De novo missense variants in FBXO11 alter its protein expression and subcellular localization

Proteasomal activation ameliorates neuronal phenotypes linked to FBXO11-deficiency

Haploinsufficiency of FBXO11, encoding a ubiquitin ligase complex subunit, is associated with a variable neurodevelopmental disorder. So far, the underlying nervous system-related pathomechanisms are poorly understood, and specific therapies are lacking. Using a combined approach, we established an FBXO11-deficient human stem cell-based neuronal model using CRISPR-Cas9 and a Drosophila model using tissue-specific knockdown techniques. We performed transcriptomic analyses on iPSC-derived neurons and molecular phenotyping in both models. RNA sequencing revealed disrupted transcriptional networks related to processes important for neuronal development, such as differentiation, migration, and cell signaling. Consistently, we found that loss of FBXO11 leads to neuronal phenotypes such as impaired neuronal migration and abnormal proliferation/differentiation balance in human cultured neurons and impaired dendritic development and behavior in Drosophila. Interestingly, application of three different proteasome-activating substances could alleviate FBXO11-deficiency-associated phenotypes in both human neurons and flies. One of these substances is the long-approved drug Verapamil, opening the possibility of drug repurposing in the future. Our study shows the importance of FBXO11 for neurodevelopment and highlights the reversibility of related phenotypes, opening an avenue for potential development of therapeutic approaches through drug repurposing.

Cullin-RING Ubiquitin Ligases in Neurodevelopment and Neurodevelopmental Disorders

Ubiquitination is a dynamic and tightly regulated post-translational modification essential for modulating protein stability, trafficking, and function to preserve cellular homeostasis. This process is orchestrated through a hierarchical enzymatic cascade involving three key enzymes: the E1 ubiquitin-activating enzyme, the E2 ubiquitin-conjugating enzyme, and the E3 ubiquitin ligase. The final step of ubiquitination is catalyzed by the E3 ubiquitin ligase, which facilitates the transfer of ubiquitin from the E2 enzyme to the substrate, thereby dictating which proteins undergo ubiquitination. Emerging evidence underscores the critical roles of ubiquitin ligases in neurodevelopment, regulating fundamental processes such as neuronal polarization, axonal outgrowth, synaptogenesis, and synaptic function. Mutations in genes encoding ubiquitin ligases and the consequent dysregulation of these pathways have been increasingly implicated in a spectrum of neurodevelopmental disorders, including autism spectrum disorder, intellectual disability, and attention-deficit/hyperactivity disorder. This review synthesizes current knowledge on the molecular mechanisms underlying neurodevelopment regulated by Cullin-RING ubiquitin ligases-the largest subclass of ubiquitin ligases-and their involvement in the pathophysiology of neurodevelopmental disorders. A deeper understanding of these mechanisms holds significant promise for informing novel therapeutic strategies, ultimately advancing clinical outcomes for individuals affected by neurodevelopmental disorders.

The miR-155-5p/FBXO11 axis inhibits the progression of gastric cancer via the mTOR pathway

Background

Gastric cancer (GC) is a leading cause of cancer-related death. MicroRNAs (miRNAs or miRs) play a crucial role in the pathology of GC, including cell proliferation, invasion, and metastasis. In this study, genes targeted by miR-155-5p were predicted using bioinformatic tools. We found that the expression of miR-155-5p in GC cell lines differed relative to the expression of F-box protein 11 (FBXO11), which is involved in the regulation of cellular processes. This study sought to examine the function of miR-155-5p and the precise mechanism underlying its regulatory function in modulating proliferation and apoptosis in GC.

Methods

The luciferase reporter assay results showed that miR-155-5p bound directly to the three prime untranslated region (3'-UTR) of FBXO11, which further downregulated FBXO11 expression. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and Western-blot analyses confirmed that miR-155-5p negatively regulated the messenger RNA (mRNA) and protein expression of FBXO11. The effects of FBXO11 on cell proliferation and apoptosis in GC cell lines was further examined using Cell Counting Kit-8 (CCK-8) and flow cytometry.

Results

We found that FBXO11 promoted proliferation and decreased apoptosis in GC cells. Conversely, rescue experiments showed that the knockdown of FBXO11 limited the effects of miR-155-5p on the proliferation and apoptosis of GC cells, providing further evidence that FBXO11 is a functional target of miR-155-5p. Further, the overexpression of miR-155-5p inhibited cell growth via the targeted inhibition of FBXO11 that regulated mammalian target of rapamycin (mTOR) signaling pathway in the GC cells.

Conclusions

Overall, these results showed that miR-155-5p may serve as a tumor suppressor in GC and that the miR-155-5p/FBXO11 axis regulates tumor progression via the mTOR signaling pathway. Consequently, our findings may lead to the development a novel treatment strategy for GC.

Clinical and genetic characteristics of a case of Koolen-De Vries syndrome caused by KANSL1 gene mutation and literature review: A case report

RATIONALE

Koolen-De Vries syndrome (KdVS, OMIM: 612452), also known as 17q21.31 microdeletion syndrome, is an autosomal dominant genetic disease. In the study, we analyze of clinical phenotype and gene variation of a child with Koolen-De Vries syndrome, review the literature to improve the understanding of the disease.

PATIENT CONCERNS

The patient is a male, aged 1 month and 3 days. The patient has poor airway development, difficulty weaning from respiratory support, seizures, and recurrent low granulocyte counts.

DIAGNOSES

High-throughput sequencing showed a heterozygous mutation NM_001193466.1: c.1574_1578del (P.525HFS *24) in the KANSL1 gene of the proband, which was considered a new mutation since neither of his parents carried this mutation based on Sanger sequencing results. Combining clinical features and genetic results, the proband was diagnosed as KdVS.

INTERVENTIONS AND OUTCOMES

The patient was in good condition after receiving bronchoscopy and laser interventional therapy, meeting the criteria for discharge. Follow-up for 1 year and 6 months indicated that the patient's physical signs were normal and there was no recurrence.

LESSONS

According to literature review, KdVS is a multi-organ disease characterized by feeding difficulties, seizures, characteristic facial features, dysplasia of the respiratory system and cardiac abnormalities. In this study, laryngeal malacia accounted for 23.2% of the clinical manifestations of KdVS patients, limb convulsions/seizures accounted for 62.5%, and cardiac development defects accounted for 23.5%. The disease was rare in China and had a variety of clinical manifestations. The summary of reported cases can enable doctors to have more understanding of the disease. The new mutations enrich the KANSL1 gene mutation spectrum.

FBXO11 variants are associated with intellectual disability and variable clinical manifestation in Chinese affected individuals

F-box protein 11 (FBXO11) is a member of F-Box protein family, which has recently been proved to be associated with intellectual developmental disorder with dysmorphic facies and behavioral abnormalities (IDDFBA, OMIM: 618089). In this study, 12 intellectual disability individuals from 5 Chinese ID families were collected, and whole exome sequencing (WES), sanger sequencing, and RNA sequencing (RNA-seq) were conducted. Almost all the affected individuals presented with mild to severe intellectual disability (12/12), global developmental delay (10/12), speech and language development delay (8/12) associated with a range of alternate features including increased body weight (7/12), short stature (6/12), seizures (3/12), reduced visual acuity (4/12), hypotonia (1/12), and auditory hallucinations and hallucinations (1/12). Distinguishingly, malformation was not observed in all the affected individuals. WES analysis showed 5 novel FBXO11 variants, which include an inframe deletion variant, a missense variant, two frameshift variants, and a partial deletion of FBXO11 (exon 22-23). RNA-seq indicated that exon 22-23 deletion of FBXO11 results in a new mRNA structure. Conservation and protein structure prediction demonstrated deleterious effect of these variants. The DEGs analysis revealed 148 differentially expressed genes shared among 6 affected individuals, which were mainly associated with genes of muscle and immune system. Our research is the first report of FBXO11-associated IDDFBA in Chinese individuals, which expands the genetic and clinical spectrum of this newly identified NDD/ID syndrome.

De novo structure prediction of meteorin and meteorin-like protein for identification of domains, functional receptor binding regions, and their high-risk missense variants

Meteorin (Metrn) and Meteorin-like (Metrnl) are homologous secreted proteins involved in neural development and metabolic regulation. In this study, we have performed de novo structure prediction and analysis of both Metrn and Metrnl using Alphafold2 (AF2) and RoseTTAfold (RF). Based on the domain and structural homology analysis of the predicted structures, we have identified that these proteins are composed of two functional domains, a CUB domain and an NTR domain, connected by a hinge/loop region. We have identified the receptor binding regions of Metrn and Metrnl using the machine-learning tools ScanNet and Masif. These were further validated by docking Metrnl with its reported KIT receptor, thus establishing the role of each domain in the receptor interaction. Also, we have studied the effect of non-synonymous SNPs on the structure and function of these proteins using an array of bioinformatics tools and selected 16 missense variants in Metrn and 10 in Metrnl that can affect the protein stability. This is the first study to comprehensively characterize the functional domains of Metrn and Metrnl at their structural level and identify the functional domains, and protein binding regions. This study also highlights the interaction mechanism of the KIT receptor and Metrnl. The predicted deleterious SNPs will allow further understanding of the role of these variants in modulating the plasma levels of these proteins in disease conditions such as diabetes.Communicated by Ramaswamy H. Sarma.

How many phenotypes for the FBXO11 related disease? Report on a new patient with a tricho-rhino-phalangeal like phenotype

Here we report the case of a young boy with developmental delay, thin sparse hair, early closure of the anterior fontanel, bilateral choanal atresia, brachyturicephaly; and dysmorphic features closely resembling those seen in trichorhinophalangeal syndrome (TRPS). These features include sparse hair, sparse lateral eyebrows, a bulbous pear shaped nose, a long philtrum, thin lips, small/hypoplastic nails, pes planovalgus; bilateral cone-shaped epiphyses at the proximal 5th phalanx, slender long bones, coxa valga, mild scoliosis, and delayed bone age. Given that TRPS had been excluded by a thorough genetic analysis, whole exome sequencing was performed and a heterozygous likely pathogenic variant was identified in the FBXO11 gene (NM_001190274.2: c.1781A > G; p. His594Arg), confirming the diagnosis of the newly individualized IDDFBA syndrome: Intellectual Developmental Disorder, dysmorphic Facies, and Behavioral Abnormalities (OMIM# 618,089). Our findings further delineate the clinical spectrum linked to FBXO11 and highlight the importance of investigating further cases with mutations in this gene to establish a potential genotype-phenotype correlation.

Elucidating the clinical and molecular spectrum of SMARCC2-associated NDD in a cohort of 65 affected individuals

PURPOSE

Coffin-Siris and Nicolaides-Baraitser syndromes are recognizable neurodevelopmental disorders caused by germline variants in BAF complex subunits. The SMARCC2 BAFopathy was recently reported. Herein, we present clinical and molecular data on a large cohort.

METHODS

Clinical symptoms for 41 novel and 24 previously published affected individuals were analyzed using the Human Phenotype Ontology. For genotype-phenotype correlations, molecular data were standardized and grouped into non-truncating and likely gene-disrupting (LGD) variants. Missense variant protein expression and BAF-subunit interactions were examined using 3D protein modeling, co-immunoprecipitation, and proximity-ligation assays.

RESULTS

Neurodevelopmental delay with intellectual disability, muscular hypotonia, and behavioral disorders were the major manifestations. Clinical hallmarks of BAFopathies were rare. Clinical presentation differed significantly, with LGD variants being predominantly inherited and associated with mildly reduced or normal cognitive development, whereas non-truncating variants were mostly de novo and presented with severe developmental delay. These distinct manifestations and non-truncating variant clustering in functional domains suggest different pathomechanisms. In vitro testing showed decreased protein expression for N-terminal missense variants similar to LGD.

CONCLUSION

This study improved SMARCC2 variant classification and identified discernible SMARCC2-associated phenotypes for LGD and non-truncating variants, which were distinct from other BAFopathies. The pathomechanism of most non-truncating variants has yet to be investigated.

Identification of two novel autism genes, TRPC4 and SCFD2, in Qatar simplex families through exome sequencing

This study investigated the genetic underpinnings of autism spectrum disorder (ASD) in a Middle Eastern cohort in Qatar using exome sequencing. The study identified six candidate autism genes in independent simplex families, including both four known and two novel autosomal dominant and autosomal recessive genes associated with ASD. The variants consisted primarily of de novo and homozygous missense and splice variants. Multiple individuals displayed more than one candidate variant, suggesting the potential involvement of digenic or oligogenic models. These variants were absent in the Genome Aggregation Database (gnomAD) and exhibited extremely low frequencies in the local control population dataset. Two novel autism genes, TRPC4 and SCFD2, were discovered in two Qatari autism individuals. Furthermore, the D651A substitution in CLCN3 and the splice acceptor variant in DHX30 were identified as likely deleterious mutations. Protein modeling was utilized to evaluate the potential impact of three missense variants in DEAF1, CLCN3, and SCFD2 on their respective structures and functions, which strongly supported the pathogenic natures of these variants. The presence of multiple de novo mutations across trios underscored the significant contribution of de novo mutations to the genetic etiology of ASD. Functional assays and further investigations are necessary to confirm the pathogenicity of the identified genes and determine their significance in ASD. Overall, this study sheds light on the genetic factors underlying ASD in Qatar and highlights the importance of considering diverse populations in ASD research.

New ocular findings in a patient with a novel pathogenic variant in the FBXO11 gene

Intellectual developmental disorder with dysmorphic facies and behavioral abnormalities (IDDFBA) is a recently described autosomal dominant entity caused by pathogenic variants, mostly de novo, in the FBXO11 gene. It presents in the first years of life with highly variable clinical manifestations. The main features of IDDFBA include borderline-to-severe intellectual disability, behavioral problems, hypotonia, facial dysmorphisms, minor skeletal abnormalities, and recurrent infections. Although eye problems, such as refractive errors, eye misalignment and minor visual changes, have been described in about 48% of patients, a major ocular defect, namely, bilateral optic nerve hypoplasia, has been reported in the literature only once. We report an 8-year-old boy with a novel de novo pathogenic variant in FBXO11 gene (NM_001190274.1: c.1166dup, p.Cys390Metfs∗3) and a complex ophthalmological phenotype, consisting of right microphthalmia, very shallow anterior chamber, and persistent pupillary membrane, right dense nuclear cataract, bilateral optic nerve hypoplasia, and bilateral horizontal manifest nystagmus.

Impaired Neurodevelopmental Genes in Slovenian Autistic Children Elucidate the Comorbidity of Autism With Other Developmental Disorders

Autism spectrum disorders (ASD) represent a phenotypically heterogeneous group of patients that strongly intertwine with other neurodevelopmental disorders (NDDs), with genetics playing a significant role in their etiology. Whole exome sequencing (WES) has become predominant in molecular diagnostics for ASD by considerably increasing the diagnostic yield. However, the proportion of undiagnosed patients still remains high due to complex clinical presentation, reduced penetrance, and lack of segregation analysis or clinical information. Thus, reverse phenotyping, where we first identified a possible genetic cause and then determine its clinical relevance, has been shown to be a more efficient approach. WES was performed on 147 Slovenian pediatric patients with suspected ASD. Data analysis was focused on identifying ultrarare or “single event” variants in ASD-associated genes and further expanded to NDD-associated genes. Protein function and gene prioritization were performed on detected clinically relevant variants to determine their role in ASD etiology and phenotype. Reverse phenotyping revealed a pathogenic or likely pathogenic variant in ASD-associated genes in 20.4% of patients, with subsequent segregation analysis indicating that 14 were de novo variants and 1 was presumed compound heterozygous. The diagnostic yield was further increased by 2.7% by the analysis of ultrarare or “single event” variants in all NDD-associated genes. Protein function analysis established that genes in which variants of unknown significance (VUS) were detected were predominantly the cause of intellectual disability (ID), and in most cases, features of ASD as well. Using such an approach, variants in rarely described ASD-associated genes, such as SIN3B, NR4A2, and GRIA1, were detected. By expanding the analysis to include functionally similar NDD genes, variants in KCNK9, GNE, and other genes were identified. These would probably have been missed by classic genotype–phenotype analysis. Our study thus demonstrates that in patients with ASD, analysis of ultrarare or “single event” variants obtained using WES with the inclusion of functionally similar genes and reverse phenotyping obtained a higher diagnostic yield despite limited clinical data. The present study also demonstrates that most of the causative genes in our cohort were involved in the syndromic form of ASD and confirms their comorbidity with other developmental disorders.