KRAS G12C-mutant driven non-small cell lung cancer (NSCLC)

KRAS G12C mutations in non-small cell lung cancer (NSCLC) partially respond to KRAS G12C covalent inhibitors. However, early adaptive resistance occurs due to rewiring of signaling pathways, activating receptor tyrosine kinases, primarily EGFR, but also MET and ligands. Evidence indicates that treatment with KRAS G12C inhibitors (sotorasib) triggers the MRAS:SHOC2:PP1C trimeric complex. Activation of MRAS occurs from alterations in the Scribble and Hippo-dependent pathways, leading to YAP activation. Other mechanisms that involve STAT3 signaling are intertwined with the activation of MRAS. The high-resolution MRAS:SHOC2:PP1C crystallization structure allows in silico analysis for drug development. Activation of MRAS:SHOC2:PP1C is primarily Scribble-driven and downregulated by HUWE1. The reactivation of the MRAS complex is carried out by valosin containing protein (VCP). Exploring these pathways as therapeutic targets and their impact on different chemotherapeutic agents (carboplatin, paclitaxel) is crucial. Comutations in STK11/LKB1 often co-occur with KRAS G12C, jeopardizing the effect of immune checkpoint (anti-PD1/PDL1) inhibitors.

Monogenic systemic lupus erythematosus onset in a 13-year-old boy with Noonan like-syndrome: a case report and literature review

BACKGROUND

Childhood systemic lupus erythematosus (cSLE) has been considered as a polygenic autoimmune disease; however, a monogenic lupus-like phenotype is emerging with the recent recognition of several related novel high-penetrance genetic variants. RASopathies, a group of disorders caused by mutations in the RAS/MAPK pathway, have been recently described as a cause of monogenic lupus.

CASE PRESENTATION

We present a 13-year-old boy with Noonan-like syndrome with loose anagen hair who developed a monogenic lupus. The renal biopsy confirmed a class III lupus nephritis and identified the presence of zebra bodies.

CONCLUSIONS

RASopathies represent a cause of monogenic lupus. We report a new case of monogenic lupus in a child with Noonan-like syndrome with loose anagen hair. Lupus nephritis which has never been described in this context, may be part of the presentation. The presence of zebra bodies in SLE or RASopathies in unclear, but no other known conditions (Fabry disease or drugs) were identified as the cause of zebra bodies in our patient.

circCPA4 induces malignant behaviors of prostate cancer via miR-491-5p/SHOC2 feedback loop

OBJECTIVE

circCPA4 has been defined to be an oncogenic gene. This study examined whether circCPA4 regulates Prostate Cancer (PC) development and revealed its molecular mechanism.

METHODS

PC tissues and PC cell lines were collected, in which circCPA4/miR-491-5p/SHOC2 levels were evaluated by RT-qPCR and immunoblot. Colony formation assay and EdU assay assessed cell proliferation, flow cytometry measured apoptosis, and Transwell assessed invasion and migration. Ki-67, cleaved caspase-3, E-cadherin, and N-cadherin were evaluated by immunoblot. Based on the luciferase reporter assay and RIP assay the authors investigated the targeting relationship between circCPA4/miR-491-5p/SHOC2. The effect of circCPA4 on tumor growth was evaluated by xenotransplantation in nude mice.

RESULTS

circCPA4 and SHOC2 levels were abundant while miR-491-5p expression was low in PC. Loss of circCPA4 decreased the proliferation and EdU-positive rate of PC cells, enhanced apoptosis, and inhibited invasion, migration, and EMT. Upregulation of circCPA4 forced the malignant behaviors of PC cells, and this promotion could be abolished when miR-491-5p was overexpressed or SHOC2 was silenced. CircCAP4 competitively decoyed miR-491-5p mediating SHOC2 expression. circCAP4 suppression inhibited PC tumor growth.

CONCLUSION

circCAP4 acts as a novel oncogenic factor in PC, accelerating the malignant behavior of PC cells via miR-491-5p/SHOC2 interaction. This novel ceRNA axis may be a potential target for PC drug development and targeted therapy in the future.

SHOC2 mediates the drug-resistance of triple-negative breast cancer cells to everolimus

Aberrant activation of the mTOR pathway is a characteristic alteration in triple-negative breast cancer, but the mTOR pathway inhibitor everolimus is not effective for the triple-negative breast cancer (TNBC) patients. Presently, we showed that the activation of ERK pathway was an important mechanism of resistance to everolimus in TNBC cells in this study. SHOC2, a key protein mediating the Ras-Raf-ERK pathway, could act as a scaffolding protein to facilitate the activation of the pathway by mediating the interaction of key components of the pathway. Our results showed that everolimus activated the Raf-ERK pathway by promoting the interaction between SHOC2 and c-Raf and that knockdown of SHOC2 significantly inhibited the Raf-ERK pathway induced by everolimus. We further demonstrated that SHOC2 expression levels were closely related to the sensitivity of TNBC cells to everolimus and that interference with SHOC2 expression in combination with everolimus had significant effects on the cell cycle progression and apoptosis in vitro experiments. Western blotting analysis showed that cell cycle regulators and apoptosis-related proteins were significantly altered by the combination treatment. Xenograft model also demonstrated that knockdown of SHOC2 significantly increased the sensitivity of tumor to everolimus in nude mice. In conclusion, our study showed that SHOC2 is a key factor in regulating the sensitivity of TNBC cells to everolimus and that combined therapy may be a more effective therapeutic approach for TNBC patients.

Structural insights into the role of SHOC2-MRAS-PP1C complex in RAF activation

RAF activation is a key step for signalling through the mitogen-activated protein kinase (MAPK) pathway. The SHOC2 protein, along with MRAS and PP1C, forms a high affinity, heterotrimeric holoenzyme that activates RAF kinases by dephosphorylating a specific phosphoserine. Recently, our research, along with that of three other teams, has uncovered valuable structural and functional insights into the SHOC2-MRAS-PP1C (SMP) holoenzyme complex. In this structural snapshot, we review SMP complex assembly, the dependency on the bound-nucleotide state of MRAS, the substitution of MRAS by the canonical RAS proteins and the roles of SHOC2 and MRAS on PP1C activity and specificity. Furthermore, we discuss the effect of several RASopathy mutations identified within the SMP complex and explore potential therapeutic approaches for targeting the SMP complex in RAS/RAF-driven cancers and RASopathies.

Lipid profile in Noonan syndrome and related disorders: trend by age, sex and genotype

Background

RASopathies are developmental disorders caused by dysregulation of the RAS-MAPK signalling pathway, which contributes to the modulation of multiple extracellular signals, including hormones and growth factors regulating energetic metabolism, including lipid synthesis, storage, and degradation.

Subjects and methods

We evaluated the body composition and lipid profiles of a single-centre cohort of 93 patients with a molecularly confirmed diagnosis of RASopathy by assessing height, BMI, and total cholesterol, HDL, triglycerides, apolipoprotein, fasting glucose, and insulin levels, in the context of a cross sectional and longitudinal study. We specifically investigated and compared anthropometric and haematochemistry data between the Noonan syndrome (NS) and Mazzanti syndrome (NS/LAH) groups.

Results

At the first evaluation (9.5 ± 6.2 years), reduced growth (-1.80 ± 1.07 DS) was associated with a slightly reduced BMI (-0.34 DS ± 1.15 DS). Lipid profiling documented low total cholesterol levels (< 5th percentile) in 42.2% of the NS group; in particular, in 48.9% of PTPN11 patients and in 28.6% of NS/LAH patients compared to the general population, with a significant difference between males and females. A high proportion of patients had HDL levels lower than the 26th percentile, when compared to the age- and sex-matched general population. Triglycerides showed an increasing trend with age only in NS females. Genotype-phenotype correlations were also evident, with particularly reduced total cholesterol in about 50% of patients with PTPN11 mutations with LDL-C and HDL-C tending to decrease during puberty. Similarly, apolipoprotein A1 and apolipoprotein B deficits were documented, with differences in prevalence associated with the genotype for apolipoprotein A1. Fasting glucose levels and HOMA-IR were within the normal range.

Conclusion

The present findings document an unfavourable lipid profile in subjects with NS, in particular PTPN11 mutated patients, and NS/LAH. Further studies are required to delineate the dysregulation of lipid metabolism in RASopathies more systematically and confirm the occurrence of previously unappreciated genotype-phenotype correlations involving the metabolic profile of these disorders.

LncRNA FALEC increases the proliferation, migration and drug resistance of cholangiocarcinoma through competitive regulation of miR-20a-5p/SHOC2 axis

BACKGROUND

LncRNA is an important regulatory factor in the human genome. We aim to explore the roles of LncFALEC and miR-20a-5p/SHOC2 axis on the proliferation, migration, and Fluorouracil (5-FU) resistance of cholangiocarcinoma (CCA).

METHODS

In this study, the expression of FALEC and miR-20a-5p in CCA tissues and cell lines (HuCCT1, QBC939, and Huh-28) was detected by RT-qPCR. The FALEC in 5-FU-resistant CCA cell lines (QBC939-R, Huh-28-R) was knocked down to evaluate its effects on cell proliferation, migration, invasion, and drug resistance.

RESULTS

Our analysis showed that compared with the adjacent non-tumor tissues, FALEC was significantly higher in the CCA tissues and even higher in the samples from 5-FU-resistant patients. Knockdown FALEC increased the sensitivity of 5-FU and decreased migration and invasion of CCA cells. Dual luciferase reporter confirmed that FALEC sponges miR-20a-5p and down-regulated its expression. Moreover, SHOC2 leucine-rich repeat scaffold protein (SHOC2) was the target gene of miR-20a-5p. We found overexpression of FALEC (FALEC-OE) increased resistance of CCA cells to 5-FU significantly, which might contribute to increased SHOC2 expression and activation of the ERK1/2 signaling pathway.

CONCLUSIONS

In summary, our study revealed that down-regulation of FALEC could inhibit the proliferation, migration, and invasion of CCA cells in vitro by regulating the miR-20a-5p/SHOC2 axis and participating in 5-FU resistance by mediating the ERK1/2 signaling pathway.

Case report: A de novo RASopathy-causing SHOC2 variant in a Chinese girl with noonan syndrome-like with loose anagen hair

Pathogenic variants in the RASopathy-causing SHOC2 gene have been suggested to cause Noonan syndrome-like with loose anagen hair (NS/LAH). This condition is characterized by facial features resembling Noonan syndrome (NS), short stature, growth hormone deficiency (GHD), cognitive deficits, cardiac defects, and ectodermal abnormalities, including easily pluckable, sparse, thin, slow-growing hair, hyperpigmented skin and hypernasal voice. The mutation spectrum of SHOC2 is narrow, and only 8 pathogenic variants have been identified. Here, we report a 5-year-3-month-old Chinese female who displays characteristics typical of NS and has normal neurodevelopment. Trio-based whole-exome sequencing (WES) revealed a de novo variant (c.1231A>G, p.Thr411Ala) in SHOC2. This variant has been recently reported in one subject in the literature who displayed facial features typical of NS and also presented with significant speech delays, moderate intellectual disabilities, epilepsy, bilateral sensorineural deafness and renal dysplasia. The differential phenotypes between these subjects deserve to be further investigated. Next, we reviewed the clinical pictures of NS/LAH and noticed that a recurrent SHOC2 Ser2Gly variant was more likely to result in delayed neurodevelopment and short stature, compared to other SHOC2 variants. And growth hormone (GH) therapy could improve height prognosis. It was noticed that the slight sleep problems and friendly and relatively mature personality observed in our patient may be a novel phenotype of NS/LAH. Our study reconfirms the pathogenic nature of the SHOC2 Thr411Ala variant. It also provides insights into the genotype-phenotype relationship in NS/LAH and a foundation for its genetic counseling, diagnosis and treatment.

lncRNA MALAT1 regulates the resistance of breast cancer cells to paclitaxel via the miR-497-5p/SHOC2 axis

Aim: To explore the roles of lncRNA MALAT1 and SHOC2 in breast cancer, and the potential connections to chemotherapy resistance in breast cancer. Materials & methods: Paclitaxel-resistant breast cancer cells were induced by gradually increasing intermittent doses. Bioinformatic analyses were performed to predict the regulated miRNAs of MALAT1. Results: High expressions of MALAT1 and SHOC2 contribute to paclitaxel resistance in breast cancer cells. MALAT1 sponges miR-497-5p enhance SHOC2 expression in paclitaxel-resistant breast cancer cells and contribute to paclitaxel resistance in breast cancer cells. Conclusion: Patients with high expression of MALAT1 and SHOC2 have a poorer response to paclitaxel. Upregulation of miR-497-5p could improve the treatment response to paclitaxel in patients with breast cancer by inhibiting MALAT1 and SHOC2.

Polycistronic baculovirus expression of SUGT1 enables high-yield production of recombinant leucine-rich repeat proteins and protein complexes

The SHOC2-MRAS-PPP1CA (SMP) complex is a holoenzyme that plays a vital role in the MAP kinase signaling pathway. Previous attempts to produce this challenging three-protein complex have relied on co-infection with multiple viruses and the use of affinity tags to attempt to isolate functional recombinant protein complexes. Leucine-rich repeat containing proteins have been historically challenging to express, and we hypothesized that co-expression of appropriate chaperones may be necessary for optimal production. We describe here how the SUGT1 chaperone can, in conjunction with polycistronic protein expression in baculovirus-infected insect cells, dramatically enhance production yield and quality of recombinant SHOC2, the SMP complex, and other leucine-rich repeat proteins.

A Leucine-Rich Repeat Protein Provides a SHOC2 the RAS Circuit: a Structure-Function Perspective

SHOC2 is a prototypical leucine-rich repeat protein that promotes downstream receptor tyrosine kinase (RTK)/RAS signaling and plays important roles in several cellular and developmental processes. Gain-of-function germ line mutations of SHOC2 drive the RASopathy Noonan-like syndrome, and SHOC2 mediates adaptive resistance to mitogen-activated protein kinase (MAPK) inhibitors. Similar to many scaffolding proteins, SHOC2 facilitates signal transduction by enabling proximal protein interactions and regulating the subcellular localization of its binding partners. Here, we review the structural features of SHOC2 that mediate its known functions, discuss these elements in the context of various binding partners and signaling pathways, and highlight areas of SHOC2 biology where a consensus view has not yet emerged.

Clinical and molecular analysis of 26 individuals with Noonan syndrome in a reference institution in Colombia

Our aim was to characterize the phenotype and genotype of individuals with Noonan syndrome in Colombia. There are published cohorts of Noonan individuals from several countries in Latin America including Brazil, Chile, and Argentina, but none from Colombia. We described 26 individuals with NS from a single large referral center in the South West of Colombia using an established database in the genetics department and hospital records search using ICD-10 codes. All patients included in this study were evaluated by a medical geneticist and have molecular confirmation of NS diagnosis. The median age at referral was 3.5 years (range, 0-39), and at molecular diagnosis was 5 years (range, 0-40). Patients mostly originated from the southwest region of Colombia (19/26, 73%). Pathogenic variants in PTPN11 are the most common cause of NS in Colombian individuals followed by SHOC2 and SOS1 variants. The prevalence of cardiomyopathy was low in this population compared to other populations. Further research is needed with a larger sample size and including different regions of Colombia to correlate our findings. This study provides new information about time to diagnosis of NS in Colombia, genotypes, and provides important information to help develop guidelines for diagnosis and management of this disease in the region.

Synthetic Lethal Interaction of SHOC2 Depletion with MEK Inhibition in RAS-Driven Cancers

The mitogen-activated protein kinase (MAPK) pathway is a critical effector of oncogenic RAS signaling, and MAPK pathway inhibition may be an effective combination treatment strategy. We performed genome-scale loss-of-function CRISPR-Cas9 screens in the presence of a MEK1/2 inhibitor (MEKi) in KRAS-mutant pancreatic and lung cancer cell lines and identified genes that cooperate with MEK inhibition. While we observed heterogeneity in genetic modifiers of MEKi sensitivity across cell lines, several recurrent classes of synthetic lethal vulnerabilities emerged at the pathway level. Multiple members of receptor tyrosine kinase (RTK)-RAS-MAPK pathways scored as sensitizers to MEKi. In particular, we demonstrate that knockout, suppression, or degradation of SHOC2, a positive regulator of MAPK signaling, specifically cooperated with MEK inhibition to impair proliferation in RAS-driven cancer cells. The depletion of SHOC2 disrupted survival pathways triggered by feedback RTK signaling in response to MEK inhibition. Thus, these findings nominate SHOC2 as a potential target for combination therapy.

The FBXW7-SHOC2-Raptor Axis Controls the Cross-Talks between the RAS-ERK and mTORC1 Signaling Pathways

FBXW7 is a tumor suppressive E3 ligase, whereas RAS-ERK and mechanistic target of rapamycin kinase (mTORC1) are two major oncogenic pathways. Whether and how FBXW7 regulates these two oncogenic pathways are unknown. Here, we showed that SHOC2, a RAS activator, is a FBXW7 substrate. Growth stimuli trigger SHOC2 phosphorylation on Thr⁵⁰⁷ by the mitogen-activated protein kinase (MAPK) signal, which facilitates FBXW7 binding for ubiquitylation and degradation. FBXW7-mediated SHOC2 degradation terminates the RAS-MAPK signals and inhibits proliferation. Furthermore, SHOC2 selectively binds to Raptor to competitively inhibit the Raptor-mTOR binding to inactivate mTORC1 and induce autophagy, whereas Raptor binding of SHOC2 inhibits the SHOC2-RAS binding to block the MAPK pathway and proliferation. Finally, SHOC2 is overexpressed in pancreatic cancer, which correlated with poor patient survival. SHOC2 mutations were found in lung cancer tissues with gain-of-function activity. Collectively, the SHOC2-Raptor interaction triggers negative cross-talk between RAS-ERK and mTORC1 pathways, whereas FBXW7 regulates both pathways by targeting SHOC2 for ubiquitylation and degradation.

ADA2 deficiency in a patient with Noonan syndrome-like disorder with loose anagen hair: The co-occurrence of two rare syndromes

Noonan syndrome-like disorder with loose anagen hair (NS/LAH) is one of the RASopathies, a group of clinically related developmental disorders caused by germline mutations in genes that encode components acting in the RAS/MAPK pathway. Among RASopathies, NS/LAH (OMIM 607721) is an extremely rare, multiple anomaly syndrome characterized by dysmorphic facial features similar to those observed in Noonan syndrome along with some distinctive ectodermal findings including easily pluckable, sparse, thin, and slow-growing hair. ADA2 deficiency (DADA2, OMIM 615688) is a monogenic autoinflammatory disorder caused by homozygous or compound heterozygous mutations in ADA2, with clinical features including recurrent fever, livedo racemosa, hepatosplenomegaly, and strokes as well as immune dysregulation. This is the first report of NS/LAH and ADA2 deficiency in the same individual. We report on a patient presenting with facial features, recurrent infections and ectodermal findings in whom both the clinical and molecular diagnoses of NS/LAH and ADA2 deficiency were established, respectively.

SHOC2 complex-driven RAF dimerization selectively contributes to ERK pathway dynamics

The ERK signaling pathway is hyperactivated in a majority of cancers. However, because it mediates myriad physiological responses, the clinical efficacy of current ERK pathway inhibitors has been severely limited by toxicity. This study uncovers both SHOC2 phosphatase complex-dependent and -independent mechanisms of RAF and ERK activation that are differentially engaged in a context and spatio-temporal–dependent manner. KRAS oncogenic signaling preferentially depends on SHOC2 dependent-mechanisms, which thus presents a therapeutic opportunity. This study provides a molecular framework for how targeting the SHOC2-holophosphatase regulatory node of the RAF activation process provides a mechanism for selective inhibition of ERK signaling.

Despite the crucial role of RAF kinases in cell signaling and disease, we still lack a complete understanding of their regulation. Heterodimerization of RAF kinases as well as dephosphorylation of a conserved “S259” inhibitory site are important steps for RAF activation but the precise mechanisms and dynamics remain unclear. A ternary complex comprised of SHOC2, MRAS, and PP1 (SHOC2 complex) functions as a RAF S259 holophosphatase and gain-of-function mutations in SHOC2, MRAS, and PP1 that promote complex formation are found in Noonan syndrome. Here we show that SHOC2 complex-mediated S259 RAF dephosphorylation is critically required for growth factor-induced RAF heterodimerization as well as for MEK dissociation from BRAF. We also uncover SHOC2-independent mechanisms of RAF and ERK pathway activation that rely on N-region phosphorylation of CRAF. In DLD-1 cells stimulated with EGF, SHOC2 function is essential for a rapid transient phase of ERK activation, but is not required for a slow, sustained phase that is instead driven by palmitoylated H/N-RAS proteins and CRAF. Whereas redundant SHOC2-dependent and -independent mechanisms of RAF and ERK activation make SHOC2 dispensable for proliferation in 2D, KRAS mutant cells preferentially rely on SHOC2 for ERK signaling under anchorage-independent conditions. Our study highlights a context-dependent contribution of SHOC2 to ERK pathway dynamics that is preferentially engaged by KRAS oncogenic signaling and provides a biochemical framework for selective ERK pathway inhibition by targeting the SHOC2 holophosphatase.

Clinical and functional characterization of a novel RASopathy-causing SHOC2 mutation associated with prenatal-onset hypertrophic cardiomyopathy

SHOC2 is a scaffold protein mediating RAS-promoted activation of mitogen-activated protein kinase (MAPK) signaling in response to extracellular stimuli. A recurrent activating mutation in SHOC2 (p.Ser2Gly) causes Mazzanti syndrome, a RASopathy characterized by features resembling Noonan syndrome and distinctive ectodermal abnormalities. A second mutation (p.Met173Ile) supposed to cause loss-of-function was more recently identified in two individuals with milder phenotypes. Here, we report on the third RASopathy-causing SHOC2 mutation (c.807_808delinsTT, p.Gln269_His270delinsHisTyr), which was found associated with prenatal-onset hypertrophic cardiomyopathy. Structural analyses indicated a possible impact of the mutation on the relative orientation of the two SHOC2's leucine-rich repeat domains. Functional studies provided evidence of its activating role, revealing enhanced binding of the mutant protein to MRAS and PPP1CB, and increased signaling through the MAPK cascade. Differing from SHOC2 ^S2G , SHOC2 ^{Q269_H270delinsHY} is not constitutively targeted to the plasma membrane. These data document that diverse mechanisms in SHOC2 functional dysregulation converge toward MAPK signaling upregulation.

The MTORC1-mediated autophagy is regulated by the FBXW7-SHOC2-RPTOR axis

MTORC1 is a well-known key regulator of macroautophagy/autophagy. However, the underlying regulatory mechanisms of MTORC1 activity remains elusive. We showed recently that SHOC2, a RAS activator, competes with MTOR for RPTOR (but not RICTOR) binding, leading to MTORC1 inactivation, autophagy induction and cell survival, whereas RPTOR competes with RAS for SHOC2 binding to inactivate RAS-MAPK and suppresses growth. Interestingly, SHOC2 is subjected to FBXW7 regulation. Upon growth stimulation, MAP2K1 phosphorylates SHOC2 on T507 to facilitate its binding with FBXW7B/FBXW7β for ubiquitination and degradation to terminate growth signaling, thus establishing a negative feedback loop. Human cancers with FBXW7 inactivation and SHOC2 overexpression would squeeze RPTOR from MTORC1, leading to MTORC1 inactivation and autophagy induction. Collectively, we propose a new mode of the FBXW7-SHOC2-RPTOR axis in control of MTORC1 activity that affects autophagy and cancer cell survival.

Recurrent Erythema Nodosum in a Child with a SHOC2 Gene Mutation

We report the case of a 6-year-old male who developed recurrent erythema nodosum (EN) at the age of 3 years. The patient exhibited hypertelorism, low-set ears, micrognathia, moderate intellectual disability, thin long fingers, loose anagen hair, and prominent palmoplantar wrinkles. A heterozygous single nucleotide variant in the SHOC2 gene (c.4 A > G, p.S2G) was identified. Patients with a SHOC2 mutation exhibit a unique combination of ectodermal abnormalities including darkly pigmented skin and loose anagen hair. This report is the first to describe EN in a patient with SHOC2 mutation, and to examine the patient's hair using scanning electron microscopy. We hypothesize that the RAS/MAPK pathway is associated with the pathogenesis of cutaneous lesions in patients with SHOC2 mutations via autoinflammation and disturbance of epithelial stem cells.

SHOC2-MRAS-PP1 complex positively regulates RAF activity and contributes to Noonan syndrome pathogenesis

Dephosphorylation of the inhibitory "S259" site on RAF kinases (S259 on CRAF, S365 on BRAF) plays a key role in RAF activation. The MRAS GTPase, a close relative of RAS oncoproteins, interacts with SHOC2 and protein phosphatase 1 (PP1) to form a heterotrimeric holoenzyme that dephosphorylates this S259 RAF site. MRAS and SHOC2 function as PP1 regulatory subunits providing the complex with striking specificity against RAF. MRAS also functions as a targeting subunit as membrane localization is required for efficient RAF dephosphorylation and ERK pathway regulation in cells. SHOC2's predicted structure shows remarkable similarities to the A subunit of PP2A, suggesting a case of convergent structural evolution with the PP2A heterotrimer. We have identified multiple regions in SHOC2 involved in complex formation as well as residues in MRAS switch I and the interswitch region that help account for MRAS's unique effector specificity for SHOC2-PP1. MRAS, SHOC2, and PPP1CB are mutated in Noonan syndrome, and we show that syndromic mutations invariably promote complex formation with each other, but not necessarily with other interactors. Thus, Noonan syndrome in individuals with SHOC2, MRAS, or PPPC1B mutations is likely driven at the biochemical level by enhanced ternary complex formation and highlights the crucial role of this phosphatase holoenzyme in RAF S259 dephosphorylation, ERK pathway dynamics, and normal human development.

Cleft palate and hypopituitarism in a patient with Noonan-like syndrome with loose anagen hair-1

Noonan syndrome (NS), the most common of the RASopathies, is a developmental disorder caused by heterozygous germline mutations in genes encoding proteins in the RAS-MAPK signaling pathway. Noonan-like syndrome with loose anagen hair (NSLH, including NSLH1, OMIM #607721 and NSLH2, OMIM #617506) is characterized by typical features of NS with additional findings of macrocephaly, loose anagen hair, growth hormone deficiency in some, and a higher incidence of intellectual disability. All NSLH1 reported cases to date have had an SHOC2 c.4A>G, p.Ser2Gly mutation; NSLH2 cases have been reported with a PPP1CB c.146G>C, p.Pro49Arg mutation, or c.166G>C, p.Ala56Pro mutation. True cleft palate does not appear to have been previously reported in individuals with NS or with NSLH. While some patients with NS have had growth hormone deficiency (GHD), other endocrine abnormalities are only rarely documented. We present a female patient with NSLH1 who was born with a posterior cleft palate, micrognathia, and mild hypotonia. Other findings in her childhood and young adulthood years include hearing loss, strabismus, and hypopituitarism with growth hormone, thyroid stimulating hormone (TSH), and gonadotropin deficiencies. The SHOC2 mutation may be responsible for this patient's additional features of cleft palate and hypopituitarism.

Systemic lupus erythematosus in a patient with Noonan syndrome-like disorder with loose anagen hair 1: More than a chance association

Systemic lupus erythematosus (SLE) has been reported among patients with RASopathy. Five patients have been reported: three with SHOC2 variants, one with a PTPN11 variant, and one with a KRAS variant. SHOC2 variant might represent a relatively common predisposing factor for SLE among the RASopathy genes. However, the clinical details were only reported for two patients, while information on the remaining patient appeared only in a tabular format with minimal clinical description. Here, we report a patient with a SHOC2 variant and SLE. The proband was a 28-year-old male patient with intellectual disabilities, a short stature, dysmorphic facial features, and thin hair. He developed hypertrophic cardiomyopathy and afebrile generalized seizures at the ages of 7 and 18 years, respectively. At the age of 24 years, he presented with a 3-day history of intermittent fever accompanied by right chest pain and a malar butterfly rash. He fulfilled both the American College of Rheumatology (ACR) criteria and the Systemic Lupus International Collaborating Clinics (SLICC) criteria for SLE and was successfully treated with prednisolone. Medical exome sequencing identified a de novo SHOC2 variant (c.4A > G, p.S2G). The present report of a second patient who fulfills both the ACR criteria and the SLICC criteria of SLE. We suggest that the association between SHOC2 variant and SLE represents more than a chance association. In the event of fever of unknown origin in patients with constitutional SHOC2 pathogenic variant, SLE should be suspected.

Noonan syndrome-like disorder with loose anagen hair: a second case with neuroblastoma

Noonan-like syndrome with loose anagen hair (NSLH), also known as Mazzanti syndrome, is a RASopathy characterized by craniofacial features resembling Noonan syndrome, cardiac defects, cognitive deficits and behavioral issues, reduced growth generally associated with GH deficit, darkly pigmented skin, and an unique combination of ectodermal anomalies. Virtually all cases of NSLH are caused by an invariant and functionally unique mutation in SHOC2 (c.4A>G, p.Ser2Gly). Here, we report on a child with molecularly confirmed NSLH who developed a neuroblastoma, first suspected at the age 3 months by abdominal ultrasound examination. Based on this finding, scanning of the SHOC2 coding sequence encompassing the c.4A>G change was performed on selected pediatric cohorts of malignancies documented to occur in RASopathies (i.e., neuroblastoma, brain tumors, rhabdomyosarcoma, acute lymphoblastic, and myeloid leukemia), but failed to identify a functionally relevant cancer-associated variant. While these results do not support a major role of somatic SHOC2 mutations in these pediatric cancers, this second instance of neuroblastoma in NSLAH suggests a possible predisposition to this malignancy in subjects heterozygous for the c.4A>G SHOC2 mutation.

Moyamoya syndrome in a patient with Noonan-like syndrome with loose anagen hair

BACKGROUND

Noonan-like syndrome with loose anagen hair is one of the RASopathies characterized by Noonan syndrome-like features with unique ectodermal abnormalities. This syndrome is caused by mutations in the SHOC2 gene. We encountered a patient with moyamoya syndrome associated with Noonan-like syndrome with loose anagen hair presenting with transient ischemic attacks.

PATIENT DESCRIPTION

A 6-year-old girl was diagnosed with Noonan-like syndrome with loose anagen hair because of profound short stature and ectodermal anomalies such as sparse and easily pluckable hair. A heterozygous mutation of c.4A>G (p.S2G) in the SHOC2 gene was identified, and recombinant human growth hormone therapy was initiated at 8 years of age. At age 10, she manifested recurrent left hemiplegia. Moreover, cerebrovascular imaging revealed occlusion or narrowing of both internal carotid arteries and both middle cerebral arteries with distal moyamoya-like vessels. She is treated with aspirin and calcium channel blocker.

CONCLUSIONS

We describe the first case of Noonan-like syndrome with loose anagen hair associated with moyamoya syndrome, although it has been reported to be associated with a few cases of other RASopathies, including Noonan, cardiofaciocutaneous, and Costello syndromes. This report emphasizes the associations between cerebrovascular anomalies and Noonan-like syndrome with loose anagen hair.

Phenotypic variability associated with the invariant SHOC2 c.4A>G (p.Ser2Gly) missense mutation

Noonan-like syndrome with loose anagen hair (NS/LAH; OMIM 607721) is a developmental disorder clinically related to Noonan syndrome (NS) and characterized by facial dysmorphisms, postnatal growth retardation, cardiac anomalies (in particular dysplasia of the mitral valve and septal defects), variable neurocognitive impairment, and florid ectodermal features. A distinctive trait of NS/LAH is its association with easily pluckable, slow growing, sparse, and thin hair. This rare condition is due to the invariant c.4A > G missense (p.Ser2Gly) change in SHOC2, which encodes a regulatory protein that participate in RAS signaling. Here we report two patients with molecularly confirmed NS/LAH, with extremely different phenotypic expression, in particular concerning the severity of the cardiac phenotype and neurocognitive profile. While the first available clinical records outlined a relatively homogeneous phenotype in NS/LAH, the present data emphasize that the phenotype spectrum associated with this invariant mutation is wider than previously recognized.

A Novel SHOC2 Variant in Rasopathy

Rasopathies are a group of genetic disorders caused by germline mutations in multiple genes of the Extracellular signal-Regulated Kinases 1 and 2 (ERK1/2) pathway. The only previously identified missense mutation in SHOC2, a scaffold protein of the ERK1/2 pathway, led to Noonan-like syndrome with loose anagen hair. Here, we report a novel mutation in SHOC2(c.519G>A; p.M173I) that leads to a Rasopathy with clinical features partially overlapping those occurring in Noonan and cardiofaciocutaneous syndromes. Studies to clarify the significance of this SHOC2 variant revealed that the mutant protein has impaired capacity to interact with protein phosphatase 1c (PP1c), leading to insufficient activation of RAF-1 kinase. This SHOC2 variant thus is unable to fully rescue ERK1/2 activity in cells depleted of endogenous SHOC2. We conclude that SHOC2 mutations can cause a spectrum of Rasopathy phenotypes in heterozygous individuals. Importantly, our work suggests that individuals with mild Rasopathy symptoms may be underdiagnosed.

Severe craniosynostosis with Noonan syndrome phenotype associated with SHOC2 mutation: clinical evidence of crosslink between FGFR and RAS signaling pathways

Dysregulation in the RAS signaling cascade results in a family of malformation syndromes called RASopathies. Meanwhile, alterations in FGFR signaling cascade are responsible for various syndromic forms of craniosynostosis. In general, the phenotypic spectra of RASopathies and craniosynostosis syndromes do not overlap. Recently, however, mutations in ERF, a downstream molecule of the RAS signaling cascade, have been identified as a cause of complex craniosynostosis, suggesting that the RAS and FGFR signaling pathways can interact in the pathogenesis of malformation syndromes. Here, we document a boy with short stature, developmental delay, and severe craniosynostosis involving right coronal, bilateral lambdoid, and sagittal sutures with a de novo mutation in exon1 of SHOC2 (c.4A>G p.Ser2Gly). This observation further supports the existence of a crosslink between the RAS signaling cascade and craniosynostosis. In retrospect, the propositus had physical features suggestive of a dysregulated RAS signaling cascade, such as fetal pleural effusion, fetal hydrops, and atrial tachycardia. In addition to an abnormal cranial shape, which has been reported for this specific mutation, craniosynostosis might be a novel associated phenotype. In conclusion, the phenotypic combination of severe craniosynostosis and RASopathy features observed in the propositus suggests an interaction between the RAS and FGFR signaling cascades. Patients with craniosynostosis in combination with any RASopathy feature may require mutation screening for molecules in the FGFR-RAS signaling cascade.

Pulmonary interstitial glycogenosis in a patient ultimately diagnosed with Noonan syndrome

We describe an infant prenatally diagnosed with hydrops fetalis ultimately found to have Noonan syndrome (NS). Prior to genetic confirmation of diagnosis, lung biopsy was performed which revealed widespread pulmonary interstitial glycogenosis (PIG), abnormal alveolarization, and mild inflammation. Although genetic alterations have been identified in NS, the mutations are heterogeneous and the diagnosis remains one of clinical suspicion. The combination of PIG and NS has not yet been documented in the literature. While the underlying pathophysiologic mechanism of PIG is unclear, we suggest that the mitogen-activated protein kinase signal transduction pathway members (PTPN11, KRAS, SOS1, RAF1, SHOC2, NRAS) involved in cellular growth factor signaling, which are affected in NS, can provide clues. In addition, this case demonstrates that empiric corticosteroids can be considered in complicated cases since biopsy did reveal an inflammatory component, not typically noted in PIG.

Rare copy number variations containing genes involved in RASopathies: deletion of SHOC2 and duplication of PTPN11

BACKGROUND

RASopathies are a group of disorders related to Noonan syndrome that with dysregulated RAS-mitogen-activated protein kinase (MAPK) signaling pathway. Noonan syndrome (NS, OMIM# 163950) is a both phenotypically and genotypically variable disorder. We and other researchers have demonstrated that copy number variations underlie a small percentage of patients with RASopathies.

RESULTS

In a cohort of 12 clinically characterized patients with congenital heart defect (CHD) and features suggestive of Noonan syndrome or Noonan like syndrome without known causative gene mutation, we performed an Illumina SNP-array analysis to identify the pathogenic copy number variations (Human660W-Quad Chip, Beadstation Scanner and GenomeStudio V2011 software). We identifed two rare copy number variations harboring genes involved in RAS- MAPK signaling pathway of RASopathy. One is a 24 Mb duplication of 12q24.1-24.3 containing PTPN11 and the other is a 183 kb deletion of 10q25.2 including SHOC2. The SNP-array results were further validated by quantitative PCR (qPCR). This is might be the first report suggesting that haploinsufficiency of SHOC2 can result in a RASopathy-like phenotype.

CONCLUSIONS

Our findings provide additional support that copy number variations containing disease-causing genes of RAS/MAPK pathway play a minor role in RASopathies or related disorders. We recommend the use of microarrays in Noonan syndrome like patients without identified mutations in the causative genes.

Expanding the SHOC2 mutation associated phenotype of Noonan syndrome with loose anagen hair: structural brain anomalies and myelofibrosis

Noonan syndrome is a heterogenous rasopathy typically presenting with short stature, characteristic facial features, cardiac abnormalities including pulmonic valve stenosis, ASD and hypertrophic cardiomyopathy (HCM), cryptorchidism, ectodermal abnormalities, and learning differences. The phenotype is variable, and limited genotype phenotype correlation exists with SOS1 mutations often associated with normal cognition and stature, RAF1 mutations entailing a high HCM risk, and certain PTPN11 mutations predisposing to juvenile myelomonocytic leukemia. The recently identified SHOC2 mutation (p.Ser2Gly) causes Noonan syndrome with loose anagen hair. We report five patients with this mutation. All had skin hyperpigmentation, sparse light colored hair, increased fine wrinkles, ligamentous laxity, developmental delay, and 4/4 had a structural cardiac anomaly. Hypotonia and macrocephaly occurred in 4/5 (80%); 3/5 (60%) had polyhydramnios, increased birth weight or required use of a feeding tube. Distinctive brain abnormalities included relative megalencephaly and enlarged subarachnoid spaces suggestive of benign external hydrocephalus, and a relatively small posterior fossa as indicated by a vertical tentorium. The combination of a large brain with a small posterior fossa likely resulted in the high rate of cerebellar tonsillar ectopia (3/4; 75%). Periventricular nodular heterotopia was seen in one patient with a thick and dysplastic corpus callosum. We report on the first hematologic neoplasm, myelofibrosis, in a 2-year-old patient with SHOC2 mutation. Myelofibrosis is exceedingly rare in children and young adults. The absence of a somatic JAK2 mutation, seen in the majority of patients with myelofibrosis, is noteworthy as it suggests that germline or somatic SHOC2 mutations are causally involved in myelofibrosis.