Codon Changes Research Articles

Study on dual oxidase maturation factor 1 gene mutations in patients with congenital hypothyroidism combined with thyroid goiter

Objective To screen the dual oxidase maturation factor 1 (DUOXA1) gene mutations in children with congenital hypothyroidism (CH) and thyroid goiter from Shandong Province, China, and to identify the gene mutation type and characteristics of DUOXA1 gene mutations in order to provide some evidence for gene diagnosis and therapy of CH. Methods A cohort of 52 cases of CH with thyroid goiter and 100 normal controls were selected according to neonatal screening system in Shandong Province whose genomic DNA was isolated from peripheral blood leukocytes with a standard phenol chloroform method.The whole coding sequence (CDS) of DUOXA1 gene was amplified with 8 pairs of sequence specific primers by using PCR.The PCR products were directly sequenced with Sanger sequencing to detect new mutations types of DUOXA1 gene.The sequencing data were compared to the DUOXA1 gene reference sequence (National Center for Biotechnology Information: RefSeq: NG_033105.1) to see if there was any mutation.A χ2test was done for the gene frequency of discovered single nucleotide polymorphisms (SNP). Results There was no mutation in CDS of 52 CH patients with thyroid goiter and 100 normal controls.However, a SNP (rs75981505, c.398G>T) which was an missense mutation and could lead to a change of the codon from CGC to CTC, was found in 9 CH patients with thyroid goiter and 11 normal controls in the exon 7.The corresponding amino acid arginine was replaced by histidine(p.Arg133His). There was no significant difference in the SNP rate between CH patients with thyroid goiter and normal controls (17.3% vs 11.0%, χ2 =1.24, P>0.05). Conclusion DUOXA1 gene mutation rate is very low which may not be the main cause of CH patients with thyroid goiter in the population of Shandong Province. Key words: Congenital hypothyroidism; Dual oxidase maturation factor 1; Thyroid goiter; Mutation

Abstract 1932: The importance of RNA editing enzymes in glioblastoma

Abstract This study was supported by AIRC. Glioblastoma (or grade IV astrocytomas) is a highly heterogeneous and deadly malignant brain tumor and one of the most incurable form of cancer in human that urgently needs new therapeutic targets. There is great interest in elucidating all the molecular basis and functional importance of genetics and epigenetic mechanisms occurring in glioblastoma. In our laboratory, we investigate whether essential post-transcriptional event (such as the A-to-I RNA editing) is a possible molecular mechanism involved in the appearance/progression of glioblastoma. A-to-I RNA editing modifies the nucleotide sequence of RNA target molecules. The ADARs (Adenosine Deaminases that Act on RNA) are the enzymes responsible for this conversion acting on pre-mRNAs or non-coding RNAs (such as microRNA). Inosine, is recognized by the translation and splicing machineries, as Guanosine. Therefore, ADARs can play a direct and critical role in generating alternative protein isoforms (by codon changes and splicing pattern alterations) and modulating gene expression levels (by editing microRNAs and/or 3’-UTRs). In mammals, there are three different ADAR enzymes (ADAR1-3). The deregulation of ADAR2 activity has been connected with several neurological human diseases and Adar2 knockout animals show a lethal neurological phenotype. We demonstrated a direct correlation between a progressive decrease of ADAR2 editing activity and the increased grade of malignancy in paediatric astrocytomas (from grade I to grade IV). We show that the rescue of ADAR2 in glioblastoma cells is able to significantly inhibit in vivo glioblastoma tumor growth. Differently, when we decrease the expression of ADAR2 in malignant but not tumorigenic astrocytoma cell line (A172) we observed a boost of several cancers cell features such as cell proliferation, migration and colony formation. By integrating deep-sequencing and array approaches with bioinformatics analyses and molecular studies, we observed that ADAR2 is essential to edit a small number of mature miRNAs and to significantly modulate the expression of about 90 miRNAs in glioblastoma cells that may contribute to cancer progression. Our findings disclose an additional layer of complexity in miRNome regulation and provide information to better dissect the impact of ADAR2 editing enzyme in glioblastoma. Citation Format: Angela Gallo. The importance of RNA editing enzymes in glioblastoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1932.

Successful antibiotic treatment of pulmonary disease caused by Mycobacterium abscessus subsp. abscessus with C-to-T mutation at position 19 in erm(41) gene: case report

BackgroundMycobacterium abscessus complex (MABC) is the most drug resistant of the mycobacterial pathogens. M. abscessus subsp. abscessus encodes a functional erythromycin ribosomal methylase gene, erm(41), causing inducible macrolide resistance. However, some clinical isolates of M. abscessus subsp. abscessus harboring nonfunctional erm(41) were susceptible to macrolide, even after extended incubation of 14 days. Loss of function of the erm(41) genes was associated with a T-to-C substitution at position 28 of the gene (T28C), leading to an amino acid change from Trp to Arg at codon 10. Pulmonary disease caused by M. abscessus subsp. abscessus strains with an nonfunctional erm(41) (C28 sequevar) may be responsive to macrolide-containing antibiotic regimens. Therefore, all M. abscessus subsp. abscessus strains with a functional erm(41) (T28 sequevar) were thought to be resistant to macrolide with extended incubation. Here, we report the first case of pulmonary disease caused by a strain of M. abscessus subsp. abscessus which was susceptible to macrolide due to T19 sequevar of erm(41) gene.Case presentationA 62-year-old Korean female was referred to our hospital due to chronic cough, sputum, and hemoptysis lasting more than 5 months. The patient’s sputum was positive for acid-fast bacilli staining and nontuberculous mycobacteria (NTM) were isolated twice from sputum specimens. The isolate was identified as M. abscessus subsp. abscessus. The isolate had a point mutation of C → T at position 19 (C19 → T) in the erm(41) gene, instead of expected C28 sequevar of erm(41), and had no rrl mutation. The isolate displayed a clarithromycin susceptible phenotype with an Arg → Stop codon change in erm(41). The patient was successfully treated with a macrolide-containing regimen.ConclusionThis is the first case of pulmonary disease caused by a strain of M. abscessus subsp. abscessus showing clarithromycin susceptible phenotype due to T19 sequevar of the erm(41) gene. The erm(41) gene is clinically important, and non-functional erm alleles may be an important issue for the management of MABC lung disease. The presence of a non-functional erm(41) allele in M. abscessus subsp. abscessus isolates may be associated with better outcomes.

A Common Polymorphism in HIBCH Influences Methylmalonic Acid Concentrations in Blood Independently of Cobalamin

Methylmalonic acid (MMA) is a by-product of propionic acid metabolism through the vitamin B12 (cobalamin)-dependent enzyme methylmalonyl CoA mutase. Elevated MMA concentrations are a hallmark of several inborn errors of metabolism and indicators of cobalamin deficiency in older persons. In a genome-wide analysis of 2,210 healthy young Irish adults (median age 22 years) we identified a strong association of plasma MMA with SNPs in 3-hydroxyisobutyryl-CoA hydrolase (HIBCH, p = 8.42× 10(-89)) and acyl-CoA synthetase family member 3 (ACSF3, p = 3.48× 10(-19)). These loci accounted for 12% of the variance in MMA concentration. The most strongly associated SNP (HIBCH rs291466; c:2T>C) causes a missense change of the initiator methionine codon (minor-allele frequency = 0.43) to threonine. Surprisingly, the resulting variant, p.Met1?, is associated with increased expression of HIBCH mRNA and encoded protein. These homozygotes had, on average, 46% higher MMA concentrations than methionine-encoding homozygotes in young adults with generally low MMA concentrations (0.17 [0.14-0.21] μmol/L; median [25(th)-75(th) quartile]). The association between MMA levels and HIBCH rs291466 was highly significant in a replication cohort of 1,481 older individuals (median age 79 years) with elevated plasma MMA concentrations (0.34 [0.24-0.51] μmol/L; p = 4.0× 10(-26)). In a longitudinal study of 185 pregnant women and their newborns, the association of this SNP remained significant across the gestational trimesters and in newborns. HIBCH is unique to valine catabolism. Studies evaluating flux through the valine catabolic pathway in humans should account for these variants. Furthermore, this SNP could help resolve equivocal clinical tests where plasma MMA values have been used to diagnose cobalamin deficiency.

Genetic variations of the coding region of the melanocortin receptor 1 (MC1R) gene in the fox.

The melanocortin 1 receptor (MC1R) gene plays an important role in the control of coat colour in mammals. Genetic variation of the MC1R gene and the relationship between genotype and coat colour are not well understood. Studies in the fox may improve our understanding of gene influence on coat colour in dogs and cats. To investigate coat colour associated mutations in the coding region of MC1R gene in foxes. A total of 118 foxes, comprising 70 red foxes (Vulpes vulpes) (19 red, 10 white silver, 29 silver and 12 chocolate foxes) and 48 arctic foxes (Vulpes lagopus) (9 dominant white blue foxes and 39 normal blue foxes) were included in the study. Evaluation of the DNA sequence of the coding region of MC1R gene and its polymorphisms. Eight polymorphic sites (single nucleotide polymorphisms, SNPs) distributed throughout the 954-bp coding region of the fox MC1R gene were detected. Among them, c.13G>T, c.124A>G, c.289G>A, c.373T>C and c.839 T>G were mis-sense mutations, which resulted in codon change of p.G5C, p.N42D, p.V97I, p.C125R and p.F280C, respectively. Mutation and haplotype analysis indicated that c.373T>C was associated with black and brown pigmented phenotypes in foxes, and c.13G>T and c.839T>G were important in distinguishing V. lagopus and V. vulpes. SNP c.373T>C in the coding region of the MC1R gene is probably associated with the brown phenotype of chocolate foxes.

Synonymous Codon Changes in Measles (HMV) and Canine Distemper (CDV) Viral Nucleic Acid Sequences Result in Gene‐Specific Changes in Levels of Viral Protein Expression

The purpose of this study was to characterize the effects of human and canine codon optimization on expression of viral proteins from HMV and CDV nucleic acid sequences. All the codon changes made were synonymous in that the amino acid coded for was unchanged. The human and canine CUB optimized HMV and CDV sequences had increased nucleic acid and codon identity as compared to the WT sequences. Protein expression from human and canine CUB optimized and sub‐optimized constructs of the N, F, M, H and P/C proteins was assessed in transfected human (293 HEK) and canine (A‐72) cells using fluorescence, Cellomic and, for proteins for which antibodies were available, western analysis.Results1) codon optimization increased protein expression of HMV and CDV N and F proteins in both cell lines; 2) synonymous codon changes did not affect expression of the HMV and CDV P and C and the HMV M proteins, but both optimization and sub‐optimization to canine CUB increased expression of the CDV M protein in human cells; 3) synonymous codon changes increased expression of the HMV H protein in both cell lines, but did not significantly affect CDV H protein expression. Overall both CUB optimization and sub‐optimization affected protein expression independent of viral infection in ways that varied with the gene and cell type, and differed between HMV and CDV. These results indicate that synonymous codon changes in viral nucleic acid sequences can alter protein expression in a variety of ways, some of which are likely to impact viral pathogenicity.Support or Funding InformationThis project was sponsored by the Department of Defense Threat Reduction Agency. The content of the information does not necessarily reflect the position or the policy of the federal government, and no official endorsement should be inferred.

Dynamic changes of driver genes' mutations across clinical stages in nine cancer types.

The driver genes play critical roles for tumorigenesis, and the number of identified driver genes reached plateau. But how they act during different cancer development stages is lack of knowledge. We investigated 138 driver genes’ mutation changes across clinical stages using 3,477 cases in nine cancer types from the Cancer Genome Atlas (TCGA) and constructed their temporal order relationships. We also examined the codon changes for the widely mutated TP53 and PIK3CA in tumor stages. Combinations of one to three driver genes specifically dominated in each cancer. Across the clinical stages, we categorized three patterns for the behaviors of driver genes’ mutation changes in the nine cancer types: recurrently mutated in all the stages and triggering other mutations; certain mutations lost meanwhile other mutations emerged; mutations dominated across entire stages, while other mutations gradually appeared or disappeared. We observed different codon changes dominated in different stages and revealed mutations recurrently occurring on the hotspot regions of the coding sequence may be the core factor for driver genes’ tumorigenesis. Our results highlighted the dynamic changes of oncogenesis roles in different clinical stages and suggested different diagnostic decision making according to the clinical stages of patients.

Further studies on the role of the residue 890 cysteine to tyrosine mutation in the M70 primase ORF of the temperature-sensitive mutant (tsm5) of murine cytomegalovirus.

A mutation (C890Y) introduced into the M70 primase gene of murine cytomegalovirus (MCMV) resulted in reduced viral replication in murine embryo fibroblasts at 40°C and the mutant was severely attenuated in vivo. The attenuated replication of the M70 mutant was also observed in Raw 264.7 macrophages at 37°C, demonstrating that the mutation produced a defective rather than an unstable protein possibly reducing the amount of functional protein under different environmental conditions. Many synonymous mutations were introduced into this ORF by changing codon preferences that should reduce the efficiency of gene translation, but not change protein sequence or structure. Two Bacterial Artificial Chromosome (BAC) constructs were produced with 155 codons (at the distal third of the M70 gene) changed to MCMV less preferred codons and with either cysteine (BAC70(155Cys) ) or tyrosine (BAC70(155Tyr) ) at residue 890. Upon transfection of these BACs into NIH 3T3 cells, only BAC70(155Cys) produced virus and this mutant Mt70(155Cys) replicated similarly to its revertant and the wt MCMV K181 (Perth) variant. A metagenomic analysis of the protein structure of the primase using PredictProtein showed that the change from cysteine (M70Cys) to tyrosine (M70Tyr) has a marked effect on protein structure. However, when the cysteine residue was replaced by serine (M70Ser) or methionine (M70Met), which produced mutant viruses with a wild-type phenotype, the predicted structure was similar to the wild-type structure. J. Med. Virol. 88:1613-1621, 2016. © 2016 Wiley Periodicals, Inc.

Precise Editing of the Zebrafish Genome Made Simple and Efficient

We present simple and efficient methods for creating heritable modifications of the zebrafish genome. Precisely modified alleles are generated by homologous recombination between the host genome and dsDNA donor molecules, stimulated by the induction of chromosomally targeted double-strand breaks. Several kilobase-long tracts of genome sequence can be replaced. Tagging donor sequences with reporter genes that can be subsequently excised improves recovery of edited alleles by an order of magnitude and facilitates recovery of recessive and phenotypically silent conditional mutations. We generate and demonstrate functionality of (1) alleles with a single codon change, (2) an allele encoding an epitope-tagged version of an endogenous protein, (3) alleles expressing reporter proteins, and (4) a conditional allele in which an exon is flanked by recombinogenic loxP sites. Our methods make recovery of a broad range of genome editing events very practicable, significantly advancing applicability of the zebrafish for studying normal biological processes and modeling diseases.

Large-Effect Beneficial Synonymous Mutations Mediate Rapid and Parallel Adaptation in a Bacterium.

Contrary to previous understanding, recent evidence indicates that synonymous codon changes may sometimes face strong selection. However, it remains difficult to generalize the nature, strength, and mechanism(s) of such selection. Previously, we showed that synonymous variants of a key enzyme-coding gene (fae) of Methylobacterium extorquens AM1 decreased enzyme production and reduced fitness dramatically. We now show that during laboratory evolution, these variants rapidly regained fitness via parallel yet variant-specific, highly beneficial point mutations in the N-terminal region of fae. These mutations (including four synonymous mutations) had weak but consistently positive impacts on transcript levels, enzyme production, or enzyme activity. However, none of the proposed mechanisms (including internal ribosome pause sites or mRNA structure) predicted the fitness impact of evolved or additional, engineered point mutations. This study shows that synonymous mutations can be fixed through strong positive selection, but the mechanism for their benefit varies depending on the local sequence context.

Mutant p53 and ETS2, a Tale of Reciprocity.

TP53 is one of the most frequently inactivated tumor suppressor genes in human cancer. However, unlike other tumor suppressor genes whose expression is lost, TP53 is usually inactivated as a result of a single nucleotide change within the coding region. Typically, these single nucleotide mutations result in a codon change that creates an amino acid substitution. Thus, unlike other tumor suppressor genes whose expression is lost due to genetic or epigenetic changes, the p53 gene primarily suffers missense mutations, and therefore, the cells retain and express a mutant form of the p53 protein (mtp53). It is now well established that mtp53 contributes to tumor development through its gain-of-function (GOF) activities. These GOF activities can arise from novel protein–protein interactions that can either disable other tumor suppressors (e.g., p63 and p73) or enable oncogenes such as ETS2, an ETS family member. In this review, I will focus on the identification of the mtp53/ETS2 complex and outline the diverse activities that this transcriptional regulatory complex controls to promote cancer.

Comparative sequence analysis of domain I of Plasmodium falciparum apical membrane antigen 1 from Saudi Arabia and worldwide isolates

The apical membrane antigen 1 of Plasmodium falciparum (PfAMA1) plays a crucial role in erythrocyte invasion and is a target of protective antibodies. Although domain I of PfAMA1 has been considered a promising vaccine component, extensive sequence diversity in this domain could compromise an effective vaccine design. To explore the extent of sequence diversity in domain I of PfAMA1, P. falciparum-infected blood samples from Saudi Arabia collected between 2007 and 2009 were analyzed and compared with those from worldwide parasite populations. Forty-six haplotypes and a novel codon change (M190V) were found among Saudi Arabian isolates. The haplotype diversity (0.948±0.004) and nucleotide diversity (0.0191±0.0008) were comparable to those from African hyperendemic countries. Positive selection in domain I of PfAMA1 among Saudi Arabian parasite population was observed because nonsynonymous nucleotide substitutions per nonsynonymous site (dN) significantly exceeded synonymous nucleotide substitutions per synonymous site (dS) and Tajima's D and its related statistics significantly deviated from neutrality in the positive direction. Despite a relatively low prevalence of malaria in Saudi Arabia, a minimum of 17 recombination events occurred in domain I. Genetic differentiation was significant between P. falciparum in Saudi Arabia and parasites from other geographic origins. Several shared or closely related haplotypes were found among parasites from different geographic areas, suggesting that vaccine derived from multiple shared epitopes could be effective across endemic countries.

Characterization of Genomic Variants Associated with Scout and Recruit Behavioral Castes in Honey Bees Using Whole-Genome Sequencing.

Among forager honey bees, scouts seek new resources and return to the colony, enlisting recruits to collect these resources. Differentially expressed genes between these behaviors and genetic variability in scouting phenotypes have been reported. Whole-genome sequencing of 44 Apis mellifera scouts and recruits was undertaken to detect variants and further understand the genetic architecture underlying the behavioral differences between scouts and recruits. The median coverage depth in recruits and scouts was 10.01 and 10.7 X, respectively. Representation of bacterial species among the unmapped reads reflected a more diverse microbiome in scouts than recruits. Overall, 1,412,705 polymorphic positions were analyzed for associations with scouting behavior, and 212 significant (p-value < 0.0001) associations with scouting corresponding to 137 positions were detected. Most frequent putative transcription factor binding sites proximal to significant variants included Broad-complex 4, Broad-complex 1, Hunchback, and CF2-II. Three variants associated with scouting were located within coding regions of ncRNAs including one codon change (LOC102653644) and 2 frameshift indels (LOC102654879 and LOC102655256). Significant variants were also identified on the 5’UTR of membrin, and 3’UTRs of laccase 2 and diacylglycerol kinase theta. The 60 significant variants located within introns corresponded to 39 genes and most of these positions were > 1000 bp apart from each other. A number of these variants were mapped to ncRNA LOC100578102, solute carrier family 12 member 6-like gene, and LOC100576965 (meprin and TRAF-C homology domain containing gene). Functional categories represented among the genes corresponding to significant variants included: neuronal function, exoskeleton, immune response, salivary gland development, and enzymatic food processing. These categories offer a glimpse into the molecular support to the behaviors of scouts and recruits. The level of association between genomic variants and scouting behavior observed in this study may be linked to the honey bee’s genomic plasticity and fluidity of transition between castes.

Characterisation and functional implications of the two new HLA-G alleles found in Amerindian and Caribbean populations

HLA-G polymorphism has been found to be relatively low in all world populations. In the present paper two new HLA-G molecules are described in ancient American natives. A new HLA-G molecule from a Ecuador Amerindian individual (male) showed four codon changes with respect to HLA-G*01:01:01. Silent changes at α1 domain (residue 57, Pro, CCG→CCA) and α2 domain (residue 93, His, CAC→CAT and residue 100, Gly, GGC→GGT) and one productive change in α3 domain (residue 219 changed from Arg to Trp). This α3 change may dramatically alter HLA-G interactions with beta-2 microglobulin, CD8, ILT-2 and ILT-4 ligands present in subsets of T, B, NK, monocytes, macrophages and dentritic cells. Another HLA-G new molecule was found in a woman from Hispaniola Island, Dominican Republic (Sto Domingo): it presented a silent change at α2 domain residue 107, Gly, GGA→GGT and non-silent change at residue 178, Met→Thr (with respect to HLA-G*01:01:01) which is close to class I molecule/clonotypic T cell receptor interaction sites. Functional implications of these findings are discussed.

Abstract B12: Targeted sequencing of ovarian clear cell carcinomas reveals intertumor heterogeneity and distinct clustering related to mutational load.

Abstract Objective: Ovarian clear cell carcinomas (OCCCs) constitute a rare ovarian cancer subtype. Despite relatively clear clinical features, OCCCs can be difficult to distinguish morphologically from other epithelial ovarian cancers. OCCC gene expression signatures capturing not only the morphology but also the biology of this tumor subtype have been described, and a previous study using comparative genomic hybridization showed that OCCCs are indeed heterogeneous. Still, only a few genes have been analyzed using gene sequencing techniques. In the present study we aimed to further characterize OCCCs and their histotype specific genetic changes using targeted sequencing of 60 well-established cancer genes. Increased knowledge about genetic aberrations in OCCCs may help to guide future development of targeted treatments and improve the outcome for these patients. Methods: Formalin fixed, paraffin-embedded (FFPE) tumor tissue was collected from 11 primary OCCCs, diagnosed at the Skane University Hospital, Lund, Sweden (1998-2013). One sample was excluded due to poor DNA quality. For the remaining 10 samples, 600 ng genomic DNA/sample was used for single strand targeted DNA sequencing using the SureSeq™ solid tumor panel consisting of 60 key genes involved in cancer evolution, including ovarian cancer. The panel covers all coding exons in the included genes, and is validated for research use on FFPE samples. The publicly available ENSEMBL database was used to classify the mutations according to severity across the genes. Serious mutations, defined as major non-conservative amino acid changes, splice or frameshift variants or changes in stop codons, affecting single nucleotide variations (SNVs) or insertions or deletions of DNA bases (indels) were used for further analyses. The mutation call cut-off was set to 20% and the reading depth ≥300x, and unsupervised hierarchical clustering of the tumor samples was performed. Results: &amp;gt;99% of the target bases had a 30x coverage across all samples, and the mean target coverage was 534x. Using the 20% cut-off, approximately 300 mutations were detected in the 60 genes across the 10 tumor samples. Unsupervised hierarchical clustering revealed two distinct clusters related to mutational load. Mutations in genes previously reported to be affected in OCCCs, such as ARID1A and ERBB2, were identified. Whereas ARID1A was mainly affected in one cluster, mutations in genes signifying a highly malignant phenotype, such as BRCA1 and BRCA2 dominated in the other. Genes in signaling pathways often affected in malignant tumors, as e.g. the RAS pathway, however, were unaffected. Other mutations detected in this dataset were ZFHX3 and KMT2C. KMT2C was the only highly mutated gene across both clusters. The clustering pattern was not related to age of FFPE blocks or tumor cell content. Conclusions: In the present study we show that OCCCs are genetically heterogeneous. The variation in mutation rate is in line with a previous publication, and points to differences in tumor biology that may be important for tumor behavior and thus patient outcome. The highly mutated genes may help in guiding trials of targeted treatments; the methyl transferase gene KMT2C, also known as MLL3, may potentially be one such target. Rearrangements of this gene are well-described in acute leukemias. Interestingly, KMT2C/MLL3 is also reported to be a mutational cancer driver gene in renal clear cell carcinomas according to the TCGA. Likewise, ZFHX3 has recently been reported in endometrial clear cell carcinomas. Despite the small size of this study it points to the well-established fact that ovarian cancer is not one single disease, and also confirms that even the rare OCCCs seem to harbor different biological features which may be of potential clinical importance. Citation Format: Jenny-Maria Jönsson, Nicolai Skovbjerg Arildsen, Anna Ebbesson, Sofia Westbom-Fremer, Anna Måsbäck, Susanne Malander, Mef Nilbert, Ingrid Hedenfalk. Targeted sequencing of ovarian clear cell carcinomas reveals intertumor heterogeneity and distinct clustering related to mutational load. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: Exploiting Vulnerabilities; Oct 17-20, 2015; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(2 Suppl):Abstract nr B12.

Weaver Syndrome-Associated EZH2 Protein Variants Show Impaired Histone Methyltransferase Function In Vitro.

ABSTRACTWeaver syndrome (WS) is a rare congenital disorder characterized by generalized overgrowth, macrocephaly, specific facial features, accelerated bone age, intellectual disability, and susceptibility to cancers. De novo mutations in the enhancer of zeste homolog 2 (EZH2) have been shown to cause WS. EZH2 is a histone methyltransferase that acts as the catalytic agent of the polycomb‐repressive complex 2 (PRC2) to maintain gene repression via methylation of lysine 27 on histone H3 (H3K27). Functional studies investigating histone methyltransferase activity of mutant EZH2 from various cancers have been reported, whereas WS‐associated mutations remain poorly characterized. To investigate the role of EZH2 in WS, we performed functional studies using artificially assembled PRC2 complexes containing mutagenized human EZH2 that reflected the codon changes predicted from patients with WS. We found that WS‐associated amino acid alterations reduce the histone methyltransferase function of EZH2 in this in vitro assay. Our results support the hypothesis that WS is caused by constitutional mutations in EZH2 that alter the histone methyltransferase function of PRC2. However, histone methyltransferase activities of different EZH2 variants do not appear to correlate directly with the phenotypic variability between WS patients and individuals with a common c.553G>C (p.Asp185His) polymorphism in EZH2.

Codon Usage in Signal Sequences Affects Protein Expression and Secretion Using Baculovirus/Insect Cell Expression System

By introducing synonymous mutations into the coding sequences of GP64sp and FibHsp signal peptides, the influences of mRNA secondary structure and codon usage of signal sequences on protein expression and secretion were investigated using baculovirus/insect cell expression system. The results showed that mRNA structural stability of the signal sequences was not correlated with the protein production and secretion levels, and FibHsp was more tolerable to codon changes than GP64sp. Codon bias analyses revealed that codons for GP64sp were well de-optimized and contained more non-optimal codons than FibHsp. Synonymous mutations in GP64sp sufficiently increased its average codon usage frequency and resulted in dramatic reduction of the activity and secretion of luciferase. Protein degradation inhibition assay with MG-132 showed that higher codon usage frequency in the signal sequence increased the production as well as the degradation of luciferase protein, indicating that the synonymous codon substitutions in the signal sequence caused misfolding of luciferase instead of slowing down the protein production. Meanwhile, we found that introduction of more non-optimal codons into FibHsp could increase the production and secretion levels of luciferase, which suggested a new strategy to improve the production of secretory proteins in insect cells.

A case of keratitis-ichthyosis-deafness syndrome complicated by cutaneous squamous cell carcinoma: mutation analysis of the GJB2 gene and literature review

Objective To analyze mutations in the GJB2 gene in a Chinese patient with keratitis-ichthyosis-deafness (KID) syndrome complicated by cutaneous squamous cell carcinoma. Methods Clinical data were collected from a patient with KID syndrome complicated by cutaneous squamous cell carcinoma. Peripheral blood samples were obtained from the patient and her parents, and DNA was extracted from these blood samples. PCR was performed to amplify the exon 2 of the GJB2 gene followed by direct DNA sequencing. Results A mutation (c.148G > A) was identified at position 148 in exon 2 of the GJB2 gene, which caused a codon change from GAC to AAC and resulted in the substitution of aspartate by asparagine at position 50 in the connexin26 (Cx26) protein (p.Asp50Asn). In addition, another mutation (c.79G > A) , which led to the substitution of valine by isoleucine at codon 27 in Cx26 (p.Val27Ile) , was found at position 79 in exon 2 of the GJB2 gene. Neither of the two mutations was detected in the patient's parents. Literature review revealed that 13 cases of KID syndrome complicated by cutaneous squamous cell carcinoma had been reported in abroad, and the mutation c.148G > A was detected in the GJB2 gene in all the 7 cases finally diagnosed by gene sequencing. Conclusion GJB2 gene mutations may be responsible for the clinical phenotype of KID syndrome in this Chinese patient, and the mutation c.148G > A may be related to the development of cutaneous squamous cell carcinoma. Key words: Mutation; Carcinoma, squamous cell; GJB2 gene; Keratitis-ichthyosis-deafness syndrome

Exome Sequencing in Myeloma Pedigrees Implicates RAS1 and NOTCH Signaling Are Involved in Inherited Myeloma Risk

Multiple Myeloma (MM) is a cancer of plasma cells with poor prognosis. Although, MM has been shown to be highly heritable in genealogy studies, no inherited risk-alleles have been identified. We hypothesize MM heritability is in part due to rare, germline variation that can be discovered in high-risk pedigrees.High-risk MM pedigrees were identified using the Utah Population Database which contains both genealogical and state cancer records. High-risk pedigrees were defined to have statistical excess of MM (p < 0.05). In this study we whole-exome sequenced germline DNA from 42 MM cases from high-risk pedigrees. Best practice variant calling, joint genotyping, and quality control were performed on the cases, a set of background controls from the 1000 Genome Project (1000G), and a small set of local controls (for technical artifacts), and resulted in 607,908 variants. We prioritized variants that were: 1) shared by at least 3 related MM cases, 2) absent in local controls, and 3) rare (frequency ≤ 0.01 in 1000G). This prioritization resulted in 116 variants of interest.Of the 116 variants, 3 MM cases in one high-risk pedigree shared multiple variants on chromosome 1p36.11-35.1. To formally assess whether these variants were inherited from a common founder we performed shared genome segment analysis using high-density SNP genotyping. We identified a region at 1p36.11-35.1, 8.9 Mb in length (p = 6.0 × 10-4; 22,000 simulations), providing positive evidence for segregation from a common founder.The segregating variants identified from exome sequencing in this region are in the genes CNKSR1, ARID1A, and SDC3. All three variants are individually predicted to be moderately deleterious. The variant in CNKSR1 falls in a splice region and has minor allele frequency of 0.004 in the 1000G Europeans. This variant was also observed in 3 additional cases in our sequencing set, indicating a strong enrichment of this variant in our high-risk MM cases (6/42 = 0.143). CNKSR1 is involved in the RAS1 and NOTCH signaling pathways and is a known target for cancer therapy. The variants in ARID1A and SDC3 both result in non-synonymous codon changes. ARID1A is commonly mutated across cancers and has been associated with accelerated tumor growth in hepatocellular carcinomas. SDC3 also interacts with NOTCH signaling, a pathway involved in MM growth (especially in patients with MAF translocations) and osteoclastogenesis. The variants in ARID1A and SDC3 are not carried by other cases in our sequencing set, which may indicate the combination of these variants is important to confer risk in the pedigree, or merely that the variants are hitchhikers on the segregating chromosome.Germline risk-alleles will shed light on the genetic factors involved in MM susceptibility and ultimately may provide new avenues for screening, diagnosis and treatment. Here we have identified evidence for segregating variants in a high-risk pedigree that implicate the RAS1 and NOTCH signaling pathways as involved in MM risk. Future work includes confirmation sequencing in the pedigree and a broader set of MM cases, and functional follow-up of the variants and their role in disruption of the genes and pathways. DisclosuresNo relevant conflicts of interest to declare.

Introns Structure Patterns of Variation in Nucleotide Composition in Arabidopsis thaliana and Rice Protein-Coding Genes.

Plant genomes present a continuous range of variation in nucleotide composition (G + C content). In coding regions, G + C-poor species tend to have unimodal distributions of G + C content among genes within genomes and slight 5′–3′ gradients along genes. In contrast, G + C-rich species display bimodal distributions of G + C content among genes and steep 5′–3′ decreasing gradients along genes. The causes of these peculiar patterns are still poorly understood. Within two species (Arabidopsis thaliana and rice), each representative of one side of the continuum, we studied the consequences of intron presence on coding region and intron G + C content at different scales. By properly taking intron structure into account, we showed that, in both species, intron presence is associated with step changes in nucleotide, codon, and amino acid composition. This suggests that introns have a barrier effect structuring G + C content along genes and that previous continuous characterizations of the 5′–3′ gradients were artifactual. In external gene regions (located upstream first or downstream last introns), species-specific factors, such as GC-biased gene conversion, are shaping G + C content whereas in internal gene regions (surrounded by introns), G + C content is likely constrained to remain within a range common to both species.