Loss-of-function of KMT5B leads to neurodevelopmental disorder and impairs neuronal development and neurogenesis

Mutant p53 confers chemoresistance by activating KMT5B-mediated DNA repair pathway in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC), a malignancy arising from the nasopharyngeal epithelium, is common in the east and southeast area of Asia. Treatments for locally advanced and recurrent NPC include chemotherapy (usually combined with 5-Fluorouracil, 5-FU) and radiotherapy, but response is limited due to chemo-resistance. p53 mutation is a critical factor for 5-FU resistance in some cancers, but its role in NPC chemo-resistance remains unclear. Here, we demonstrate that p53(R280T), a common p53 somatic mutation found in multiple NPC tumor samples, induces gain-of-function upregulation of DNA repair genes which leads to 5-FU resistance in NPC. p53(R280T) specifically upregulates the expression of DNA repair-associated gene KMT5B by binding to its promoter, which leads to 5-FU resistance. Depletion of KMT5B in NPCs restores 5-FU induced DNA damages and improve the efficacy of 5-FU. By screening compounds affecting KMT5B expression, we identify curcumin as an effective down-regulator of KMT5B in NPC cells. We therefore evaluate the therapeutic potential of a 5-FU/curcumin combination to treat NPC and discover that curcumin enhances the efficacy of 5-FU to suppress NPC tumor growth. In summary, our findings indicate that mutant p53 and its regulated DNA repair genes serve as potential therapeutic targets to reverse 5-FU resistance for NPC patients.

Role of RB1 in neurodegenerative diseases: inhibition of post-mitotic neuronal apoptosis via Kmt5b

During the development of the vertebrate nervous system, 50% of the nerve cells undergo apoptosis shortly after formation. This process is important for sculpting tissue during morphogenesis and removing transiently functional cells that are no longer needed, ensuring the appropriate number of neurons in each region. Dysregulation of neuronal apoptosis can lead to neurodegenerative diseases. However, the molecular events involved in activating and regulating the neuronal apoptosis program are not fully understood. In this study, we identified several RB1 mutations in patients with neurodegenerative diseases. Then, we used a zebrafish model to investigate the role of Rb1 in neuronal apoptosis. We showed that Rb1-deficient mutants exhibit a significant hindbrain neuronal apoptosis, resulting in increased microglia infiltration. We further revealed that the apoptotic neurons in Rb1-deficient zebrafish were post-mitotic neurons, and Rb1 inhibits the apoptosis of these neurons by regulating bcl2/caspase through binding to Kmt5b. Moreover, using this zebrafish mutant, we verified the pathogenicity of the R621S and L819V mutations of human RB1 in neuronal apoptosis. Collectively, our data indicate that the Rb1-Kmt5b-caspase/bcl2 axis is crucial for protecting post-mitotic neurons from apoptosis and provides an explanation for the pathogenesis of clinically relevant mutations.

Novel KMT5B variant associated with neurodevelopmental disorder in a Chinese family: A case report

Background

We report here the clinical and genetic features of KMT5B-related neurodevelopmental disorder caused by a novel heterozygous frameshift variant in KMT5B in a Chinese family.

Case presentation

A 7-year-old Chinese boy with mild-to-moderate intellectual disability, significant language impairment, motor disability, and coordination difficulties presented to our hospital because he "could not speak and did not look at others." He was diagnosed with autism spectrum disorder previously owing to developmental delays in cognition, language expression, and understanding. The child also had variable nonspecific features including macrocephaly, wide button-hole space and nasal bridge, low ear, social behavior disorder, and foot deformities. Exome sequencing (ES) revealed that both the proband and his younger brother had inherited a novel heterozygous frameshift variant c.438_439ins[ASD; KT192064.1:1_310] of the KMT5B gene from their father. Bioinformatics analysis showed that the novel mutation affected the structure of the KMT5B pre-SET domain, mainly in the α-helix region. According to the American College of Medical Genetics and Genomics (ACMG) guidelines, this type of variant was eventually determined to be likely pathogenic (PVS1+PM2_P).

Conclusions

Our investigation expands the mutation spectrum of KMT5B to help us to better understand KMT5B-related neurodevelopmental disorder.

Characterizing proteomic and transcriptomic features of missense variants in amyotrophic lateral sclerosis genes

Within recent years, there has been a growing number of genes associated with amyotrophic lateral sclerosis (ALS), resulting in an increasing number of novel variants, particularly missense variants, many of which are of unknown clinical significance. Here, we leverage the sequencing efforts of the ALS Knowledge Portal (3864 individuals with ALS and 7839 controls) and Project MinE ALS Sequencing Consortium (4366 individuals with ALS and 1832 controls) to perform proteomic and transcriptomic characterization of missense variants in 24 ALS-associated genes. The two sequencing datasets were interrogated for missense variants in the 24 genes, and variants were annotated with gnomAD minor allele frequencies, ClinVar pathogenicity classifications, protein sequence features including Uniprot functional site annotations, and PhosphoSitePlus post-translational modification site annotations, structural features from AlphaFold predicted monomeric 3D structures, and transcriptomic expression levels from Genotype-Tissue Expression. We then applied missense variant enrichment and gene-burden testing following binning of variation based on the selected proteomic and transcriptomic features to identify those most relevant to pathogenicity in ALS-associated genes. Using predicted human protein structures from AlphaFold, we determined that missense variants carried by individuals with ALS were significantly enriched in β-sheets and α-helices, as well as in core, buried or moderately buried regions. At the same time, we identified that hydrophobic amino acid residues, compositionally biased protein regions and regions of interest are predominantly enriched in missense variants carried by individuals with ALS. Assessment of expression level based on transcriptomics also revealed enrichment of variants of high and medium expression across all tissues and within the brain. We further explored enriched features of interest using burden analyses and identified individual genes were indeed driving certain enrichment signals. A case study is presented for SOD1 to demonstrate proof-of-concept of how enriched features may aid in defining variant pathogenicity. Our results present proteomic and transcriptomic features that are important indicators of missense variant pathogenicity in ALS and are distinct from features associated with neurodevelopmental disorders.

Pleiotropy of autism-associated chromatin regulators

Gene ontology analyses of high-confidence autism spectrum disorder (ASD) risk genes highlight chromatin regulation and synaptic function as major contributors to pathobiology. Our recent functional work in vivo has additionally implicated tubulin biology and cellular proliferation. As many chromatin regulators, including the ASD risk genes ADNP and CHD3, are known to directly regulate both tubulins and histones, we studied the five chromatin regulators most strongly associated with ASD (ADNP, CHD8, CHD2, POGZ and KMT5B) specifically with respect to tubulin biology. We observe that all five localize to microtubules of the mitotic spindle in vitro in human cells and in vivo in Xenopus. Investigation of CHD2 provides evidence that mutations present in individuals with ASD cause a range of microtubule-related phenotypes, including disrupted localization of the protein at mitotic spindles, cell cycle stalling, DNA damage and cell death. Lastly, we observe that ASD genetic risk is significantly enriched among tubulin-associated proteins, suggesting broader relevance. Together, these results provide additional evidence that the role of tubulin biology and cellular proliferation in ASD warrants further investigation and highlight the pitfalls of relying solely on annotated gene functions in the search for pathological mechanisms.

Machine learning approach combined with causal relationship inferring unlocks the shared pathomechanism between COVID-19 and acute myocardial infarction

Background

Increasing evidence suggests that people with Coronavirus Disease 2019 (COVID-19) have a much higher prevalence of Acute Myocardial Infarction (AMI) than the general population. However, the underlying mechanism is not yet comprehended. Therefore, our study aims to explore the potential secret behind this complication.

Materials and methods

The gene expression profiles of COVID-19 and AMI were acquired from the Gene Expression Omnibus (GEO) database. After identifying the differentially expressed genes (DEGs) shared by COVID-19 and AMI, we conducted a series of bioinformatics analytics to enhance our understanding of this issue.

Results

Overall, 61 common DEGs were filtered out, based on which we established a powerful diagnostic predictor through 20 mainstream machine-learning algorithms, by utilizing which we could estimate if there is any risk in a specific COVID-19 patient to develop AMI. Moreover, we explored their shared implications of immunology. Most remarkably, through the Bayesian network, we inferred the causal relationships of the essential biological processes through which the underlying mechanism of co-pathogenesis between COVID-19 and AMI was identified.

Conclusion

For the first time, the approach of causal relationship inferring was applied to analyzing shared pathomechanism between two relevant diseases, COVID-19 and AMI. Our findings showcase a novel mechanistic insight into COVID-19 and AMI, which may benefit future preventive, personalized, and precision medicine.

Graphical abstract

Mechanism of KMT5B haploinsufficiency in neurodevelopment in humans and mice

Pathogenic variants in KMT5B, a lysine methyltransferase, are associated with global developmental delay, macrocephaly, autism, and congenital anomalies (OMIM# 617788). Given the relatively recent discovery of this disorder, it has not been fully characterized. Deep phenotyping of the largest (n = 43) patient cohort to date identified that hypotonia and congenital heart defects are prominent features that were previously not associated with this syndrome. Both missense variants and putative loss-of-function variants resulted in slow growth in patient-derived cell lines. KMT5B homozygous knockout mice were smaller in size than their wild-type littermates but did not have significantly smaller brains, suggesting relative macrocephaly, also noted as a prominent clinical feature. RNA sequencing of patient lymphoblasts and Kmt5b haploinsufficient mouse brains identified differentially expressed pathways associated with nervous system development and function including axon guidance signaling. Overall, we identified additional pathogenic variants and clinical features in KMT5B-related neurodevelopmental disorder and provide insights into the molecular mechanisms of the disorder using multiple model systems.