinstein-Taybi syndrome is a rare genetic multisystem disorder with an estimated prevalence between 1 per 100,000-125,000 live births. Diagnosis is usually clinical and subsequent to birth. In fact, the rarity of the syndrome and the presence of aspecific morphologic anomalies make prenatal diagnosis challenging. The aim of our work is to analyze ultrasonographic findings, detectable with a combination of 2D and 3D techniques, which may increase the sensitivity of in utero diagnosis of this condition. We report a case of a sonographic prenatal diagnosis of broad and angulated thumbs and halluces and of an abnormal ductus venosus at 21 weeks of gestational age. These findings allowed us to suspect Rubinstein-Taybi syndrome. An accurate ultrasonographic examination may allow a prenatal diagnosis of those syndromes which are usually diagnosed after birth.

A long non-coding RNA LNBC3 facilitates non-small cell lung cancer progression by stabilizing BCL6

Background

The non‐small cell lung cancer (NSCLC) is a common malignancy worldwide. Numerous reports have shown the critical role of long non‐coding RNAs (lncRNAs) in NSCLC. However, the role of a novel lncRNA named LNBC3 is still unknown.

Methods

By lncRNA profiling, novel lncRNAs related to NSCLC were identified. LNBC3 expression was quantified by qRT‐PCR. Migration and viability assays were performed to evaluate the function of LNBC3 in vitro. In vivo xenograft model was conducted to determine the oncogenic functions of LNBC3. RNA immunoprecipitation (RIP) followed by mass spectrometry (MS) was utilized to identify BCL6 as LNBC3 binding target.

Results

LNBC3 is markedly overexpressed in tumor tissues and NSCLC cell lines. Higher LNBC3 levels correlated with advanced TNM stages, larger tumor size, and metastasis. LNBC3 promoted NSCLC migration and viability. The in vivo experiments demonstrated that xenograft tumor growth and proliferation were facilitated with increasing LNBC3 levels. The antisense oligonucleotides (ASOs) targeting LNBC3 substantially inhibited lung cancer progression. Mechanistic studies showed that LNBC3 could interact with BCL6 leading to BCL6 stabilization through reduced proteasomal degradation.

Conclusions

Collectively, our data have identified a novel lncRNA LNBC3 in NSCLC progression. The LNBC3‐BCL6 axis might be a potential target for pharmaceutical intervention.