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The 9th International RASopathies Symposium.

The RASopathies are a group of congenital disorders with overlapping clinical manifestations that are caused by pathogenic germline or early somatic variants that result in the hyperactivation of the RAS/mitogen-activated protein kinase (MAPK) signaling pathway. Given the heterogeneous clinical presentations of these disorders that involve abnormalities across multiple organ systems, multidisciplinary clinical management and progress in scientific research are essential for optimal patient diagnosis and care. The 9th International RASopathies Symposium, a biennial meeting, was organized by the patient advocacy group RASopathies Network and showcased recent discoveries, case studies, and advances in preclinical research. Participants, who included scientists, clinicians, industry representatives, patients, and family advocates, explored knowledge gaps, innovative clinical approaches, and lived experiences of individuals with a RASopathy. Sessions centered around organ systems were introduced with a patient perspective to highlight the burden of disease, continued with presentations from established and early-career investigators. Overall, the RASopathies Symposia serve as a catalyst for sustained community collaboration focused on enhancing patient health and accelerating the translation of discoveries into effective treatments.

Humans

Solid tumours in RASopathies: insights from a large monocentric cohort and systematic review of the literature.

BACKGROUND: Dysregulation of the RAS-mitogen-activated protein kinase signalling pathway underlies RASopathies, a family of neurodevelopmental disorders associated with variable cancer predisposition. However, the prevalence and spectrum of solid tumours and the contribution of specific variants to tumour susceptibility remain poorly defined. METHODS: We assessed solid tumour prevalence and spectrum in the largest single-centre cohort of individuals with RASopathies (n=138), excluding neurofibromatosis type 1 and integrated these findings with a systematic literature review to evaluate tumour distribution and genotype-phenotype correlations. RESULTS: In our cohort, at least one solid tumour was identified in 10.8% of individuals with Noonan syndrome (NS), 47.8% with Costello syndrome (CS) and 7.3% with cardiofaciocutaneous syndrome (CFCS). Malignant tumours occurred in 5.4%, 30.4% and 2.4%, respectively. CS showed the highest tumour burden, frequently with multiple primary tumours, predominantly of the bladder. In NS, low-grade central nervous system (CNS) tumours were most common, particularly among individuals carrying PTPN11 variants. Tumour onset occurred with a median age of 19, 14 and 13 years in NS, CS and CFCS, respectively. Literature data analysis identified candidate variants in HRAS, PTPN11 and SOS1 genes associated with increased risk for solid tumours, which differed from mutational hotspots reported in childhood leukaemia or sporadic cancers. CONCLUSION: Solid tumour risk in RASopathies is syndrome-dependent and genotype-dependent, with CS showing a high burden of bladder tumours and NS mainly associated with CNS tumours. These findings may support tailored surveillance strategies.

Human Genetics

Ras-MAPK pathway in patients with lupus nephritis.

BACKGROUND: Pathogenic mutations in genes encoding components of the Ras/mitogen-activated protein kinase (Ras-MAPK) pathway cause RASopathy. Here, we describe five unrelated patients with SLE carrying mutations associated with RASopathy and investigate the activity of the Ras-MAPK pathway. METHODS: Pathogenic variants were identified by whole-exome/whole-genome sequencing. The activity of the Ras-MAPK pathway in peripheral blood mononuclear cells (PBMC) and kidneys was evaluated using RNA sequencing and datasets from the nephroseq database, respectively. RESULTS: Five (likely) pathogenic variants in four Ras-MAPK genes were identified, including NRAS: c.G38A: p.G13D; ARAF: c.C1435T: p.R479C; KRAS: c.T341C: p.V114A; PTPN11: c.G455A: p.R152H and NRAS: c.G34A: p.G12S. Kidney injury is the main feature, presenting with nephrotic syndrome (2/5), proteinuria and haematuria (2/5). Acute kidney injury and rapidly progressive nephritic syndrome were noted in one patient each. Other clinical features included mucocutaneous lesions (5/5), cardiac involvement (4/5) and arthralgia (3/5). Laboratory abnormalities included hypocomplementaemia (5/5), presence of antiphospholipid antibodies (4/5), decreased regulatory T cells (3/3), pancytopenia (3/5) and persistent monocytosis (2/5). Kidney biopsy revealed lupus nephritis. Most patients responded well to standard therapy, with the exception of the patient with the NRAS p.G13D mutation who died. The Ras-MAPK pathway was activated in both PBMC and kidney of patients with LN as indicated by increased expression of NRAS, KRAS, RIT1, MRAS, PPP1CB, SHOC2, SOS2 and MAP2K1, as well as decreased expression of negative regulators of the Ras-MAPK pathway, CBL, LZTR1 and NF1. CONCLUSION: Kidney involvement may be the main feature of the clinical spectrum of RASopathy. Genetic screening should be considered for patients with early onset lupus.

Humans

Costello Syndrome Associated With Somatic Mosaicism of Rare p.Gly13Asp HRAS Variant: Expanding the Phenotypic Spectrum.

BACKGROUND: Costello syndrome (CS) is a rare RASopathy, mostly caused by de novo heterozygous pathogenic variants in the HRAS gene. Over 80% of cases involve the germline p.Gly12Ser variant, resulting in a fairly uniform phenotype of neuro-cardio-facio-cutaneous involvement with an increased risk of malignancy. Consequences of other rare HRAS variants are less well understood due to the limited number of reported cases. METHODS: An adult, young woman was referred due to sparse, slow-growing scalp hair, Blaschko-linear hyperpigmentation, acanthosis nigricans, palmoplantar hyperkeratosis, and joint hyperlaxity. Molecular, imaging, and detailed laboratory studies were performed. RESULTS: Although initial clinical exome- and whole-exome sequencing (WES) were inconclusive, indicating possible mosaicism, subsequent WES from hair-derived DNA samples revealed somatic mosaicism for the rare HRAS p.Gly13Asp variant. Brain MRIs showed a cerebral cavernoma, while cardiological evaluation, urinalysis, abdominal, and pelvic ultrasound were unremarkable. Nevertheless, she remains under close follow-up. CONCLUSION: Among the ten reported individuals carrying the p.Gly13Asp variant, our patient is only the second with confirmed mosaicism and the fifth mosaic CS case described to date. This case expands the phenotypic spectrum of CS and highlights the need for multi-tissue analysis in attenuated or atypical presentations to ensure a correct diagnosis, oncological risk assessment, and informed genetic and reproductive counseling.

Humans

ASXL1 truncating variants in BOS and myeloid leukemia drive shared disruption of Wnt-signaling pathways but have differential isoform usage of RUNX3.

BACKGROUND: Rare variants in epigenes (a.k.a. chromatin modifiers), a class of genes that control epigenetic regulation, are commonly identified in both pediatric neurodevelopmental syndromes and as somatic variants in cancer. However, little is known about the extent of the shared disruption of signaling pathways by the same epigene across different diseases. To address this, we study an epigene, Additional Sex Combs-like 1 (ASXL1), where truncating heterozygous variants cause Bohring-Opitz syndrome (BOS, OMIM #605039), a germline neurodevelopmental disorder, while somatic variants are driver events in acute myeloid leukemia (AML). No BOS patients have been reported to have AML. METHODS: This study explores common pathways dysregulated by ASXL1 variants in patients with BOS and AML. We analyzed whole blood transcriptomic and DNA methylation data from patients with BOS and AML with ASXL1-variant (AML-ASXL1) and examined differential exon usage and cell proportions. RESULTS: Our analyses identified common molecular signatures between BOS and AML-ASXL1 and highlighted key biomarkers, including VANGL2, GRIK5 and GREM2, that are dysregulated across samples with ASXL1 variants, regardless of disease type. Notably, our data revealed significant de-repression of posterior homeobox A (HOXA) genes and upregulation of Wnt-signaling and hematopoietic regulator HOXB4. While we discovered many shared epigenetic and transcriptomic features, we also identified differential splice isoforms in RUNX3 where the long isoform, p46, is preferentially expressed in BOS, while the shorter p44 isoform is expressed in AML-ASXL1. CONCLUSION: Our findings highlight the strong effects of ASXL1 variants that supersede cell-type and even disease states. This is the first direct comparison of transcriptomic and methylation profiles driven by pathogenic variants in a chromatin modifier gene in distinct diseases. Similar to RASopathies, in which pathogenic variants in many genes lead to overlapping phenotypes that can be treated by inhibiting a common pathway, our data identifies common pathways for ASXL1 variants that can be targeted for both disease states. Comparative approaches of high-penetrance genetic variants across cell types and disease states can identify targetable pathways to treat multiple diseases. Finally, our work highlights the connections of epigenes, such as ASXL1, to an underlying stem-cell state in both early development and in malignancy.

Humans

Genotype-phenotype correlations with autism spectrum disorder-related traits in noonan syndrome and noonan syndrome with multiple lentigines: a cross-sectional study.

BACKGROUND: Noonan syndrome (NS) and Noonan syndrome with multiple lentigines (NSML) are neurodevelopmental conditions caused by genetic variants leading to upregulated signaling in the RAS-MAPK pathway. While previous research has focused on genetic variability in cognitive and cardiac phenotypes, behavioral phenotypes, and their correlations across genetic variants and within the PTPN11 gene remain poorly characterized. METHODS: This study included 121 individuals with NS (PTPN11: 88, SOS1: 18, RAF1: 6, KRAS: 2, RIT1: 3, NRAS: 2, LZTR1: 2, SOS2: 1) and seven individuals with NSML (PTPN11), compared to age- and sex-matched typically developing (TD) (N = 71). Behavioral questionnaires assessed social responsiveness and ASD-related traits (using SRS-2), and emotional problems (using CBCL) to identify genetic variant-specific behavioral profiles. Biochemical profiling of SHP2 activity in PTPN11-associated NS variants examined genotype-phenotype relationships. RESULTS: Compared to TD individuals, those with PTPN11-associated NS, NSML, and SOS1-associated NS exhibited clinically elevated scores, indicating increased ASD-related behaviors, poorer social functioning, and heightened emotional problems. Genetic variant comparisons revealed that individuals with PTPN11-associated NS and NSML exhibited greater ASD-related challenges than those with RAF1. Individuals with NSML exhibit elevated attention problems compared to all other genetic groups. Logistic regression results suggested each one-unit increase in SHP2 fold activation for PTPN11-associated NS corresponded to a 64% higher likelihood of markedly elevated restricted and repetitive behaviors, suggesting genotype-phenotype links. LIMITATIONS: Small sample sizes for rarer variants, leading to unequal group sizes across subgroups, with PTPN11 variants comprising most of the NS group. Future research should address these sampling constraints and conduct functional studies to clarify variant impacts. Longitudinal assessments could elucidate behavioral phenotype trajectories. CONCLUSIONS: This study underscores the importance of genetic variant-specific research to understand unique behavioral phenotypes in NS and NSML. Our findings indicate a higher risk for ASD-related symptoms in PTPN11-associated NS and NSML compared to other variants. Additionally, individuals with PTPN11-associated NS and higher SHP2 fold activation exhibited greater impairments in restricted and repetitive behaviors, suggesting SHP2 activation variations may contribute to phenotypic variability. By linking ASD-related symptoms to biochemical predictors in PTPN11-associated NS, this study may inform future targeted treatment approaches.

Humans