LEOPARD Syndrome Research Articles

Regulation of apoptosis in HL‐1 cardiomyocytes by phosphorylation of the receptor tyrosine kinase EphA2 and protection by lithocholic acid

Heart failure and atrial fibrillation are associated with apoptosis of cardiomyocytes, suggesting common abnormalities in pro-apoptotic cardiac molecules. Activation of the receptor tyrosine kinase EphA2 causes apoptosis in vitro, and dysregulation of EphA2-dependent signalling is implicated in LEOPARD and Noonan syndromes associated with cardiomyopathy. Molecular pathways and regulation of EphA2 signalling in the heart are poorly understood. Here we elucidated the pathways of EphA2-dependent apoptosis and evaluated a therapeutic strategy to prevent EphA2 activation and cardiac cell death. EphA2 signalling was studied in an established model of doxazosin-induced apoptosis in HL-1 cells. Apoptosis was measured with TUNEL assays and as cell viability using a formazan method. Western blotting and siRNA for EphA2 were also used. Apoptosis induced by doxazosin (EC(50) = 17.3 μM) was associated with EphA2 activation through enhanced phosphorylation (2.2-fold). Activation of pro-apoptotic downstream factors, phospho-SHP-2 (3.9-fold), phospho-p38 MAPK (2.3-fold) and GADD153 (1.6-fold) resulted in cleavage of caspase 3. Furthermore, two anti-apoptotic enzymes were suppressed (focal adhesion kinase, by 41%; phospho-Akt, by 78%). Inactivation of EphA2 with appropriate siRNA mimicked pro-apoptotic effects of doxazosin. Finally, administration of lithocholic acid (LCA) protected against apoptosis by increasing EphA2 protein levels and decreasing EphA2 phosphorylation. EphA2 phosphorylation and activation of SHP-2 are critical steps in apoptosis. Reduction of EphA2 phosphorylation by LCA may represent a novel approach for future anti-apoptotic treatment of heart failure and atrial fibrillation.

Targeting SHP2 phosphatase in Myeloproliferative Neoplasms

Targeting SHP2 phosphatase in Myeloproliferative Neoplasms

Sudden Cardiac Death in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a common disorder of cardiac muscle associated with sudden cardiac death (SCD). HCM is defined by increased left ventricular wall thickness or mass, in the absence of abnormal loading conditions to account for the observed abnormality.1 In most adults, the disease is inherited as an autosomal dominant trait and is caused by mutations in cardiac sarcomere protein genes.1 Histologically, HCM is characterized by myocardial disarray, fibrosis, and small vessel disease.2 Macroscopically, the hypertrophy is typically asymmetrical and 25% of patients have resting left ventricular outflow tract obstruction (LVOTO).3 SCD in HCM is caused mainly by ventricular arrhythmias that can be effectively treated by implantable cardioverter defibrillator (ICD) therapy. Identification of patients at high risk is a cornerstone of management and research during the past 4 decades has recognized a number of phenotypic characteristics that can be used to identify those patients who might benefit from an ICD. ### Genetics and Pathogenesis In infants and children, HCM is often associated with syndromes (eg Noonan’s syndrome, LEOPARD syndrome) and metabolic diseases (eg, glycogen storage diseases).1 In adults and adolescents, HCM is primarily caused by mutations in cardiac sarcomeric protein genes, and is inherited in an autosomal dominant manner.1 Mutations in these genes can be found in ≈60% of patients, and MYBPC3 and MYH7 mutations account for the majority of cases. Genotype–phenotype correlations are weak, with significant interfamily and intrafamily phenotypic variability. Exactly how HCM develops as a consequence of sarcomere protein gene mutations is not known.4 ### Sudden Cardiac Death and Underlying Mechanisms Existing data indicate that most patients with HCM die from cardiac causes,5–7 but this may reflect referral bias from centers reporting on mortality in HCM. Although the data do not exist, based on prevalence of 1/500,8 it is likely that most patients with HCM remain …

Paraneoplastic disseminated lentigines heralding aggressive Langerhans cell sarcoma

Dear Editor, A 21-year-old man presented with a rapidly growing (9 cm), non-tender right flank mass with superficial excoriation and inflammation (Fig. 1a). The lesion was accompanied by rapid onset of disseminated brown papules, involving the torso, back, and limbs (Fig. 1b). Facial and axillary skins were spared, and there was no particular direction of spread. The skin patches did not coalesce or show pruritus or inflammation. There was also weight loss of 15 lb in 3 months. A positron emission tomogram scan (PET) showed FDG uptake in the right waist (SUV 5.8) and right groin (SUV 2.1) (Fig. 1c). Wide margin resection of the mass and lymph node excision was performed with clear margins. Histology of both specimens showed sheets and loose clusters of pleomorphic malignant cells infiltrating the dermis and subcutis with frequent mitosis (Fig. 1d). In view of the anaplastic morphology and unusual presentation, extensive immunophenotyping was performed. The cells were positive for CD1a, S100, and Langerin stains. They were negative for melanocytic markers (HMB45, melan-A, MITF) EMA, cytokeratin (CK, Cam 5.2, 34betaE12), actin, desmin, CD31, CD34, c-kit, B and T markers (CD20, CD79a, CD3), CD68, CD30, CD56, CD21, MPO, and ALK1. Electron microscopy for Birbeck granules was not performed. The picture was compatible with Langerhans cell sarcoma (LCS). A separate skin biopsy of a pigmented lesion on the torso showed elongated rete ridges with increased basal melanin pigmentation within keratinocytes and the tips, with no increased Langerhans cells and no evidence of malignancy or dysplasia. The lesion was compatible with common lentigo. The patient was treated with consolidation radiotherapy to the primary sites, but there was no regression of the skin lentiges. Fig. 1 a Clinical photo showing the flank mass with impending ulceration. b Widespread lentiginous lesion all over the trunk heralding the rapid growth of the malignant lesion. c PET with maximum intensity projection showing two sites of active lesions in the ... In the World Health Organization classification, LCS is the malignant end of the spectrum of benign Langerhans cell histiocytosis (LCH) [1]. The typical LCH cell is replaced by pleomorphic tumor cells in the LCS, only identifiable by phenotype or ultrastructure. Initial unifocal subcutaneous involvement is not unusual. However progressive disease, especially with multifocal dissemination, is highly fatal, despite multi-agent chemotherapy. It remains to be seen whether systemic progression may occur in our patient. Our patient demonstrated two hitherto unreported phenomena, namely paraneoplastic manifestation of LCS and acquired rampant disseminated lentigines as a new paraneoplastic dermatosis. The clinical history and histological findings do not suggest an underlying disseminated cutaneous LCH. Common paraneoplastic dermatoses (e.g., acanthocis nigricans) are well characterized and are putatively caused by neoplastic humoral secretions. Acquired melanocytic nevi are mostly related to solar exposure and are therefore localized. Recently, some cases of acral lentigines are debated to be paraneoplastic [2]. Disseminated lentigines are usually only found in familial lentiginosis syndromes (e.g., LEOPARD syndrome, Peutz–Jeghers, Carney complex, PTEN hamartoma syndrome). The neoplastic associations of these syndromes come from their primary systemic gene mutations [3]. The rapidly acquired disseminated growth of lentigines in our case is highly unusual and is somewhat induced by the abnormal aggressive transformation of the LCS cells. Skin pigmentation is usually under exquisite humoral control [4], and cutaneous Langerhans cells interact closely with melanocytes and keratinocytes [5]. It is impossible, however, to retrospectively work out the exact mechanism how the localized growth induced a systemic pigment response, since interval archival specimens are unavailable and the list of possible mediators are extensive. In any case, extirpation of the primary lesion appeared to halt further skin lesions.

LEOPARD syndrome

LEOPARD syndrome (LS) is a rare hereditary disorder, characterised mainly by skin, facial and cardiac abnormalities. We report on the case of a six-year-old Djiboutian with typical features of LS. Multiple cardiovascular problems are described, including pulmonary infundibular, valvular and supra-valvular stenosis. A favourable course was observed after successful cardiac surgery. This is the first reported case of LS from the horn of Africa.

Microduplication of 3p25.2 encompassing RAF1 associated with congenital heart disease suggestive of Noonan syndrome

Noonan syndrome (NS) is a clinically variable and genetically heterogeneous disorder with congenital heart defects (CHD), short stature, and craniofacial dysmorphisms. Gain-of-function mutations in RAF1 can cause NS and the highly related NS with multiple lentigines (previously known as LEOPARD syndrome). Here we report on a 15-year-old male with NS phenotype: short stature, heart defects, low posterior hairline, facial malformations, malformed left ear with sensorineural hearing loss, widely spaced nipples, and unilateral upper limb anomaly. Using high-resolution SNP array technology, we identified in this patient a 0.25 Mb microduplication at 3p25.2 in which RAF1 is located. Sequence analysis did not identify mutations in genes associated with Holt-Oram syndrome. These findings suggest that duplications of genomic regions encompassing RAF1 could cause NS and are consistent with the notion that rare copy number variations encompassing causative genes may underlie a small percentage of patients with syndromic CHD like NS.

High-purity enrichment of functional cardiovascular cells from human iPS cells

A variety of human inherited heart diseases affect the normal functions of cardiomyocytes (CMs), endothelial cells (ECs), or smooth muscle cells (SMCs). To study human heart disease and generate cardiac cells for basic and translational research, an efficient strategy is needed for production of cardiac lineages from human stem cells. In the present study, a highly reproducible method was developed that can simultaneously enrich a large number of CMs and cardiac SMCs and ECs from human induced pluripotent stem (iPS) cells with high purity. Human multipotent cardiovascular progenitor cells were generated from human iPS cells, followed by selective differentiation of the multipotent cardiovascular progenitor cells into CMs, ECs, and SMCs. With further fluorescence-activated cell sorting, each of the three cardiovascular cell types could be enriched with high purity (>90%). These enriched cardiovascular cells exhibited specific gene expression signatures and normal functions when assayed both in vitro and in vivo. Moreover, CMs purified from iPS cells derived from a patient with LEOPARD syndrome, a disease characterized by cardiac hypertrophy, showed the expected up-regulated expression of genes associated with cardiac hypertrophy. Overall, our technical advance provides the means for generating a renewable resource of pure human cardiovascular cells that can be used to dissect the mechanisms of human inherited heart disease and for the future development of drug and cell therapeutics for heart disease.

Abstract 2150: The role of SHP2 in HER2+ breast cancer

Abstract Breast cancer is the most common malignancy and the second most common cause of cancer related death in women. HER2+ over-expressing (HER2+) tumors comprise 20% to 25% of all cases and are associated with a poor prognosis. The discovery of HER2 monoclonal antibody-based therapeutics has greatly improved patient prognosis. However, patients suffer relapse and de novo resistance. Thus it is important to determine additional therapeutic targets in HER2+ breast cancer that might be used in combination with current therapies to improve patient survival. SHP2 (PTPN11) is a non-receptor protein-tyrosine phosphatase (PTP) that contains two SH2 domains at its N-terminus, a central PTP domain and a C-terminal proline-rich tail. Previous studies suggest that Shp2 is required for Ras/Erk signaling downstream of most growth factor receptors and integrins. Heterozygous germ-line PTPN11 mutations cause Noonan Syndrome and LEOPARD syndrome, which are associated with leukemia and cancer predisposition. Somatic PTPN11 mutations cause juvenile myelomonocytic leukemia (JMML) and several other neoplasms. We have discovered that Shp2 is required in Neu-mediated tumorigenesis in the MMTV-NIC mouse model; furthermore, SHP2-depleted human HER2+ BT-474 has defective tumorigenesis in nude mice. SHP2 is required in anchorage-independent growth in 4 HER2+ breast cancer cell lines, though its effect on growth on plastics appears minimal. I hypothesize that SHP2 is required for HER2+ breast tumor initiation and maintenance. I further hypothesize that SHP2 functions through specific substrates/interacting proteins in HER2+ breast cancer cells, possibly molecules that are involved in anchorage-independent proliferation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2150. doi:1538-7445.AM2012-2150

KRAS gene mutations in Noonan syndrome familial cases cluster in the vicinity of the switch II region of the G‐domain: Report of another family with metopic craniosynostosis

Noonan syndrome (NS) and Noonan-related disorders [cardio-facio-cutaneous (CFC), Costello, Noonan syndrome with multiple lentigines (NS-ML), and neurofibromatosis-Noonan syndromes (NFNS)] are a group of developmental disorders caused by mutations in genes of the RAS/MAPK pathway. Mutations in the KRAS gene account for only a small proportion of affected Noonan and CFC syndrome patients that present an intermediate phenotype between these two syndromes, with more frequent and severe intellectual disability in NS and less ectodermal involvement in CFC syndrome, as well as atypical clinical findings such as craniosynostosis. Recently, the first familial case with a novel KRAS mutation was described. We report on a second vertical transmission (a mother and two siblings) with a novel mutation (p.M72L), in which the proband has trigonocephaly and the affected mother and sister, prominent ectodermal involvement. Metopic suture involvement has not been described before, expanding the main different cranial sutures which can be affected in NS and KRAS gene mutations. The gene alteration found in the studied family is in close proximity to the one reported in the other familial case (close to the switch II region of the G-domain), suggesting that this specific region of the gene could have less severe effects on intellectual ability than the other KRAS gene mutations found in NS patients and be less likely to hamper reproductive fitness.

Successful treatment of progressive hypertrophic cardiomyopathy with heart transplantation and rhapamycine in an infant with LEOPARD syndrome due to a heterozygous mutation in the PTPN11-gene (Q510E)

Successful treatment of progressive hypertrophic cardiomyopathy with heart transplantation and rhapamycine in an infant with LEOPARD syndrome due to a heterozygous mutation in the PTPN11-gene (Q510E)

SHP-2 acts via ROCK to regulate the cardiac actin cytoskeleton

Noonan syndrome is one of the most common causes of human congenital heart disease and is frequently associated with missense mutations in the protein phosphatase SHP-2. Interestingly, patients with acute myelogenous leukemia (AML), acute lymphoblastic leukemia (ALL), juvenile myelomonocytic leukemia (JMML) and LEOPARD syndrome frequently carry a second, somatically introduced subset of missense mutations in SHP-2. To determine the cellular and molecular mechanisms by which SHP-2 regulates heart development and, thus, understand how Noonan-associated mutations affect cardiogenesis, we introduced SHP-2 encoding the most prevalent Noonan syndrome and JMML mutations into Xenopus embryos. Resulting embryos show a direct relationship between a Noonan SHP-2 mutation and its ability to cause cardiac defects in Xenopus; embryos expressing Noonan SHP-2 mutations exhibit morphologically abnormal hearts, whereas those expressing an SHP-2 JMML-associated mutation do not. Our studies indicate that the cardiac defects associated with the introduction of the Noonan-associated SHP-2 mutations are coupled with a delay or arrest of the cardiac cell cycle in M-phase and a failure of cardiomyocyte progenitors to incorporate into the developing heart. We show that these defects are a result of an underlying malformation in the formation and polarity of cardiac actin fibers and F-actin deposition. We show that these defects can be rescued in culture and in embryos through the inhibition of the Rho-associated, coiled-coil-containing protein kinase 1 (ROCK), thus demonstrating a direct relationship between SHP-2N308D and ROCK activation in the developing heart.

SHP-2 acts via ROCK to regulate the cardiac actin cytoskeleton

Noonan syndrome is one of the most common causes of human congenital heart disease and is frequently associated with missense mutations in the protein phosphatase SHP-2. Interestingly, patients with acute myelogenous leukemia (AML), acute lymphoblastic leukemia (ALL), juvenile myelomonocytic leukemia (JMML) and LEOPARD syndrome frequently carry a second, somatically introduced subset of missense mutations in SHP-2. To determine the cellular and molecular mechanisms by which SHP-2 regulates heart development and, thus, understand how Noonan-associated mutations affect cardiogenesis, we introduced SHP-2 encoding the most prevalent Noonan syndrome and JMML mutations into Xenopus embryos. Resulting embryos show a direct relationship between a Noonan SHP-2 mutation and its ability to cause cardiac defects in Xenopus; embryos expressing Noonan SHP-2 mutations exhibit morphologically abnormal hearts, whereas those expressing an SHP-2 JMML-associated mutation do not. Our studies indicate that the cardiac defects associated with the introduction of the Noonan-associated SHP-2 mutations are coupled with a delay or arrest of the cardiac cell cycle in M-phase and a failure of cardiomyocyte progenitors to incorporate into the developing heart. We show that these defects are a result of an underlying malformation in the formation and polarity of cardiac actin fibers and F-actin deposition. We show that these defects can be rescued in culture and in embryos through the inhibition of the Rho-associated, coiled-coil-containing protein kinase 1 (ROCK), thus demonstrating a direct relationship between SHP-2(N308D) and ROCK activation in the developing heart.

Abstract P190: Role of mTOR Signaling in LEOPARD-Syndrome-Associated Hypertrophic Cardiomyopathy

The identification of mutations in PTPN11 (encoding the protein tyrosine phosphatase Shp2) in families with congenital heart disease has facilitated mechanistic studies of various cardiovascular defects. However, the roles of normal and mutant Shp2 in the developing heart are still poorly understood. In particular, how Shp2 loss-of-function (LOF) mutations cause LEOPARD Syndrome, which is characterized by congenital heart defects such as pulmonary valve stenosis and hypertrophic cardiomyopathy (HCM), remains unclear. We employed both in vitro and in vivo models to investigate signaling mechanisms downstream of Q510E-Shp2, a particularly aggressive mutation leading to early-onset HCM. In cultured rat neonatal cardiomyocytes, Q510E-Shp2 expression significantly increased cell size. This increase was accompanied by hyperactivation of signaling through mammalian target of rapamycin (mTOR). mTOR inhibition with rapamycin reversed the pro-hypertrophic effects of Q510E-Shp2 in culture. Mice with cardiomyocyte-specific overexpression of Q510E-Shp2 starting before birth also showed up-regulation of signaling through Akt/mTOR/p70S6K and developed HCM in the early neonatal period. Q510E-Shp2 expression increased cardiomyocyte sizes and septum thickness, and caused cardiomyocyte disarray and fibrosis. Echocardiographically, hearts were hypocontractile and displayed increased wall thicknesses. Importantly, rapamycin administration rescued the Q510E-Shp2-induced phenotype in vivo. Our studies establish a role for mTOR signaling in HCM caused by the LOF mutation Q510E-Shp2. Pharmacological inhibition of mTOR was sufficient to rescue the HCM phenotype in both models. These findings have important implications not only for the development of novel therapeutic approaches for LEOPARD Syndrome patients, but also for closely related forms of congenital heart disease such as Noonan Syndrome.

ThePTPN11loss-of-function mutation Q510E-Shp2 causes hypertrophic cardiomyopathy by dysregulating mTOR signaling

The identification of mutations in PTPN11 (encoding the protein tyrosine phosphatase Shp2) in families with congenital heart disease has facilitated mechanistic studies of various cardiovascular defects. However, the roles of normal and mutant Shp2 in the developing heart are still poorly understood. Furthermore, it remains unclear how Shp2 loss-of-function (LOF) mutations cause LEOPARD Syndrome (also termed Noonan Syndrome with multiple lentigines), which is characterized by congenital heart defects such as pulmonary valve stenosis and hypertrophic cardiomyopathy (HCM). In normal hearts, Shp2 controls cardiomyocyte size by regulating signaling through protein kinase B (Akt) and mammalian target of rapamycin (mTOR). We hypothesized that Shp2 LOF mutations dysregulate this pathway, resulting in HCM. For our studies, we chose the Shp2 mutation Q510E, a dominant-negative LOF mutation associated with severe early onset HCM. Newborn mice with cardiomyocyte-specific overexpression of Q510E-Shp2 starting before birth displayed increased cardiomyocyte sizes, heart-to-body weight ratios, interventricular septum thickness, and cardiomyocyte disarray. In 3-mo-old hearts, interstitial fibrosis was detected. Echocardiographically, ventricular walls were thickened and contractile function was depressed. In ventricular tissue samples, signaling through Akt/mTOR was hyperactivated, indicating that the presence of Q510E-Shp2 led to upregulation of this pathway. Importantly, rapamycin treatment started shortly after birth rescued the Q510E-Shp2-induced phenotype in vivo. If rapamycin was started at 6 wk of age, HCM was also ameliorated. We also generated a second mouse model in which cardiomyocyte-specific Q510E-Shp2 overexpression started after birth. In contrast to the first model, these mice did not develop HCM. In summary, our studies establish a role for mTOR signaling in HCM caused by Q510E-Shp2. Q510E-Shp2 overexpression in the cardiomyocyte population alone was sufficient to induce the phenotype. Furthermore, the pathomechanism was triggered pre- but not postnatally. However, postnatal rapamycin treatment could still reverse already established HCM, which may have important therapeutic implications.

Induced Pluripotent Stem Cell-Derived Cardiomyocytes and Long QT Syndrome: Is Personalized Medicine Ready for Prime Time?

See related article, pages 841–847 The study by Malan et al1 in this issue of the Circulation Research presents elegant data about induced pluripotent stem cell (iPSC)-derived myocytes2 from a mouse model of long QT syndrome (LQTS) type 3.3 The study is an important contribution that adds to a highly innovative field that is trying to define the role of iPSC technology in the understanding of inherited arrhythmias. In this accompanying editorial, I provide an overview of the previous studies in the field, comment on the contribution of Malan et al,1 and conclude by discussing some of the challenges in the field. The technique to differentiate cardiac myocytes from pluripotent stem cells is quite recent and it was introduced by the seminal article published in 2006 by Takahashi and Yamanaka,2 who used a combination of four retrovirally transduced transcription factors ( Oct3/4 , Sox2 , Klf4 , and c-Myc ) to generate iPSCs from mouse somatic cells. The importance of this technology was immediately recognized and it was rapidly applied to human cells.4 In the past few years, several investigators have refined protocols to optimize differentiation of iPSCs into cardiac myocytes and to characterize their properties. In analogy with myocardial cells derived from human embryonic cells,5 iPSC-derived myocytes differentiate into three cell types: nodal, atrial, and ventricular myocytes and present physiological adaptation of action potential duration to changes in heart rate and normal response to beta adrenergic stimulation.6 Furthermore, the presence of key ion channels7 and regulators of intracellular calcium physiology,8 as well as the preservation of the sarcomeric structure,9 have been confirmed in iPSC-derived myocytes. This comprehensive set of data provided a solid background to test the hypothesis that the differentiation of iPSC-derived cardiac cells from patients with inherited cardiac …

Implantable cardioverter defibrillator for progressive hypertrophic cardiomyopathy in a patient with LEOPARD syndrome and a novel PTPN11 mutation Gln510His

LEOPARD syndrome (LS), generally caused by heterozygous mutations in the PTPN11 gene, is a rare autosomal-dominant multiple congenital anomaly condition, characterized by skin, facial, and cardiac abnormalities. Prognosis appears to be related to the type of structural, myocardial, and arrhythmogenic cardiac disease, especially hypertrophic cardiomyopathy (HCM). We report on a woman with LS and a novel Gln510His mutation in PTPN11, who had progressive HCM with congestive heart failure and nonsustained ventricular tachycardia, successfully treated with implantable cardioverter defibrillator (ICD). Comparing our patient to the literature suggests that specific mutations at codon 510 in PTPN11 (Gln510Glu, Gln510His, but not Gln510Pro) might be a predictor of fatal cardiac events in LS. Molecular risk stratification and careful evaluations for an indication of ICD implantation are likely to be beneficial in managing patients with LS and HCM.

A Case Report on Aural Rehabilitation after Cochlear Implantation in a Child with LEOPARD syndrome

A Case Report on Aural Rehabilitation after Cochlear Implantation in a Child with LEOPARD syndrome

La tachycardie atriale néonatale : association non fortuite avec le syndrome de Costello. À propos de 2 cas

Costello syndrome is a rare association of symptoms caused by de novo germline mutations of the HRAS oncogene interfering in the RAS/mitogen-activated protein kinase (MAPK) signal transduction pathway. Mutations in this pathway are also responsible for Noonan syndrome and the related cardiofaciocutaneous syndrome (CFC) as well as LEOPARD syndrome. The 4 syndromes share phenotypic resemblances concerning patients' morphology but also regarding associated cardiac disease, namely hypertrophic cardiomyopathy, pulmonary stenosis, and atrial septal defect. The electrocardiogram often shows an upper deviation of the QRS axis. Arrhythmias are rare but, if present, are particularly typical of CS. We describe herein two newborn infants with Costello syndrome revealed by atrial tachycardia associated with characteristic morphological and cardiac features of syndromes related to mutations in the RAS/MAPK pathway.

Two novel germline KRAS mutations: expanding the molecular and clinical phenotype

Noonan and Cardio-facio-cutaneous (CFC) syndromes are characterized by typical dysmorphic features, cardiac defects, short stature, variable ectodermal anomalies, and intellectual disability. Both belong to the Ras/mitogen-activated protein kinase pathway group of disorders and clinical features overlap other related conditions, notably LEOPARD and Costello syndromes. KRAS mutations account for about 2% of reported Noonan and <5% of reported CFC cases. The mutation spectrum includes recurrent missense changes clustering in particular domains of the KRAS protein and conferring gain-of-function. We report three patients from two unrelated families with novel missense KRAS mutations, p.K147E and p.Y71H. Both mutations affect a residue which is highly conserved in KRAS and other RAS isoforms. One of the families includes a mother and son pair who represent the first report of a vertically transmitted KRAS mutation. In addition, the mother and son pair had peripheral neuropathy, complicated by Charcot arthropathy in the mother. An unusual phenotypic effect of the specific KRAS mutation or a coincidence of two independent disorders may be considered. KRAS mutation-associated phenotypes appear to be subject to considerable clinical heterogeneity. All three cases highlight the challenges of clinical assessment in KRAS mutation-positive patients, and the utility of molecular testing as an adjunct to diagnosis.

Cardiomyopathy with alopecia and palmoplantar keratoderma (CAPK) is caused by a JUP mutation

Inherited desmosomal cardiocutaneous syndromes are characterized by the quartet of woolly hair, palmoplantar keratoderma (PPK), skin fragility and cardiac abnormalities, which are caused by mutations in genes coding for desmosomal proteins. We describe a previously unrecognized autosomal recessive syndrome in a family with arrhythmogenic right ventricular cardiomyopathy associated with alopecia and PPK (named CAPK). Genetic investigation of the family led us to find a homozygous disease-causing mutation, p.R265H, in JUP which encodes plakoglobin, a well-described member of the desmosome complex. This study expands the clinical spectrum of disorders associated with germline mutations affecting desmosomal proteins by describing a novel phenotype.