Pathogenesis of multiple lentigines in LEOPARD syndrome with PTPN11 gene mutation

Melanoma and LEOPARD Syndrome: Understanding the Role of PTPN11 Mutations in Melanomagenesis

Abstract is missing (Short communication)

CLEC12B is a melanocytic gene regulating the color of the skin

Pigmentation of the human skin is a complex process regulated by many genes. However, only a few have a profound impact on melanogenesis. Transcriptome analysis of pigmented skin compared to vitiligo skin devoid of melanocytes, allowed us to unravel CLEC12B as a melanocytic gene. We demonstrated that CLEC12B, a C-type lectin receptor, is highly expressed in melanocytes, and that its expression is decreased in dark skin compared to white skin. CLEC12B directly recruits and activates SHP-1 and SHP-2 through its ITIM domain and promotes CREB degradation, leading to downregulation of the downstream MITF pathway. CLEC12B ultimately controls melanin production and pigmentation in vitro and in a model of reconstructed human epidermis. The identification of CLEC12B in melanocyte demonstrates that C-type lectin receptors exert function beyond immunity and inflammation. It also provides insights in the understanding of the melanocyte biology and regulation of melanogenesis.

The First Vietnamese Patient of LEOPARD Syndrome due to a PTPN11 Mutation: A Case Report and Review of the Literature

LEOPARD syndrome is a rare congenital anomaly that involves several organs. Patients with this syndrome develop multiple lentigines resembling a leopard's hide. LEOPARD is an acronym of the major features constituting the syndrome including lentigines, electrocardiographic conduction defects, ocular hypertelorism, pulmonary valve stenosis, anomalies of genitalia, retardation of growth, and deafness. The syndrome is rare, and only 200 cases have been reported yet worldwide. We present the case of an 8-year-old female patient who visited the Ho Chi Minh City Hospital of Dermato-Venereology because of multiple brownish-black "dots" on her face and body. On examination, she also showed abnormalities in the maxillofacial bones, vertebrae, shoulders, sternum, and teeth, as well as deaf-mutism and growth retardation, which are typical of LEOPARD syndrome. Genetic analysis revealed a PTPN11 gene mutation in this case. To the best of our knowledge, this is the first case of LEOPARD syndrome reported in Vietnam.

PTPN11 hypomethylation is associated with gastric cancer progression

Protein tyrosine phosphatase non-receptor type 11 (PTPN11) encodes the tyrosine phosphatase SHP-2 that is overexpressed in gastric cancer (GC). In the present study, the association of PTPN11 methylation levels with the incidence of GC and its correlation with SHP-2 overexpression were investigated. The methylation levels of PTPN11 in tumor and adjacent normal tissues of 112 GC patients were assessed by quantitative methylation specific PCR (qMSP). The Cancer Genome Atlas (TCGA) public database was used to analyze the association between PTPN11 methylation and PTPN11 expression. Survival analyses were conducted in order to evaluate the prognostic value of PTPN11 methylation for GC. The results of the qMSP analysis indicated that the methylation levels of PTPN11 in GC tumor tissues were significantly decreased compared with those noted in the normal adjacent tissues (mean with standard deviation: 40.91±26.33 vs. 51.99±37.37, P=0.007). An inverse correlation between PTPN11 methylation levels and PTPN11 mRNA expression levels (P=4×10^-6, r=-0.237) was noted. Subgroup analyses indicated that the association of PTPN11 hypomethylation with the incidence of GC was specific to male subjects (P=0.015), heavy drinking patients (P=0.019), patients with poor tumor differentiation (P=0.010) and patients with tumor node and metastasis (TNM) stage III+IV (P=0.008). Kaplan-Meier analyses and log-rank test suggested that PTPN11 hypomethylation was not associated with GC patient overall survival (P=0.605) and recurrence (P=0.485), although it could predict the recurrence of GC patients up to and including 60 years (≤60, P=0.049). The results indicated that PTPN11 levels were hypomethylated in GC patients. TCGA data analysis suggested that PTPN11 hypomethylation could cause an upregulation in the transcription levels of PTPN11. Although, this may explain the pattern of SHP-2 overexpression in GC, additional studies are required to verify this hypothesis. The association of PTPN11 hypomethylation with GC incidence may be specific to male patients, heavy drinking patients, patients with poor tumor differentiation and patients with TNM stage of III+IV. PTPN11 hypomethylation can be considered a biomarker for the recurrence of GC patients with an age of 60 years or lower.

Therapeutic potential of targeting SHP2 in human developmental disorders and cancers

Src homology 2 (SH2)-containing protein tyrosine phosphatase 2 (SHP2), encoded by PTPN11, regulates cell proliferation, differentiation, apoptosis and survival via releasing intramolecular autoinhibition and modulating various signaling pathways, such as mitogen-activated protein kinase (MAPK) pathway. Mutations and aberrant expression of SHP2 are implicated in human developmental disorders, leukemias and several solid tumors. As an oncoprotein in some cancers, SHP2 represents a rational target for inhibitors to interfere. Nevertheless, its tumor suppressive effect has also been uncovered, indicating the context-specificity. Even so, two types of SHP2 inhibitors including targeting catalytic pocket and allosteric sites have been developed associated with resolved cocrystal complexes. Herein, we describe its structure, biological function, deregulation in human diseases and summarize recent advance in development of SHP2 inhibitors, trying to give an insight into the therapeutic potential in future.

LEOPARD Syndrome with PTPN11 Gene Mutation in Three Family Members Presenting with Different Phenotypes

LEOPARD syndrome (LS) is a rare autosomal dominant disorder that is characterized by multiple lentigines and various congenital anomalies. The clinical diagnosis of LS requires molecular confirmation. The most frequently reported mutations in LS patients are in the protein tyrosine phosphatase nonreceptor type 11 gene, PTPN11 . Herein, we report the cases of three family members from two generations who are affected by LS and all carry the PTPN11 mutation c.836A > G (p.Tyr279Cys), identified by next-generation sequencing, while exhibiting different phenotypes.

Importance of cardiovascular examination in patients with multiple lentigines: two cases of LEOPARD syndrome with hypertrophic cardiomyopathy

Introduction LEOPARD syndrome is a rare genetic disorder characterised by lentigines, electrocardiographic conduction abnormalities, ocular hypertelorism, pulmonary stenosis, abnormal genitalia, retardation of growth and sensorineural deafness. Clinical manifestations are often mild, which may result in difficult and late diagnosis. Cardiac involvement may have a significant impact on the prognosis, however, appearance of severe abnormalities such as hypertrophic cardiomyopathy usually precedes the occurrence of multiple lentigines and may be asymptomatic. Case presentation We report two cases of LEOPARD syndrome with hypertrophic cardiomyopathy in a 10-year-old girl and an 18-year-old boy. In both cases, multiple lentigines, ocular hypertelorism and growth retardation were present. The first patient was followed up at the paediatric cardiology clinic due to the risk of progression of septal hypertrophy and pressure gradient across the left ventricular outflow tract, the second patient underwent surgery for a moderate obstruction of the left ventricular outflow tract with uncomplicated post-operative follow-up. Conclusion In both presented patients, hypertrophic cardiomyopathy was clinically silent and the murmur over the precordium was the sole cardiac abnormality revealed during routine visit. A detailed cardiologic examination should be considered in the patients with suspicion of LEOPARD syndrome since the ventricular hypertrophy is thought to precede the occurrence of lentigines and progress over time.

The RASopathy Family: Consequences of Germline Activation of the RAS/MAPK Pathway

Noonan syndrome [NS; Mendelian Inheritance in Men (MIM) #163950] and related syndromes [Noonan syndrome with multiple lentigines (formerly called LEOPARD syndrome; MIM #151100), Noonan-like syndrome with loose anagen hair (MIM #607721), Costello syndrome (MIM #218040), cardio-facio-cutaneous syndrome (MIM #115150), type I neurofibromatosis (MIM #162200), and Legius syndrome (MIM #611431)] are a group of related genetic disorders associated with distinctive facial features, cardiopathies, growth and skeletal abnormalities, developmental delay/mental retardation, and tumor predisposition. NS was clinically described more than 50 years ago, and disease genes have been identified throughout the last 3 decades, providing a molecular basis to better understand their physiopathology and identify targets for therapeutic strategies. Most of these genes encode proteins belonging to or regulating the so-called RAS/MAPK signaling pathway, so these syndromes have been gathered under the name RASopathies. In this review, we provide a clinical overview of RASopathies and an update on their genetics. We then focus on the functional and pathophysiological effects of RASopathy-causing mutations and discuss therapeutic perspectives and future directions.

SHP-2 Activating Mutation Promotes Malignant Biological Behaviors of Glioma Cells

Background

This study investigated the mechanism underlying the activating mutation of SHP-2 in promoting malignant biological behaviors of glioma cells.

Material/Methods

The SHP-2 empty plasmid pcDNA3.1 and SHP-2 activating mutation plasmid pcDNA3.1 SHP-2 ^D61G mutant eukaryotic expression vectors were designed; stable SHP-2-expressing cells transfected with pcDNA3.1 SHP-2 ^D61G mutant were set as the mutation group; cells transfected with pcDNA3.1 were set as the empty vector group; and cells without transfection were set as the control group. The cell reproductive capacity in each group was measured by MTT method. The invasion ability of cells in vitro was detected by Transwell chamber assay, the cell apoptosis in each group was detected by Annexin-V/PE dual-staining method, and the clone formation ability of cells in vitro was detected by Tablet clone-forming assay. The activation of ERK1/2, ARK, and p38MAPK signal pathways in each group was determined by Western blot.

Results

After transfection, the expression of SHP-2 protein in the mutant group was significantly higher than that in the control group and empty vector group. The proliferation ability of transfected cells, the apoptosis rate, the invasion ability, and the expression levels of phosphorylated ERK1/2, AKT, and p38 in the mutation group was significantly higher than in the empty vector group and the control group (P<0.05). Moreover, the cell clone formation ability of the mutation group was obviously enhanced (P<0.05).

Conclusions

The activating mutation of SHP-2 can lead to malignant changes in biological behaviors of glioma cells, and the specific mechanism may be related to the activation of ERK1/2, AKT, and p38 signal pathway. SHP-2 protein may become a new target for anti-malignant transformation of glioma.

Molecular screening strategies for NF1-like syndromes with café-au-lait macules (Review)

Multiple café-au-lait macules (CALM) are usually associated with neurofibromatosis type 1 (NF1), one of the most common hereditary disorders. However, a group of genetic disorders presenting with CALM have mutations that are involved in human skin pigmentation regulation signaling pathways, including KIT ligand/KIT proto‑oncogene receptor tyrosine kinase and Ras/mitogen‑activated protein kinase. These disorders, which include Legius syndrome, Noonan syndrome with multiple lentigines or LEOPARD syndrome, and familial progressive hyperpigmentation) are difficult to distinguish from NF1 at early stages, using skin appearance alone. Furthermore, certain syndromes are clinically overlapping and molecular testing is a vital diagnostic method. The present review aims to provide an overview of these 'NF1‑like' inherited diseases and recommend a cost‑effective strategy for making a clear diagnosis among these diseases with an ambiguous borderline.

An Update on Neurofibromatosis Type 1: Not Just Café-au-Lait Spots, Freckling, and Neurofibromas. An Update. Part I. Dermatological Clinical Criteria Diagnostic of the Disease

Neurofibromatosis type 1 (NF1) is the most common neurocutaneous syndrome and probably the one best known to dermatologists, who are generally the first physicians to suspect its diagnosis. Although the genetic locus of NF1 was identified on chromosome 17 in 1987, diagnosis of the disease is still mainly based on clinical observations and the diagnostic criteria of the National Institute of Health, dating from 1988. Cutaneous manifestations are particularly important because café-au-lait spots, freckling on flexural areas, and cutaneous neurofibromas comprise 3 of the 7 clinical diagnostic criteria. However, café-au-lait spots and freckling can also be present in other diseases. These manifestations are therefore not pathognomonic and are insufficient for definitive diagnosis in the early years of life. NF1 is a multisystemic disease associated with a predisposition to cancer. A multidisciplinary follow-up is necessary and dermatologists play an important role.

Lentiginous phenotypes caused by diverse pathogenic genes (SASH1 and PTPN11): clinical and molecular discrimination

Pathogenic mutations in genes (SASH1 and PTPN11) can cause a rare genetic disorder associated with pigmentation defects and the well-known LEOPARD syndrome, respectively. Both conditions presented with lentiginous phenotypes. The aim of this study was to arrive at definite diagnoses of three Chinese boys with clinically suspected lentigines-related syndromes. ADAR1, ABCB6, SASH1 and PTPN11 were candidate genes for mutational screening. Sanger sequencing was performed to identify the mutations, whereas bioinformatic analysis was used to predict the pathogenicity of novel missense mutations. Two novel mutations c.1537A>C (p.Ser513Arg) and 1527_1530dupAAGT (p.Leu511Lysfs*21) in SASH1 and a common p.Thr468Met mutation in PTPN11 were detected in three pediatric patients with lentiginous phenotypes, respectively. Comparisons between clinical presentations showed that SASH1-related phenotypes can exhibit hyper- and hypopigmentation on the trunk and extremities, similar to dyschromatosis, while scattered café au-lait spots usually appeared in PTPN11-related LEOPARD syndrome. Furthermore, the similarity in the clinical presentations of Peutz-Jeghers syndrome, Laugier-Hunziker syndrome, xeroderma pigmentosum, neurofibromatosis type I, suggesting that these conditions should be added into the differential diagnoses of lentiginous phenotypes.