Prevalence of Immunological Defects in a Cohort of 97 Rubinstein-Taybi Syndrome Patients

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.

Chromatinopathies: insight in clinical aspects and underlying epigenetic changes

Chromatinopathies (CPs), a group of rare inborn defects characterized by chromatin state imbalance, have evolved from initially resembling Cornelia de Lange syndrome to encompass a wide array of genetic diseases with diverse clinical presentations. The CPs classification now includes human developmental disorders caused by germline mutations in epigenes, genes that regulate the epigenome. Recent advances in next-generation sequencing have enabled the association of 154 epigenes with CPs, revealing distinctive DNA methylation patterns known as episignatures.It has been shown that episignatures are unique for a particular CP or share similarities among specific CP subgroup. Consequently, these episignatures have emerged as promising biomarkers for diagnosing and treating CPs, differentiating subtypes, evaluating variants of unknown significance, and facilitating targeted therapies tailored to the underlying epigenetic dysregulation.The following review was conducted to collect, summarize, and analyze data regarding CPs in such aspects as clinical evaluation encompassing long-term patient care, underlying epigenetic changes, and innovative molecular and bioinformatic methodologies that have been devised for the assessment of CPs. We have also shed light on promising novel treatment options that have surfaced in recent research and presented a synthesis of ongoing clinical trials, contributing to the current understanding of the dynamic and evolving nature of CPs investigation.

Antibody Deficiency in Patients with Biallelic KARS1 Mutations

Biallelic KARS1 mutations cause KARS-related diseases, a rare syndromic condition encompassing central and peripheral nervous system impairment, heart and liver disease, and deafness. KARS1 encodes the t-RNA synthase of lysine, an aminoacyl-tRNA synthetase, involved in different physiological mechanisms (such as angiogenesis, post-translational modifications, translation initiation, autophagy and mitochondrial function). Although patients with immune-hematological abnormalities have been individually described, results have not been collectively discussed and functional studies investigating how KARS1 mutations affect B cells have not been performed. Here, we describe one patient with severe developmental delay, sensoneurinal deafness, acute disseminated encephalomyelitis, hypogammaglobulinemia and recurrent infections. Pathogenic biallelic KARS1 variants (Phe291Val/ Pro499Leu) were associated with impaired B cell metabolism (decreased mitochondrial numbers and activity). All published cases of KARS-related diseases were identified. The corresponding authors and researchers involved in the diagnosis of inborn errors of immunity or genetic syndromes were contacted to obtain up-to-date clinical and immunological information. Seventeen patients with KARS-related diseases were identified. Recurrent/severe infections (9/17) and B cell abnormalities (either B cell lymphopenia [3/9], hypogammaglobulinemia [either IgG, IgA or IgM; 6/15] or impaired vaccine responses [4/7]) were frequently reported. Immunoglobulin replacement therapy was given in five patients. Full immunological assessment is warranted in these patients, who may require detailed investigation and specific supportive treatment.

Common Variable Immunodeficiency: More Pathways than Roads to Rome

Fifty years have elapsed since the term common variable immunodeficiency (CVID) was introduced to accommodate the many and varied antibody deficiencies being identified in patients with suspected inborn errors of immunity (IEIs). Since then, how the term is understood and applied for diagnosis and management has undergone many revisions, though controversy persists on how exactly to define and classify CVID. Many monogenic disorders have been added under its aegis, while investigations into polygenic, epigenetic, and somatic contributions to CVID susceptibility have gained momentum. Expansion of the overall IEI landscape has increasingly revealed genotypic and phenotypic overlap between CVID and various other immunological conditions, while increasingly routine genotyping of CVID patients continues to identify an incredible diversity of pathophysiological mechanisms affecting even single genes. Though many questions remain to be answered, the lessons we have already learned from CVID biology have greatly informed our understanding of adaptive, but also innate, immunity.

B Cells at the Cross-Roads of Autoimmune Diseases and Auto-Inflammatory Syndromes

Whereas autoimmune diseases are mediated primarily by T and B cells, auto-inflammatory syndromes (AIFS) involve natural killer cells, macrophages, mast cells, dendritic cells, different granulocyte subsets and complement components. In contrast to autoimmune diseases, the immune response of patients with AIFS is not associated with a breakdown of immune tolerance to self-antigens. Focusing on B lymphocyte subsets, this article offers a fresh perspective on the multiple cross-talks between both branches of innate and adaptive immunity in mounting coordinated signals that lead to AIFS. By virtue of their potential to play a role in adaptive immunity and to exert innate-like functions, B cells can be involved in both promoting inflammation and mitigating auto-inflammation in disorders that include mevalonate kinase deficiency syndrome, Kawasaki syndrome, inflammatory bone disorders, Schnitzler syndrome, Neuro-Behçet's disease, and neuromyelitis optica spectrum disorder. Since there is a significant overlap between the pathogenic trajectories that culminate in autoimmune diseases, or AIFS, a more detailed understanding of their respective roles in the development of inflammation could lead to designing novel therapeutic avenues.

A Case of Common Variable Immunodeficiency with CREBP Gene Mutation without Rubinstein Taybi Syndrome Features

Hypogammaglobulinemias, based on inborn errors of immunity, are primary immunodeficiencies (PIDs) that can also be diagnosed for the first time in adulthood. Common variable immunodeficiency (CVID) is a multifactorial disease often symptomatic due to antibody deficiency. In addition, some PIDs are classified into the category of immunodeficiencies with syndromic features due to their accompanying clinical findings unrelated to immunity. In this article, a patient with CVID who was diagnosed in adulthood and who was revealed to have a mutation specific to Rubinstein–Taybi syndrome and clinical features reminiscent of this syndrome only after molecular tests was presented.

Rubinstein–Taybi Syndrome in a Filipino Infant with a Novel CREBBP Gene Pathogenic Variant

Rubinstein–Taybi syndrome (RSTS) is a rare genetic disorder characterized by dysmorphic facial features, broad thumbs and halluces, intellectual disability, and postnatal growth retardation. This report presents a male infant with microcephaly and characteristic facial features, namely, low anterior hairline, hirsutism, thin upper lip and micrognathia, broad thumbs and first toes, cryptorchidism, recurrent pneumonia, developmental delay, and growth retardation. Genetic testing showed a novel pathogenic variant in the CREBBP gene which is consistent with the clinical diagnosis of RSTS.

Genetic Diagnosis of Rubinstein–Taybi Syndrome With Multiplex Ligation-Dependent Probe Amplification (MLPA) and Whole-Exome Sequencing (WES): Case Series With a Novel CREBBP Variant

Rubinstein–Taybi Syndrome (RSTS) is a rare congenital disease with distinctive facial features, broadening of the thumbs and halluces, and developmental delay. RSTS is caused by de novo genetic alterations in CREBBP and the homologous EP300 genes. In this study, we established a genetic diagnostic protocol by integrating multiplex ligation-dependent probe amplification (MLPA) and whole-exome sequencing (WES). Five patients clinically diagnosed with RSTS were enrolled for genetic testing. Germline DNA was extracted from the peripheral blood of the patients and their families. One patient (case 1) was identified as harboring a large heterozygous deletion in the 16p13.3 region, spanning the CREBBP gene. Three patients (Cases 2–4) harbored different CREBBP variants (c.2608C>T:p.Gln870Ter,c.4404_4405del:p.Thr1468fs,c.3649C>T:p.Gln1217Ter). No causative variants were identified for the fifth RSTS patient (case 5). Here, we propose a molecular diagnostic protocol that identified causative genetic alterations in 4/5 of the patients, yielding a molecular diagnostic rate of 80%. Given the rarity of RSTS, more research is needed to explore its pathogenesis and mechanism.

Identical EP300 variant leading to Rubinstein-Taybi syndrome with different clinical and immunologic phenotype

The Rubinstein-Taybi syndrome (RSTS) is a rare developmental disorder characterized by craniofacial dysmorphisms, broad thumbs and toes, intellectual disability, growth deficiency, and recurrent infections. Mutations in the cyclic adenosine monophosphate response element-binding protein (CREB)-binding protein (CREBBP) or in the E1A-associated protein p300 (EP300) genes have been demonstrated in 55% (RSTS1) and up to 8% of the patients (RSTS2), respectively. Dysfunction of immune response has been reported in a subgroup of individuals with RSTS. Here we characterize two patients carrying the same EP300 variant and distinctive RSTS features (including congenital heart abnormalities, short stature, feeding problems, and gastroesophageal reflux). Whole exome sequencing did not support a dual molecular diagnosis hypothesis. Nonetheless, patients showed distinct clinical manifestations and immunological features. The most severe phenotype was associated with reduced T-cell production and diversity. This latter feature was confirmed in a control group of four RSTS patients.

Secondary hemophagocytic lymphohystiocytosis in a Rubinstein Taybi syndrome patient

Rubinstein-Taybi syndrome (RSTS) is an autosomal dominant disorder, caused by variants in CREBBP or EP300. Affected individuals present with distinctive craniofacial features, broad thumbs and/or halluces, intellectual disability and immunodeficiency. Here we report on one RSTS patient who experienced hemophagocytic lymphohystiocytosis (HLH) and disseminated herpes virus 1 ( HSV-1) disease. The clinical picture of RSTS is expanding to include autoinflammatory, autoimmune, and infectious complications. Prompt treatment of HLH and disseminated HSV-1 can lower the mortality rate of these life-threatening conditions.

Leveraging the Mendelian disorders of the epigenetic machinery to systematically map functional epigenetic variation

Although each Mendelian Disorder of the Epigenetic Machinery (MDEM) has a different causative gene, there are shared disease manifestations. We hypothesize that this phenotypic convergence is a consequence of shared epigenetic alterations. To identify such shared alterations, we interrogate chromatin (ATAC-seq) and expression (RNA-seq) states in B cells from three MDEM mouse models (Kabuki [KS] type 1 and 2 and Rubinstein-Taybi type 1 [RT1] syndromes). We develop a new approach for the overlap analysis and find extensive overlap primarily localized in gene promoters. We show that disruption of chromatin accessibility at promoters often disrupts downstream gene expression, and identify 587 loci and 264 genes with shared disruption across all three MDEMs. Subtle expression alterations of multiple, IgA-relevant genes, collectively contribute to IgA deficiency in KS1 and RT1, but not in KS2. We propose that the joint study of MDEMs offers a principled approach for systematically mapping functional epigenetic variation in mammals.

Identification of key miRNAs affecting broilers with valgus-varus deformity by RNA sequencing and analysis of miRNA-mRNA interactions

Valgus-varus Deformity (VVD) leg disease often affects chickens raised in modern large-scale breeding operations. Losses due to VVD are costly to farmers, and the condition also causes significant suffering in affected birds. In this study, we profiled RNAs from the spleens of VVD (BS) and healthy (JS) broilers using high-throughput sequencing to identify miRNAs that might be involved in the development of the disease. Fifty differentially expressed miRNAs (DEMs) were found, of which 30 were up-regulated and 20 were down-regulated in VVD-affected birds (|log 2 Fold Change| ≥ 1 and q-value < 0.05). DEMs were matched with putative target genes and 864 target genes were found. Gene Ontology (GO) analyses of these target genes showed that they were significantly enriched in the "cytoplasm" term (q-value < 0.05), and most of the target genes were enriched in "cellular component". Kyoto encyclopedia of genes and genomes (KEGG) analysis showed that they were significantly enriched in 11 signaling pathways (P-value < 0.05), including metabolic pathways, 2-oxocarboxylic acid metabolism, regulation of actin cytoskeleton, purine metabolism, endocytosis and so on. And we found that they were enriched in immune-related pathways in which MAPK, Notch, JAK-Stat, Toll-like receptor, p53 and other single pathways were involved in the development of skeletal diseases. Differentially expressed mRNAs obtained from our previous study were used to construct an interaction network consisting of 16 DEMs and 21 differentially expressed mRNAs (|log 2 Fold Change| ≥ 1 and q-value < 0.05). We found that miR-12247-5p, miR-15c-5p, miR-15b-5p, FKBP5 and HSP90AB1 were at the center of network interaction. This study provides a foundation for further investigations of the pathogenesis and genetic mechanisms underlying VVD.

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.