We describe two new missense mutations in the glucose-6-phosphate dehydrogenase (G6PD) gene associated with chronic hemolytic anemia: mutation 1205CÆÆA in exon 10 predicts the amino acid change 402ThrÆÆAsn in the bb-sheet M of the polypeptide chain, within the dimer interface (G6PD Covão do Lobo); mutation 1366GÆÆA in exon 12 predicts the amino acid substitution 456AspÆÆHis in the aa-helix N, at the protein surface (G6PD Figueira da Foz).

Ullrich congenital muscular dystrophy (UCMD) is a disabling and life-threatening disorder resulting from either recessive or dominant mutations in genes encoding collagen VI. Although the majority of the recessive UCMD cases have frameshift or nonsense mutations in COL6A1, COL6A2, or COL6A3, recessive structural mutations in the COL6A2 C-globular region are emerging also. However, the underlying molecular mechanisms have remained elusive. Here we identified a homozygous COL6A2 E624K mutation (C1 subdomain) and a homozygous COL6A2 R876S mutation (C2 subdomain) in two UCMD patients. The consequences of the mutations were investigated using fibroblasts from patients and cells stably transfected with the mutant constructs. In contrast to expectations based on the clinical severity of these two patients, secretion and assembly of collagen VI were moderately affected by the E624K mutation but severely impaired by the R876S substitution. The E624K substitution altered the electrostatic potential of the region surrounding the metal ion-dependent adhesion site, resulting in a collagen VI network containing thick fibrils and spots with densely packed microfibrils. The R876S mutation prevented the chain from assembling into triple-helical collagen VI molecules. The minute amount of collagen VI secreted by the R876S fibroblasts was solely composed of a faster migrating chain corresponding to the C2a splice variant with an alternative C2 subdomain. In transfected cells...

Background: A limited number of mutations in the GH secretagogue receptor gene (GHSR) have been described in patients with short stature. Objective: To analyze GHSR in idiopathic short stature (ISS) children including a subgroup of constitutional delay of growth and puberty (CDGP) patients. Subjects and methods: The GHSR coding region was directly sequenced in 96 independent patients with ISS, 31 of them with CDGP, in 150 adults, and in 197 children with normal stature. The pharmacological consequences of GHSR non-synonymous variations were established using in vitro cell-based assays. Results: Five different heterozygous point variations in GHSR were identified (c.-6 G>C, c.251G>T (p.Ser84Ile), c.505G>A (p.Ala169Thr), c.545 T>C (p.Val182Ala), and c.1072G>A (p.Ala358Thr)), all in patients with CDGP. Neither these allelic variants nor any other mutations were found in 694 alleles from controls. Functional studies revealed that two of these variations (p.Ser84Ile and p. Val182Ala) result in a decrease in basal activity that was in part explained by a reduction in cell surface expression. The p.Ser84Ile mutation was also associated with a defect in ghrelin potency. These mutations were identified in two female patients with CDGP (at the age of 13 years...

Von Hippel-Lindau disease is an autosomal dominantly inherited familial cancer syndrome predisposing to retinal and central nervous system haemangioblastomas, renal cell carcinoma, and phaeochromocytoma. VHL disease shows variable expression and interfamilial differences in predisposition to phaeochromocytoma. In a previous study of 65 VHL kindreds with defined VHL mutations we detected significant differences between VHL families with and without phaeochromocytoma such that missense mutations were more common and large deletions or protein truncating mutations less frequent in phaeochromocytoma positive families. To investigate the significance and cause of this association further, we studied 138 VHL kindreds for germline mutations and calculated the age related tumour risks for different classes of VHL gene mutations. Using SSCP, heteroduplex and Southern analysis we identified a germline VHL gene mutation in 101 families (73%). Direct sequencing of the VHL coding region further increased the mutation detection rate to 81%. In addition to precise presymptomatic diagnosis, identification of a VHL gene mutation can provide an indication of the likely phenotype. We found that large deletions and mutations predicted to cause a truncated protein were associated with a lower risk of phaeochromocytoma (6% and 9% at 30 and 50 years...

Hereditary multiple exostoses (HME), a dominantly inherited genetic disorder characterized by multiple cartilaginous tumors, is caused by mutations in members of the EXT gene family, EXT1 or EXT2. The corresponding gene products, exostosin-1 (EXT1) and exostosin-2 (EXT2), are type II transmembrane glycoproteins which form a Golgi-localized heterooligomeric complex that catalyzes the polymerization of heparan sulfate (HS). Although the majority of the etiological mutations in EXT are splice-site, frameshift, or nonsense mutations that result in premature termination, 12 missense mutations have also been identified. Furthermore, two of the reported etiological missense mutations (G339D and R340C) have been previously shown to abrogate HS biosynthesis (McCormick et al. 1998). Here, a functional assay that detects HS expression on the cell surface of an EXT1-deficient cell line was used to test the remaining missense mutant exostosin proteins for their ability to rescue HS biosynthesis in vivo. Our results show that EXT1 mutants bearing six of these missense mutations (D164H, R280G/S, and R340S/H/L) are also defective in HS expression, but surprisingly, four (Q27K, N316S, A486V, and P496L) are phenotypically indistinguishable from wild-type EXT1. Three of these four “active” mutations affect amino acids that are not conserved among vertebrates and invertebrates...

To obtain more information of the functional domains of the NPC1 protein, the mutational spectrum and the level of immunoreactive protein were investigated in skin fibroblasts from 30 unrelated patients with Niemann-Pick C1 disease. Nine of them were characterized by mild alterations of cellular cholesterol transport (the “variant” biochemical phenotype). The mutations showed a wide distribution to nearly all NPC1 domains, with a cluster (11/32) in a conserved NPC1 cysteine-rich luminal loop. Homozygous mutations in 14 patients and a phenotypically defined allele, combined with a new mutation, in a further 10 patients allowed genotype/phenotype correlations. Premature-termination–codon mutations, the three missense mutations in the sterol-sensing domain (SSD), and A1054T in the cysteine-rich luminal loop all occurred in patients with infantile neurological onset and “classic” (severe) cholesterol-trafficking alterations. By western blot, NPC1 protein was undetectable in the SSD missense mutations studied (L724P and Q775P) and essentially was absent in the A1054T missense allele. Our results thus enhance the functional significance of the SSD and demonstrate a correlation between the absence of NPC1 protein and the most severe neurological form. In the remaining missense mutations studied...

The accumulation of mildly deleterious missense mutations in individual human genomes has been proposed to be a genetic basis for complex diseases. The plausibility of this hypothesis depends on quantitative estimates of the prevalence of mildly deleterious de novo mutations and polymorphic variants in humans and on the intensity of selective pressure against them. We combined analysis of mutations causing human Mendelian diseases, of human-chimpanzee divergence, and of systematic data on human genetic variation and found that ∼20% of new missense mutations in humans result in a loss of function, whereas ∼27% are effectively neutral. Thus, the remaining 53% of new missense mutations have mildly deleterious effects. These mutations give rise to many low-frequency deleterious allelic variants in the human population, as is evident from a new data set of 37 genes sequenced in >1,500 individual human chromosomes. Surprisingly, up to 70% of low-frequency missense alleles are mildly deleterious and are associated with a heterozygous fitness loss in the range 0.001–0.003. Thus, the low allele frequency of an amino acid variant can, by itself, serve as a predictor of its functional significance. Several recent studies have reported a significant excess of rare missense variants in candidate genes or pathways in individuals with extreme values of quantitative phenotypes. These studies would be unlikely to yield results if most rare variants were neutral or if rare variants were not a significant contributor to the genetic component of phenotypic inheritance. Our results provide a justification for these types of candidate-gene (pathway) association studies and imply that mutation-selection balance may be a feasible evolutionary mechanism underlying some common diseases.

The TECTA gene encodes alpha-tectorin (TECTA), a major noncollagenous component of the tectorial membrane (TM). In humans, mutations in TECTA lead to either dominant (DFNA8/A12) or recessive (DFNB21) forms of nonsyndromic hearing loss. All missense mutations in TECTA that have been reported thus far are associated with the dominant subtype, whereas those leading to recessive deafness are all inactivating mutations. In this paper, we characterize a spontaneous missense mutation (c.1046C > A, p.A349D) arising in the mouse Tecta gene that is, unlike all previously reported missense mutations in TECTA, recessive. The morphological phenotype of the TectaA349D/A349D mouse resembles but is not identical to that previously described for the documentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} egin{document}$$Tecta^{{{Delta { ext{ENT}}} mathord{left/ {vphantom {{Delta { ext{ENT}}} {Delta { ext{ENT}}}}} ight. kern- ulldelimiterspace} {Delta { ext{ENT}}}}} $$end{document} mouse. As in the documentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} egin{document}$$Tecta^{{{Delta { ext{ENT}}} mathord{left/ {vphantom {{Delta { ext{ENT}}} {Delta { ext{ENT}}}}} ight. kern- ulldelimiterspace} {Delta { ext{ENT}}}}} $$end{document} mouse...

Driver mutations are somatic mutations that provide growth advantage to tumor cells, while passenger mutations are those not functionally related to oncogenesis. Distinguishing drivers from passengers is challenging because drivers occur much less frequently than passengers, they tend to have low prevalence, their functions are multifactorial and not intuitively obvious. Missense mutations are excellent candidates as drivers, as they occur more frequently and are potentially easier to identify than other types of mutations. Although several methods have been developed for predicting the functional impact of missense mutations, only a few have been specifically designed for identifying driver mutations. As more mutations are being discovered, more accurate predictive models can be developed using machine learning approaches that systematically characterize the commonality and peculiarity of missense mutations under the background of specific cancer types. Here, we present a cancer driver annotation (CanDrA) tool that predicts missense driver mutations based on a set of 95 structural and evolutionary features computed by over 10 functional prediction algorithms such as CHASM, SIFT, and MutationAssessor. Through feature optimization and supervised training...

Hereditary Hemorrhagic Telangiectasia syndrome (HHT) or Rendu-Osler-Weber (ROW) syndrome is an autosomal dominant vascular disorder. Two most common forms of HHT, HHT1 and HHT2, have been linked to mutations in the endoglin (ENG) and activin receptor-like kinase 1 (ACVRL1or ALK1) genes respectively. This work was designed to examine the pathogenicity of 23 nucleotide variations in ACVRL1 gene detected in more than 400 patients. Among them, 14 missense mutations and one intronic variant were novels, and 8 missense mutations were previously identified with questionable implication in HHT2. The functionality of missense mutations was analyzed in response to BMP9 (specific ligand of ALK1), the maturation of the protein products and their localization were analyzed by western blot and fluorescence microscopy. The splicing impairment of the intronic and of two missense mutations was examined by minigene assay. Functional analysis showed that 18 out of 22 missense mutations were defective. Splicing analysis revealed that one missense mutation (c.733A>G, p.Ile245Val) affects the splicing of the harboring exon 6. Similarly, the intronic mutation outside the consensus splicing sites (c.1048+5G>A in intron 7) was seen pathogenic by splicing study. Both mutations induce a frame shift creating a premature stop codon likely resulting in mRNA degradation by NMD surveillance mechanism. Our results confirm the haploinsufficiency model proposed for HHT2. The affected allele of ACVRL1 induces mRNA degradation or the synthesis of a protein lacking the receptor activity. Furthermore...

Premature ovarian failure (POF) is a heterogeneous disease. Though dozens of candidate genes have been identified for the genetic etiology of POF, it is largely unexplained in majority of patients. Recently, Wt1+/R394W mice was found to present POF-like phenotype, which indicates that WT1 might be a plausible candidate gene for non-syndromic POF. The coding region of WT1 gene was screened in 384 patients with POF and 6 novel variations were identified, including two missense mutations (p. Pro126Ser in exon1 and p. Arg370His in exon7) and four intronic variants (c.647-27C > T, c.647-13G > C, c.647-13G > A in intron1 and c.950 + 14T > C in intron 4). In vitro experiments showed that both mutant p. Pro126Ser and p. Arg370His repressed the expression of Amh and Cdh1, and induced the expression of Fshr and Cyp19 in mRNA level (P < 0.05). The expression changes of AMH, FSHR, CYP19 and CDH1 were confirmed by western blot. These genes (AMH, FSHR, CYP19 and CDH1) are required for granular cells (GCs) proliferation, differentiation and oocyte-GCs interaction. The novel mutant p. P126S and p. R370H in the WT1 gene potentially impaired GCs differentiation and oocyte-GCs interaction, which might result in loss of follicles prematurely. Therefore...

Familial Mediterranean fever (FMF) is a recessively inherited disorder characterized by dramatic episodes of fever and serosal inflammation. This report describes the cloning of the gene likely to cause FMF from a 115-kb candidate interval on chromosome 16p. Three different missense mutations were identified in affected individuals, but not in normals. Haplotype and mutational analyses disclosed ancestral relationships among carrier chromosomes in populations that have been separated for centuries. The novel gene encodes a 3.7-kb transcript that is almost exclusively expressed in granulocytes. The predicted protein, pyrin, is a member of a family of nuclear factors homologous to the Ro52 autoantigen. The cloning of the FMF gene promises to shed light on the regulation of acute inflammatory responses.; Available online 21 December 2000.

In patients with Niemann–Pick disease type C (NPC), an autosomal recessive lipid storage disorder, neurodegeneration can occur in early life. Vertical ophthalmoplegia and extrapyramidal signs may be seen. Cholestatic jaundice and hepatosplenomegaly occur frequently in patients with early onset disease, with bone marrow biopsies showing diffuse infiltration of foamy histiocytes. Cholesterol esterification in skin fibroblasts is reduced, resulting in intracellular accumulation of cholesterol. NPC1 mutations are responsible for the disease in ~95% of patients. NPC1 encodes a 1278 amino acid protein which contains 13 transmembrane domains. Over 130 mutations have been identified in NPC1, with over a third present within an NPC1 specific cysteine-rich domain positioned in a large extracellular loop. It has been proposed that the defect in cholesterol homoeostasis is the cause of neuronal apoptosis, but the precise role of the NPC1 protein and the functional implications of its mutations remain unknown. Although NPC is routinely diagnosed by biochemical analysis, identification of molecular defects helps confirm the diagnosis and enables family studies, and rapid, accurate prenatal diagnosis. This report describe the analysis of the NPC1 gene in five Taiwanese/Chinese patients with NPC. Six novel NPC1 mutations (N968S...

A frequently mutated gene causing X-linked intellectual disability is the Aristaless related homeobox (ARX) gene. Nonsense mutations, polyalanine tract expansions and missense mutations in ARX are implicated in a range of intellectual disability phenotypes with or without additional features including epilepsy, infantile spasms, hand dystonia, lissencephaly, autism and dysarthria. Severe phenotypes, such as X-linked lissencephaly with abnormal genitalia (XLAG), are frequently observed in individuals with missense or nonsense mutations clustered in the conserved paired-type homeodomain. In this report we have identified a novel point mutation (c.1135C>A, p.R379S) in the homeodomain of ARX in a patient with infantile spasms and intellectual disability. We investigated this and other missense mutations (R332P, R332H, R332C, T333N and R379L) in residues of the nuclear localisation sequences (NLS) flanking either end of the ARX homeodomain, associated with XLAG and Proud syndrome phenotypes. The NLS regions in the ARX homeodomain are required for correct nuclear transport due to binding to the import protein, Importin 13 (IPO13). Moreover, the arginine residues involved with these mutations (position 5 and 52 of the paired-type homeodomain) are invariant in all 26 family members containing this homeodomain and are frequent sites of missense and non-sense mutations associated with a range of diseases. In this study we demonstrate missense mutations in either the N-terminal or C-terminal NLS regions of the ARX homeodomain cause significant disruption to nuclear localisation of the mutant transcription factor protein in vitro. Surprisingly...

Background: Aristaless related homeobox (ARX) is a paired-type homeobox gene. ARX function is frequently affected by naturally occurring mutations. Nonsense mutations, polyalanine tract expansions and missense mutations in ARX cause a range of intellectual disability and epilepsy phenotypes with or without additional features including hand dystonia, lissencephaly, autism or dysarthria. Severe malformation phenotypes, such as X-linked lissencephaly with ambiguous genitalia (XLAG), are frequently observed in individuals with protein truncating or missense mutations clustered in the highly conserved paired-type homeodomain. Results: We have identified two novel point mutations in the R379 residue of the ARX homeodomain; c.1135C>A, p.R379S in a patient with infantile spasms and intellectual disability and c.1136G>T, p.R379L in a patient with XLAG. We investigated these and other missense mutations (R332P, R332H, R332C, T333N: associated with XLAG and Proud syndrome) predicted to affect the nuclear localisation sequences (NLS) flanking either end of the ARX homeodomain. The NLS regions are required for correct nuclear import facilitated by Importin 13 (IPO13). We demonstrate that missense mutations in either the N- or C-terminal NLS regions of the homeodomain cause significant disruption to nuclear localisation of the ARX protein in vitro. Surprisingly...

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Medicina, Departamento de Bioquímica. Fecha de lectura: 30-01-2015; BRCA1 germline mutations are associated with significantly increased lifetime risk of developing breast and ovarian cancers. However, taking into account considerable differences in disease manifestation among mutation carriers, it is probable that various BRCA1 mutations lead to formation of distinct phenotypes and haploinsufficiency effects and that both type and location of the mutation could play an important role in cancer initiation. PARP inhibitors are currently one of the most promising agents for treatment of tumors deficient in BRCA1 or BRCA2. However, cancer patients carrying germline mutation in BRCA1/2 genes show a big variability in the responses to PARP inhibitors in clinical trials. Thus, we were interested in investigating whether and how BRCA1 mutation type influences the response of cells to PARP inhibitors We used a panel of lymphoblastoid cell lines (LCLs) derived either from heterozygous BRCA1 mutation carriers or non-carriers in order to study haploinsufficiency effects of various mutation types (truncating vs missense). LCLs carrying truncating mutations showed significantly lower BRCA1 mRNA and protein levels and higher levels of gamma-H2AX than control cells or LCLs harboring missense mutation...

Ingo Mellinghoff and colleagues sequenced theEGFR gene in glioblastoma samples and cell lines and identified missense mutations in the extracellular domain that suggest a new mechanism for EGFR activation.

Los objetivos de esta tesis fueron: 1- Optimizar la amplificación de los 29 exones correspondientes al gen de ADAMTS13 y realizar la secuenciación completa del gen en pacientes con PTT congénita y 2- Realizar la expresión “in vitro" de la primera nueva mutación descripta en Argentina A4085T (sustitución de un ácido aspártico (D) por una valina (V) en la posición 1362). Evaluar la actividad proteolítica intra y extracelular de la ADAMTS13 resultante para analizar cómo impacta sobre los mecanismos de biosíntesis y secreción de la ADAMTS13. Los experimentos se realizaron en cultivos de células HEK 293 transfectadas con las construcciones plasmídicas de la secuencia WT y del mutante A4085T sintetizado a partir del plásmido WT por mutagénesis sitio-dirigida para evaluar cuál es el dominio afectado y cómo impacta sobre los mecanismos de biosíntesis y secreción de la ADAMTS13. Estos estudios ayudaron a una mejor evaluación del exón 29 del dominio CUB-2. Para medir el antígeno y la actividad de ADAMTS13 en células, sobrenadantes y células transfectadas con vector de expresión de ADAMTS13 WT y de A4085T, se utilizaron técnicas de ELISA con sustratos cromogénicos, técnicas de SDS-PAGE, inmuno-transferencia y microscopia de inmunofluorescencia. Se observó que la mutación produce acumulación intracelular de ADAMTS13. La nueva mutación D1362V identificada en el dominio CUB-2 codificada por el exón 29...

MYH9 has been proposed as a major genetic risk locus for a spectrum of non-diabetic end stage kidney disease (ESKD). We use recently released sequences from the 1000 Genomes Project to identify two western African specific missense mutations (S342G and I384M) in the neighbouring APOL1 gene, and demonstrate that these are more strongly associated with ESKD than previously reported MYH9 variants. We also show that the distribution of these risk variants in African populations is consistent with the pattern of African ancestry ESKD risk previously attributed to the MYH9 gene. Additional associations were also found among other members of the APOL gene family, and we propose that ESKD risk is caused by western African variants in members of the APOL gene family, which evolved to confer protection against pathogens, such as Trypanosoma.; Comment: 25 pages, 6 figures

Patients with hereditary glutathione synthetase (GS) (EC 6.3.2.3) deficiency present with variable clinical pictures, presumably related to the nature of the mutations involved. In order to elucidate the relationship between genotype, enzyme function and