Oculo-facio-cardio-dental (OFCD) syndrome: The first Italian case of BCOR and co-occurring OTC gene deletion

Genetic Alterations in a Large Population of Italian Patients Affected by Neurodevelopmental Disorders

Neurodevelopmental disorders are a group of complex multifactorial disorders characterized by cognitive impairment, communication deficits, abnormal behaviour, and/or motor skills resulting from abnormal neural development. Copy number variants (CNVs) are genetic alterations often associated with neurodevelopmental disorders. We evaluated the diagnostic efficacy of the array-comparative genomic hybridization (a-CGH) method and its relevance as a routine diagnostic test in patients with neurodevelopmental disorders for the identification of the molecular alterations underlying or contributing to the clinical manifestations. In the present study, we analysed 1800 subjects with neurodevelopmental disorders using a CGH microarray. We identified 208 (7%) pathogenetic CNVs, 2202 (78%) variants of uncertain significance (VOUS), and 504 (18%) benign CNVs in the 1800 patients analysed. Some alterations contain genes potentially related to neurodevelopmental disorders including CHRNA7, ANKS1B, ANKRD11, RBFOX1, ASTN2, GABRG3, SHANK2, KIF1A SETBP1, SNTG2, CTNNA2, TOP3B, CNTN4, CNTN5, and CNTN6. The identification of interesting significant genes related to neurological disorders with a-CGH is therefore an essential step in the diagnostic procedure, allowing a better understanding of both the pathophysiology of these disorders and the mechanisms underlying their clinical manifestations.

Oculo-facio-cardio-dental (OFCD) syndrome: a case report

BACKGROUND

Oculo-facio-cardio-dental (OFCD) syndrome is a rare condition that affects the eyes, face, heart, and teeth of patients. One notable dental characteristic of OFCD is radiculomegaly, or root gigantism, which highlights the role of dentists in detecting this syndrome. OFCD is an X-linked dominant syndrome that results from a variant in the BCOR gene. Our study presents the first documented case of OFCD in Vietnam and reports a novel BCOR gene variant observed in this case.

CASE PRESENTATION

A 19-year-old Vietnamese female patient with an extremely long root with an abscess was clinically examined for the expression of OFCDs. The radiograph and the variant in BCOR gene were also evaluated. We identified abnormalities in the teeth, as well as ocular, facial, and cardiac features, with radiculomegaly of the canines being a specific symptom for OFCDs. The patient's genetic analysis revealed a pathogenic heterozygous deletion at intron 11 of the BCOR gene, representing a novel variant.

CONCLUSION

Oculo-facio-cardio-dental syndrome (OFCD) is an extremely rare condition characterized by abnormalities in the eyes, face, heart, and teeth, often caused by variants in the BCOR gene. Radiculomegaly, or enlarged dental roots, is a key diagnostic feature of OFCD, and early detection is crucial for preventing future dental complications.

D-aspartate oxidase gene duplication induces social recognition memory deficit in mice and intellectual disabilities in humans

The D-aspartate oxidase (DDO) gene encodes the enzyme responsible for the catabolism of D-aspartate, an atypical amino acid enriched in the mammalian brain and acting as an endogenous NMDA receptor agonist. Considering the key role of NMDA receptors in neurodevelopmental disorders, recent findings suggest a link between D-aspartate dysmetabolism and schizophrenia. To clarify the role of D-aspartate on brain development and functioning, we used a mouse model with constitutive Ddo overexpression and D-aspartate depletion. In these mice, we found reduced number of BrdU-positive dorsal pallium neurons during corticogenesis, and decreased cortical and striatal gray matter volume at adulthood. Brain abnormalities were associated with social recognition memory deficit at juvenile phase, suggesting that early D-aspartate occurrence influences neurodevelopmental related phenotypes. We corroborated this hypothesis by reporting the first clinical case of a young patient with severe intellectual disability, thought disorders and autism spectrum disorder symptomatology, harboring a duplication of a chromosome 6 region, including the entire DDO gene.

Identification of a De Novo Deletion by Using A-CGH Involving PLNAX2: An Interesting Candidate Gene in Psychomotor Developmental Delay

Psychomotor developmental delay is a disorder with a prevalence of 12–18% in the pediatric population, characterized by the non-acquisition of motor, cognitive and communication skills during the child’s development, in relation to chronological age. An appropriate neuropsychomotor evaluation and the use of new technologies, such as Array Comparative Genomic Hybridization (a-CGH) and Next-generation sequencing (NGS), can contribute to early diagnosis and improving the quality of life. In this case, we have analyzed a boy aged 2 years and 8 months, with a diagnosis of psychomotor developmental delay, mainly in the area of communication and language. The a-CGH analysis identified three de novo deletions of uncertain clinical significance, involving PLXNA2 (1q32.2), PRELID2, GRXCR2 and SH3RF2 (5q32), RIMS1 (6q13), and a heterozygous duplication of maternal origin involved three genes: HELZ, PSMD12 and PITPNC1 (17q24.2). Among all these alterations, our attention focused on the PLXNA2 gene because of the central function that plexin 2 carries out in the development of the central nervous system. However, all genes detected in the analysis could contribute to the phenotypic characteristics of the patient.

Combined aCGH and Exome Sequencing Analysis Improves Autism Spectrum Disorders Diagnosis: A Case Report

Background and Objectives: The development and standardization of genome-wide technologies able to carry out high-resolution, genomic analyses in a cost- and time-affordable way is increasing our knowledge regarding the molecular bases of complex diseases like autism spectrum disorder (ASD). ASD is a group of heterogeneous diseases with multifactorial origins. Genetic factors seem to be involved, albeit they remain still largely unknown. Here, we report the case of a child with a clinical suspicion of ASD investigated by using such a genomic high-resolution approach. Materials and Methods: Both array comparative genomic hybridization (aCGH) and exome sequencing were carried out on the family trio. aCGH was performed using the 4 × 180 K SurePrint G3 Human CGH Microarray, while the Human All Exon V7 targeted SureSelect XT HS panel was used for exome sequencing. Results: aCGH identified a paternally inherited duplication of chromosome 7 involving the CNTNAP2 gene, while 5 potentially clinically-relevant variants were identified by exome sequencing. Conclusions: Within the identified genomic alterations, the CNTNAP2 gene duplication may be related to the patient’s phenotype. Indeed, this gene has already been associated with brain development and cognitive functions, including language. The paternal origin of the alteration cannot exclude an incomplete penetrance. Moreover, other genomic factors may act as phenotype modifiers combined with CNTNAP2 gene duplication. Thus, the case reported herein strongly reinforces the need to use extensive genomic analyses to shed light on the bases of complex diseases.

A novel deletion mutation in the BCOR gene is associated with oculo-facio-cardio-dental syndrome: a case report

Background

Oculo-facio-cardio-dental syndrome is a rare X-linked dominant syndrome, characterized by radiculomegaly, congenital cataracts, dysmorphic facial features, and congenital heart disease. Because of the rarity, this syndrome could be misdiagnosed by the clinician, especially for the infant who may present only one to two systems involved.

Case presentation

Here we report a 3-month-old female infant presenting with typical clinical manifestations of oculo-facio-cardio-dental syndrome, like ocular, facial, cardiac, and skeletal abnormalities, and the genetic analyses of the proband and her parents were provided. Genetic evaluations were completed using whole exon sequencing, which revealed a novel heterozygous mutation between exons 7 and 14 of the BCOR gene(OMIM:300485) in this patient but not in her parents. This mutation is likely to encode a premature stop codon producing a truncated protein. Our patient was diagnosed early enough to allow for the cardiac defects to be treated first, and she will be closely followed up to ensure that any new presentations are treated in a timeous manner.

Conclusion

This patient fits the diagnostic criteria for oculo-facio-cardio-dental syndrome and is the youngest oculo-facio-cardio-dental syndrome patient ever reported, which is most important for her prognosis. In addition, this manuscript also describes a novel potenitally causative mutation for this syndrome.

OFCD syndrome and extraembryonic defects are revealed by conditional mutation of the Polycomb-group repressive complex 1.1 (PRC1.1) gene BCOR

BCOR is a critical regulator of human development. Heterozygous mutations of BCOR in females cause the X-linked developmental disorder Oculofaciocardiodental syndrome (OFCD), and hemizygous mutations of BCOR in males cause gestational lethality. BCOR associates with Polycomb group proteins to form one subfamily of the diverse Polycomb repressive complex 1 (PRC1) complexes, designated PRC1.1. Currently there is limited understanding of differing developmental roles of the various PRC1 complexes. We therefore generated a conditional exon 9-10 knockout Bcor allele and a transgenic conditional Bcor expression allele and used these to define multiple roles of Bcor, and by implication PRC1.1, in mouse development. Females heterozygous for Bcor exhibiting mosaic expression due to the X-linkage of the gene showed reduced postnatal viability and had OFCD-like defects. By contrast, Bcor hemizygosity in the entire male embryo resulted in embryonic lethality by E9.5. We further dissected the roles of Bcor, focusing on some of the tissues affected in OFCD through use of cell type specific Cre alleles. Mutation of Bcor in neural crest cells caused cleft palate, shortening of the mandible and tympanic bone, ectopic salivary glands and abnormal tongue musculature. We found that defects in the mandibular region, rather than in the palate itself, led to palatal clefting. Mutation of Bcor in hindlimb progenitor cells of the lateral mesoderm resulted in 2/3 syndactyly. Mutation of Bcor in Isl1-expressing lineages that contribute to the heart caused defects including persistent truncus arteriosus, ventricular septal defect and fetal lethality. Mutation of Bcor in extraembryonic lineages resulted in placental defects and midgestation lethality. Ubiquitous over expression of transgenic Bcor isoform A during development resulted in embryonic defects and midgestation lethality. The defects we have found in Bcor mutants provide insights into the etiology of the OFCD syndrome and how BCOR-containing PRC1 complexes function in development.

Genetic analysis resolves differential diagnosis of a familial syndromic dilated cardiomyopathy: A new case of Alström syndrome

BACKGROUND

Syndromic dilated cardiomyopathy (DCM) includes a group of complex disorders with a very heterogeneous genetic etiology, leading to delay in definitive diagnosis. Conversely, an early genetic diagnosis is very important in determining the disease course, the prognosis, and may guide personalized treatments and family counseling.

METHODS

We analyzed two brothers with a multisystemic disorder, including dilated cardiomyopathy, diabetes, bilateral neurosensorial hearing loss, and optic atrophy, using different genetic approaches, namely mitochondrial DNA sequencing, comparative genomic hybridization-array (a-CGH) and whole exome sequencing (WES).

RESULTS

Sequencing of the wide mitochondrial genome revealed, in both brothers, the known homoplasmic variant rs2853826 in the subunit 3 of the NADH dehydrogenase gene (MT-ND3), whose pathogenicity was conflicting. Comparative genomic hybridization-array analysis revealed in both patients and their father two heterozygous deletions in Phosphodiesterase 4d-Interacting Protein (PDE4DIP) and Protocadherin-related 15 (PCDH15) genes, respectively. The use of WES detected a pathogenetic mutation in ALMS1, enabling the definitive diagnosis of Alström syndrome.

CONCLUSION

We demonstrated how the diagnosis of a complex heterogeneous disease may be difficult, due to several overlapping manifestations and the possible interaction of more genetic variants that could lead to a more severe and complex phenotype. This paper strongly evidences how genomics is revolutionizing the diagnosis of rare complex disease, representing one of the most essential steps to enable a definitive diagnosis and to establish the etiology for diseases, such as syndromic DCM.

Expression of Normal or Mutated X-Linked BCOR Transcripts in OFCD iPSCs

Reprogramming diseased cells with mutated genes into induced pluripotent stem cells (iPSCs) can allow studies of disease mechanism and correct the mutation. Oculofaciocardiodental (OFCD) syndrome is a developmental disorder caused by heterozygous mutations in the X-linked BCL-6 corepressor (BCOR) gene. In this present study, we aimed to reprogram stem cells from a tooth apical papilla (SCAP) of a patient with OFCD, termed SCAP-O, into iPSCs. The SCAP-O carry a copy of the BCOR gene having 1 nucleotide deletion in 1 of the alleles, therefore harboring a mixture of cells expressing either normal (SCAP-O^BCOR-WT) or mutated (SCAP-O^BCOR-mut) BCOR transcripts. We subcloned SCAP-O and separated SCAP-O^BCOR-WT and SCAP-O^BCOR-mut as verified by sequencing. The selected subclone SCAP-O^BCOR-mut expressed only the mutated BCOR transcripts and remained in such condition after multiple passages. We reprogrammed SCAP-O and subclone SCAP-O^BCOR-mut into transgene-free iPSCs using an excisable lentiviral vector system (hSTEMCCA-loxP) carrying 4 reprogramming factors in a single cassette, followed by removal of transgenes via Cre-mediated excision. We found that after reprogramming SCAP-O or subclone SCAP-O^BCOR-mut into iPSCs, some of the iPSC clones expressed either solely the normal BCOR-WT or BCOR-mut transcripts, while other clones expressed both BCOR-WT and BCOR-mut transcripts. This is our first step toward establishing OFCD study models by generating isogenic control BCOR-WT iPSCs versus BCOR-mut iPSCs.

Congenital cataracts in females caused by BCOR mutations; report of six further families demonstrating clinical variability and diverse genetic mechanisms

BACKGROUND

Pathogenic variants in the BCOR gene have been identified in males with X-linked recessive microphthalmia and in females with X-linked dominant oculofaciocardiodental (OFCD) syndrome. This latter condition has previously been regarded as rare but the increased availability of genetic testing in recent years has led to the identification of a greater number of patients.

METHODS

We report the clinical and molecular findings in a series of 10 patients with pathogenic BCOR variants from 5 families, all seen in a single institution over a two year period.

RESULTS

We emphasize the phenotypic variability in this cohort and the diverse genetic mechanisms involved which included point mutations and deletions of BCOR as well as the occurrence of gonadal and somatic mosaicism.

CONCLUSION

In this report we demonstrate the novel findings of four newly identified variants in BCOR associated with an OFCD phenotype, and suggest that the frequency of this condition in females presenting with congenital cataract, including unilateral cataract, is more common than anticipated. We demonstrate the utility of screening for genetic causes of congenital cataract. Although gonadal mosaicism in OFCD had previously been reported, we demonstrate the presence of somatic mosaicism where BCOR mutations may only be detected in DNA from tissues other than blood such as buccal cells.

A novel deletion mutation, c.1296delT in the BCOR gene, is associated with oculo-facio-cardio-dental syndrome

The purpose of the present study was to analyze the clinical phenotypes of a girl with oculo-facio-cardio-dental (OFCD) syndrome and to identify the potential pathogenic mutation responsible for her disease. The patient underwent detailed clinical examinations and phenotype data were collected over a follow-up period of 9 years. Mutation analysis of the candidate gene BCOR was performed with polymerase chain reaction and Sanger sequencing. BCOR of 60 unrelated normal individuals were also sequenced as a control group. Clinical phenotyping and follow-up study results indicate that this patient had multiple system anomalies including ocular, facial, cardiac, dental, and limb malformations. In addition, papilloma of the choroid plexus was identified, which represents the first report of this phenotype in an OFCD patient. A novel deletion mutation, c.1296delT in exon 4 of the BCOR gene, was identified in this patient and was not found in her parents or in 60 normal unrelated individuals. This deletion was a frameshift mutation and is proposed to encode a premature stop codon, thus producing a truncated protein. Our patient fitted the diagnostic criteria for OFCD syndrome and we report the first papilloma of the choroid plexus in an OFCD patient, expanding the recognized phenotypic spectrum of this disease. Meanwhile, we identified a novel deletion mutation that may cause OFCD syndrome.

Expanding the phenotype of the X-linked BCOR microphthalmia syndromes

Two distinct syndromes arise from pathogenic variants in the X-linked gene BCOR (BCL-6 corepressor): oculofaciocardiodental (OFCD) syndrome, which affects females, and a severe microphthalmia ('Lenz'-type) syndrome affecting males. OFCD is an X-linked dominant syndrome caused by a variety of BCOR null mutations. As it manifests only in females, it is presumed to be lethal in males. The severe male X-linked recessive microphthalmia syndrome ('Lenz') usually includes developmental delay in addition to the eye findings and is caused by hypomorphic BCOR variants, mainly by a specific missense variant c.254C > T, p.(Pro85Leu). Here, we detail 16 new cases (11 females with 4 additional, genetically confirmed, affected female relatives; 5 male cases each with unaffected carrier mothers). We describe new variants and broaden the phenotypic description for OFCD to include neuropathy, muscle hypotonia, pituitary underdevelopment, brain atrophy, lipoma and the first description of childhood lymphoma in an OFCD case. Our male X-linked recessive cases show significant new phenotypes: developmental delay (without eye anomalies) in two affected half-brothers with a novel BCOR variant, and one male with high myopia, megalophthalmos, posterior embryotoxon, developmental delay, and heart and bony anomalies with a previously undescribed BCOR splice site variant. Our female OFCD cases and their affected female relatives showed variable features, but consistently had early onset cataracts. We show that a mosaic carrier mother manifested early cataract and dental anomalies. All female carriers of the male X-linked recessive cases for whom genetic confirmation was available showed skewed X-inactivation and were unaffected. In view of the extended phenotype, we suggest a new term of X-linked BCOR-related syndrome.

Ocular findings in a patient with oculofaciocardiodental (OFCD) syndrome and a novel BCOR pathogenic variant

PURPOSE

To report a case of OFCD associated with a de novo BCOR pathogenic variant and highlight the ocular findings and possible mechanisms.

METHODS

A retrospective chart review of the patient's ocular and systemic findings was performed. The patient underwent diagnostic whole exome sequencing (WES).

RESULTS

The patient had a comprehensive eye exam in infancy demonstrating bilateral congenital cataracts consisting of posterior lenticonus with a posterior cortical opacity. She also had blepharoptosis with a hooded appearance and retinal pigment hypertrophy of the inferior retina bilaterally. Systemic findings include atrial septal defect, patent ductus arteriosus, congenital clubfoot, syndactyly, tethered cord, and laryngeal cleft. WES identified a de novo heterozygous R1136X pathogenic variant in the BCOR gene.

CONCLUSION

The typical ocular manifestation of OFCD syndrome is congenital cataracts, which can have a significant impact on visual development and so should be considered in patients with multiple medical issues that may fit the diagnosis. A comprehensive eye exam in these patients is thus warranted.

Histone lysine methylation and congenital heart disease: From bench to bedside (Review)

Histone post-translational modifications (PTM) as one of the key epigenetic regulatory mechanisms that plays critical role in various biological processes, including regulating chromatin structure dynamics and gene expression. Histone lysine methyltransferase contributes to the establishment and maintenance of differential histone methylation status, which can recognize histone methylated sites and build an association between these modifications and their downstream processes. Recently, it was found that abnormalities in the histone lysine methylation level or pattern may lead to the occurrence of many types of cardiovascular diseases, such as congenital heart disease (CHD). In order to provide new theoretical basis and targets for the treatment of CHD from the view of developmental biology and genetics, this review discusses and elaborates on the association between histone lysine methylation modifications and CHD.