Publications by authors named "Francesca Pantaleoni"

43 Publications

SPEN haploinsufficiency causes a neurodevelopmental disorder overlapping proximal 1p36 deletion syndrome with an episignature of X chromosomes in females.

Am J Hum Genet 2021 03 16;108(3):502-516. Epub 2021 Feb 16.

Division of Medical Genetics, Department of Pediatrics, UPMC Children's Hospital of Pittsburgh, Pittsburgh, PA 15224, USA.

Deletion 1p36 (del1p36) syndrome is the most common human disorder resulting from a terminal autosomal deletion. This condition is molecularly and clinically heterogeneous. Deletions involving two non-overlapping regions, known as the distal (telomeric) and proximal (centromeric) critical regions, are sufficient to cause the majority of the recurrent clinical features, although with different facial features and dysmorphisms. SPEN encodes a transcriptional repressor commonly deleted in proximal del1p36 syndrome and is located centromeric to the proximal 1p36 critical region. Here, we used clinical data from 34 individuals with truncating variants in SPEN to define a neurodevelopmental disorder presenting with features that overlap considerably with those of proximal del1p36 syndrome. The clinical profile of this disease includes developmental delay/intellectual disability, autism spectrum disorder, anxiety, aggressive behavior, attention deficit disorder, hypotonia, brain and spine anomalies, congenital heart defects, high/narrow palate, facial dysmorphisms, and obesity/increased BMI, especially in females. SPEN also emerges as a relevant gene for del1p36 syndrome by co-expression analyses. Finally, we show that haploinsufficiency of SPEN is associated with a distinctive DNA methylation episignature of the X chromosome in affected females, providing further evidence of a specific contribution of the protein to the epigenetic control of this chromosome, and a paradigm of an X chromosome-specific episignature that classifies syndromic traits. We conclude that SPEN is required for multiple developmental processes and SPEN haploinsufficiency is a major contributor to a disorder associated with deletions centromeric to the previously established 1p36 critical regions.
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http://dx.doi.org/10.1016/j.ajhg.2021.01.015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8008487PMC
March 2021

When to test fetuses for RASopathies? Proposition from a systematic analysis of 352 multicenter cases and a postnatal cohort.

Genet Med 2021 Feb 10. Epub 2021 Feb 10.

Pediatrics Department, Medical Genetics Division, CHU Sainte-Justine, Montreal, QC, Canada.

Purpose: Recent studies have identified suggestive prenatal features of RASopathies (e.g., increased nuchal translucency [NT], cystic hygroma [CH], hydrops, effusions, congenital heart diseases [CHD], polyhydramnios, renal anomalies). Our objective is to clarify indications for RASopathy prenatal testing. We compare genotype distributions between pre- and postnatal populations and propose genotype-phenotype correlations.

Methods: Three hundred fifty-two chromosomal microarray-negative cases sent for prenatal RASopathy testing between 2012 and 2019 were collected. For most, 11 RASopathy genes were tested. Postnatal cohorts (25 patients with available prenatal information and 108 institutional database genotypes) and the NSeuroNet database were used for genotypic comparisons.

Results: The overall diagnostic yield was 14% (50/352), with rates >20% for effusions, hydrops, and CHD. Diagnostic yield was significantly improved in presence of hypertrophic cardiomyopathy (HCM), persistent or associated CH, any suggestive finding combined with renal anomaly or polyhydramnios, or ≥2 ultrasound findings. Largest prenatal contributors of pathogenic variants were PTPN11 (30%), RIT1 (16%), RAF1 (14%), and HRAS (12%), which considerably differ from their prevalence in postnatal populations. HRAS, LZTR1, and RAF1 variants correlated with hydrops/effusions, and RIT1 with prenatal onset HCM.

Conclusion: After normal chromosomal microarray, RASopathies should be considered when any ultrasound finding of lymphatic dysplasia or suggestive CHD is found alone or in association.
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http://dx.doi.org/10.1038/s41436-020-01093-7DOI Listing
February 2021

De Novo VPS4A Mutations Cause Multisystem Disease with Abnormal Neurodevelopment.

Am J Hum Genet 2020 12 12;107(6):1129-1148. Epub 2020 Nov 12.

Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, UK; Department of Medical Genetics, University of Cambridge, Cambridge CB2 0QQ, UK. Electronic address:

The endosomal sorting complexes required for transport (ESCRTs) are essential for multiple membrane modeling and membrane-independent cellular processes. Here we describe six unrelated individuals with de novo missense variants affecting the ATPase domain of VPS4A, a critical enzyme regulating ESCRT function. Probands had structural brain abnormalities, severe neurodevelopmental delay, cataracts, growth impairment, and anemia. In cultured cells, overexpression of VPS4A mutants caused enlarged endosomal vacuoles resembling those induced by expression of known dominant-negative ATPase-defective forms of VPS4A. Proband-derived fibroblasts had enlarged endosomal structures with abnormal accumulation of the ESCRT protein IST1 on the limiting membrane. VPS4A function was also required for normal endosomal morphology and IST1 localization in iPSC-derived human neurons. Mutations affected other ESCRT-dependent cellular processes, including regulation of centrosome number, primary cilium morphology, nuclear membrane morphology, chromosome segregation, mitotic spindle formation, and cell cycle progression. We thus characterize a distinct multisystem disorder caused by mutations affecting VPS4A and demonstrate that its normal function is required for multiple human developmental and cellular processes.
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http://dx.doi.org/10.1016/j.ajhg.2020.10.012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7820634PMC
December 2020

The clinical significance of A2ML1 variants in Noonan syndrome has to be reconsidered.

Eur J Hum Genet 2021 Mar 20;29(3):524-527. Epub 2020 Oct 20.

Institute of Human Genetics, University Hospital Magdeburg, Magdeburg, Germany.

The RASopathies are a group of clinically and genetically heterogeneous developmental disorders caused by dysregulation of the RAS/MAPK signalling pathway. Variants in several components and regulators of this pathway have been identified as the pathogenetic cause. In 2015, missense variants in A2ML1 were reported in three unrelated families with clinical diagnosis of Noonan syndrome (NS) and a zebrafish model was presented showing heart and craniofacial defects similar to those caused by a NS-associated Shp2 variant. However, a causal role of A2ML1 variants in NS has not been confirmed since. Herein, we report on 15 individuals who underwent screening of RASopathy-associated genes and were found to carry rare variants in A2ML1, including variants previously proposed to be causative for NS. In cases where parental DNA was available, the respective A2ML1 variant was found to be inherited from an unaffected parent. Seven index patients carrying an A2ML1 variant presented with an alternate disease-causing genetic aberration. These findings underscore that current evidence is insufficient to support a causal relation between variants in A2ML1 and NS, questioning the inclusion of A2ML1 screening in diagnostic RASopathy testing.
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http://dx.doi.org/10.1038/s41431-020-00743-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7940614PMC
March 2021

Variants of SOS2 are a rare cause of Noonan syndrome with particular predisposition for lymphatic complications.

Eur J Hum Genet 2021 Jan 12;29(1):51-60. Epub 2020 Aug 12.

Institute of Human Genetics, University Hospital Magdeburg, Magdeburg, Germany.

RASopathies are caused by variants in genes encoding components or modulators of the RAS/MAPK signaling pathway. Noonan syndrome is the most common entity among this group of disorders and is characterized by heart defects, short stature, variable developmental delay, and typical facial features. Heterozygous variants in SOS2, encoding a guanine nucleotide exchange factor for RAS, have recently been identified in patients with Noonan syndrome. The number of published cases with SOS2-related Noonan syndrome is still limited and little is known about genotype-phenotype correlations. We collected previously unpublished clinical and genotype data from 17 individuals carrying a disease-causing SOS2 variant. Most individuals had one of the previously reported dominant pathogenic variants; only four had novel changes at the established hotspots for variants that affect protein function. The overall phenotype of the 17 patients fits well into the spectrum of Noonan syndrome and is most similar to the phenotype observed in patients with SOS1-related Noonan syndrome, with ectodermal anomalies as common features and short stature and learning disabilities as relatively infrequent findings compared to the average Noonan syndrome phenotype. The spectrum of heart defects in SOS2-related Noonan syndrome was consistent with the known spectrum of cardiac anomalies in RASopathies, but no specific heart defect was particularly predominating. Notably, lymphatic anomalies were extraordinarily frequent, affecting more than half of the patients. We therefore conclude that SOS2-related Noonan syndrome is associated with a particularly high risk of lymphatic complications that may have a significant impact on morbidity and quality of life.
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http://dx.doi.org/10.1038/s41431-020-00708-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7852574PMC
January 2021

Enhanced MAPK1 Function Causes a Neurodevelopmental Disorder within the RASopathy Clinical Spectrum.

Am J Hum Genet 2020 09 27;107(3):499-513. Epub 2020 Jul 27.

Institute of Human Genetics, University Hospital Magdeburg, 39120 Magdeburg, Germany.

Signal transduction through the RAF-MEK-ERK pathway, the first described mitogen-associated protein kinase (MAPK) cascade, mediates multiple cellular processes and participates in early and late developmental programs. Aberrant signaling through this cascade contributes to oncogenesis and underlies the RASopathies, a family of cancer-prone disorders. Here, we report that de novo missense variants in MAPK1, encoding the mitogen-activated protein kinase 1 (i.e., extracellular signal-regulated protein kinase 2, ERK2), cause a neurodevelopmental disease within the RASopathy phenotypic spectrum, reminiscent of Noonan syndrome in some subjects. Pathogenic variants promote increased phosphorylation of the kinase, which enhances translocation to the nucleus and boosts MAPK signaling in vitro and in vivo. Two variant classes are identified, one of which directly disrupts binding to MKP3, a dual-specificity protein phosphatase negatively regulating ERK function. Importantly, signal dysregulation driven by pathogenic MAPK1 variants is stimulus reliant and retains dependence on MEK activity. Our data support a model in which the identified pathogenic variants operate with counteracting effects on MAPK1 function by differentially impacting the ability of the kinase to interact with regulators and substrates, which likely explains the minor role of these variants as driver events contributing to oncogenesis. After nearly 20 years from the discovery of the first gene implicated in Noonan syndrome, PTPN11, the last tier of the MAPK cascade joins the group of genes mutated in RASopathies.
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http://dx.doi.org/10.1016/j.ajhg.2020.06.018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7477014PMC
September 2020

Refinement of the clinical and mutational spectrum of UBE2A deficiency syndrome.

Clin Genet 2020 08 3;98(2):172-178. Epub 2020 Jun 3.

Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù, IRCSS, Rome, Italy.

UBE2A deficiency, that is, intellectual disability (ID) Nascimento type (MIM 300860), is an X-linked syndrome characterized by developmental delay, moderate to severe ID, seizures, dysmorphisms, skin anomalies, and urogenital malformations. Forty affected subjects have been reported thus far, with 31 cases having intragenic UBE2A variants. Here, we report on additional eight affected subjects from seven unrelated families who were found to be hemizygous for previously unreported UBE2A missense variants (p.Glu62Lys, p.Arg95Cys, p.Thr99Ala, and p.Arg135Trp) or small in-frame deletions (p.Val81_Ala83del, and p.Asp101del). A wide phenotypic spectrum was documented in these subjects, ranging from moderate ID associated with mild dysmorphisms to severe features including congenital heart defects (CHD), severe cognitive impairment, and pineal gland tumors. Four variants affected residues (Glu62, Arg95, Thr99 and Asp101) that contribute to stabilizing the structure of the E3 binding domain. The three-residue in-frame deletion, p.Val81_Ala83del, resulted from aberrant processing of the transcript. This variant and p.Arg135Trp mapped to regions of the protein located far from the E3 binding region, and caused variably accelerated protein degradation. By reviewing available clinical information, we revise the clinical and molecular profile of the disorder and document genotype-phenotype correlations. Pineal gland cysts/tumors, CHD and hypogammaglobulinemia emerge as recurrent features.
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http://dx.doi.org/10.1111/cge.13775DOI Listing
August 2020

Pathogenic PTPN11 variants involving the poly-glutamine Gln -Gln -Gln stretch highlight the relevance of helix B in SHP2's functional regulation.

Hum Mutat 2020 06 11;41(6):1171-1182. Epub 2020 Mar 11.

Institute of Human Genetics, University Hospital of Magdeburg, Otto-von-Guericke-University, Magdeburg, Germany.

Germline PTPN11 mutations cause Noonan syndrome (NS), the most common disorder among RASopathies. PTPN11 encodes SHP2, a protein tyrosine-phosphatase controlling signaling through the RAS-MAPK and PI3K-AKT pathways. Generally, NS-causing PTPN11 mutations are missense changes destabilizing the inactive conformation of the protein or enhancing its binding to signaling partners. Here, we report on two PTPN11 variants resulting in the deletion or duplication of one of three adjacent glutamine residues (Gln -to-Gln ). While p.(Gln257dup) caused a typical NS phenotype in carriers of a first family, p.(Gln257del) had incomplete penetrance in a second family. Missense mutations involving Gln had previously been reported in NS. This poly-glutamine stretch is located on helix B of the PTP domain, a region involved in stabilizing SHP2 in its autoinhibited state. Molecular dynamics simulations predicted that changes affecting this motif perturb the SHP2's catalytically inactive conformation and/or substrate recognition. Biochemical data showed that duplication and deletion of Gln variably enhance SHP2's catalytic activity, while missense changes involving Gln affect substrate specificity. Expression of mutants in HEK293T cells documented their activating role on MAPK signaling, uncoupling catalytic activity and modulation of intracellular signaling. These findings further document the relevance of helix B in the regulation of SHP2's function.
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http://dx.doi.org/10.1002/humu.24007DOI Listing
June 2020

A novel disorder involving dyshematopoiesis, inflammation, and HLH due to aberrant CDC42 function.

J Exp Med 2019 12 10;216(12):2778-2799. Epub 2019 Oct 10.

Baylor-Hopkins Center for Mendelian Genomics, Houston, TX.

Hemophagocytic lymphohistiocytosis (HLH) is characterized by immune dysregulation due to inadequate restraint of overactivated immune cells and is associated with a variable clinical spectrum having overlap with more common pathophysiologies. HLH is difficult to diagnose and can be part of inflammatory syndromes. Here, we identify a novel hematological/autoinflammatory condition (NOCARH syndrome) in four unrelated patients with superimposable features, including neonatal-onset cytopenia with dyshematopoiesis, autoinflammation, rash, and HLH. Patients shared the same de novo mutation (Chr1:22417990C>T, p.R186C) and altered hematopoietic compartment, immune dysregulation, and inflammation. mutations had been associated with syndromic neurodevelopmental disorders. In vitro and in vivo assays documented unique effects of p.R186C on CDC42 localization and function, correlating with the distinctiveness of the trait. Emapalumab was critical to the survival of one patient, who underwent successful bone marrow transplantation. Early recognition of the disorder and establishment of treatment followed by bone marrow transplant are important to survival.
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http://dx.doi.org/10.1084/jem.20190147DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6888978PMC
December 2019

Activating Mutations of RRAS2 Are a Rare Cause of Noonan Syndrome.

Am J Hum Genet 2019 06 23;104(6):1223-1232. Epub 2019 May 23.

Département de Génétique, Assistance Publique des Hôpitaux de Paris (AP-HP) Hôpital Robert Debré, 75019 Paris, France; INSERM UMR 1141 - Université de Paris, 75019 Paris, France.

Aberrant signaling through pathways controlling cell response to extracellular stimuli constitutes a central theme in disorders affecting development. Signaling through RAS and the MAPK cascade controls a variety of cell decisions in response to cytokines, hormones, and growth factors, and its upregulation causes Noonan syndrome (NS), a developmental disorder whose major features include a distinctive facies, a wide spectrum of cardiac defects, short stature, variable cognitive impairment, and predisposition to malignancies. NS is genetically heterogeneous, and mutations in more than ten genes have been reported to underlie this disorder. Despite the large number of genes implicated, about 10%-20% of affected individuals with a clinical diagnosis of NS do not have mutations in known RASopathy-associated genes, indicating that additional unidentified genes contribute to the disease, when mutated. By using a mixed strategy of functional candidacy and exome sequencing, we identify RRAS2 as a gene implicated in NS in six unrelated subjects/families. We show that the NS-causing RRAS2 variants affect highly conserved residues localized around the nucleotide binding pocket of the GTPase and are predicted to variably affect diverse aspects of RRAS2 biochemical behavior, including nucleotide binding, GTP hydrolysis, and interaction with effectors. Additionally, all pathogenic variants increase activation of the MAPK cascade and variably impact cell morphology and cytoskeletal rearrangement. Finally, we provide a characterization of the clinical phenotype associated with RRAS2 mutations.
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http://dx.doi.org/10.1016/j.ajhg.2019.04.013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6562003PMC
June 2019

Activating MRAS mutations cause Noonan syndrome associated with hypertrophic cardiomyopathy.

Hum Mol Genet 2020 07;29(11):1772-1783

Institute of Human Genetics, University Hospital, Magdeburg, Germany.

The RASopathies are a group of genetic syndromes caused by upregulated RAS signaling. Noonan syndrome (NS), the most common entity among the RASopathies, is characterized mainly by short stature, cardiac anomalies and distinctive facial features. Mutations in multiple RAS-MAPK pathway-related genes have been associated with NS and related phenotypes. We describe two unrelated patients presenting with hypertrophic cardiomyopathy (HCM) and dysmorphic features suggestive of NS. One of them died in the neonatal period because of cardiac failure. Targeted sequencing revealed de novo MRAS variants, c.203C > T (p.Thr68Ile) and c.67G > C (p.Gly23Arg) as causative events. MRAS has only recently been related to NS based on the observation of two unrelated affected individuals with de novo variants involving the same codons here found mutated. Gly23 and Thr68 are highly conserved residues, and the corresponding codons are known hotspots for RASopathy-associated mutations in other RAS proteins. Functional analyses documented high level of activation of MRAS mutants due to impaired GTPase activity, which was associated with constitutive plasma membrane targeting, prolonged localization in non-raft microdomains, enhanced binding to PPP1CB and SHOC2 protein, and variably increased MAPK and PI3K-AKT activation. This report provides additional evidence that a narrow spectrum of activating mutations in MRAS represents another rare cause of NS, and that MRAS has to be counted among the RASopathy genes predisposing to HCM. Moreover, our findings further emphasize the relevance of the MRAS-SHOC2-PPP1CB axis in the control of MAPK signaling, and the contribution of both MAPK and PI3K-AKT pathways in MRAS functional upregulation.
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http://dx.doi.org/10.1093/hmg/ddz108DOI Listing
July 2020

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

Hum Mutat 2019 08 6;40(8):1046-1056. Epub 2019 May 6.

Molecular Genetics Unit, Fondazione Casa Sollievo della Sofferenza, IRCCS, San Giovanni Rotondo, Italy.

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 , SHOC2 is not constitutively targeted to the plasma membrane. These data document that diverse mechanisms in SHOC2 functional dysregulation converge toward MAPK signaling upregulation.
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http://dx.doi.org/10.1002/humu.23767DOI Listing
August 2019

NBAS pathogenic variants: Defining the associated clinical and facial phenotype and genotype-phenotype correlations.

Hum Mutat 2019 06 18;40(6):721-728. Epub 2019 Mar 18.

Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù IRCSS, Rome, Italy.

The pathogenic variants in the neuroblastoma-amplified sequence (NBAS) are associated with a clinical spectrum involving the hepatic, skeletal, ocular, and immune systems. Here, we report on two unrelated subjects with a complex phenotype solved by whole-exome sequencing, who shared a synonymous change in NBAS that was documented to affect the transcript processing and co-occurring with a truncating change. Starting from these two cases, we systematically assessed the clinical information available for all subjects with biallelic NBAS pathogenic variants (73 cases in total). We revealed a recognizable facial profile (hypotelorism, thin lips, pointed chin, and "progeroid" appearance) determined by using DeepGestalt facial recognition technology, and we provide evidence for the occurrence of genotype-phenotype correlations. Notably, severe hepatic involvement was associated with variants affecting the NBAS-Nter and Sec39 domains, whereas milder liver involvement and immunodeficiency were generally associated with variants located at the N-terminus and C-terminus of the protein. Remarkably, no patient was reported to carry two nonsense variants, suggesting lethality of complete NBAS loss-of-function.
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http://dx.doi.org/10.1002/humu.23734DOI Listing
June 2019

Dominant Noonan syndrome-causing LZTR1 mutations specifically affect the Kelch domain substrate-recognition surface and enhance RAS-MAPK signaling.

Hum Mol Genet 2019 03;28(6):1007-1022

Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù, Rome, Italy.

Noonan syndrome (NS), the most common RASopathy, is caused by mutations affecting signaling through RAS and the MAPK cascade. Recently, genome scanning has discovered novel genes implicated in NS, whose function in RAS-MAPK signaling remains obscure, suggesting the existence of unrecognized circuits contributing to signal modulation in this pathway. Among these genes, leucine zipper-like transcriptional regulator 1 (LZTR1) encodes a functionally poorly characterized member of the BTB/POZ protein superfamily. Two classes of germline LZTR1 mutations underlie dominant and recessive forms of NS, while constitutional monoallelic, mostly inactivating, mutations in the same gene cause schwannomatosis, a cancer-prone disorder clinically distinct from NS. Here we show that dominant NS-causing LZTR1 mutations do not affect significantly protein stability and subcellular localization. We provide the first evidence that these mutations, but not the missense changes occurring as biallelic mutations in recessive NS, enhance stimulus-dependent RAS-MAPK signaling, which is triggered, at least in part, by an increased RAS protein pool. Moreover, we document that dominant NS-causing mutations do not perturb binding of LZTR1 to CUL3, a scaffold coordinating the assembly of a multimeric complex catalyzing protein ubiquitination but are predicted to affect the surface of the Kelch domain mediating substrate binding to the complex. Collectively, our data suggest a model in which LZTR1 contributes to the ubiquitinationof protein(s) functioning as positive modulator(s) of the RAS-MAPK signaling pathway. In this model, LZTR1 mutations are predicted to variably impair binding of these substrates to the multi-component ligase complex and their efficient ubiquitination and degradation, resulting in MAPK signaling upregulation.
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http://dx.doi.org/10.1093/hmg/ddy412DOI Listing
March 2019

Mutations in KCNK4 that Affect Gating Cause a Recognizable Neurodevelopmental Syndrome.

Am J Hum Genet 2018 10;103(4):621-630

Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù, IRCCS, 00146 Rome, Italy. Electronic address:

Aberrant activation or inhibition of potassium (K) currents across the plasma membrane of cells has been causally linked to altered neurotransmission, cardiac arrhythmias, endocrine dysfunction, and (more rarely) perturbed developmental processes. The K channel subfamily K member 4 (KCNK4), also known as TRAAK (TWIK-related arachidonic acid-stimulated K channel), belongs to the mechano-gated ion channels of the TRAAK/TREK subfamily of two-pore-domain (K2P) K channels. While K2P channels are well known to contribute to the resting membrane potential and cellular excitability, their involvement in pathophysiological processes remains largely uncharacterized. We report that de novo missense mutations in KCNK4 cause a recognizable syndrome with a distinctive facial gestalt, for which we propose the acronym FHEIG (facial dysmorphism, hypertrichosis, epilepsy, intellectual disability/developmental delay, and gingival overgrowth). Patch-clamp analyses documented a significant gain of function of the identified KCNK4 channel mutants basally and impaired sensitivity to mechanical stimulation and arachidonic acid. Co-expression experiments indicated a dominant behavior of the disease-causing mutations. Molecular dynamics simulations consistently indicated that mutations favor sealing of the lateral intramembrane fenestration that has been proposed to negatively control K flow by allowing lipid access to the central cavity of the channel. Overall, our findings illustrate the pleiotropic effect of dysregulated KCNK4 function and provide support to the hypothesis of a gating mechanism based on the lateral fenestrations of K2P channels.
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http://dx.doi.org/10.1016/j.ajhg.2018.09.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6174320PMC
October 2018

TARP syndrome: Long-term survival, anatomic patterns of congenital heart defects, differential diagnosis and pathogenetic considerations.

Eur J Med Genet 2019 Jun 3;62(6):103534. Epub 2018 Sep 3.

Medical Genetics, Department of Pediatrics, Ospedale Pediatrico Bambino Gesù, Rome, Italy.

TARP syndrome (TARPS) is an X-linked syndromic condition including Robin sequence, congenital heart defects, developmental delay, feeding difficulties and talipes equinovarus, as major features. The disease is caused by inactivating mutations in RBM10 which encodes for a RNA binding motif protein involved in transcript processing. We herein report a male born from healthy and non-consanguineous parents, presenting prenatal record of intrauterine fetal growth retardation, and postnatal features including growth and developmental delays, CNS abnormalities, facial dysmorphisms, bilateral syndactyly at the hands, talipes equinovarus and congenital heart defects. By using trio-based Whole Exome Sequencing approach, a maternally inherited RBM10 frameshift variant causing decay of the RBM10 transcript was identified. Despite the syndrome is considered lethal in affected males, our subject with molecularly confirmed TARPS is still alive at 11 years of age supporting the chance of surviving. Long-term surviving in TARPS is extremely rare and should be considered in genetic counselling and clinical follow up of the syndrome. We provide the natural history of the syndrome, reviewing the major clinical characteristics. Congenital heart defects are confirmed as specific diagnostic markers for the syndrome. In addition, cardiac anatomical details are defining a possible clinical overlap with syndromic conditions related to the hedgehog pathway and/or primary cilium anomalies as Oral-Facial-Digital or Smith-Lemli-Opitz syndromes.
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http://dx.doi.org/10.1016/j.ejmg.2018.09.001DOI Listing
June 2019

Biallelic mutations in early-onset, variably progressive neurodegeneration.

Neurology 2018 07 29;91(4):e319-e330. Epub 2018 Jun 29.

From the Genetics and Rare Diseases Research Division (V.M., G.C., T.R., M.D.N., A.C., F.P., R.C., M.T.), Ospedale Pediatrico Bambino Gesù; Department of Oncology and Molecular Medicine (E.F., S.M.) and Confocal Microscopy Unit (S.C.), Core Facilities, Istituto Superiore di Sanità, Rome, Italy; Center for Human Disease Modeling (Z.K., M.M.K., N.K.), Duke University School of Medicine, Durham, NC; Institutes of Neurology (G.P., S.S.) and Nuclear Medicine (D.D.G.), Università Cattolica del Sacro Cuore, Fondazione Policlinico Universitario A. Gemelli, Rome, Italy; Department of Genetics (H.G., N.M.), Faculty of Science, Shahid Chamran University of Ahvaz; Narges Medical Genetics and Prenatal Diagnosis Laboratory (H.G., N.M., A. Sedaghat, J.Z., G.R.S.), Kianpars, Ahvaz; Research and Clinical Center for Infertility (M.D.), Yazd Reproductive Sciences Institute, Medical Genetics Research Centre (M.D., M.Y.V.M.), and Department of Medical Genetics (M.Y.V.M.), Shahid Sadoughi University of Medical Sciences, Yazd, Iran; Department of Experimental Medicine (A.T., V.C.), Università "Sapienza," Rome, Italy; Genetics and Molecular Cell Sciences Research Centre (Y.J., R.M.), St. George's University of London, UK; Department of Paediatric Neurology (R.A.M.), Golestan Medical, Educational, and Research Center, and Department of Medical Genetics (G.R.S.), Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences, Iran; University of Exeter Medical School (A.R.J.), RILD, Royal Devon & Exeter Hospital, UK; and Department of Neurology (A. Sherafat), Kerman University of Medical Sciences, Iran.

Objective: To characterize clinically and molecularly an early-onset, variably progressive neurodegenerative disorder characterized by a cerebellar syndrome with severe ataxia, gaze palsy, dyskinesia, dystonia, and cognitive decline affecting 11 individuals from 3 consanguineous families.

Methods: We used whole-exome sequencing (WES) (families 1 and 2) and a combined approach based on homozygosity mapping and WES (family 3). We performed in vitro studies to explore the effect of the nontruncating mutation on protein function and the effect of impaired SQSTM1 function on autophagy. We analyzed the consequences of sqstm1 down-modulation on the structural integrity of the cerebellum in vivo using zebrafish as a model.

Results: We identified 3 homozygous inactivating variants, including a splice site substitution (c.301+2T>A) causing aberrant transcript processing and accelerated degradation of a resulting protein lacking exon 2, as well as 2 truncating changes (c.875_876insT and c.934_936delinsTGA). We show that loss of SQSTM1 causes impaired production of ubiquitin-positive protein aggregates in response to misfolded protein stress and decelerated autophagic flux. The consequences of sqstm1 down-modulation on the structural integrity of the cerebellum in zebrafish documented a variable but reproducible phenotype characterized by cerebellum anomalies ranging from depletion of axonal connections to complete atrophy. We provide a detailed clinical characterization of the disorder; the natural history is reported for 2 siblings who have been followed up for >20 years.

Conclusions: This study offers an accurate clinical characterization of this recently recognized neurodegenerative disorder caused by biallelic inactivating mutations in and links this phenotype to defective selective autophagy.
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http://dx.doi.org/10.1212/WNL.0000000000005869DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6070386PMC
July 2018

A Child with Diminished Linear Growth and Waddling Gait.

J Pediatr 2018 10 8;201:297-297.e1. Epub 2018 May 8.

University of Trieste Trieste, Italy; Pediatrics Institute for Maternal and Child Health-IRCCS "Burlo Garofolo" Trieste, Italy.

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http://dx.doi.org/10.1016/j.jpeds.2018.04.007DOI Listing
October 2018

Functional Dysregulation of CDC42 Causes Diverse Developmental Phenotypes.

Am J Hum Genet 2018 02 25;102(2):309-320. Epub 2018 Jan 25.

GeneDX, Gaithersburg, MD 20877, USA.

Exome sequencing has markedly enhanced the discovery of genes implicated in Mendelian disorders, particularly for individuals in whom a known clinical entity could not be assigned. This has led to the recognition that phenotypic heterogeneity resulting from allelic mutations occurs more commonly than previously appreciated. Here, we report that missense variants in CDC42, a gene encoding a small GTPase functioning as an intracellular signaling node, underlie a clinically heterogeneous group of phenotypes characterized by variable growth dysregulation, facial dysmorphism, and neurodevelopmental, immunological, and hematological anomalies, including a phenotype resembling Noonan syndrome, a developmental disorder caused by dysregulated RAS signaling. In silico, in vitro, and in vivo analyses demonstrate that mutations variably perturb CDC42 function by altering the switch between the active and inactive states of the GTPase and/or affecting CDC42 interaction with effectors, and differentially disturb cellular and developmental processes. These findings reveal the remarkably variable impact that dominantly acting CDC42 mutations have on cell function and development, creating challenges in syndrome definition, and exemplify the importance of functional profiling for syndrome recognition and delineation.
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http://dx.doi.org/10.1016/j.ajhg.2017.12.015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5985417PMC
February 2018

Novel mutations and their genotype-phenotype correlations in patients with Noonan syndrome, using next-generation sequencing.

Adv Med Sci 2018 Mar 26;63(1):87-93. Epub 2017 Sep 26.

Medical Genetics Research Center, Mashhad University of Medical Sciences, Mashhad, Iran. Electronic address:

Purpose: Noonan Syndrome (NS) is an autosomal dominant disorder with many variable and heterogeneous conditions. The genetic basis for 20-30% of cases is still unknown. This study evaluates Iranian Noonan patients both clinically and genetically for the first time.

Materials/methods: Mutational analysis of PTPN11 gene was performed in 15 Iranian patients, using PCR and Sanger sequencing at phase one. Then, as phase two, Next Generation Sequencing (NGS) in the form of targeted resequencing was utilized for analysis of exons from other related genes. Homology modelling for the novel founded mutations was performed as well. The genotype, phenotype correlation was done according to the molecular findings and clinical features.

Results: Previously reported mutation (p.N308D) in some patients and a novel mutation (p.D155N) in one of the patients were identified in phase one. After applying NGS methods, known and new variants were found in four patients in other genes, including: CBL (p. V904I), KRAS (p. L53W), SOS1 (p. I1302V), and SOS1 (p. R552G). Structural studies of two deduced novel mutations in related genes revealed deficiencies in the mutated proteins. Following genotype, phenotype correlation, a new pattern of the presence of intellectual disability in two patients was registered.

Conclusions: NS shows strong variable expressivity along the high genetic heterogeneity especially in distinct populations and ethnic groups. Also possibly unknown other causative genes may be exist. Obviously, more comprehensive and new technologies like NGS methods are the best choice for detection of molecular defects in patients for genotype, phenotype correlation and disease management.
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http://dx.doi.org/10.1016/j.advms.2017.07.001DOI Listing
March 2018

Identification of novel and hotspot mutations in the channel domain of ITPR1 in two patients with Gillespie syndrome.

Gene 2017 Sep 8;628:141-145. Epub 2017 Jul 8.

Unit of Neuromuscular and Neurodegenerative Disorders, Laboratory of Molecular Medicine, Department of Neurosciences, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy. Electronic address:

ITPR1 encodes an intracellular receptor for inositol 1,4,5-trisphosphate (InsP3) which is highly expressed in the cerebellum and is involved in the regulation of Ca2+ homeostasis. Missense mutations in the InsP3-binding domain (IRBIT) of ITPR1 are frequently associated with early onset cerebellar atrophy. Gillespie syndrome is characterized by congenital ataxia, mild to moderate intellectual disability and iris hypoplasia. Dominant or recessive ITPR1 mutations have been recently associated with this form of syndromic ataxia. We performed next generation sequencing in two simplex families with Gillespie syndrome and identified de novo pathological mutations localized in the C-terminal channel domain of ITPR1 in both patients: a recurrent deletion (p.Lys2596del) and a novel missense mutation (p.Asn2576Ile) close to a point of constriction in the Ca pore. Our study expands the mutational spectrum of ITPR1 and confirms that ITPR1 screening should be implemented in patients with congenital cerebellar ataxia with or without iris hypoplasia.
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http://dx.doi.org/10.1016/j.gene.2017.07.017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5607352PMC
September 2017

Genotype and phenotype spectrum of NRAS germline variants.

Eur J Hum Genet 2017 06 3;25(7):823-831. Epub 2017 May 3.

Institute of Human Genetics, University Hospital Magdeburg, Magdeburg, Germany.

RASopathies comprise a group of disorders clinically characterized by short stature, heart defects, facial dysmorphism, and varying degrees of intellectual disability and cancer predisposition. They are caused by germline variants in genes encoding key components or modulators of the highly conserved RAS-MAPK signalling pathway that lead to dysregulation of cell signal transmission. Germline changes in the genes encoding members of the RAS subfamily of GTPases are rare and associated with variable phenotypes of the RASopathy spectrum, ranging from Costello syndrome (HRAS variants) to Noonan and Cardiofaciocutaneous syndromes (KRAS variants). A small number of RASopathy cases with disease-causing germline NRAS alterations have been reported. Affected individuals exhibited features fitting Noonan syndrome, and the observed germline variants differed from the typical oncogenic NRAS changes occurring as somatic events in tumours. Here we describe 19 new cases with RASopathy due to disease-causing variants in NRAS. Importantly, four of them harbored missense changes affecting Gly12, which was previously described to occur exclusively in cancer. The phenotype in our cohort was variable but well within the RASopathy spectrum. Further, one of the patients (c.35G>A; p.(Gly12Asp)) had a myeloproliferative disorder, and one subject (c.34G>C; p.(Gly12Arg)) exhibited an uncharacterized brain tumour. With this report, we expand the genotype and phenotype spectrum of RASopathy-associated germline NRAS variants and provide evidence that NRAS variants do not spare the cancer-associated mutation hotspots.
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http://dx.doi.org/10.1038/ejhg.2017.65DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5520077PMC
June 2017

Expanding the phenotypic spectrum of truncating POGZ mutations: Association with CNS malformations, skeletal abnormalities, and distinctive facial dysmorphism.

Am J Med Genet A 2017 Jul 7;173(7):1965-1969. Epub 2017 May 7.

Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù, IRCCS, Rome, Italy.

Exome sequencing has led to the comprehension of the molecular bases of several forms of neurodevelopmental disorders, a clinically heterogeneous group of diseases characterized by intellectual disability (ID) and autism spectrum disorder (ASD). De novo mutations in POGZ has been causally linked to isolated ASD and syndromic ID, only recently. Here we report on a 15 year-old girl in whom exome sequencing allowed to identify a de novo POGZ truncating mutation as the molecular cause underlying a complex phenotype apparently not fitting any recognized syndrome. We describe the evolution of her clinical features with age, and review published clinical data of patients with POGZ mutations to systematically analyze the clinical spectrum associated with mutations. Our finding expands the clinical and molecular spectrum of POGZ mutations. Revision of the literature indicate that moderate to severe ID, microcephaly, variable CNS malformations, reduced growth, brachytelephalangy, and facial dysmorphism represent recurrent features associated with POGZ mutations.
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http://dx.doi.org/10.1002/ajmg.a.38255DOI Listing
July 2017

Aberrant HRAS transcript processing underlies a distinctive phenotype within the RASopathy clinical spectrum.

Hum Mutat 2017 07 3;38(7):798-804. Epub 2017 May 3.

Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù, Rome, Italy.

RASopathies are a group of rare, clinically related conditions affecting development and growth, and are caused by germline mutations in genes encoding signal transducers and modulators with a role in the RAS signaling network. These disorders share facial dysmorphia, short stature, variable cognitive deficits, skeletal and cardiac defects, and a variable predisposition to malignancies. Here, we report on a de novo 10-nucleotide-long deletion in HRAS (c.481_490delGGGACCCTCT, NM_176795.4; p.Leu163ProfsTer52, NP_789765.1) affecting transcript processing as a novel event underlying a RASopathy characterized by developmental delay, intellectual disability and autistic features, distinctive coarse facies, reduced growth, and ectodermal anomalies. Molecular and biochemical studies demonstrated that the deletion promotes constitutive retention of exon IDX, which is generally skipped during HRAS transcript processing, and results in a stable and mildly hyperactive GDP/GTP-bound protein that is constitutively targeted to the plasma membrane. Our findings document a new mechanism leading to altered HRAS function that underlies a previously unappreciated phenotype within the RASopathy spectrum.
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http://dx.doi.org/10.1002/humu.23224DOI Listing
July 2017

Clinical spectrum of Kabuki-like syndrome caused by HNRNPK haploinsufficiency.

Clin Genet 2018 02 25;93(2):401-407. Epub 2017 Apr 25.

Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù, Rome, Italy.

Kabuki syndrome is a genetically heterogeneous disorder characterized by postnatal growth retardation, skeletal abnormalities, intellectual disability, facial dysmorphisms and a variable range of organ malformations. In ~30% of affected individuals, the underlying genetic defect remains unknown. A small number of inactivating heterozygous HNRNPK mutations has recently been reported to be associated with a condition partially overlapping or suggestive of Kabuki syndrome. Here, we report on an 11-year-old girl with a complex phenotype in whom the diagnosis of KS was suggested but molecular testing for the known causative disease genes was negative. Whole-exome sequencing identified a previously undescribed de novo truncating mutation in HNRNPK as the molecular defect underlying the trait. Analysis of available records of patients with HNRNPK haploinsufficiency was performed to delineate the associated clinical phenotype and outline their distinguishing features in comparison with the KS clinical spectrum. The clinical profile associated with inactivating HNRNPK mutations supports the idea that the associated disorder should be considered as a distinct nosologic entity clinically related to KS, and that the condition should be considered in differential diagnosis with KS, in particular in subjects exhibiting brain malformation (nodular heterotopia), craniosynostosis, and polydactyly.
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http://dx.doi.org/10.1111/cge.13029DOI Listing
February 2018

Structural, Functional, and Clinical Characterization of a Novel PTPN11 Mutation Cluster Underlying Noonan Syndrome.

Hum Mutat 2017 04 7;38(4):451-459. Epub 2017 Feb 7.

Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù, IRCCS, Rome, Italy.

Germline mutations in PTPN11, the gene encoding the Src-homology 2 (SH2) domain-containing protein tyrosine phosphatase (SHP2), cause Noonan syndrome (NS), a relatively common, clinically variable, multisystem disorder. Here, we report on the identification of five different PTPN11 missense changes affecting residues Leu , Leu , and Arg in 16 unrelated individuals with clinical diagnosis of NS or with features suggestive for this disorder, specifying a novel disease-causing mutation cluster. Expression of the mutant proteins in HEK293T cells documented their activating role on MAPK signaling. Structural data predicted a gain-of-function role of substitutions at residues Leu and Arg exerted by disruption of the N-SH2/PTP autoinhibitory interaction. Molecular dynamics simulations suggested a more complex behavior for changes affecting Leu , with possible impact on SHP2's catalytic activity/selectivity and proper interaction of the PTP domain with the regulatory SH2 domains. Consistent with that, biochemical data indicated that substitutions at codons 262 and 265 increased the catalytic activity of the phosphatase, while those affecting codon 261 were only moderately activating but impacted substrate specificity. Remarkably, these mutations underlie a relatively mild form of NS characterized by low prevalence of cardiac defects, short stature, and cognitive and behavioral issues, as well as less evident typical facial features.
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http://dx.doi.org/10.1002/humu.23175DOI Listing
April 2017

Activating Mutations Affecting the Dbl Homology Domain of SOS2 Cause Noonan Syndrome.

Hum Mutat 2015 Nov 3;36(11):1080-7. Epub 2015 Aug 3.

Bambino Gesù Children's Hospital, Istituto di Ricovero e Cura a Carattere Scientifico, Rome, 00165, Italy.

The RASopathies constitute a family of autosomal-dominant disorders whose major features include facial dysmorphism, cardiac defects, reduced postnatal growth, variable cognitive deficits, ectodermal and skeletal anomalies, and susceptibility to certain malignancies. Noonan syndrome (NS), the commonest RASopathy, is genetically heterogeneous and caused by functional dysregulation of signal transducers and regulatory proteins with roles in the RAS/extracellular signal-regulated kinase (ERK) signal transduction pathway. Mutations in known disease genes account for approximately 80% of affected individuals. Here, we report that missense mutations altering Son of Sevenless, Drosophila, homolog 2 (SOS2), which encodes a RAS guanine nucleotide exchange factor, occur in a small percentage of subjects with NS. Four missense mutations were identified in five unrelated sporadic cases and families transmitting NS. Disease-causing mutations affected three conserved residues located in the Dbl homology (DH) domain, of which two are directly involved in the intramolecular binding network maintaining SOS2 in its autoinhibited conformation. All mutations were found to promote enhanced signaling from RAS to ERK. Similar to NS-causing SOS1 mutations, the phenotype associated with SOS2 defects is characterized by normal development and growth, as well as marked ectodermal involvement. Unlike SOS1 mutations, however, those in SOS2 are restricted to the DH domain.
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http://dx.doi.org/10.1002/humu.22834DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4604019PMC
November 2015

Activating mutations in RRAS underlie a phenotype within the RASopathy spectrum and contribute to leukaemogenesis.

Hum Mol Genet 2014 Aug 4;23(16):4315-27. Epub 2014 Apr 4.

Genetica Clinica Pediatrica, Clinica Pediatrica Università Milano Bicocca, Fondazione MBBM, A.O. S. Gerardo, Monza 20900, Italy.

RASopathies, a family of disorders characterized by cardiac defects, defective growth, facial dysmorphism, variable cognitive deficits and predisposition to certain malignancies, are caused by constitutional dysregulation of RAS signalling predominantly through the RAF/MEK/ERK (MAPK) cascade. We report on two germline mutations (p.Gly39dup and p.Val55Met) in RRAS, a gene encoding a small monomeric GTPase controlling cell adhesion, spreading and migration, underlying a rare (2 subjects among 504 individuals analysed) and variable phenotype with features partially overlapping Noonan syndrome, the most common RASopathy. We also identified somatic RRAS mutations (p.Gly39dup and p.Gln87Leu) in 2 of 110 cases of non-syndromic juvenile myelomonocytic leukaemia, a childhood myeloproliferative/myelodysplastic disease caused by upregulated RAS signalling, defining an atypical form of this haematological disorder rapidly progressing to acute myeloid leukaemia. Two of the three identified mutations affected known oncogenic hotspots of RAS genes and conferred variably enhanced RRAS function and stimulus-dependent MAPK activation. Expression of an RRAS mutant homolog in Caenorhabditis elegans enhanced RAS signalling and engendered protruding vulva, a phenotype previously linked to the RASopathy-causing SHOC2(S2G) mutant. Overall, these findings provide evidence of a functional link between RRAS and MAPK signalling and reveal an unpredicted role of enhanced RRAS function in human disease.
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http://dx.doi.org/10.1093/hmg/ddu148DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4103678PMC
August 2014

Decreased bone mineral density in Costello syndrome.

Mol Genet Metab 2014 Jan 16;111(1):41-5. Epub 2013 Aug 16.

Center for Rare Diseases, Department of Pediatrics, Università Cattolica del Sacro Cuore, Rome, Italy. Electronic address:

Introduction: Costello syndrome (CS) is a multisystemic disorder characterized by postnatal reduced growth, facial dysmorphism, cardiac defects, cognitive impairment, skin and musculo-skeletal anomalies, and predisposition to certain cancers. CS is caused by activating germline mutations in the HRAS proto-oncogene. Similar to what is observed in other RASopathies, CS causative HRAS mutations promote enhanced signal flow through the RAF-MEK-ERK and PI3K-AKT signaling cascades. While decreased bone mineralization has been documented in other RASopathies, such as neurofibromatosis type 1 and Noonan syndrome, systematic studies investigating bone mineral density (BMD) are lacking in CS.

Materials And Methods: Dual-energy X-ray absorptiometry (DXA) was utilized to assess BMD and body composition (fat and fat-free mass) in a cohort of subjects with molecularly confirmed diagnosis of CS (n = 9) and age-matched control individuals (n = 29). Using general linear regression, subtotal body (total body less head), lumbar, femoral neck and femur BMD parameters were compared considering age, sex, body mass index (BMI) and Tanner stage. Blood and urine biomarkers of bone metabolism were also assessed.

Results: All individuals with CS showed significantly lower mean values of subtotal, lumbar and femoral neck BMD compared to the control group (p ≤ 0.01). Similarly, mean total body mass and fat-free mass parameters were lower among the CS patients than in controls (p < 0.01). Low 25-OH vitamin D concentration was documented in all individuals with CS, with values below the reference range in two patients. No significant correlation between vitamin D levels and BMD parameters was observed.

Discussion: CS belongs to a family of developmental disorders, the RASopathies, that share skeletal defects as a common feature. The present data provide evidence that, similar to what is recently seen in NF1 and NS, bone homeostasis is impaired in CS. The significant decrease in BMD and low levels of vitamin D documented in the present cohort, along with the risk for pathologic fractures reported in adult individuals with CS, testifies the requirement for a preventive treatment to alleviate evolutive complications resulting from dysregulated bone metabolism.
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http://dx.doi.org/10.1016/j.ymgme.2013.08.007DOI Listing
January 2014

Immune modulation by zoledronic acid in human myeloma: an advantageous cross-talk between Vγ9Vδ2 T cells, αβ CD8+ T cells, regulatory T cells, and dendritic cells.

J Immunol 2011 Aug 13;187(4):1578-90. Epub 2011 Jul 13.

Laboratorio di Ematologia Oncologica, Centro di Ricerca in Medicina Sperimentale, 10126 Torino, Italy.

Vγ9Vδ2 T cells play a major role as effector cells of innate immune responses against microbes, stressed cells, and tumor cells. They constitute <5% of PBLs but can be expanded by zoledronic acid (ZA)-treated monocytes or dendritic cells (DC). Much less is known about their ability to act as cellular adjuvants bridging innate and adaptive immunity, especially in patients with cancer. We have addressed this issue in multiple myeloma (MM), a prototypic disease with several immune dysfunctions that also affect γδ T cells and DC. ZA-treated MM DC were highly effective in activating autologous γδ T cells, even in patients refractory to stimulation with ZA-treated monocytes. ZA inhibited the mevalonate pathway of MM DC and induced the intracellular accumulation and release into the supernatant of isopentenyl pyrophosphate, a selective γδ T cell activator, in sufficient amounts to induce the proliferation of γδ T cells. Immune responses against the tumor-associated Ag survivin (SRV) by MHC-restricted, SRV-specific CD8(+) αβ T cells were amplified by the concurrent activation of γδ T cells driven by autologous DC copulsed with ZA and SRV-derived peptides. Ancillary to the isopentenyl pyrophosphate-induced γδ T cell proliferation was the mevalonate-independent ZA ability to directly antagonize regulatory T cells and downregulate PD-L2 expression on the DC cell surface. In conclusion, ZA has multiple immune modulatory activities that allow MM DC to effectively handle the concurrent activation of γδ T cells and MHC-restricted CD8(+) αβ antitumor effector T cells.
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http://dx.doi.org/10.4049/jimmunol.1002514DOI Listing
August 2011