Null variants and deletions in BRWD3 cause an X-linked syndrome of mild-moderate intellectual disability, macrocephaly, and obesity: A series of 17 patients.

BRWD3 has been described as a cause of X-linked intellectual disability, but relatively little is known about the specific phenotype. We report the largest BRWD3 patient series to date, comprising 17 males with 12 distinct null variants and 2 partial gene deletions. All patients presented with intellectual disability, which was classified as moderate (65%) or mild (35%). Behavioral issues were present in 75% of patients, including aggressive behavior, attention deficit/hyperactivity and/or autistic spectrum disorders. Mean head circumference was +2.8 SD (2.8 standard deviations above the mean), and mean BMI was +2.0 SD (in the context of a mean height of +1.3 SD), indicating a predominant macrocephaly/obesity phenotype. Shared facial features included a tall chin, prognathism, broad forehead, and prominent supraorbital ridge. Additional features, reported in a minority (<30%) of patients included cryptorchidism, neonatal hypotonia, and small joint hypermobility. This study delineates the clinical features associated with BRWD3 null variants and partial gene deletions, and suggests that BRWD3 should be included in the differential diagnosis of patients with an overgrowth-intellectual disability (OGID) phenotype, particularly in male patients with a mild or moderate intellectual disability associated with macrocephaly and/or obesity.

MRX93 syndrome (BRWD3 gene): five new patients with novel mutations.

Overgrowth syndromes (OGS) comprise a heterogeneous group of disorders whose main characteristic is that either the weight, height, or head circumference are above the 97th centile or 2 to 3 SD above the mean for age and sex. Additional features, such as facial dysmorphism, developmental delay or intellectual disability (ID), congenital anomalies, neurological problems and an increased risk of neoplasia are usually associated with OGS. Genetic analysis in patients with overlapping clinical features is essential, to distinguish between two or more similar conditions, and to provide appropriate genetic counseling and recommendations for follow up. In the present paper, we report five new patients (from four unrelated families) with an X-linked mental retardation syndrome with overgrowth (XMR93 syndrome), also known as XLID-BRWD3-related syndrome. The main features of these patients include ID, macrocephaly and dysmorphic facial features. XMR93 syndrome is a recently described disorder caused by mutations in the Bromodomain and WD-repeat domain-containing protein 3 (BRWD3) gene. This article underscores the importance of genetic screening by exome sequencing for patients with OGS and ID with unclear clinical diagnosis, and expands the number of reported individuals with XMR93 syndrome, highlighting the clinical features of this unusual disease.

Intragenic Microdeletion of ULK4 and Partial Microduplication of BRWD3 in Siblings with Neuropsychiatric Features and Obesity.

ULK4 and BRWD3 deletions have been identified in patients with developmental/language delay and intellectual disability. Both genes play pivotal roles in brain development. In particular, ULK4 encodes serine/threonine kinases that are critical for the development and function of the nervous system, while BRWD3 plays a crucial role in ubiquitination, as part of the ubiquitin/proteasome system. We report on 2 brothers, aged 7.6 and 20 years, presenting with cognitive impairment, epilepsy, autistic features, hearing loss, and obesity. Array-CGH analysis demonstrated 2 rare CNVs in both siblings: a paternally inherited microdeletion of ∼145 kb at 3p22.1, disrupting the ULK4 gene, and a maternally inherited microduplication of ∼117 kb at Xq21.1 including only the BRWD3 gene. As already described for other recurrent syndromes with variable phenotype, these findings are challenging in genetic counseling because of an evident variable penetrance. We discuss the possible correlations between the clinical phenotype of our patients and the function of the genes involved in these microrearrangements.

Intellectual disability-associated dBRWD3 regulates gene expression through inhibition of HIRA/YEM-mediated chromatin deposition of histone H3.3.

Many causal mutations of intellectual disability have been found in genes involved in epigenetic regulations. Replication-independent deposition of the histone H3.3 variant by the HIRA complex is a prominent nucleosome replacement mechanism affecting gene transcription, especially in postmitotic neurons. However, how HIRA-mediated H3.3 deposition is regulated in these cells remains unclear. Here, we report that dBRWD3, the Drosophila ortholog of the intellectual disability gene BRWD3, regulates gene expression through H3.3, HIRA, and its associated chaperone Yemanuclein (YEM), the fly ortholog of mammalian Ubinuclein1. In dBRWD3 mutants, increased H3.3 levels disrupt gene expression, dendritic morphogenesis, and sensory organ differentiation. Inactivation of yem or H3.3 remarkably suppresses the global transcriptome changes and various developmental defects caused by dBRWD3 mutations. Our work thus establishes a previously unknown negative regulation of H3.3 and advances our understanding of BRWD3-dependent intellectual disability.

Further clinical and molecular characterization of an XLID syndrome associated with BRWD3 variants, a gene implicated in the leukemia-related JAK-STAT pathway.

BACKGROUND: Since the first description of a BRWD3-associated nonsydromic intellectual disability (ID) disorder in 2007, 21 additional families have been reported in the literature. METHODS: Using exome sequencing (ES) and international data sharing, we identified 14 additional unrelated individuals with pathogenic BRWD3 variants (12 males and 2 females, including one with skewed X-inactivation). We reviewed the 31 previously published cases in the literature with clinical data available, and describe the collective phenotypes of 43 males and 2 females, with 33 different BRWD3 variants. RESULTS: The most common features in males (excluding one patient with a mosaic variant) included ID (39/39 males), speech delay (24/25 males), postnatal macrocephaly (28/35 males) with prominent forehead (18/25 males) and large ears (14/26 males), and obesity (12/27 males). Both females presented with macrocephaly, speech delay, and epilepsy, while epilepsy was only observed in 4/41 males. Among the 28 variants with available segregation reported, 19 were inherited from unaffected mothers and 9 were de novo. CONCLUSION: This study demonstrates that the BRWD3-related phenotypes are largely non-specific, leading to difficulty in clinical recognition of this disorder. A genotype-first approach, however, allows for the more efficient diagnosis of the BRWD3-related nonsyndromic ID. The refined clinical features presented here may provide additional diagnostic assistance for reverse phenotyping efforts.

Variants in BRWD3 associated with X-linked partial epilepsy without intellectual disability.

AIMS: Etiology of the majority patients with idiopathic partial epilepsy (IPE) remains elusive. We thus screened the potential disease-associated variants in the patients with IPE. METHODS: Trios-based whole exome sequencing was performed in a cohort of 320 patients with IPE. Frequency and molecular effects of variants were predicted. RESULTS: Three novel BRWD3 variants were identified in five unrelated cases with IPE, which were four male cases and one female case. The variants included two recurrent missense variants (c.836C>T/p.Thr279Ile and c.4234A>C/p.Ile1412Leu) and one intronic variant close to splice site (c.2475 + 6A>G). The two missense variants were located in WD40 repeat domain and bromodomain, respectively. They were predicted to be damaging by silico tools and change hydrogen bonds with surrounding amino acids. The frequency of mutant alleles in this cohort was significantly higher than that in the controls of East Asian and all population of gnomAD. All these variants were inherited from the asymptomatic mothers. Four male cases presented frequent seizures at onset, while the female case only had two fever-triggered seizures. They showed good responses to valproate and lamotrigine, then finally became seizure free. All the cases had no intellectual disability. Further analysis demonstrated that all previously reported destructive variants of BRWD3 caused intellectual disability, while missense variants located in WD40 repeat domains and bromodomains of BRWD3 were associated with epilepsy. CONCLUSION: BRWD3 gene is potentially associated with X-linked partial epilepsy without intellectual disability. The genotypes and locations of BRWD3 variants may explain for their phenotypic variation.

Heterozygous Deletion of Chromosome 15q13.3 in a Boy with Developmental Regression, Global Developmental Delay, Hypotonia, and Short Stature.

Two causes of intellectual disability are 15q13.3 deletion syndrome and BRWD3 X-linked intellectual disability. 15q13.3 deletion syndrome causes a heterogenous phenotype including intellectual disability (ID), developmental delay (DD), autism spectrum disorder, epilepsy/seizures, schizophrenia, attention deficit hyperactivity disorder, visual defects, hypotonia, and short stature. BRWD3 variants are rare, and the clinical presentation is largely unknown. Presented here is a 34-month-old male with developmental regression, global DD, hypotonia, and short stature. In this study, the patient and his mother underwent a whole-genome array screening. Sorting intolerant from tolerant (SIFT) and polymorphism phenotyping v2 (PolyPhen-2) analyses were performed to determine the pathogenicity of the BRWD3 mutation. Array comparative genomic hybridization showed a heterozygous, pathogenic deletion of at least 1.6 Mb from the cytogenetic band 15q13.2q13.3 and a BRWD3 variant of unknown clinical significance. This combination of genetic mutations has never been reported together and neither disorder is known to cause developmental regression. The mechanism of developmental regression is undefined but is of great importance due to the opportunity to develop therapies for these patients.

DDB1 binds histone reader BRWD3 to activate the transcriptional cascade in adipogenesis and promote onset of obesity.

Obesity has become a global pandemic. Identification of key factors in adipogenesis helps to tackle obesity and related metabolic diseases. Here, we show that DDB1 binds the histone reader BRWD3 to promote adipogenesis and diet-induced obesity. Although typically recognized as a component of the CUL4-RING E3 ubiquitin ligase complex, DDB1 stimulates adipogenesis independently of CUL4. A DDB1 mutant that does not bind CUL4A or CUL4B fully restores adipogenesis in DDB1-deficient cells. Ddb1+/- mice show delayed postnatal development of white adipose tissues and are protected from diet-induced obesity. Mechanistically, by interacting with BRWD3, DDB1 is recruited to acetylated histones in the proximal promoters of ELK1 downstream immediate early response genes and facilitates the release of paused RNA polymerase II, thereby activating the transcriptional cascade in adipogenesis. Our findings have uncovered a CUL4-independent function of DDB1 in promoting the transcriptional cascade of adipogenesis, development of adipose tissues, and onset of obesity.

Diagnostic Yields of Trio-WES Accompanied by CNVseq for Rare Neurodevelopmental Disorders.

OBJECTIVE: This study is to investigate the diagnostic yield of the combination of trio whole exome sequencing (Trio-WES) and copy number variation sequencing (CNVseq) for rare neurodevelopmental disorders (NDDs). METHODS: Clinical data from consecutive pediatric patients who were diagnosed with rare NDDs that were suspected to be monogenic disorders, who were admitted to our hospital from April 2017 to March 2019, and who underwent next generation sequencing (NGS) were extracted from the medical records. Patients for whom Trio-WES and CNVseq data were available were enrolled in this study. Sanger sequencing was applied for the validation of the variants identified by Trio-WES. Sequence alignment and structural modeling were conducted for analyzing the possibility of the variants in the onset of the NDDs. RESULTS: In total, 54 patients were enrolled in this study, with the median age of 15 (8-26) months. A total of 242 phenotypic abnormalities belonging to 20 different systems were identified in the cohort. Twenty-four patients were diagnosed by Trio-WES, eight patients were diagnosed by CNVseq, and one case was identified by both WES and CNVseq. Compared with Trio-WES, the diagnosis rate of Trio-WES accompanied by CNVseq was significantly higher (P = 0.016). Trio-WES identified 36 variants in 26 different genes, among which 27 variants were novel. CNVseq detected four duplications and eight deletions, ranging from 310 kb to 23.27 Mb. Our case examples demonstrated the high heterogeneity of NDDs and showed the challenges of rare NDDs for physicians. CONCLUSION: The significantly higher diagnosis rate of Trio-WES accompanied by CNVseq makes this strategy a potential alternative to the most widely used approaches for pediatric children with rare and undiagnosed NDDs.

Clinical phenotype and genetic analysis of BRWD3 gene variation related infantile epileptic spasm syndrome / 中华神经科杂志

Objective:To investigate the clinical phenotype and genetic characteristics of infantile epileptic spasm syndrome caused by BRWD3 gene mutation. Methods:Clinical data of a child with BRWD3 related infantile epileptic spasm syndrome who was admitted to Department of Pediatric Neurology of Linyi People′s Hospital on August 2, 2019 were collected and followed up, whole exome sequencing technology and Sanger sequencing were applied to verify the child and his parents, and the pathogenicity of mutation site was analyzed. The studies till June 2023 were searched with keywords of " BRWD3" in both English and Chinese databases of China National Knowledge Infrastructure, Wanfang, Online Mendelian Inheritance in Man, and PubMed. The clinical phenotype and genetic characteristics of patients with BRWD3 related epilepsy were summarized. Results:The patient was a 4 years and 4 months old boy, with a clinical phenotype including severe global development delay, focal seizures (the onset age was 4 months), epileptic spasm (the onset age was 6 months), autism, megacephaly, high forehead as well as hypsarrhythmia. The whole exome sequencing results showed a de novo and frameshift variation c.4318_4319del(p.Q1441Efs*20)(NM_153252) in the BRWD3 gene, and the variation was interpreted as pathogenic (PVS1+PS2+PM2) according to the American College of Medical Genetics and Genomics variant classification criteria and guidelines. A total of 7 English literature articles were retrieved reporting 16 cases of BRWD3 gene related epilepsy in children (including 1 case of infantile epileptic spasm syndrome), and there has been no report in China yet. Totally there were 17 cases of BRWD3 gene related epilepsy including this case. All the cases showed X chromosome dominant inheritance, of whom 15 cases showed minor variations, including 7 missense variations, 3 frameshift variations, 3 splicing variations, 2 nonsense variations, and the remaining 2 cases showed large segment deletions. A total of 15 different variants were found. The phenotypes of the 17 patients mainly included epileptic seizures (17/17), intellectual disability (10/17), motor development disorder (7/17), speech impairment (9/17), megacephaly (8/17), facial malformation (8/17), autism (4/17) and hypotonia (4/17). The common seizure types were found to be focal seizures, occasionally epileptic spasm seizures and tonic seizures. Conclusions:BRWD3 gene variation related epilepsy is an X chromosome dominant genetic disease with a wide clinical phenotype spectrum. BRWD3 gene mutation c.4318_4319del(p.Q1441Efs *20) could cause infantile epileptic spasm syndrome, manifested as severe global developmental delay, epileptic spasm, focal seizures, autism, craniofacial malformation and hypsarrhythmia. This research enriches BRWD3 gene mutation spectrum.

Clinical assessment of five patients with BRWD3 mutation at Xq21.1 gives further evidence for mild to moderate intellectual disability and macrocephaly.

Truncating mutations of the BRWD3 gene have been reported in two distinct families with in total four patients so far. By using array-CGH, we detected a 74 Kb de novo deletion encompassing exons 11 through 41 of BRWD3 at Xq21.1 in a 20 year old boy presenting with syndromic intellectual disability. In addition, by using exome sequencing, we ascertained a family with a BRWD3 nonsense mutation, p.Tyr1131*, in four males with intellectual disability. We compared the clinical presentation of these five patients to that of the four patients already described in the literature for further delineation of the clinical spectrum in BRWD3-related intellectual disability. The main symptoms are mild to moderate intellectual disability (n = 9/9) with speech delay (n = 8/8), behavioral disturbances (n = 7/8), macrocephaly (n = 7/9), dysmorphic facial features (n = 9/9) including prominent forehead, pointed chin, deep-set eyes, abnormal ears, and broad hands and feet (n = 6/6), and skeletal symptoms (n = 7/7) like pes planus, scoliosis, kyphosis and cubitus valgus.

A prenatally ascertained, maternally inherited 14.8 Mb duplication of chromosomal bands Xq13.2-q21.31 associated with multiple congenital abnormalities in a male fetus.

Duplications of the X chromosome are rare cytogenetic findings, and have been associated with an abnormal phenotype in the male offspring of apparently normal or near normal female carriers. We report on the prenatal diagnosis of a duplication on the long arm of chromosome X from chromosomal band Xq13.2 to q21.31 in a male fetus with increased nuchal translucency in the first trimester and polyhydramnios at 22 weeks of gestation. Amniocentesis was undertaken and cytogenetic analysis revealed additional chromosomal material in the long arm of chromosome X at position Xq13. Analysis with high resolution array CGH revealed the additional material is in fact a duplication of the region Xq13.2-q21.13. The duplication is 14.8 Mb in size and includes fourteen genes: SLC16A2, KIAA2022, ABCB7, ZDHHC15, ATRX, MAGT1, ATP7A, PGK1, TBX22, BRWD3, POU3F4, ZNF711, POF1B and CHM. Analysis of the parents revealed the mother to be a carrier of the same duplication. After elected termination of the pregnancy at 28 weeks a detailed autopsy of the fetus allowed for genotype-phenotype correlations.

Comparative profiling of plasma proteome from breast cancer patients reveals thrombospondin-1 and BRWD3 as serological biomarkers

Breast cancer is the most common cancer in women worldwide. It is necessary to identify biomarkers for early detection, to make accurate prognoses, and to monitor for any recurrence of the cancer. In order to identify potential breast cancer biomarkers, we analyzed the plasma samples of women diagnosed with breast cancer and age-matched normal healthy women by mTRAQ-based stable isotope-labeling mass spectrometry. We identified and quantified 204 proteins including thrombospondin-1 (THBS1) and bromodomain and WD repeat-containing protein 3 (BRWD3) which were increased by more than 5-fold in breast cancer plasma. The plasma levels of the two proteins were evaluated by Western blot assay to confirm for their diagnostic value as serum markers. A 1.8-fold increase in BRWD3 was observed while comparing the plasma levels of breast cancer patients (n = 54) with age-matched normal healthy controls (n = 30), and the area under the receiver operating characteristic curve (AUC) was 0.917. THBS1 was detected in pooled breast cancer plasma at the ratio similar to mTRAQ ratio (> 5-fold). The AUC value for THBS1 was 0.875. The increase of THBS1 was more prominent in estrogen receptor negative and progesterone receptor negative patients than receptor-positive patients. Our results are evidence of the diagnostic value of THBS1 in detecting breast cancer. Based on our findings, we suggest a proteomic method for protein identification and quantification lead to effective biomarker discovery.