LEOPARD Syndrome Research Articles

CSIG-06. BRAF GERMLINE MUTATIONS AND PREDISPOSITION TO BRAIN TUMORS

Abstract We report on two BRAF-mutated children and discuss genetic counseling regarding predisposition to brain tumors. Molecular analysis of the PTPN11 gene and twelve other genes in the RAS-MAPK pathway was carried out in a series of 54 dysmorphic patients with suspected Rasopathies. Two heterozygous BRAF germline mutations were detected in two 7-year-old girls, at exon 6 and 12 respectively. Both patients had the distinctive facial appearance of cardio-facio-cutaneous syndrome (CFC) type 1. Patients with CFC are rare and characterized by phenotypic and genetic heterogeneity, with overlaps with Noonan syndrome. While nearly 75% of CFC cases have germline BRAF mutations, the frequency of BRAF mutations is inferior in Noonan and LEOPARD syndromes. BRAF mutations in CFC are often found in the cysteine-rich domain of the BRAF protein (exons 6, 11, 12, 13, 14, 15 and 16). Conversely, somatic BRAF mutations are more common, grouped into classes according to their kinase activity level, and have been associated with a variety of malignancies, including pediatric and adult brain tumors (low- and high-grade gliomas, glioblastomas and low-grade astrocytomas). BRAF V600E is the most common somatic mutation, but other mutations are currently being identified. Many of these mutations are within the kinase domain, while others are located across the gene and have less well-understood functional consequences. Germinal V600E mutation has been described once, in a CFC patient having a severe phenotype. Nevertheless, it seems that patients with germline BRAF mutations and gliomas have not yet been reported. Given the rarity of CFC, it is unclear whether there is a high risk of brain tumors. Further molecular studies will enable us to refine recommendations for the prevention, monitoring and care of people with germline BRAF mutations, given the success of BRAF inhibitors in certain cancers, with encouraging results in gliomas.

Atypical Multifocal Granular Cell Tumor with FLT3 Y842C Somatic Mutation: A case report and a review of the literature.

Granular cell tumors (GCT) are predominantly benign neoplasms composed by cells with abundant eosinophilic granular cytoplasm. Although the majority of GCTs exhibit a benign clinical course, a minority display cytological atypia and may exhibit aggressive, cancer-like behavior. Definitive evidence of malignancy in GCTs is reliably established only through the presence of metastasis. Addi- tionally, a subset of GCTs demonstrates a high rate of recurrence, underscoring the need for better prog- nostic markers. Therefore, it is crucial to identify molecular markers associated with aggressive behavior in GCTs. Molecular analysis may be particularly beneficial in cases exhibiting cytological atypia to in- form clinical outcome prognostication and guide therapeutic strategies. In this case report, a 45-year-old female with multiple gastrointestinal GCTs is pre- sented. The patient did not have any genetic syndromes commonly associated with GCT, such as neu- rofibromatosis type 1, Noonan syndrome or LEOPARD syndrome. The tumors not only demonstrated nuclear atypia, but also harbored a unique FLT3 Y842C somatic alteration identified by next-genera- tion sequencing. The patient remains asymptomatic and under endoscopic surveillance two years after diagnosis and complete resection of the neoplasms. We presented an exceedingly rare case of multifocal atypical GCT in an adult without any previously known genetic syndrome. A tumoral FLT3 Y842C point mutation not previously reported in GCT was discovered. Although the precise significance of this finding is uncertain, FLT3 Y842C has been cataloged as likely pathogenic in ClinVar. This report underscores the potential predictive utility of next-generation sequencing in the characterization and management of rare neoplasms.

Age-related retinal degeneration resulting from the deletion of Shp2 tyrosine phosphatase in photoreceptor neurons

Shp2, a critical SH2-domain-containing tyrosine phosphatase, is essential for cellular regulation and implicated in metabolic disruptions, obesity, diabetes, Noonan syndrome, LEOPARD syndrome, and cancers. This study focuses on Shp2 in rod photoreceptor cells, revealing its enrichment, particularly in rods. Deletion of Shp2 in rods leads to age-dependent photoreceptor degeneration. Shp2 targets occludin (OCLN), a tight junction protein, and its deletion reduces OCLN expression in the retina and retinal pigment epithelium (RPE). The isolation of actively translating mRNAs from rods lacking Shp2, followed by RNA sequencing, reveals alterations in cell cycle regulation. Additionally, altered retinal metabolism is observed in retinal cells lacking Shp2. Our studies indicate that Shp2 is crucial for maintaining the structure and function of photoreceptors.

SHP2 as a primordial epigenetic enzyme expunges histone H3 pTyr-54 to amend androgen receptor homeostasis

Mutations that decrease or increase the activity of the tyrosine phosphatase, SHP2 (encoded by PTPN11), promotes developmental disorders and several malignancies by varying phosphatase activity. We uncovered that SHP2 is a distinct class of an epigenetic enzyme; upon phosphorylation by the kinase ACK1/TNK2, pSHP2 was escorted by androgen receptor (AR) to chromatin, erasing hitherto unidentified pY54-H3 (phosphorylation of histones H3 at Tyr54) epigenetic marks to trigger a transcriptional program of AR. Noonan Syndrome with Multiple Lentigines (NSML) patients, SHP2 knock-in mice, and ACK1 knockout mice presented dramatic increase in pY54-H3, leading to loss of AR transcriptome. In contrast, prostate tumors with high pSHP2 and pACK1 activity exhibited progressive downregulation of pY54-H3 levels and higher AR expression that correlated with disease severity. Overall, pSHP2/pY54-H3 signaling acts as a sentinel of AR homeostasis, explaining not only growth retardation, genital abnormalities and infertility among NSML patients, but also significant AR upregulation in prostate cancer patients.

Paternally Inherited Noonan Syndrome Caused by a PTPN11 Variant May Exhibit Mild Symptoms: A Case Report and Literature Review.

Noonan syndrome (NS)/Noonan syndrome with multiple lentigines (NSML) is commonly characterized by distinct facial features, a short stature, cardiac problems, and a developmental delay of variable degrees. However, as many as 50% of individuals diagnosed with NS/NSML have a mildly affected parent or relative due to variable expressivity and possibly incomplete penetrance of the disorder, and those who are recognized to have NS only after a diagnosis are established in a more obviously affected index case. In order to collect intergenerational data reported from previous studies, electronic journal databases containing information on the molecular genetics of PTPN11 were searched from 2000 to 2022. We present a case of a proband with a PTPN11 variant (c.1492C > T/p.Arg498Trp) inherited from an asymptomatic father, displaying only mild intellectual disability without classical symptoms of NS. Among our cases and the reported NS cases caused by the PTPN11 p.Arg498Trp variant, cardiac abnormalities (6/11), facial dysmorphism (7/11), skin pigmentation (4/11), growth problems (4/11), and sensorineural hearing loss (2/11) have been observed. NS/NSML patients with the PTPN11 p.Arg498Trp variant tend to exhibit relatively lower frequencies of skin pigmentation, facial dysmorphism and cardiac abnormalities and mild symptoms compared to those carrying any other mutated PTPN11. Paternally inherited NS/NSML caused by a PTPN11 p.Arg498Trp variant, including our cases, may exhibit relatively lower frequencies of abnormal features and mild symptoms. This could be ascribed to potential gene-gene interactions, gene-environment interactions, the gender and phenotype of the transmitting parent, or ethnic differences that influence the clinical phenotype.

Natural history and outcomes in paediatric RASopathy-associated hypertrophic cardiomyopathy.

This study aimed to describe the natural history and predictors of all-cause mortality and sudden cardiac death (SCD)/equivalent events in children with a RASopathy syndrome and hypertrophic cardiomyopathy (HCM). This is a retrospective cohort study from 14 paediatric cardiology centres in the United Kingdom and Ireland. We included children <18years with HCM and a clinical and/or genetic diagnosis of a RASopathy syndrome [Noonan syndrome (NS), NS with multiple lentigines (NSML), Costello syndrome (CS), cardiofaciocutaneous syndrome (CFCS), and NS with loose anagen hair (NS-LAH)]. One hundred forty-nine patients were recruited [111 (74.5%) NS, 12 (8.05%) NSML, 6 (4.03%) CS, 6 (4.03%) CFCS, 11 (7.4%) Noonan-like syndrome, and 3 (2%) NS-LAH]. NSML patients had higher left ventricular outflow tract (LVOT) gradient values [60 (36-80) mmHg, P=0.004]. Over a median follow-up of 197.5 [inter-quartile range (IQR) 93.58-370] months, 23 patients (15.43%) died at a median age of 24.1 (IQR 5.6-175.9) months. Survival was 96.45% [95% confidence interval (CI) 91.69-98.51], 90.42% (95% CI 84.04-94.33), and 84.12% (95% CI 75.42-89.94) at 1, 5, and 10years, respectively, but this varied by RASopathy syndrome. RASopathy syndrome, symptoms at baseline, congestive cardiac failure (CCF), non-sustained ventricular tachycardia (NSVT), and maximal left ventricular wall thickness were identified as predictors of all-cause mortality on univariate analysis, and CCF, NSVT, and LVOT gradient were predictors for SCD or equivalent event. These findings highlight a distinct category of patients with Noonan-like syndrome with a milder HCM phenotype but significantly worse survival and identify potential predictors of adverse outcome in patients with RASopathy-related HCM.

Leopard syndrome without lentigenes: A rare presentation and literature review

Abstract: Leopard syndrome (LS) has presentations of lentigines, conduction abnormalities in the heart, hypertelorism of the eyes, stenosis of the pulmonary artery, cryptorchidism, mental retardation, and sensorineural deafness. Another condition known as Noonan syndrome (NS) has many overlapping symptoms. LS is due to germ-line mutations in the PTPN11 gene. The same genetic mutation also leads to NS. Here, we described a 10-year-old male child presented with failure to thrive, decreased appetite, large atrial septal defect, and developmental delay and later on diagnosed with LS by whole-genome sequencing. In this case, characteristic lentigines are absent, which puts the pediatrician in a dilemma. However, by using the diagnostic criteria set by Voron since 1976, we are able to reach a clinical diagnosis of LS.

Natural history and predictors of all-cause mortality and major arrhythmic cardiac events in pediatric RASopathy associated hypertrophic cardiomyopathy

Abstract The RASopathies are a group of developmental disorders caused by germline variants in components of the RAS-MAPK pathway, commonly associated with hypertrophic cardiomyopathy (HCM). The aim of this study was to describe the natural history and predictors of all-cause mortality and major arrhythmic cardiac events (MACE) in a large, multi-centre cohort of paediatric patients with a RASopathy syndrome and HCM. One-hundred-and-forty-nine patients were included (111 (74.5%) Noonan Syndrome (NS); 12 (8.05%) Noonan Syndrome with Multiple Lentigines (NSML); 6 (4.03%) Costello Syndrome (CS); 6 (4.03%) Cardiofaciocutaneous Syndrome (CFCS); and 14 (9.4%) with Noonan-like syndrome patients). NSML patients had higher maximal left ventricular wall thickness (MLVWT) (z score 17.02 (10.57-32.78), p=0.004] and higher left ventricular outflow tract (LVOT) gradient values (60mmHg, 36-80, p=0.019), with no other significant echocardiographic differences between RASopathy syndromes. Over a median follow up of 197.5 months (93.58-370), 23 patients (15.43%) died, at a median age of 48.94 months (3.29-175.84). Overall survival was 96.45% (91.69-98.51), 90.42% (84.04-94.33) and 84.12 (75.42-89.94) at 1, 5 and 10 years, respectively, but this was varied according to RASopathy syndrome. RASopathy syndrome, specifically Noonan-like syndrome (Hazard ratio 4.18, p=0.032) and congestive cardiac failure admission (Hazard ratio 7.35, p=0.037) were independent predictors of all-cause mortality and LVOT gradient was an independent predictor for MACE (Hazard ratio 1.02, p=0.025). These findings highlight a distinct category of patients with Noonan-like syndrome with a milder HCM phenotype but significantly worse survival and identify predictors of adverse outcome in patients with RASopathy-related HCM.

Prevalence of myocarditis and its contribution to the course of primary myocardial hypertrophy

Aim. To assess the incidence of myocarditis in patients with primary myocardial hypertrophy and to study its contribution to the disease course.Material and methods. The study included 100 patients with primary left ventricular myocardial hypertrophy, 52 men and 48 women (mean age, 51,5±15,7 years; followup period 10,4 [2,1; 36,1] months). All patients underwent electrocardiography, 24-hour electrocardiographic monitoring, echocardiography, as well as DNA analysis (n=96), myocardium pathological study (n=29), cardiac magnetic resonance imaging (n=31), cardiac multislice computed tomography (n=26), assessment of anti-cardiac antibodies (n=43), free light chain level in serum and urine by immunofixation method (n=10); 99mTc-pyrophosphate myocardial scintigraphy (n=5); biopsy of the rectal mucosa and/or subcutaneous fat for amyloid (n=9).Results. In 68%, true (sarcomeric) hypertrophic cardiomyopathy (HCM) was diagnosed, in 16% — amyloidosis with cardiac involvement, in 10% — storage diseases, in 3% — neuromuscular diseases, in 2% — myocardial hypertrophy was combined with severe restriction (mixed phenotype), and in 1% — LEOPARD syndrome. Concomitant myocarditis was diagnosed in 30% of patients. In HCM, myocarditis was detected in 31% of cases. These patients had a significantly higher heart failure class (heart failure class 3 [2; 3] vs 2 [1; 3], p=0,026) and mortality (33,3% vs 6,4%, p=0,01). In amyloidosis, the incidence of myocarditis was 31,3%. In these patients, ventricular tachycardia was observed significantly more often: 80,0% vs 18,2% (p=0,036). The prevalence of concomitant myocarditis in the subgroup of storage diseases was 30%: 2 patients with Fabry disease and 1 patient with Danon disease. Of the three patients with neuromuscular diseases, myocarditis was diagnosed in 1. In the subgroups with the restrictive phenotype and LEOPARD syndrome, no cases of myocarditis were recorded. Treatment of myocarditis made it possible to stabilize the patients' condition.Conclusion. Concomitant myocarditis led to heart failure progression, worsening ventricular arrhythmias and, as a consequence, an increased risk of sudden cardiac death. It is necessary to actively diagnose and treat myocarditis in patients with primary myocardial hypertrophy.

SAT580 Incidental Diagnosis Of Genetic Variant PTPN11 Noonan Syndrome With Multiple Lentigines, Sensorineural Hearing Loss And Rheumatoid Arthritis In Adult Female With Hashimoto’s Thyroiditis. Case Report

Abstract Disclosure: M.M. Eid: None. T. Zahra: None. J. Vargas-Jerez: None. Introduction: Hashimoto’s thyroiditis (HT, chronic lymphocytic thyroiditis, autoimmune thyroiditis) and Rheumatoid arthritis (RA) are autoimmune disorders, affect mainly females (1). Noonan syndrome with Multiple Lentigines (NSML, Leopard Syndrome) is a rare multigenetic autosomal dominant disorder. It includes cerebrovascular and cardiac anomalies, facial phenotype, hearing abnormality and developmental delay (2). Case: 41 yo, Female with history of HT since 2002 (high TSH, thyroid peroxidase antibody more than 1000 u/ml, low FT4 and FT3) on levothyroxine 150mcg/day. Recently moved to the USA from EL Salvador. Presented for initial evaluation. Denied smoking, alcohol, allergy. Maternal aunt with thyroid disease. Had menstrual irregularities, no previous attempt to conceive. Review of system: 5 months of pain, swelling and morning stiffness for 1 hour in hand joints, hearing difficulty for 2 years, painless brown skin spots for years, childhood learning difficulty and constipation. Physical examination body weight 139Ib, height 162cm, Stable vitals, diffuse lentigines. Head: board forehead, hypertelorism, high arched eye brows, micrognathia, low set ears. Heart: normal heart sounds, no murmur. No thyromegaly, nystagmus or vertigo. Hand: swelling of metacarpophalangeal and proximal interphalangeal joints. Laboratory work up TSH 8 normal 0.27 to 4.2 uIU/ml, FT4 0.8 normal 0.9-1.8 ng/dl, A1C 5.7, positive rheumatoid factor 199IU/ml, anti-CCP antibody &amp;gt; 250U, ANA 1/320, ESR 61ml/hr, negative anti-tissue transglutaminase antibody, normal liver and kidney function tests and complete blood count. Hand X-ray: decrease joint space and bone erosion. Thyroid US: normal size, vascularity, no nodule. Normal Echocardiogram, EKG and chest X ray. Internal auditory canal MRI: no masses or abnormal enhancement. DEXA Scan: osteopenia of femur and lumbar spine. She was diagnosed with seropositive RA, B/L sensorineural hearing loss (SNHL) more on right side. Genetic test revealed heterozygous pathogenic variant of PTPN11 gene consistent with NSML and negative for Neurofibromatosis type 1. Kept on prednisone and methotrexate, levothyroxine was increased 162mcg/day. Conclusion: Autoimmune disorders have a common pathogenesis including humoral and cell mediated immunity, autoimmune oxidative stress, UV radiation exposure, genetic linkage and biochemical changes. Diagnosis of one autoimmune disorder increases the possibility of other autoimmune disorders (1). NSML has a variable presentation. PTPN11-NSML is usually associated with SNHL and cardiac anomalies as pulmonary stenosis. It is infrequent to diagnose NSML with HT and structurally normal heart like our case(2).

RASopathies and cardiac manifestations.

As binary switches, RAS proteins switch to an ON/OFF state during signaling and are on a leash under normal conditions. However, in RAS-related diseases such as cancer and RASopathies, mutations in the genes that regulate RAS signaling or the RAS itself permanently activate the RAS protein. The structural basis of this switch is well understood; however, the exact mechanisms by which RAS proteins are regulated are less clear. RAS/MAPK syndromes are multisystem developmental disorders caused by germline mutations in genes associated with the RAS/mitogen-activated protein kinase pathway, impacting 1 in 1,000-2,500 children. These include a variety of disorders such as Noonan syndrome (NS) and NS-related disorders (NSRD), such as cardio facio cutaneous (CFC) syndrome, Costello syndrome (CS), and NS with multiple lentigines (NSML, also known as LEOPARD syndrome). A frequent manifestation of cardiomyopathy (CM) and hypertrophic cardiomyopathy associated with RASopathies suggest that RASopathies could be a potential causative factor for CM. However, the current supporting evidence is sporadic and unclear. RASopathy-patients also display a broad spectrum of congenital heart disease (CHD). More than 15 genes encode components of the RAS/MAPK signaling pathway that are essential for the cell cycle and play regulatory roles in proliferation, differentiation, growth, and metabolism. These genes are linked to the molecular genetic pathogenesis of these syndromes. However, genetic heterogeneity for a given syndrome on the one hand and alleles for multiple syndromes on the other make classification difficult in diagnosing RAS/MAPK-related diseases. Although there is some genetic homogeneity in most RASopathies, several RASopathies are allelic diseases. This allelism points to the role of critical signaling nodes and sheds light on the overlap between these related syndromes. Even though considerable progress has been made in understanding the pathophysiology of RASopathy with the identification of causal mutations and the functional analysis of their pathophysiological consequences, there are still unidentified causal genes for many patients diagnosed with RASopathies.

Prospects for diagnostics and treatment of neurofibromatosis type 1 in Russia

Purpose of the study. Analysis of available data on modern methods of diagnosis and treatment of neurofibromatosis type 1 (NF1) and their application in the Russian Federation. Material and Methods. The search for relevant sources was carried out in the Scopus, Web of Science, PubMed, Elibrary systems, including publications from February 1992 to December 2022. Of the 1873 scientific articles found, 48 were used to write a systematic review. Results. Neurofibromatosis type 1 (NF1) is caused by germline heterozygous mutations in the NF1 gene, which encodes the neurofibromin protein, which suppresses mitogen-activated signaling pathways necessary for cell proliferation. Clinical manifestations of NF1 are similar to Peutz–Jeghers, Laugier–Hunziker, Rusalkab–Muret–Smith, Bannayan–Zonnana, LEOPARD syndromes, neurofibromatosis type 2 and lipomatosis; therefore, to confirm the diagnosis, the most important criterion is the detection of a gene mutation by sequencing, since there are no mutagenesis hotspots in the NF1 gene. To detect 17q11.2 locus microdeletions, MLPA method is used. In Russia, such methods of molecular genetic identification of NF1 were carried out in Moscow and in the Republic of Bashkortostan. Surgical interventions using a neodymium laser and therapy with mitogen-activated protein kinase inhibitors are the most effective for the treatment of tumor syndrome. Scientific results of the use of a surgical laser in the treatment of plexiform neurofibromas and extramedullary tumors of the spinal cord have been published in Russia. Treatment of NF1 with selumetinib in Russia was announced by the interregional public organization for assistance to patients with neurofibromatosis “22/17”, which provides the drug to children with inoperable neurofibromas free of charge. Conclusion. In modern medicine, it is necessary to widely use methods for identifying mutations in the NF1 gene by creating universal panels of targeted sequencing. This will allow not only the differential diagnosis of NF1, but also the identification of the cause of chemoresistance of sporadic malignant neoplasms for the introduction of mitogen-activated protein kinase inhibitors in their treatment. Combination of this method with surgical excision of neurofibromas using a neodymium laser is optimal.

PA05 A rare case of cardiocutaneous syndrome in a young child

Abstract A 19-month-old infant came to our attention showing clinical signs consistent with focal keratoderma limited to the palms and soles, dystrophic pachyonychia of all his nails and scalp alopecia characterized by sparse curly hair. His oral cavity examination revealed periodontitis, early tooth decay and notching of the incisor teeth. The patient is the second child of a nonconsanguineous, otherwise healthy couple. No other family members were reported to have similar skin and oral alterations. Based on the characteristic appearance of his cutaneous lesions, he was investigated for a palmoplantar keratoderma disorder and was subjected to genetic testing. Results confirmed a mutation within DSP, a gene responsible for encoding the most abundant component of desmosomes, a major cell adhesion junction, particularly prominent in epidermal and cardiac tissue. Mutations in genes encoding desmosomal components are known to be associated with a broad spectrum of phenotypical alterations of skin and hair structures. The same genetic anomaly accounts for 40–50% of cases of arrhythmogenic cardiomyopathy (Pigors M, Schwieger-Briel A, Cosgarea R et al. Desmoplakin mutations with palmoplantar keratoderma, woolly hair and cardiomyopathy. Acta Derm Venereol 2015; 95:337–40). Despite being asymptomatic, our young patient was referred to cardiology for further investigations and surveillance. At the age of 7 years, routine electrocardiography revealed new conduction abnormalities. An echocardiogram confirmed a dilated cardiomyopathy that, combined with the previously described cutaneous and oral alterations, led to a diagnosis of cardiocutaneous syndrome. An overview of the clinical features associated with desmoplakin mutations reported in medical literature illustrates the complexity of this group of disorders and their genotype–phenotype correlations, which cannot be easily predicted. Our reported case is a paradigmatic example of diagnostic difficulties often encountered when facing concomitant dermatological and oral conditions in the same patient, emphasizing the importance of recognizing oral, dental and skin signs to be a potential risk factor for hidden cardiac diseases.

Discovering potential inhibitors of Raf proto-oncogene serine/threonine kinase 1: a virtual screening approach towards anticancer drug development

Raf proto-oncogene serine/threonine kinase 1 (RAF1 or c-Raf) is a serine/threonine protein kinase crucial in regulating cell growth, differentiation, and survival. Any disruption or overexpression of RAF1 can result in neoplastic transformation and other disorders such as cardiomyopathy, Noonan syndrome, leopard syndrome, etc. RAF1 has been identified as a potential therapeutic target in drug development against various complex diseases, including cancer, due to its remarkable role in disease progression. Here, we carried out a multitier virtual screening study involving different in-silico approaches to discover potential inhibitors of RAF1. After applying the Lipinski rule of five, we retrieved all phytocompounds from the IMPPAT database based on their physicochemical properties. We performed a molecular docking-based virtual screening and got top hits with the best binding affinity and ligand efficiency. Then we screened out the selected hits using the PAINS filter, ADMET properties, and other druglike features. Eventually, PASS evaluation identifies two phytocompounds, Moracin C and Tectochrysin, with appreciable anti-cancerous properties. Finally, all-atom molecular dynamics simulation (MDS) followed by interaction analysis was performed on the elucidated compounds in complex with RAF1 for 200 ns to investigate their time-evolution dynamics and interaction mechanism. Molecular mechanics Poisson–Boltzmann surface area (MM-PBSA) and Dynamical Cross-Correlation Matrix (DCCM) analyses then followed these results from the simulated trajectories. According to the results, the elucidated compounds stabilize the RAF1 structure and lead to fewer conformational alterations. The results of the current study indicated that Moracin C and Tectochrysin could serve as potential inhibitors of RAF1 after required validation. Communicated by Ramaswamy H. Sarma

Abstract 873: The mechanisms of SHP2 activation in cancer and neurodevelopmental disorder

Abstract The Src homology 2 domain-containing phosphatase 2 (SHP2) is a nonreceptor protein tyrosine phosphatase that regulates Ras/MAPK pathway, leading to cell proliferation. SHP2 mutations are commonly associated with human malignancies and neurodevelopmental disorders (NDDs). Somatic SHP2 mutations are associated with many types of cancer including sporadic juvenile myelomonocytic leukemia, acute myeloid leukemia, breast, gastric, lung, melanoma, and colorectal cancers, while heterozygous germline mutations are linked to NDDs such as Noonan and LEOPARD syndromes. Interestingly, different mutations at the same genomic loci of the gene result in different disease phenotypes, either cancer or NDDs. Patients with NDDs have a higher chance of developing cancer, suggesting a linkage between cancer and NDDs, and between their mutations. SHP2 consists of two SH2 domains (nSH2 and cSH2), a phosphatase (PTP) domain, and a flexible C-terminal tail. In autoinhibition, SHP2 is catalytically inactive, adopting a closed conformation in which the DE-loop of nSH2 blocks the catalytic site of PTP. The binding of nSH2 to the phosphotyrosine (pY)-motif relieve the autoinhibition via disruption of the nSH2-PTP interface. To depict mechanism of the mutation-associated activation of SHP2, extensive molecular dynamics simulations were performed for SHP2 protein with the mutations related to cancer and NDDs. The dynamics and conformational alterations of the wild type, cancer mutants (E76K, D61Y, D61V), and NDD mutants (E76D, D61G) of SHP2 were compared. Collective results showed that both cancer and NDD mutations weaken the nSH2-PTP interface, facilitating the SHP2 activation. Interestingly, cancer mutations induce stronger destruction at the nSH2-PTP interface than the NDD mutations. The PTP domain exhibits two pockets, orthosteric and allosteric pockets, at the interface with nSH2. In autoinhibition, the orthosteric pocket provides a binding site for D61 of nSH2, and the allosteric pocket accommodates E76 and A72 of nSH2. During the simulations, we observed that the mutations, E76K and E76D, reduce the interaction in the allosteric pocket, increasing the probability toward the open SHP2 conformation. This gradually weakens the interactions of D61 in the orthosteric pocket, promoting SH2 release and leading to SHP2 activation. The three mutations, D61Y, D61V, and D61G, directly disrupted the interaction in the orthosteric pocket, favoring the substrate binding. However, they do not optimize the nSH2 conformation for the pY binding and unlikely affect the interaction in the allosteric pocket. Our works explain the difference and similarity between the cancer and NDD mutations of SHP2 at the atomic level and provide deeper understanding of the mutation-induced activation of SHP2 for signal transduction through the Ras/MAPK pathway. Citation Format: Yonglan Liu, Mingzhen Zhang, Wengang Zhang, Hyunbum Jang, Ruth Nussinov. The mechanisms of SHP2 activation in cancer and neurodevelopmental disorder [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 873.

THE FEATURES AND ROLE OF SHP2 PROTEIN IN POSTNATAL MUSCLE DEVELOPMENT

SHP-2 (encoded by PTPN11) is a ubiquitously expressed protein tyrosine phosphatase required for signal transduction by multiple different cell surface receptors. Humans with carry germline SHP-2 mutations develop Noonan syndrome or LEOPARD syndrome, which are characterized by cardiovascular, neurological and skeletal abnormalities.Shp2 is an important signaling agent for growth factors and cytokines. To investigate the Ptpn11 in postnatal myogenesis of mice &nbsp;we analyzed using immunohistochemistry stem cell markers: Pax 7, Myo D, Myf 5 and Myo G in muscle cells isolated from wild type and Shp2 knockout mice. We used a conditional SHP-2 mouse mutant in which loss of expression of SHP-2 was induced in multiple tissues in response to drug administration. Our findings indicate that all these markers gradually decreased from birth to day 14 in mouse muscle cells. Here we show that Shp2, an intracellular tyrosine phosphatase with two SH2 domains, plays a critical role in mouse muscle development after birth. Our data demonstrate a molecular difference in the control and Sh2 knockout&nbsp; postnatal myogenic stem cells, and assign to Ptpn11 signaling a key function in satellite cell activity. These findings illustrate an essential role for Shp-2 in muscle growth and remodeling in adults, and reveal some of the cellular and molecular mechanisms involved. The model is predicted to be of further use in understanding how Shp-2 regulates muscle morphogenesis, which could lead to the development of novel therapies for the treatment of malformations in human patients with SHP-2 mutations.

How common are ear, nose and throat disorders in children with Noonan syndrome and other RASopathies?

Noonan syndrome and related conditions (RASopathies) are known to be associated with abnormalities in many organ systems. It is our impression that few otolaryngologists are familiar with the manifestations of these syndromes and we therefore reviewed our hospital's patient cohort to identify the prevalence of ear, nose and throat disorders in these children. We cross-referenced various hospital department databases (otolaryngology, audiology, cardiology, haematology and genetics) to try to identify as many children with Noonan and other RASopathies as possible. We then performed a retrospective review of electronic patient records. We identified 67 children with Noonan, Costello, LEOPARD and other RASopathy syndromes. Around half have been seen in otolaryngology and audiology clinics. Otitis media with effusion requiring ventilation tubes occurred in 4% of children. 10% have suffered recurrent acute otitis media. 9% have a sensorineural hearing loss. 7% have undergone adenotonsillectomy for obstructive sleep apnoea. Airway anomalies and head and neck malformations occur but are rare. Children with Noonan and other RASopathies present commonly to otolaryngology and audiology clinics. The prevalence of sensorineural hearing loss is high and audiological screening is likely to be worthwhile. Surgeons should be aware that complications of surgery are common and can be very severe, especially in those with cardiac anomalies.

Primary sudden cardiac death prevention in hypertrophic cardiomyopathy resulted from LEOPARD Syndrome

Leopard syndrome is an autosomal dominant inherited disease manifested by numerous cutaneous birthmarks, heart electrical conduction disorders, hypertelorism, pulmonary valve stenosis, deafness and hypertrophic cardiomyopathy. The disease may be accompanied by symptomatic ventricular tachycardia. In patients without the need for cardiac pacing and indications for a cardioverter-defibrillator (ICD) implantation, a completely subcutaneous system (S-ICD) may become an efficient option.

FMRP activity and control of Csw/SHP2 translation regulate MAPK-dependent synaptic transmission.

Noonan syndrome (NS) and NS with multiple lentigines (NSML) cognitive dysfunction are linked to SH2 domain-containing protein tyrosine phosphatase-2 (SHP2) gain-of-function (GoF) and loss-of-function (LoF), respectively. In Drosophila disease models, we find both SHP2 mutations from human patients and corkscrew (csw) homolog LoF/GoF elevate glutamatergic transmission. Cell-targeted RNAi and neurotransmitter release analyses reveal a presynaptic requirement. Consistently, all mutants exhibit reduced synaptic depression during high-frequency stimulation. Both LoF and GoF mutants also show impaired synaptic plasticity, including reduced facilitation, augmentation, and post-tetanic potentiation. NS/NSML diseases are characterized by elevated MAPK/ERK signaling, and drugs suppressing this signaling restore normal neurotransmission in mutants. Fragile X syndrome (FXS) is likewise characterized by elevated MAPK/ERK signaling. Fragile X Mental Retardation Protein (FMRP) binds csw mRNA and neuronal Csw protein is elevated in Drosophila fragile X mental retardation 1 (dfmr1) nulls. Moreover, phosphorylated ERK (pERK) is increased in dfmr1 and csw null presynaptic boutons. We find presynaptic pERK activation in response to stimulation is reduced in dfmr1 and csw nulls. Trans-heterozygous csw/+; dfmr1/+ recapitulate elevated presynaptic pERK activation and function, showing FMRP and Csw/SHP2 act within the same signaling pathway. Thus, a FMRP and SHP2 MAPK/ERK regulative mechanism controls basal and activity-dependent neurotransmission strength.

Multiple lentigines syndrome with positive family history: a case report and review of the literature

Multiple lentigines syndrome with positive family history: a case report and review of the literature