Prenatal presentation of multiple anomalies associated with haploinsufficiency for ARID1A

ARID1A: Multiple functions in human pregnancy

AT-rich interacting domain containing respectively protein 1 A (ARID1A), a key member of the SWItch/Sucrose Non-Fermentable (SWI/SNF) chromatin remodeling complex, has been shown to play an important role in various physiological processes and diseases including female reproductive tumors, such as ovarian cancer and breast cancer. In addition to the studies regarding ARID1A expression and function in cancer, recent findings elucidate its important role in maintaining normal tissue homeostasis and cell differentiation by controlling chromatin remodeling and transcription factors recruitment. In the context of human pregnancy, ARID1A has been implicated in several pregnancy-related complications, including gestational diabetes, preeclampsia, and intrauterine growth restriction. This review examines the current research on the role of ARID1A in pregnancy, highlighting its potential as a biomarker and therapeutic target for these complications. Understanding the involvement of ARID1A in placental function and pregnancy-related disorders may provide valuable insights for the development of novel diagnostic and therapeutic strategies.

Expanding the clinical spectrum of Coffin-Siris syndrome with anorectal malformations: Case report and review of the literature

Anorectal malformations (ARMs) represent a wide spectrum of congenital anomalies of the anus and rectum, of which more than half are syndromic. Their etiology is highly heterogeneous and still poorly understood. We report a 4-year-old girl who initially presented with an isolated ARM, and subsequently developed a global developmental delay as part of an ARID1B-related Coffin-Siris syndrome (CSS). A co-occurrence of ARMs and CSS in an individual by chance is unexpected since both diseases are very rare. A review of the literature enabled us to identify 10 other individuals with both CSS and ARMs. Among the ten individuals reported in this study, 8 had a variant in ARID1A, 2 in ARID1B, and 1 in SMARCA4. This more frequent than expected association between CSS and ARM indicates that some ARMs are most likely part of the CSS spectrum, especially for ARID1A-related CSS.

A novel SMARCC1 BAFopathy implicates neural progenitor epigenetic dysregulation in human hydrocephalus

Hydrocephalus, characterized by cerebral ventriculomegaly, is the most common disorder requiring brain surgery in children. Recent studies have implicated SMARCC1, a component of the BRG1-associated factor (BAF) chromatin remodelling complex, as a candidate congenital hydrocephalus gene. However, SMARCC1 variants have not been systematically examined in a large patient cohort or conclusively linked with a human syndrome. Moreover, congenital hydrocephalus-associated SMARCC1 variants have not been functionally validated or mechanistically studied in vivo. Here, we aimed to assess the prevalence of SMARCC1 variants in an expanded patient cohort, describe associated clinical and radiographic phenotypes, and assess the impact of Smarcc1 depletion in a novel Xenopus tropicalis model of congenital hydrocephalus. To do this, we performed a genetic association study using whole-exome sequencing from a cohort consisting of 2697 total ventriculomegalic trios, including patients with neurosurgically-treated congenital hydrocephalus, that total 8091 exomes collected over 7 years (2016-23). A comparison control cohort consisted of 1798 exomes from unaffected siblings of patients with autism spectrum disorder and their unaffected parents were sourced from the Simons Simplex Collection. Enrichment and impact on protein structure were assessed in identified variants. Effects on the human fetal brain transcriptome were examined with RNA-sequencing and Smarcc1 knockdowns were generated in Xenopus and studied using optical coherence tomography imaging, in situ hybridization and immunofluorescence. SMARCC1 surpassed genome-wide significance thresholds, yielding six rare, protein-altering de novo variants localized to highly conserved residues in key functional domains. Patients exhibited hydrocephalus with aqueductal stenosis; corpus callosum abnormalities, developmental delay, and cardiac defects were also common. Xenopus knockdowns recapitulated both aqueductal stenosis and cardiac defects and were rescued by wild-type but not patient-specific variant SMARCC1. Hydrocephalic SMARCC1-variant human fetal brain and Smarcc1-variant Xenopus brain exhibited a similarly altered expression of key genes linked to midgestational neurogenesis, including the transcription factors NEUROD2 and MAB21L2. These results suggest de novo variants in SMARCC1 cause a novel human BAFopathy we term 'SMARCC1-associated developmental dysgenesis syndrome', characterized by variable presence of cerebral ventriculomegaly, aqueductal stenosis, developmental delay and a variety of structural brain or cardiac defects. These data underscore the importance of SMARCC1 and the BAF chromatin remodelling complex for human brain morphogenesis and provide evidence for a 'neural stem cell' paradigm of congenital hydrocephalus pathogenesis. These results highlight utility of trio-based whole-exome sequencing for identifying pathogenic variants in sporadic congenital structural brain disorders and suggest whole-exome sequencing may be a valuable adjunct in clinical management of congenital hydrocephalus patients.

Prenatal Coffin-Siris Syndrome: Expanding the Phenotypic and Genotypic Spectrum of the Disease

Coffin-Siris syndrome is an autosomal dominant disorder with neurological, cardiovascular, and gastrointestinal symptoms. Patients with Coffin-Siris syndrome typically have variable degree of developmental delay or intellectual disability, muscular hypotonia, dysmorphic facial features, sparse scalp hair, but otherwise hirsutism and fifth digit nail or distal phalanx hypoplasia or aplasia. Coffin-Siris syndrome is caused by pathogenic variants in 12 different genes including SMARCB1 and ARID1A. Pathogenic SMARCB1 gene variants cause Coffin-Siris syndrome 3 whereas pathogenic ARID1A gene variants cause Coffin-Siris syndrome 2. Here, we present two prenatal Coffin-Siris syndrome cases with autosomal dominant pathogenic variants: SMARCB1 gene c.1066_1067del, p.(Leu356AspfsTer4) variant, and a novel ARID1A gene c.1920+3_1920+6del variant. The prenatal phenotype in Coffin-Siris syndrome has been rarely described. This article widens the phenotypic spectrum of prenatal Coffin-Siris syndrome with severely hypoplastic right ventricle with VSD and truncus arteriosus type III, persisting left superior and inferior caval vein, bilateral olfactory nerve aplasia, and hypoplastic thymus. A detailed clinical description of the patients with ultrasound, MRI, and post mortem pictures of the affected fetuses showing the wide phenotypic spectrum of the disease is presented.

Congenital hydrocephalus: new Mendelian mutations and evidence for oligogenic inheritance

BACKGROUND

Congenital hydrocephalus is characterized by ventriculomegaly, defined as a dilatation of cerebral ventricles, and thought to be due to impaired cerebrospinal fluid (CSF) homeostasis. Primary congenital hydrocephalus is a subset of cases with prenatal onset and absence of another primary cause, e.g., brain hemorrhage. Published series report a Mendelian cause in only a minority of cases. In this study, we analyzed exome data of PCH patients in search of novel causal genes and addressed the possibility of an underlying oligogenic mode of inheritance for PCH.

MATERIALS AND METHODS

We sequenced the exome in 28 unrelated probands with PCH, 12 of whom from families with at least two affected siblings and 9 of whom consanguineous, thereby increasing the contribution of genetic causes. Patient exome data were first analyzed for rare (MAF < 0.005) transmitted or de novo variants. Population stratification of unrelated PCH patients and controls was determined by principle component analysis, and outliers identified using Mahalanobis distance 5% as cutoff. Patient and control exome data for genes biologically related to cilia (SYScilia database) were analyzed by mutation burden test.

RESULTS

In 18% of probands, we identify a causal (pathogenic or likely pathogenic) variant of a known hydrocephalus gene, including genes for postnatal, syndromic hydrocephalus, not previously reported in isolated PCH. In a further 11%, we identify mutations in novel candidate genes. Through mutation burden tests, we demonstrate a significant burden of genetic variants in genes coding for proteins of the primary cilium in PCH patients compared to controls.

CONCLUSION

Our study confirms the low contribution of Mendelian mutations in PCH and reports PCH as a phenotypic presentation of some known genes known for syndromic, postnatal hydrocephalus. Furthermore, this study identifies novel Mendelian candidate genes, and provides evidence for oligogenic inheritance implicating primary cilia in PCH.

High molecular diagnostic yields and novel phenotypic expansions involving syndromic anorectal malformations

Evidence suggests that genetic factors contribute to the development of anorectal malformations (ARMs). However, the etiology of the majority of ARMs cases remains unclear. Exome sequencing (ES) may be underutilized in the diagnostic workup of ARMs due to uncertainty regarding its diagnostic yield. In a clinical database of ~17,000 individuals referred for ES, we identified 130 individuals with syndromic ARMs. A definitive or probable diagnosis was made in 45 of these individuals for a diagnostic yield of 34.6% (45/130). The molecular diagnostic yield of individuals who initially met criteria for VACTERL association was lower than those who did not (26.8% vs 44.1%; p = 0.0437), suggesting that non-genetic factors may play an important role in this subset of syndromic ARM cases. Within this cohort, we identified two individuals who carried de novo pathogenic frameshift variants in ADNP, two individuals who were homozygous for pathogenic variants in BBS1, and single individuals who carried pathogenic or likely pathogenic variants in CREBBP, EP300, FANCC, KDM6A, SETD2, and SMARCA4. The association of these genes with ARMs was supported by previously published cases, and their similarity to known ARM genes as demonstrated using a machine learning algorithm. These data suggest that ES should be considered for all individuals with syndromic ARMs in whom a molecular diagnosis has not been made, and that ARMs represent a low penetrance phenotype associated with Helsmoortel-van der Aa syndrome, Bardet-Biedl syndrome 1, Rubinstein-Taybi syndromes 1 and 2, Fanconi anemia group C, Kabuki syndrome 2, SETD2-related disorders, and Coffin-Siris syndrome 4.

Acetate supplementation restores cognitive deficits caused by ARID1A haploinsufficiency in excitatory neurons

Mutations in AT-rich interactive domain-containing protein 1A (ARID1A) cause Coffin-Siris syndrome (CSS), a rare genetic disorder that results in mild to severe intellectual disabilities. However, the biological role of ARID1A in the brain remains unclear. In this study, we report that the haploinsufficiency of ARID1A in excitatory neurons causes cognitive impairment and defects in hippocampal synaptic transmission and dendritic morphology in mice. Similarly, human embryonic stem cell-derived excitatory neurons with deleted ARID1A exhibit fewer dendritic branches and spines, and abnormal electrophysiological activity. Importantly, supplementation of acetate, an epigenetic metabolite, can ameliorate the morphological and electrophysiological deficits observed in mice with Arid1a haploinsufficiency, as well as in ARID1A-null human excitatory neurons. Mechanistically, transcriptomic and ChIP-seq analyses demonstrate that acetate supplementation can increase the levels of H3K27 acetylation at the promoters of key regulatory genes associated with neural development and synaptic transmission. Collectively, these findings support the essential roles of ARID1A in the excitatory neurons and cognition and suggest that acetate supplementation could be a potential therapeutic intervention for CSS.

Evidence for an association between Coffin-Siris syndrome and congenital diaphragmatic hernia

Coffin-Siris syndrome (CSS) is an autosomal dominant neurodevelopmental syndrome that can present with a variety of structural birth defects. Pathogenic variants in 12 genes have been shown to cause CSS. Most of these genes encode proteins that are a part of the mammalian switch/sucrose non-fermentable (mSWI/SNF; BAF) complex. An association between genes that cause CSS and congenital diaphragmatic hernia (CDH) has been suggested based on case reports and the analysis of CSS and CDH cohorts. Here, we describe an unpublished individual with CSS and CDH, and we report additional clinical information on four published cases. Data from these individuals, and a review of the literature, provide evidence that deleterious variants in ARID1B, ARID1A, SMARCB1, SMARCA4, SMARCE1, ARID2, DPF2, and SMARCC2, which are associated with CSS types 1-8, respectively, are associated with the development of CDH. This suggests that additional genetic testing to identify a separate cause of CDH in an individual with CSS may be unwarranted, and that comprehensive genetic testing for individuals with non-isolated CDH should include an evaluation of CSS-related genes. These data also suggest that the mSWI/SNF (BAF) complex may play an important role in diaphragm development.

Abnormal microglial polarization induced by Arid1a deletion leads to neuronal differentiation deficits

OBJECTIVE

Microglia, the prototypical innate immune cells of the central nervous system (CNS), are highly plastic and assume their phenotypes dependent on intrinsically genetic, epigenetic regulation or extrinsically microenvironmental cues. Microglia has been recognized as key regulators of neural stem/progenitor cells (NSPCs) and brain functions. Chromatin accessibility is implicated in immune cell development and functional regulation. However, it is still unknown whether and how chromatin remodelling regulates the phenotypic plasticity of microglia and exerts what kind of effects on NSPCs.

METHODS

We investigated the role of chromatin accessibility in microglia by deleting chromatin remodelling gene Arid1a using microglia-specific Cx3cr1-cre and Cx3cr1-CreERT2 mice. RNA-seq and ATAC-seq were performed to dissect the molecular mechanisms. In addition, we examined postnatal M1/M2 microglia polarization and analysed neuronal differentiation of NSPCs. Finally, we tested the effects of microglial Arid1a deletion on mouse behaviours.

RESULTS

Increased chromatin accessibility upon Arid1a ablation resulted in enhanced M1 microglial polarization and weakened M2 polarization, which led to abnormal neurogenesis and anxiety-like behaviours. Switching the polarization state under IL4 stimulation could rescue abnormal neurogenesis, supporting an essential role for chromatin remodeler ARID1A in balancing microglial polarization and brain functions.

CONCLUSIONS

Our study identifies ARID1A as a central regulator of microglia polarization, establishing a mechanistic link between chromatin remodelling, neurogenesis and mouse behaviours, and highlights the potential development of innovative therapeutics exploiting the innate regenerative capacity of the nervous system.

Prenatal diagnosis of Coffin-Siris syndrome: WHAT ARE THE FETAL FEATURES?

OBJECTIVE

To present both our center's and previously reported experience of prenatal diagnosis of Coffin-Siris syndrome (CSS) with regard to the laboratory testing and fetal features of this syndrome.

METHODS

This was a retrospective study of eight pregnancies with fetal CSS identified by prenatal or postnatal genetic testing. Clinical and laboratory data were collected and reviewed for these cases, including maternal demographics, prenatal sonographic findings, chromosomal microarray and exome sequencing (ES) results, and pregnancy outcomes.

RESULTS

A total of eight cases of fetal CSS based on molecular testing were detected. Two cases presented with an increased nuchal translucency (NT) in the first trimester. The remaining six were identified at the second trimester scan. Agenesis of the corpus callosum (ACC) was the most common sonographic finding, accounting for 5/7 (71.4%) cases in which a second trimester sonogram was performed: four had ACC as an isolated finding, and one had additional features of cerebellar hypoplasia and left congenital diaphragmatic hernia.

CONCLUSION

CSS should be included in the differential diagnosis when ACC is found by prenatal ultrasound. Both chromosomal microarray and ES should be options when counseling patients with a structurally anomalous fetus. This article is protected by copyright. All rights reserved.