Novel Nonsense Mutation In Exon Research Articles

Wolcott-Rallison syndrome due to the same mutation in EIF2AK3 (c.205G>T) in two unrelated families: A case report.

Wolcott-Rallison syndrome (WRS) is a rare autosomal recessive disorder characterized by early-onset diabetes mellitus, skeletal dysplasia and growth retardation. Other associated disorders include severe liver and renal dysfunction, and central hypothyroidism. Mutations in the eukaryotic translation initiation factor 2α kinase 3 (EIF2AK3), which is located at chromosome 2p12, are responsible for this disorder. In the present case report, the case of a 3-month old boy diagnosed as neonatal diabetes, who had acute liver failure soon afterwards is detailed. This diagnosis was confirmed through the identification of a novel nonsense mutation in exon 1 of EIF2AK3. The aim of the current case report was to raise awareness for patients with WRS with neonatal diabetes mellitus, particularly those with multiple systemic manifestations.

IL2RG hypomorphic mutation: identification of a novel pathogenic mutation in exon 8 and a review of the literature

BackgroundAtypical X-linked severe combined immunodeficiency (X-SCID) is a variant of cellular immunodeficiency due to hypomorphic mutations in the interleukin 2 receptor gamma (IL2RG) gene. Due to a leaky clinical phenotype, diagnosis and appropriate treatment are challenging in these patients.Case presentationWe report a 16-year-old patient with a Tlow B+ NK+ cellular immunodeficiency due to a novel nonsense mutation in exon 8 (p.R328X) of the IL2RG gene. Functional impairment of the IL2RG was confirmed by IL2-Janus kinase 3-signal transducer and activator of transcription signaling pathway investigation. In addition, the characteristics of the mutations previously described in 39 patients with an atypical phenotype were reviewed and analyzed from the literature.ConclusionThis is the first report of an atypical X-SCID phenotype due to an exon 8 mutation in the IL2RG gene. The variability in the phenotypic spectrum of classic X-SCID associated gene highlights the necessity of multi-disciplinary cooperation vigilance for a more accurate diagnostic workup.

Identification of Novel Mutation in EIF2AK3 Gene as a Causal Variant in a Family With Rare Disease

Wolcott-Rallison syndrome (WRS) is now identified as the most frequent cause of neonatal/early onset diabetes in patients that initiated before 6 months of age. Inheritance pattern of disease is autosomal recessive and most of patients are from populations with frequent consanguineous marriages. WRS is caused by mutations in EIF2AK3 gene which encodes eukaryotic translation initiation factor 2a kinase. Several mutations have been reported in this gene and they are almost non-sense, frameshift, missense, and splice site. Here, we analyzed the EIF2AK3 gene in an Iranian girl suspicious for WRS. Sequencing analysis of the gene identified a homozygous novel non-sense mutation in exon 9 of the gene, Y479X. J Med Cases. 2017;8(3):102-104 doi: https://doi.org/10.14740/jmc2597e

Identification of Novel Mutation in EIF2AK3 Gene as a Causal Variant in a Family With Rare Disease

Wolcott-Rallison syndrome (WRS) is now identified as the most frequent cause of neonatal/early onset diabetes in patients that initiated before 6 months of age. Inheritance pattern of disease is autosomal recessive and most of patients are from populations with frequent consanguineous marriages. WRS is caused by mutations in EIF2AK3 gene which encodes eukaryotic translation initiation factor 2a kinase. Several mutations have been reported in this gene and they are almost non-sense, frameshift, missense, and splice site. Here, we analyzed the EIF2AK3 gene in an Iranian girl suspicious for WRS. Sequencing analysis of the gene identified a homozygous novel non-sense mutation in exon 9 of the gene, Y479X. J Med Cases. 2017;8(3):102-104 doi: https://doi.org/10.14740/jmc2597e

Mutation Screening of Her-2, N-ras and Nf1 Genes in Brain Tumor Biopsies.

A deeper understanding of the complex molecular pathology of brain malignancies is needed in order to develop more effective and targeted therapies of these highly lethal disorders. In an effort to further enlighten the molecular pathology of brain oncogenesis involving the her-2 (erbB-2/neu/ngl)/N-ras/nf1 pathway, we screened the genotypes of specimens from various types of brain tumors. The studied specimens included 35 biopsies of four general categories: 13 neuroglial tumors (4 astrocytomas, 2 oligodendrogliomas, 7 glioblastomas multiforme), 14 meningiomas, 3 other nervous system tumors (2 schwannomas, 1 craniopharyngioma) and 5 metastatic tumors (such as lung carcinomas and chronic myelocytic leukemia). Screening for most common mutations in oncogenes her-2, N-ras and tumor suppressor gene nf1 was conducted with molecular hybridization techniques (Southern blotting, dot blot and single-strand conformational polymorphism (SSCP) analysis, respectively), and was confirmed by DNA sequencing. Gene amplification of her-2 was observed in only two cases (6%), namely in one glioblastoma and in one meningioma. Screening of 3 hot spot codons of the N-ras gene (12, 13 and 61) and subsequent DNA sequencing revealed mutations in 19 biopsies encompassing all categories (54%). Screening for mutations in exons of the nf1 gene by SSCP analysis detected a novel nonsense mutation in exon 31 in a unique case of a glioblastoma biopsy (3%) taken from a patient without neurofibromatosis type I. Activated N-ras appears to be a major oncogene in brain oncogenesis, exhibiting the most important role in the her-2/N-ras/nf1 pathway.

Congenital factor XIII deficiency in Pakistan: characterization of seven families and identification of four novel mutations

Deficiency of coagulation factor XIII (FXIII) belongs to the rare bleeding disorders and its incidence is higher in populations with consanguineous marriages. The aims of this study were to characterize patients and relatives from seven families with suspected FXIII deficiency from Pakistan and to identify the underlying mutations. As a first indicator of FXIII deficiency, a 5M urea clot solubility test was used. Plasma FXIII A- and B-subunit antigen levels were determined by ELISA. FXIII activity was measured with an incorporation assay. Sequencing of all exons and intron/exon boundaries of F13A was performed, and a novel splice site defect was confirmed by RT-PCR analysis. Genetic analysis revealed six different mutations in the F13A gene. Two splice site mutations were detected, a novel c.1460+1G>A mutation in the first nucleotide of intron 11 and a previously reported c.2045G>A mutation in the last nucleotide of exon 14. Neither of them was expressed at protein level. A novel nonsense mutation in exon 4, c.567T>A, p.Cys188X, was identified, leading in homozygous form to severe FXIII deficiency. Two novel missense mutations were found in exons 8 and 9, c.1040C>A, p.Ala346Asp and c.1126T>C, p.Trp375Arg, and a previously reported missense mutation in exon 10, c.1241C>T, p.Ser413Leu. All patients homozygous for these missense mutations presented with severe FXIII deficiency. We have analysed a cohort of 27 individuals and reported four novel mutations leading to congenital FXIII deficiency.

A Novel APOB Mutation Identified by Exome Sequencing Cosegregates With Steatosis, Liver Cancer, and Hypocholesterolemia

In familial hypobetalipoproteinemia, fatty liver is a characteristic feature, and there are several reports of associated cirrhosis and hepatocarcinoma. We investigated a large kindred in which low-density lipoprotein cholesterol, fatty liver, and hepatocarcinoma displayed an autosomal dominant pattern of inheritance. The proband was a 25-year-old female with low plasma cholesterol and hepatic steatosis. Low plasma levels of total cholesterol and fatty liver were observed in 10 more family members; 1 member was affected by liver cirrhosis, and 4 more subjects died of either hepatocarcinoma or carcinoma on cirrhosis. To identify the causal mutation in this family, we performed exome sequencing in 2 participants with hypocholesterolemia and fatty liver. Approximately 22 400 single nucleotide variants were identified in each sample. After variant filtering, 300 novel shared variants remained. A nonsense variant, p.K2240X, attributable to an A>T mutation in exon 26 of APOB (c.6718A>T) was identified, and this variant was confirmed by Sanger sequencing. The gentotypic analysis of 16 family members in total showed that this mutation segregated with the low cholesterol trait. In addition, genotyping of the PNPLA3 p.I148M did not show significant frequency differences between carriers and noncarriers of the c.6718A>T APOB gene mutation. We used exome sequencing to discover a novel nonsense mutation in exon 26 of APOB (p.K2240X) responsible for low cholesterol and fatty liver in a large kindred. This mutation may also be responsible for cirrhosis and liver cancer in this family.

A Novel Nonsense Mutation in the Androgen Receptor Gene Causes the Complete Androgen Insensitivity Syndrome

We identified an unusual novel nonsense mutation in exon 3 of the androgen receptor (AR) gene in a patient with complete androgen insensitivity that was persistence of Wolffian derivatives. Sequence analysis revealed a substitution (C→T) at position 2211 and a deletion of G at position 2213 in exon 3 of the AR gene, resulting in the conversion of arginine(CGG) to a stop codon (TGA) of the AR. Western blotting demonstrated a truncated AR with around 70 kd was expressed. Histology of patient's testes showed that seminiferous tubules were totally filled with Sertoli cells without germ cells. Immunohistochemistry revealed positive AR localization in the nuclei of Sertoli cells and epithelia of efferent ductule and vas deferens. AR immunoexpression was stronger in the epithelia of efferent ductule and vas deferens than in Sertoli cells. The study extends the spectrum of exon 3 mutations in the AR gene.

A case of primary selective hypoaldosteronism carrying three mutations in the aldosterone synthase (Cyp11b2) gene

An infant with a clinical phenotype of early onset hypoaldosteronism has been screened for mutation analysis of the Cyp11b2 gene encoding aldosterone synthase enzyme. We have described a novel nonsense mutation in exon 3 (c.508C>T) that gave rise to a shorter protein (Q170X) and two known concurrent missense mutations (c.594A>C in exon 3 and c.1157T>C in exon 7) that led to substitution of glutamic acid for aspartic acid at amino acid position 198 (E198D) and of valine for alanine at amino acid position 386 (V386A). The father, who carried E198D plus V386A mutations, showed a fractional sodium excretion of 1.25% that was unmodified by dietary salt restriction, suggesting a mild haploinsufficiency.We examined by in silico analysis the effect of the mutations on the secondary and tertiary structures of aldosterone synthase to explain the inefficient enzymatic activity. The Q170X mutation produced a truncated protein, which was consequently associated with a loss of catalytic activity. As predicted by JPred web system and Dock 6.3 software, the concurrent expression of E198D and V386A mutations induced a significant secondary structure rearrangement and a shift of the heme group and the 18-hydroxycorticosterone substrate from their optimal placement.

Tufting Enteropathy with EpCAM Mutations in Two Siblings

Tufting enteropathy is a rare autosomal recessive disorder presenting with early-onset severe intractable diarrhea. The epithelial cell adhesion molecule gene (EpCAM) has recently been identified as the gene responsible for tufting enteropathy. Based on histology, a diagnosis of tufting enteropathy was made in two Korean siblings. They developed chronic diarrhea and failure to thrive. They had a broad nasal bridge and micrognathia. Duodenal and colonic biopsies showed villous atrophy, disorganization of surface enterocytes, and focal crowding resembling tufts. Protracted diarrhea continued and so cyclic parenteral nutrition was supplied. The sister had juvenile rheumatoid arthritis. Mutation analysis of EpCAM identified two compound heterozygous mutations in these siblings: 1) a donor splicing site mutation in intron 5 (c.491+1G>A) and 2) a novel nonsense mutation in exon 3 (c.316A>T, Lys106X). Analysis of EpCAM will be useful for genetic counseling and prenatal diagnosis of tufting enteropathy.

A Novel Nonsense Mutation inCEP290Induces Exon Skipping and Leads to a Relatively Mild Retinal Phenotype

PURPOSE. To identify the genetic defect in a family with variable retinal phenotypes. The proband had a diagnosis of Leber congenital amaurosis (LCA), whereas her two cousins had an early-onset severe retinal dystrophy (EOSRD) with useful vision. A distant family member had retinitis pigmentosa (RP). METHODS. DNA samples of the affected family members were genotyped with 250 K genome-wide SNP microarrays. Genetic defects were localized by linkage analysis and homozygosity mapping, and candidate genes were analyzed by sequencing. Patients underwent a full ophthalmic examination. RESULTS. Compound heterozygous mutations in CEP290 were identified in the proband and her two cousins: the frequent c.2991+1655A>G founder mutation and a novel nonsense mutation in exon 7 (c.451C>T, p.Arg151X). The proband had nystagmus, hyperopia, a flat electroretinogram (ERG), and decreased visual acuity (20/250) from birth. The two cousins had minimal scotopic ERG responses at the age of 2. In one of these patients, visual acuity had reached a level of 20/32 at age 5, which is high for patients with CEP290 mutations. Analysis of the CEP290 mRNA in affected individuals revealed altered splice forms in which either exon 7 or exons 7 and 8 were skipped. In both mutant cDNA products, the open reading frame was not disrupted. Furthermore, homozygosity mapping and mutation analysis in the distant family member affected by RP revealed a homozygous mutation in MERTK, but no CEP290 mutations. This MERTK mutation was heterozygously present in the most severely affected (LCA) patient, but was absent in the two more mildly affected cousins. CONCLUSIONS. A novel nonsense mutation in CEP290 results in nonsense-associated altered splicing. That the remaining open reading frame is intact may explain the less severe phenotype observed in the two affected cousins. The additional heterozygous mutation in MERTK may clarify the more severe phenotype in the proband. This study extends the phenotypic spectrum of CEP290-associated diseases at the mild end.

Diagnosis of Fanconi Anemia in An Asymptomatic Adult with Mosaicism and a Molecular Explanation.

Abstract 4213 INTRODUCTIONFanconi Anemia (FA) is a primarily autosomal recessive disorder with a defective DNA repair pathway associated with mutations in any of 13 genes. The majority of patients reported in the literature have one or multiple congenital anomalies, including low birth weight, short stature, café au lait spots, abnormal radii and/or thumbs, structural renal abnormalities, microcephaly, and deafness, among others. About 25% of reported patients had few or none of these findings. The hazard of severe aplastic anemia peaks at 10 years of age, and patients have very high risks of acute myeloid leukemia and specific solid tumors, such as head and neck and gynecologic squamous cell carcinomas. Only six patients have been reported who were diagnosed between 40 and 50 years of age. However, patients may present as adults with neoplasms, or remain asymptomatic and undiagnosed. METHODSWe report the diagnosis of FA in the oldest known patient, an asymptomatic 55 year old woman (Case 2), identified only because she was a potential stem cell donor for her 42 year old sister (Case 1) with severe aplastic anemia. RESULTSCase 1 had a history of thrombocytopenia at 26, and anemia and thrombocytopenia during pregnancy; physical exam was normal except for a slightly deformed thumb; blood lymphocyte chromosome aberrations were increased with both diepoxybutane (DEB) and mitomycin C (MMC). The patient died following an HLA-matched bone marrow transplant from a non-FA brother. Case 2, the other of two siblings of Case 1 who were HLA matches, had higher than normal chromosome breakage in blood (3 cells with multiple radials with MMC) but not in the FA range; skin fibroblasts were diagnostic of FA, confirming hematopoietic somatic mosaicism. She had a normal appearance, a history of hypothyroidism and mitral valve prolapse, five pregnancies with five children (one miscarriage, one set of twins), a near normal blood count (Hb 13.3 g/dl, MCV 99 fl, WBC 3500/ul, and platelets 139,000/ul), and was a regular blood donor. Bone marrow cellularity and morphology were normal, but cytogenetics showed a small clone (46,XX,add(11)(q23)[6]/46,XX[14]). Complementation analysis of Case 1 indicated group A (FA-A), and molecular analysis identified two mutations in the FANCA gene. One mutation, p.S1208S (c.3624C>T) was a splice site mutation occurring in exon 36 and has been previously described. The second mutation was a novel nonsense mutation in exon 23, p.S674X (c.2021C>A). Five siblings had normal breakage results; four were heterozygous for the nonsense mutation and one was negative for both mutations. Case 2, with mosaicism for FA, had the familial splice mutation in both blood and fibroblasts, and the familial nonsense mutation in fibroblasts, but was skewed heavily toward wild-type in blood. cDNA studies confirmed that the predicted splice mutation created an alternate splice site resulting in multiple transcripts, including exon skipping, which varied in different tissues. The molecular mechanism for the loss of the nonsense mutation in the blood is most likely due to back mutation at a hot spot, which occurred in a hematopoietic stem cell which then had a selective growth advantage. CONCLUSIONSReversion of one FANCA mutation probably occurred in a hematopoietic stem cell which was selected for and repopulated the peripheral blood. A plausible explanation for the lack of FA clinical features is the leaky splice mutation which may provide sufficient levels of protein for normal function in DNA repair. Family members should be tested for FA by chromosome breakage analysis in blood (and/or fibroblasts to identify those who may be mosaics). Those who have FA are at risk of syndrome-specific solid tumors, as well as aplastic anemia, myelodysplastic syndrome, and leukemia, if a non-gene corrected hematopoietic stem cell were to emerge. Even if asymptomatic, they should not be used as stem cell transplant donors for siblings with FA, because they may fail to repopulate the recipient marrow. FA is undoubtedly underdiagnosed in adults at this time. Disclosures:No relevant conflicts of interest to declare.

Molecular Characterization of a Novel 3' Mutation in RUNX1 in a New Pedigree with Familial Platelet Disorder.

Abstract 1626Poster Board I-652 IntroductionFamilial Platelet Disorder with Propensity to Acute Myelogenous Leukemia (FPD/AML; OMIM 601399) is a rare disorder with an autosomal dominant inheritance pattern characterized by varying degrees of thrombocytopenia, clinical bleeding due to platelet dysfunction, and an increased risk of developing myeloid malignancy. To date, twenty-six families with this disorder have been described and all carry germline RUNX1 mutations as the causative genetic abnormality. The spectrum of RUNX1 mutations includes point mutations within the RUNT domain and frameshift and termination mutations throughout the body of the gene. Here we report identification of a new family with FPD with a novel nonsense mutation resulting in premature protein termination at amino acid 388. Patients and MethodsOur four generation pedigree includes a mother (II:4) diagnosed with dysplasia and normal karyotype acute myeloid leukemia now in remission after a matched sibling allogeneic stem cell transplant, and her daughter (III:2) with thrombocytopenia since childhood, excessive bleeding with childbirth, and 5q- syndrome diagnosed at 37 years old. Genomic DNA was obtained from all available family members, and RUNX1 cDNA (transcription variants a through c) was sequenced. In addition, RUNX1 cDNA was analyzed for second mutations in bone marrow samples from both patients at the time of diagnosis of their initial bone marrow malignancy. ResultsRUNX1 sequencing of germline DNA revealed heterozygosity for a novel nonsense mutation in exon 8 (c.1163C>A), which is predicted to result in premature protein truncation (p.Ser388X). Full sequencing of RUNX1 cDNA from II:4's AML does not show any secondary mutations. Our current efforts include full sequencing of RUNX1 cDNA from III:2's bone marrow malignancy as well as functional studies of the truncated protein. ConclusionsWe have identified a novel 3' RUNX1 mutation within exon 8, which is predicted to result in premature protein truncation at amino acid 388. To date, this is the most distal mutation identified in an FPD/AML pedigree. The identification of this mutation suggests that the last 100 amino acids, which are known to contain the RUNX1 inhibition domain, contribute an essential function. Further characterization of this RUNX1 mutation and its encoded truncated protein may yield insight into RUNX1's role in leukemogenesis in FPD and de novo AML. DisclosuresNo relevant conflicts of interest to declare.

Four different NCF2 mutations in six families from Turkey and an overview of NCF2 gene mutations

One of the rarest forms of autosomal recessive chronic granulomatous disease (AR-CGD) is attributable to mutations in the NCF2 gene, which encodes the polypeptide p67(phox), a key cytoplasmic protein in the phagocyte NADPH oxidase system. NCF2 is localized on chromosome 1q25, encompasses 40 kb and contains 16 exons. We report here the clinical and molecular characterization of six patients with CGD from six consanguineous Turkish families. The ages of the five female patients were between 3 and 22 years and a male patient was 2 years old; all patients showed clear clinical symptoms of CGD. The mothers of the patients did not show a bimodal histogram pattern specific for X-CGD in the dihydrorhodamine-1,2,3 (DHR) assay. Moreover, p67(phox) protein expression was not detectable using flow cytometric analysis of the patients' neutrophils except in those from patient 6, which had a diminished expression. Mutation analysis of NCF2 revealed four different homozygous mutations: a novel nonsense mutation in exon 3 c.229C>T, p.Arg77X; a novel missense mutation in exon 4 c.279C>G, p.Asp93Glu; a nonsense mutation in exon 4 c.304C>T, p.Arg102X; and a novel missense mutation in exon 6 c.605C>T, p.Ala202Val. The parents were found to be heterozygotes for these mutations. The prevalence of NCF2 mutant families is approximately 15% in our series of 40 CGD families. This high incidence of A67 CGD in Turkey is undoubtedly caused by the high incidence of consanguineous marriages. We found three new mutations in NCF2 and one previously described. These are presented together with an overview of all NCF2 mutations now known.

Identification of a Critical Novel Mutation in the Exon 1 of Androgen Receptor Gene in 2 Brothers With Complete Androgen Insensitivity Syndrome

Complete androgen insensitivity syndrome is an X-linked inherited disorder caused by mutations in the androgen receptor (AR) gene. Using polymerase chain reaction single-strand DNA conformational polymorphism and DNA sequencing, we identified a novel nonsense mutation in exon 1 of the AR gene in 2 Iranian brothers with complete androgen insensitivity syndrome. Despite a normal 46,XY karyotype, testes, and normal to elevated plasma levels of testosterone, they were born with female external genitalia and phenotype. This new mutation, a T-to-A transversion in exon 1, causes amino acid change of tyrosine (TAT) to ochre stop codon (TAA) at position 514 of the AR polypeptide. The Y514X mutation is located in a region that is normally important for the formation and function of the hormone receptor complex. We conclude that the novel Y514X mutation in the androgen receptor is the cause of complete androgen insensitivity syndrome in this family.

Six different CYBA mutations including three novel mutations in ten families from Turkey, resulting in autosomal recessive chronic granulomatous disease

One of the rarest forms of autosomal recessive chronic granulomatous disease (AR-CGD) is attributable to mutations in the CYBA gene, which encodes the alpha polypeptide of cytochrome b(558), (also known as p22-phox), a key transmembrane protein in the phagocyte NADPH oxidase system. This gene is localized on chromosome 16q24, encompasses 8.5 kb and contains six exons. We report here the clinical and molecular characterization of 12 AR-CGD patients from 10 consanguineous, unrelated Turkish families with clinical CGD and positive family history. The ages of the six male and six female patients were between 1and 18 years. Before mutation analysis, subgroup analysis of patients was made by flow cytometry with antibodies against NADPH-oxidase components and with the DHR assay (flow cytometric assay of NADPH oxidase activity in leucocytes). Mutation analysis of CYBA showed six different mutations: a frameshift insertion in exon 3 (C after C166); a missense mutation in exon 2 (p.Gly24Arg), a splice-site deletion in intron 1 (4-bp deletion +4_+7 AGTG), a novel nonsense mutation in exon 6 (p.Cys113X), a novel large deletion of exons 3-6 and a novel 1-bp deletion in exon 6 (c.408delC). All mutations were present in homozygous form and all parents investigated were found to be heterozygotes for these mutations. In our series of 40 CGD families, approximately 25% of the families have p22-phox defects, with six different mutations, including three novel mutations. The high rate of consanguineous marriages seems to be the underlying aetiology.

New pedigrees and novel mutation expand the phenotype of REEP1-associated hereditary spastic paraplegia (HSP)

The hereditary spastic paraplegias (HSP) are a heterogeneous group of conditions in which the main feature is a progressive spastic paraparesis. Mutations in the receptor expression enhancing protein 1 (REEP1) gene have recently been reported to be associated with an autosomal dominant HSP phenotype (SPG31). The objective of this study was to identify the frequency of REEP1 mutations in both autosomal dominant HSP (ADHSP) and sporadic spastic paraparesis (SSP) cases and to analyse the genotype/phenotype correlation of mutations so far described in REEP1. One hundred thirty-three index cases from large ADHSP pedigrees and 80 SSP cases were screened for mutation in REEP1 by direct sequencing. Three mutations were identified in REEP1 in the ADHSP group. A novel nonsense mutation in exon 5, c.[337C>T] (p.[Arg113X]), was associated with spastic paraparesis, amyotrophy and mitochondrial dysfunction. A second previously reported mutation, c.[606+43G>T], was identified in two pedigrees. The index case of one of these pedigrees had a peripheral neuropathy in association with spastic paraparesis, and the proband of the second pedigree had a severe spastic tetraparesis and bulbar dysfunction. No mutations were detected in the SSP cases. We report a mutation frequency of 2.3% in REEP1 in ADHSP, suggesting REEP1 mutation is a relatively uncommon cause of ADHSP in a population of patients drawn from the UK. The phenotype of ADHSP associated with REEP1 mutation is broader than initially reported. The spastic paraparesis in SPG31 may be complicated by the presence of amyotrophy, bulbar palsy and/or peripheral neuropathy.

Case report: WT1 exon 6 truncation mutation and ambiguous genitalia in a patient with Denys–Drash syndrome

Denys-Drash syndrome is a rare genetic disorder featuring the triad of congenital nephropathy, Wilms tumor, and intersex disorders (XY under-virilization or XY female). Denys-Drash syndrome is associated with constitutional mutations in the Wilms tumor suppressor gene WT1. Unlike WAGR (Wilms tumor, aniridia, genitourinary anomalies, and mental retardation) syndrome, with its complete deletion of one copy of WT1, Denys-Drash syndrome is generally caused by a dominant-negative mutation. We present a new case of Denys-Drash syndrome in a patient initially diagnosed with XY ambiguous genitalia/partial androgen insensitivity syndrome, who was found to have a novel nonsense mutation in exon 6 leading to a stop codon and hence a truncated protein. Based on lessons learned from this patient, the diagnosis of Denys-Drash syndrome should be considered in the presence of ambiguous genitalia and partial androgen insensitivity.

Beta‐sitosterolaemia: a new nonsense mutation in the ABCG5 gene

Sitosterolaemia is a rare autosomal recessive disorder characterised by elevated plasma levels of plant sterols and cholesterol. Sitosterolaemia is caused by gene mutations in either of two ATP-binding cassette (ABC) half transporters, ABCG5 and ABCG8. The plasma sterol profile and genetic analysis of a 10-year-old girl who had tuberous xanthomas is the subject of this report. Genomic DNA was isolated from white blood cells from the proband, her family and a control group of healthy people. All exons of ABCG5 and ABCG8 were sequenced. Plasma cholesterol and triglycerides were measured by routine methods. All other plasma sterols were measured by Gas Chromatography coupled to Mass Spectrometry. The proband was found to be homozygous for a single nucleotide mutation in exon 10 of the ABCG5 gene, consisting of a C to T transition at nucleotide 1336 of the coding sequence, which results in the premature termination of the ABCG5 protein at amino acid 446 (Arg446X). Her mother and brother were also homozygous for the same mutation and all had elevated plasma beta-sitosterol levels. The father was heterozygous and showed normal beta-sitosterol levels. This mutation was not found in healthy normolipidaemic subjects. We describe a novel nonsense mutation in exon 10 of the ABCG5 gene in a 10-year-old girl showing clinical and biochemical features of sitosterolaemia. This family study broadens the spectrum of the ABCG5/ABCG8 mutations causing sitosterolaemia and helps highlight the correlations between such gene mutations, biochemical phenotype and the development of cardiovascular disease.

A novel nonsense mutation in exon 2 of the factor IX gene resulting in severe haemophilia B

A novel nonsense mutation in exon 2 of the factor IX gene resulting in severe haemophilia B