Biochemical and Functional Analysis of Germline KRAS Mutations That Cause Disorders of the Noonan Syndrome Spectrum.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1431-1431 ◽  
Author(s):  
Suzanne Schubbert ◽  
Oddmund Sovik ◽  
Gideon Bollag ◽  
Hoa Nguyen ◽  
Sara L. Rowe ◽  
...  
Keyword(s):  
Noonan Syndrome ◽  
De Novo ◽  
Cell Lineage ◽  
Facial Dysmorphism ◽  
Ras Proteins ◽  
Kras Mutations ◽  
Gtp Hydrolysis ◽  
Mutant Proteins ◽  
A Cell ◽  
Biochemical Activation

Abstract Noonan syndrome is characterized by short stature, facial dysmorphism, and cardiac defects. We and our colleagues discovered novel de novo germline KRAS mutations that introduce V14I, T58I, or D153V amino acid substitutions in individuals with NS and a P34R alteration in an individual with cardio-facio-cutaneous (CFC) syndrome, which has overlapping phenotypic features with NS. Recombinant V14I and T58I K-Ras proteins display defective intrinsic GTP hydrolysis and impaired responsiveness to the GTPase activating proteins (GAPs) p120 GAP and neurofibromin. We also found that V14I and T58I K-Ras render primary hematopoietic progenitors hypersensitive to growth factors and deregulate signal transduction in a cell lineage specific manner (Nature Genetics38, 331, 2006). We recently began interrogating the P34R and D153V K-Ras mutant proteins and a novel CFC-associated F156L K-Ras mutant protein. Both P34R and D153V K-Ras display normal levels of intrinsic GTP hydrolysis. In contrast, F156L K-Ras displays defective intrinsic GTP hydrolysis that resembles oncogenic G12D K-Ras. P34R K-Ras is completely resistant to both GAPs, which is intriguing as these data suggest that the ability of GAPs to down-regulate Ras-GTP levels is dispensible for development. In contrast, D153V K-Ras is responsive to both GAPs. We expressed mutant Ras proteins in COS-7 monkey kidney cells to investigate activation of Ras and downstream effectors. Cells expressing P34R, D153V, F156L, and G12D K-Ras demonstrate elevated levels of Ras-GTP and phospho-MEK in basal and serum-starved conditions. We conclude that germline KRAS mutations that cause human disease encode proteins with distinct mechanisms of biochemical activation. Further investigation of this allele series will provide insights about the relative importance of the intrinsic Ras GTPase, GAPs, and other biochemical mechanisms in controlling the growth of different cell lineages.

scholarly journals De novo mutations in the GTP/GDP-binding region of RALA, a RAS-like small GTPase, cause intellectual disability and developmental delay

2018 ◽  
Author(s):  
Susan M. Hiatt ◽  
Matthew B. Neu ◽  
Ryne C. Ramaker ◽  
Andrew A. Hardigan ◽  
Jeremy W. Prokop ◽  
...  
Keyword(s):  
Intellectual Disability ◽  
De Novo ◽  
Small Gtpases ◽  
Small Gtpase ◽  
Facial Dysmorphism ◽  
De Novo Mutations ◽  
Binding Region ◽  
Gtp Hydrolysis ◽  
Genetic Changes ◽  
Developmental Problems

AbstractMutations that alter signaling of RAS/MAPK-family proteins give rise to a group of Mendelian diseases known as RASopathies, but the matrix of genotype-phenotype relationships is still incomplete, in part because there are many RAS-related proteins, and in part because the phenotypic consequences may be variable and/or pleiotropic. Here, we describe a cohort of ten cases, drawn from six clinical sites and over 16,000 sequenced probands, with de novo protein-altering variation in RALA, a RAS-like small GTPase. All probands present with speech and motor delays, and most have intellectual disability, low weight, short stature, and facial dysmorphism. The observed rate of de novo RALA variants in affected probands is significantly higher (p=4.93 × 10−11) than expected from the estimated mutation rate. Further, all de novo variants described here affect conserved residues within the GTP/GDP-binding region of RALA; in fact, six alleles arose at only two codons, Val25 and Lys128. We directly assayed GTP hydrolysis and RALA effector-protein binding, and all but one tested variant significantly reduced both activities. The one exception, S157A, reduced GTP hydrolysis but significantly increased RALA-effector binding, an observation similar to that seen for oncogenic RAS variants. These results show the power of data sharing for the interpretation and analysis of rare variation, expand the spectrum of molecular causes of developmental disability to include RALA, and provide additional insight into the pathogenesis of human disease caused by mutations in small GTPases.Author SummaryWhile many causes of developmental disabilities have been identified, a large number of affected children cannot be diagnosed despite extensive medical testing. Previously unknown genetic factors are likely to be the culprits in many of these cases. Using DNA sequencing, and by sharing information among many doctors and researchers, we have identified a set of individuals with developmental problems who all have changes to the same gene, RALA. The affected individuals all have similar symptoms, including intellectual disability, speech delay (or no speech), and problems with motor skills like walking. In nearly all of these cases (10 of 11), the genetic change found in the child was not inherited from either parent. The locations and biological properties of these changes suggest that they are likely to disrupt the normal functions of RALA and cause significant health problems. We also performed experiments to show that the genetic changes found in these individuals alter two key functions of RALA. Together, we have provided evidence that genetic changes in RALA can cause DD/ID. These results will allow doctors and researchers to identify additional children with the same condition, providing a clinical diagnosis to these families and leading to new research opportunities.

scholarly journals Biochemical and Functional Characterization of Germ Line KRAS Mutations

2007 ◽  
Vol 27 (22) ◽  
pp. 7765-7770 ◽  
Author(s):  
Suzanne Schubbert ◽  
Gideon Bollag ◽  
Natalya Lyubynska ◽  
Hoa Nguyen ◽  
Christian P. Kratz ◽  
...  
Keyword(s):  
Noonan Syndrome ◽  
Developmental Disorders ◽  
Germ Line ◽  
Functional Characterization ◽  
Cell Types ◽  
Missense Mutations ◽  
Ras Proteins ◽  
Kras Mutations ◽  
Cardiofaciocutaneous Syndrome

ABSTRACT Germ line missense mutations in HRAS and KRAS and in genes encoding molecules that function up- or downstream of Ras in cellular signaling networks cause a group of related developmental disorders that includes Costello syndrome, Noonan syndrome, and cardiofaciocutaneous syndrome. We performed detailed biochemical and functional studies of three mutant K-Ras proteins (P34R, D153V, and F156L) found in individuals with Noonan syndrome and cardiofaciocutaneous syndrome. Mutant K-Ras proteins demonstrate a range of gain-of-function effects in different cell types, and biochemical analysis supports the idea that the intrinsic Ras guanosine nucleotide triphosphatase (GTPase) activity, the responsiveness of these proteins to GTPase-activating proteins, and guanine nucleotide dissociation all regulate developmental programs in vivo.

scholarly journals Differential Effects of Notch Ligands Delta-1 and Jagged-1 in Human Lymphoid Differentiation

2001 ◽  
Vol 194 (7) ◽  
pp. 991-1002 ◽  
Author(s):  
Ana C. Jaleco ◽  
Hélia Neves ◽  
Erik Hooijberg ◽  
Paula Gameiro ◽  
Nuno Clode ◽  
...  
Keyword(s):  
T Cell ◽  
Notch Signaling ◽  
Cell Fate ◽  
De Novo ◽  
Cell Lineage ◽  
Differential Effects ◽  
Cell Lineages ◽  
A Cell ◽  
Fate Decision ◽  
Notch Ligands

Notch signaling is known to differentially affect the development of lymphoid B and T cell lineages, but it remains unclear whether such effects are specifically dependent on distinct Notch ligands. Using a cell coculture assay we observed that the Notch ligand Delta-1 completely inhibits the differentiation of human hematopoietic progenitors into the B cell lineage while promoting the emergence of cells with a phenotype of T cell/natural killer (NK) precursors. In contrast, Jagged-1 did not disturb either B or T cell/NK development. Furthermore, cells cultured in the presence of either Delta-1 or Jagged-1 can acquire a phenotype of NK cells, and Delta-1, but not Jagged-1, permits the emergence of a de novo cell population coexpressing CD4 and CD8. Our results thus indicate that distinct Notch ligands can mediate differential effects of Notch signaling and provide a useful system to further address cell-fate decision processes in lymphopoiesis.

scholarly journals A severe clinical phenotype of Noonan syndrome with neonatal hypertrophic cardiomyopathy in the second case worldwide with RAF1 S259Y neomutation

2019 ◽  
Vol 101 ◽  
Author(s):  
Hager Jaouadi ◽  
Amel Ben Chehida ◽  
Lilia Kraoua ◽  
Heather C. Etchevers ◽  
Laurent Argiro ◽  
...  
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Noonan Syndrome ◽  
De Novo ◽  
Mapk Pathway ◽  
Failure To Thrive ◽  
Clinical Severity ◽  
Facial Dysmorphism ◽  
Stunted Growth ◽  
Whole Exome ◽  
Tunisian Patient

AbstractNoonan syndrome and related disorders are a group of clinically and genetically heterogeneous conditions caused by mutations in genes of the RAS/MAPK pathway. Noonan syndrome causes multiple congenital anomalies, which are frequently accompanied by hypertrophic cardiomyopathy (HCM). We report here a Tunisian patient with a severe phenotype of Noonan syndrome including neonatal HCM, facial dysmorphism, severe failure to thrive, cutaneous abnormalities, pectus excavatum and severe stunted growth, who died in her eighth month of life. Using whole exome sequencing, we identified a de novo mutation in exon 7 of the RAF1 gene: c.776C > A (p.Ser259Tyr). This mutation affects a highly conserved serine residue, a main mediator of Raf-1 inhibition via phosphorylation. To our knowledge the c.776C > A mutation has been previously reported in only one case with prenatally diagnosed Noonan syndrome. Our study further supports the striking correlation of RAF1 mutations with HCM and highlights the clinical severity of Noonan syndrome associated with a RAF1 p.Ser259Tyr mutation.

scholarly journals Sexual lineage specific DNA methylation regulates Arabidopsis meiosis

2017 ◽  
Author(s):  
James Walker ◽  
Hongbo Gao ◽  
Jingyi Zhang ◽  
Billy Aldridge ◽  
Martin Vickers ◽  
...  
Keyword(s):  
Gene Expression ◽  
Dna Methylation ◽  
Arabidopsis Thaliana ◽  
De Novo ◽  
Cell Lineage ◽  
Flowering Plants ◽  
Animal Development ◽  
Eukaryotic Gene Expression ◽  
Eukaryotic Gene ◽  
A Cell

SUMMARYDNA methylation controls eukaryotic gene expression and is extensively reprogrammed to regulate animal development. However, whether developmental methylation reprogramming during the sporophytic life cycle of flowering plants regulates genes is presently unknown. Here we report a distinctive, gene-targeted RNA-directed DNA methylation (RdDM) activity in the Arabidopsis thaliana male sexual lineage that regulates gene expression in meiocytes. Loss of sexual lineage-specific RdDM causes mis-splicing of the MPS1/PRD2 gene, thereby disrupting meiosis. Our results establish a regulatory paradigm in which de novo methylation creates a cell-lineage-specific epigenetic signature that controls gene expression and contributes to cellular function in flowering plants.

scholarly journals Aspects of the biology of regeneration and repair in the human gastrointestinal tract

1998 ◽  
Vol 353 (1370) ◽  
pp. 925-933 ◽  
Author(s):  
Nicholas A. Wright
Keyword(s):  
Stem Cells ◽  
Gastric Gland ◽  
Cell Lineage ◽  
Mucosal Ulceration ◽  
Cell Lineages ◽  
Trefoil Peptides ◽  
Pyloric Mucosa ◽  
A Cell ◽  
Epidermal Growth ◽  
Altered Gene

The main pathways of epithelial differentiation in the intestine, Paneth, mucous, endocrine and columnar cell lineages are well recognized. However, in abnormal circumstances, for example in mucosal ulceration, a cell lineage with features distinct from these emerges, which has often been dismissed in the past as ‘pyloric’ metaplasia, because of its morphological resemblance to the pyloric mucosa in the stomach. However, we can conclude that this cell lineage has a defined phenotype unique in gastrointestinal epithelia, has a histogenesis that resembles that of Brunner's glands, but acquires a proliferative organization similar to that of the gastric gland. It expresses several peptides of particular interest, including epidermal growth factor, the trefoil peptides TFF1, TFF2, TFF3, lysozyme and PSTI. The presence of this lineage also appears to cause altered gene expression in adjacent indigenous cell lineages. We propose that this cell lineage is induced in gastrointestinal stem cells as a result of chronic mucosal ulceration, and plays an important part in ulcer healing; it should therefore be added to the repertoire of gastrointestinal stem cells.

scholarly journals MED12-Related (Neuro)Developmental Disorders: A Question of Causality

Genes ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 663
Author(s):  
Stijn van de Plassche ◽  
Arjan PM de Brouwer
Keyword(s):  
Developmental Disorders ◽  
De Novo ◽  
Expression Patterns ◽  
Mediator Complex ◽  
Gene Expression Patterns ◽  
Facial Dysmorphism ◽  
Regulation Of Transcription ◽  
Feeding Difficulties ◽  
Missense Variants ◽  
Pathogenic Variants

MED12 is a member of the Mediator complex that is involved in the regulation of transcription. Missense variants in MED12 cause FG syndrome, Lujan-Fryns syndrome, and Ohdo syndrome, as well as non-syndromic intellectual disability (ID) in hemizygous males. Recently, female patients with de novo missense variants and de novo protein truncating variants in MED12 were described, resulting in a clinical spectrum centered around ID and Hardikar syndrome without ID. The missense variants are found throughout MED12, whether they are inherited in hemizygous males or de novo in females. They can result in syndromic or nonsyndromic ID. The de novo nonsense variants resulting in Hardikar syndrome that is characterized by facial clefting, pigmentary retinopathy, biliary anomalies, and intestinal malrotation, are found more N-terminally, whereas the more C-terminally positioned variants are de novo protein truncating variants that cause a severe, syndromic phenotype consisting of ID, facial dysmorphism, short stature, skeletal abnormalities, feeding difficulties, and variable other abnormalities. This broad range of distinct phenotypes calls for a method to distinguish between pathogenic and non-pathogenic variants in MED12. We propose an isogenic iNeuron model to establish the unique gene expression patterns that are associated with the specific MED12 variants. The discovery of these patterns would help in future diagnostics and determine the causality of the MED12 variants.

scholarly journals Redefining interferon-producing killer dendritic cells as a novel intermediate in NK-cell differentiation

Blood ◽  
2012 ◽  
Vol 119 (19) ◽  
pp. 4349-4357 ◽  
Author(s):  
Fanny Guimont-Desrochers ◽  
Geneviève Boucher ◽  
Zhongjun Dong ◽  
Martine Dupuis ◽  
André Veillette ◽  
...  
Keyword(s):  
Dendritic Cells ◽  
Nk Cells ◽  
Adoptive Transfer ◽  
Nk Cell ◽  
Cell Lineage ◽  
Current View ◽  
Antitumoral Activity ◽  
Nk Cell Differentiation ◽  
A Cell

Abstract The cell lineage origin of IFN-producing killer dendritic cells (IKDCs), which exhibit prominent antitumoral activity, has been subject to debate. Although IKDCs were first described as a cell type exhibiting both plasmacytoid DC and natural killer (NK) cell properties, the current view reflects that IKDCs merely represent activated NK cells expressing B220, which were thus renamed B220+ NK cells. Herein, we further investigate the lineage relation of B220+ NK cells with regard to other NK-cell subsets. We surprisingly find that, after adoptive transfer, B220− NK cells did not acquire B220 expression, even in the presence of potent activating stimuli. These findings strongly argue against the concept that B220+ NK cells are activated NK cells. Moreover, we unequivocally show that B220+ NK cells are highly proliferative and differentiate into mature NK cells after in vivo adoptive transfer. Additional phenotypic, functional, and transcriptional characterizations further define B220+ NK cells as immediate precursors to mature NK cells. The characterization of these novel attributes to B220+ NK cells will guide the identification of their ortholog in humans, contributing to the design of potent cancer immunotherapies.

Sign in / Sign up

Export Citation Format

Share Document