Inheritance Of Mutation Research Articles

Genomic stability in Nicotiana plants upon silencing of the mismatch repair gene MSH2

The Mismatch Repair (MMR) system is a highly conserved pathway for the maintenance of genomic stability in many organisms. In plants, this is particularly important because of the lack of a reserved germline. Suppression of MMR leads to an accumulation of random mutations in the genome over successive generations, and thus maximizes genetic diversity. MMR deficiency has been shown to be a useful technique in plant breeding, complementary to chemical or physical mutagenesis. We have developed an artificial microRNA (amiRNA) targeting the MSH2 gene, which is generally applicable in Solanaceae. Two amiRNA precursors were inserted in a transformation vector, under the control of the CaMV 35S promoter and the meiosis active AtDMC1 promoter, respectively. Introduction of this amiRNA construct in Nicotiana tabacum and N. plumbaginifolia reduced the MSH2 transcript levels to 20–30 %. Morphological and developmental abnormalities and plants with white sectors on the first pair of leaves or on the cotyledons (referred to as ‘chimeric albinos’) appeared in the transformed Nicotiana lines at higher frequencies than in the control lines. Also, some plants which show an increased tolerance for the herbicide chlorsulfuron were found. However, the mutant phenotypes were not transmitted to subsequent generations. We conclude that the designed amiRNA was capable of suppressing the MSH2 activity, which caused the occurrence of somatic mutations. Apparently, the silencing of MSH2 was not strong enough in the germline to cause inheritable mutations.

Phenotypic heterogeneity of hereditary gynecologic cancers: a report from the Creighton hereditary cancer registry

To determine the validity of observations suggesting a significant dichotomy of gynecologic cancers determined by linkage to specific genetic defects associated with two major autosomal dominant hereditary cancer syndromes; the Creighton University Hereditary Cancer Registry was searched for female carriers of germ line mutations in BRCA1 and BRCA2, associated with the Hereditary Breast Ovarian Cancer syndrome, and in the mismatch repair (MMR) genes MLH1, MSH2 and MSH6, associated with Lynch syndrome, who were registered with invasive uterine, ovarian, fallopian tube or peritoneal cancers between January 1, 1959 and December 31, 2010. From 217 such cases, a total of 174 subjects, consisting of 95 BRCA1 and BRCA2 mutation carriers and 79 carriers of mutations in MMR genes, were identified who had current signed Health Insurance Portability and Accountability Act forms and complete primary diagnostic pathology reports and clinical records. Data meticulously extracted from these cases were categorized and statistically analyzed. There were highly significant differences between carriers of BRCA1 and BRCA2 mutations and carriers of MMR gene mutations in the proportion of serous carcinomas compared with endometrioid carcinomas of the uterus, including cervix and endometium (p < 0.002), ovaries (p < 0.001) and overall, including fallopian tube and peritoneum cancers (p < 0.001). Endometrioid carcinoma was found in one and transitional carcinoma in another of the 14 BRCA1 mutation carriers with fallopian tube cancer, and endometrioid carcinoma was found in two of four MMR gene mutation carriers with fallopian tube cancers. All other fallopian tube cancers were serous carcinomas. Seven BRCA1 and one BRCA2 mutation carriers were diagnosed with primary peritoneal serous carcinoma; no peritoneal carcinomas were registered in MMR gene mutation carriers. Nine of 14 gynecologic cancers with associated endometriosis in mutation carriers were endometrioid or endometrioid mixed carcinomas compared with just three of other histologic types. Primary breast cancers, that characterize the HBOC syndrome, were much more frequent in BRCA1 and BRCA2 mutation carriers; while multiple gynecologic cancers and associated colorectal and urinary tract cancers, which are features of Lynch syndrome, were more common in MMR gene mutation carriers. Both serous and endometrioid carcinomas were diagnosed in MMR gene mutation carriers at significantly younger ages than in BRCA1 and BRCA2 mutation carriers (p < 0.0006). These findings confirm a clear dichotomy of uterine, ovarian and fallopian tube cancers associated with inheritance of mutations in BRCA1 and BRCA2 contrasted with inheritance of MMR gene mutations. This opens possibilities for new approaches to molecular genetic research into carcinogenic pathways and raises important new considerations regarding counseling, screening, prophylaxis and treatment of mutation carriers.

Yunis-Varón Syndrome Is Caused by Mutations in FIG4, Encoding a Phosphoinositide Phosphatase

Yunis-Varón syndrome (YVS) is an autosomal-recessive disorder with cleidocranial dysplasia, digital anomalies, and severe neurological involvement. Enlarged vacuoles are found in neurons, muscle, and cartilage. By whole-exome sequencing, we identified frameshift and missense mutations of FIG4 in affected individuals from three unrelated families. FIG4 encodes a phosphoinositide phosphatase required for regulation of PI(3,5)P(2) levels, and thus endosomal trafficking and autophagy. In a functional assay, both missense substitutions failed to correct the vacuolar phenotype of Fig4-null mouse fibroblasts. Homozygous Fig4-null mice exhibit features of YVS, including neurodegeneration and enlarged vacuoles in neurons. We demonstrate that Fig4-null mice also have small skeletons with reduced trabecular bone volume and cortical thickness and that cultured osteoblasts accumulate large vacuoles. Our findings demonstrate that homozygosity or compound heterozygosity for null mutations of FIG4 is responsible for YVS, the most severe known human phenotype caused by defective phosphoinositide metabolism. In contrast, in Charcot-Marie-Tooth disease type 4J (also caused by FIG4 mutations), one of the FIG4 alleles is hypomorphic and disease is limited to the peripheral nervous system. This genotype-phenotype correlation demonstrates that absence of FIG4 activity leads to central nervous system dysfunction and extensive skeletal anomalies. Our results describe a role for PI(3,5)P(2) signaling in skeletal development and maintenance.

Diagnostic Exome Sequencing in Persons With Severe Intellectual Disability

Background The causes of intellectual disability remain largely unknown because of extensive clinical and genetic heterogeneity. Methods We evaluated patients with intellectual disability to exclude known causes of the disorder. We then sequenced the coding regions of more than 21,000 genes obtained from 100 patients with an IQ below 50 and their unaffected parents. A data-analysis procedure was developed to identify and classify de novo, autosomal recessive, and X-linked mutations. In addition, we used high-throughput resequencing to confirm new candidate genes in 765 persons with intellectual disability (a confirmation series). All mutations were evaluated by molecular geneticists and clinicians in the context of the patients' clinical presentation. Results We identified 79 de novo mutations in 53 of 100 patients. A total of 10 de novo mutations and 3 X-linked (maternally inherited) mutations that had been previously predicted to compromise the function of known intellectual-disability genes were found in 13 patients. Potentially causative de novo mutations in novel candidate genes were detected in 22 patients. Additional de novo mutations in 3 of these candidate genes were identified in patients with similar phenotypes in the confirmation series, providing support for mutations in these genes as the cause of intellectual disability. We detected no causative autosomal recessive inherited mutations in the discovery series. Thus, the total diagnostic yield was 16%, mostly involving de novo mutations. Conclusions De novo mutations represent an important cause of intellectual disability; exome sequencing was used as an effective diagnostic strategy for their detection. (Funded by the European Union and others.).

Contribution of the MLH1 -93G&gt;A Promoter Polymorphism in Modulating Susceptibility Risk in Malaysian Colorectal Cancer Patients

Colorectal cancer (CRC) exists in a more common sporadic form and less common hereditary forms, associated with the Lynch syndrome, familial adenomatous polyposis (FAP) and other rare syndromes. Sporadic CRC is believed to arise as a result of close interaction between environmental factors, including dietary and lifestyle habits, and genetic predisposition factors. In contrast, hereditary forms such as those related to the Lynch syndrome result from inheritance of germline mutations of mismatch repair (MMR) genes. However, in certain cases, the influence of low penetrance alleles in familial colorectal cancer susceptibility is also undeniable. To investigate the genotype frequencies of MLH1 promoter polymorphism -93G>A and to determine whether it could play any role in modulating familial and sporadic CRC susceptibility risk. A case-control study comprising of 104 histopathologically confirmed CRC patients as cases (52 sporadic CRC and 52 Lynch syndrome patients) and 104 normal healthy individuals as controls was undertaken. DNA was extracted from peripheral blood and the polymorphism was genotyped employing PCR-RFLP methods. The genotypes were categorized into homozygous wild type, heterozygous and homozygous variants. The risk association between these polymorphisms and CRC susceptibility risk was calculated using binary logistic regression analysis and deriving odds ratios (ORs). When risk association was investigated for all CRC patients as a single group, the heterozygous (G/A) genotype showed a significantly higher risk for CRC susceptibility with an OR of 2.273, (95%CI: 1.133-4.558 and p-value=0.021). When analyzed specifically for the 2 types of CRC, the heterozygous (G/A) genotype showed significantly higher risk for sporadic CRC susceptibility with and OR of 3.714, (95%CI: 1.416-9.740 and p-value=0.008). Despite high OR value was observed for Lynch syndrome (OR: 1.600, 95%CI: 0.715-3.581), the risk was not statistically significant (P=0.253). Our results suggest an influence of MLH1 promoter polymorphism -93G>A in modulating susceptibility risk in Malaysian CRC patients, especially those with sporadic disease.

Role of an Implantable Cardioverter Defibrillator in Emery Dreifuss Muscular Dystrophy: A Case Report and a Review of the Literature

Role of an Implantable Cardioverter Defibrillator in Emery Dreifuss Muscular Dystrophy: A Case Report and a Review of the Literature Emery dreifuss muscular dystrophy (EDMD) is one of the three most common inherited muscular dystrophies characterized by a triad of contractures, muscle weakness, and cardiac involvement (conduction abnormalities and/or cardiomyopathy). It can be inherited as X-linked recessive, autosomal dominant or autosomal recessive pattern. Cardiac involvement is evident in virtually all cases by the end of 4th decade. There is no relationship between the severity of cardiac and skeletal muscle involvement, irrespective of the mode of inheritance and type of mutations.

Successful subcutaneous glucagon use for persistent hypoglycaemia in congenital hyperinsulinism

Abstract Congenital hyperinsulinism (CHI) results from inappropriate excessive insulin secretion by the beta cells in the pancreas. A wide clinical spectrum of disease exists and a genetic diagnosis is now possible for approximately 50% of affected children. We describe a patient with atypical diffuse CHI caused by mosaic ABCC8 mutation inheritance, unmasked by paternal uniparental disomy. Hypoglycaemia persisted despite two subtotal pancreatectomies and trials of diazoxide and nifedipine were unsuccessful. Octreotide resulted in anaphylaxis, precluding its use. Continuous subcutaneous glucagon infusion was successful in restoring normoglycaemia and attenuating weight gain, with concomitant improvement of developmental milestones. No adverse effects have been encountered after >12 months of therapy. Administration problems (e.g., line crystallisation) may complicate continuous glucagon therapy; hence a practical description of infusion constitution is included. We recommend consideration of continuous subcutaneous glucagon infusion as a therapeutic option for persistent refractory hypoglycaemia in CHI.

Non‐familial cases of intellectual disability could be linked to de novo genetic mutations

Non‐familial cases of intellectual disability could be linked to de novo genetic mutations

Diagnostic Exome Sequencing in Persons with Severe Intellectual Disability

BackgroundThe causes of intellectual disability remain largely unknown because of extensive clinical and genetic heterogeneity.MethodsWe evaluated patients with intellectual disability to exclude known causes of the disorder. We then sequenced the coding regions of more than 21,000 genes obtained from 100 patients with an IQ below 50 and their unaffected parents. A data-analysis procedure was developed to identify and classify de novo, autosomal recessive, and X-linked mutations. In addition, we used high-throughput resequencing to confirm new candidate genes in 765 persons with intellectual disability (a confirmation series). All mutations were evaluated by molecular geneticists and clinicians in the context of the patients' clinical presentation.ResultsWe identified 79 de novo mutations in 53 of 100 patients. A total of 10 de novo mutations and 3 X-linked (maternally inherited) mutations that had been previously predicted to compromise the function of known intellectual-disability genes were found in 13 patients. Potentially causative de novo mutations in novel candidate genes were detected in 22 patients. Additional de novo mutations in 3 of these candidate genes were identified in patients with similar phenotypes in the confirmation series, providing support for mutations in these genes as the cause of intellectual disability. We detected no causative autosomal recessive inherited mutations in the discovery series. Thus, the total diagnostic yield was 16%, mostly involving de novo mutations.ConclusionsDe novo mutations represent an important cause of intellectual disability; exome sequencing was used as an effective diagnostic strategy for their detection. (Funded by the European Union and others.)

Genetic risk for Parkinson's disease correlates with alterations in neuronal manganese sensitivity between two human subjects

Manganese (Mn) is an environmental risk factor for Parkinson's disease (PD). Recessive inheritance of PARK2 mutations is strongly associated with early onset PD (EOPD). It is widely assumed that the influence of PD environmental risk factors may be enhanced by the presence of PD genetic risk factors in the genetic background of individuals. However, such interactions may be difficult to predict owing to the complexities of genetic and environmental interactions. Here we examine the potential of human induced pluripotent stem (iPS) cell-derived early neural progenitor cells (NPCs) to model differences in Mn neurotoxicity between a control subject (CA) with no known PD genetic risk factors and a subject (SM) with biallelic loss-of-function mutations in PARK2 and family history of PD but no evidence of PD by neurological exam. Human iPS cells were generated from primary dermal fibroblasts of both subjects. We assessed several outcome measures associated with Mn toxicity and PD. No difference in sensitivity to Mn cytotoxicity or mitochondrial fragmentation was observed between SM and CA NPCs. However, we found that Mn exposure was associated with significantly higher reactive oxygen species (ROS) generation in SM compared to CA NPCs despite significantly less intracellular Mn accumulation. Thus, this report offers the first example of human subject-specific differences in PD-relevant environmental health related phenotypes that are consistent with pathogenic interactions between known genetic and environmental risk factors for PD.

Improving Lambda Red Genome Engineering in Escherichia coli via Rational Removal of Endogenous Nucleases

Lambda Red recombineering is a powerful technique for making targeted genetic changes in bacteria. However, many applications are limited by the frequency of recombination. Previous studies have suggested that endogenous nucleases may hinder recombination by degrading the exogenous DNA used for recombineering. In this work, we identify ExoVII as a nuclease which degrades the ends of single-stranded DNA (ssDNA) oligonucleotides and double-stranded DNA (dsDNA) cassettes. Removing this nuclease improves both recombination frequency and the inheritance of mutations at the 3′ ends of ssDNA and dsDNA. Extending this approach, we show that removing a set of five exonucleases (RecJ, ExoI, ExoVII, ExoX, and Lambda Exo) substantially improves the performance of co-selection multiplex automatable genome engineering (CoS-MAGE). In a given round of CoS-MAGE with ten ssDNA oligonucleotides, the five nuclease knockout strain has on average 46% more alleles converted per clone, 200% more clones with five or more allele conversions, and 35% fewer clones without any allele conversions. Finally, we use these nuclease knockout strains to investigate and clarify the effects of oligonucleotide phosphorothioation on recombination frequency. The results described in this work provide further mechanistic insight into recombineering, and substantially improve recombineering performance.

Induction, rapid fixation and retention of mutations in vegetatively propagated banana

Mutation discovery technologies have enabled the development of reverse genetics for many plant species and allowed sophisticated evaluation of the consequences of mutagenesis. Such methods are relatively straightforward for seed-propagated plants. To develop a platform suitable for vegetatively propagated species, we treated isolated banana shoot apical meristems with the chemical mutagen ethyl methanesulphonate, recovered plantlets and screened for induced mutations. A high density of GC-AT transition mutations were recovered, similar to that reported in seed-propagated polyploids. Through analysis of the inheritance of mutations, we observed that genotypically heterogeneous stem cells resulting from mutagenic treatment are rapidly sorted to fix a single genotype in the meristem. Further, mutant genotypes are stably inherited in subsequent generations. Evaluation of natural nucleotide variation showed the accumulation of potentially deleterious heterozygous alleles, suggesting that mutation induction may uncover recessive traits. This work therefore provides genotypic insights into the fate of totipotent cells after mutagenesis and suggests rapid approaches for mutation-based functional genomics and improvement of vegetatively propagated crops.

Filamin A mutation associated with normal reading skills and dyslexia in a family with periventricular heterotopia

Periventricular heterotopia (PH) is a disorder of neuronal migration during fetal development that is characterized by morphologically normal neurons being located in an anatomically abnormal position in the mature brain. PH is usually diagnosed in patients presenting with a seizure disorder, when neuroimaging demonstrates the ectopically placed nodules of neurons. PH is a genetically and phenotypically heterogeneous disorder. The most commonly identified genetic cause is the X-linked dominant inheritance of mutations in the Filamin A (FLNA) gene. Multiple lines of evidence support the contribution of genetic factors in dyslexia. As dyslexia does not show a single-gene pattern of inheritance, it is classified as a complex genetic disorder. We have recently identified a specific reading fluency deficit in a variable group of patients with PH, in the context of normal intelligence. Here, we present a study of a mother-daughter pair who share bilateral widespread gray matter heterotopia caused by a novel mutation in FLNA and the same pattern of X-chromosome inactivation but who exhibit divergent reading and cognitive profiles. This novel observation highlights the uncertainty of using heterotopia anatomy in clinical practice to predict behavioral outcome.

CD45-deficient severe combined immunodeficiency caused by uniparental disomy

Analysis of the molecular etiologies of SCID has led to important insights into the control of immune cell development. Most cases of SCID result from either X-linked or autosomal recessive inheritance of mutations in a known causative gene. However, in some cases, the molecular etiology remains unclear. To identify the cause of SCID in a patient known to lack the protein-tyrosine phosphatase CD45, we used SNP arrays and whole-exome sequencing. The patient's mother was heterozygous for an inactivating mutation in CD45 but the paternal alleles exhibited no detectable mutations. The patient exhibited a single CD45 mutation identical to the maternal allele. Patient SNP array analysis revealed no change in copy number but loss of heterozygosity for the entire length of chromosome 1 (Chr1), indicating that disease was caused by uniparental disomy (UPD) with isodisomy of the entire maternal Chr1 bearing the mutant CD45 allele. Nonlymphoid blood cells and other mesoderm- and ectoderm-derived tissues retained UPD of the entire maternal Chr1 in this patient, who had undergone successful bone marrow transplantation. Exome sequencing revealed mutations in seven additional genes bearing nonsynonymous SNPs predicted to have deleterious effects. These findings are unique in representing a reported case of SCID caused by UPD and suggest UPD should be considered in SCID and other recessive disorders, especially when the patient appears homozygous for an abnormal gene found in only one parent. Evaluation for alterations in other genes affected by UPD should also be considered in such cases.

Expanding the Clinical Indications for α1-Antitrypsin Therapy

α(1)-Antitrypsin (AAT) is a 52-kDa circulating serine protease inhibitor. Production of AAT by the liver maintains 0.9-1.75 mg/mL circulating levels. During acute-phase responses, circulating AAT levels increase more than fourfold. In individuals with one of several inherited mutations in AAT, low circulating levels increase the risk for lung, liver and pancreatic destructive diseases, particularly emphysema. These individuals are treated with lifelong weekly infusions of human plasma-derived AAT. An increasing amount of evidence appears to suggest that AAT possesses not only the ability to inhibit serine proteases, such as elastase and proteinase-3 (PR-3), but also to exert antiinflammatory and tissue-protective effects independent of protease inhibition. AAT modifies dendritic cell maturation and promotes T regulatory cell differentiation, induces interleukin (IL)-1 receptor antagonist and IL-10 release, protects various cell types from cell death, inhibits caspases-1 and -3 activity and inhibits IL-1 production and activity. Importantly, unlike classic immunosuppressants, AAT allows undeterred isolated T-lymphocyte responses. On the basis of preclinical and clinical studies, AAT therapy for nondeficient individuals may interfere with disease progression in type 1 and type 2 diabetes, acute myocardial infarction, rheumatoid arthritis, inflammatory bowel disease, cystic fibrosis, transplant rejection, graft versus host disease and multiple sclerosis. AAT also appears to be antibacterial and an inhibitor of viral infections, such as influenza and human immunodeficiency virus (HIV), and is currently evaluated in clinical trials for type 1 diabetes, cystic fibrosis and graft versus host disease. Thus, AAT therapy appears to have advanced from replacement therapy, to a safe and potential treatment for a broad spectrum of inflammatory and immune-mediated diseases.

Phenocopies in families with essential tremor and restless legs syndrome challenge Mendelian laws. Epigenetics might provide answers

Essential Tremor (ET) and Restless Legs Syndrome (RLS) are both highly heritable neurological disorders. The frequent occurrence of multi-incident families suggests the existence of highly penetrant alleles. However, linkage analyses and positional cloning approaches performed within the last 10 years essentially failed to identify responsible mutations. Several loci were found, but their relevance was questioned given the occurrence of suspected phenocopies in many of those families. Remarkably, in some ET and RLS families with an apparent autosomal dominant mode of transmission, the proportion of affected individuals was higher than the expected 50% and therefore suggests a non-mendelian inheritance in some cases. In fact, there is increasing evidence that epigenetic modifications, which refer to changes in gene expression without changes in DNA sequence, can be transmitted to the next generation. Moreover, epigenetic information can be transferred from one allele of a gene to the other allele of the same gene; if then inherited to the next generation, the offspring consequently presents phenotypic properties related to the untransmitted allele. This phenomenon known as paramutation is well documented in plants and has recently been shown to occur also in mammals. Here, I explore the possibility that it is the epigenetic and not only the genetic state which confers disease risk in families. Inheritance of epigenetic mutations along with paramutational events have the potential to explain the non-mendelian features in the genetics of both diseases.

Abstract 3673: Molecular analysis of pheochromocytoma after maternal transmission of SDHD mutation elucidates mechanism of parent-of-origin effect.

Abstract In SDHD mutation families, paragangliomas and pheochromocytomas usually occur only after paternal transmission of the mutation. This important but unexplained parent-of-origin effect is not due to imprinting of SDHD itself, as was initially suspected, since SDHD is biallelically expressed in several tissues. In clinically affected individuals who possess a paternally inherited SDHD mutation, there is loss of the entire maternal chromosome 11 in tumour DNA, implying that tumorigenesis requires loss of not only maternal (wild type) SDHD but also a further, imprinted, tumor suppressor gene (TSG). We report the second case of an SDHD-related tumor (a pheochromocytoma in a 33 year old woman possessing the common pathogenic mutation, p.Pro81Leu) occurring after maternal transmission. It is the first reported investigation of tumor DNA in this situation. Tumor DNA revealed loss of heterozygosity (LOH) at paternal 11q23 causing loss of the wild-type SDHD allele and also LOH affecting maternal 11p15, including H19. These two LOH regions were separated by a region exhibiting clearly retained heterozygosity, containing SDHAF2 (a recently reported paraganglioma TSG), which therefore appears uninvolved here. This case provides strong molecular evidence that the tumorigenic requirement for maternal 11p15 loss (in addition to inactivation of both SDHD alleles) drives the observed parent-of-origin effect. Thus, SDHD-related tumorigenesis most likely involves a “three-hit” mechanism that includes (as one of the hits) loss of an imprinted (paternally silenced and maternally active) TSG from chromosome 11, such as H19). Tumor formation more commonly results from paternal inheritance of SDHD mutations, as the necessary loss of both the wild type SDHD allele and maternal 11p15 can then occur by a single event (loss of maternal chromosome 11). These findings have important implications regarding the clinical management of carriers of maternally inherited SDHD mutations, who we confirm can develop pheochromocytomas, and the understanding of the parent-of-origin effect. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3673. doi:1538-7445.AM2012-3673

ELOVL4 protein preferentially elongates 20:5n3 to very long chain PUFAs over 20:4n6 and 22:6n3

We hypothesized that reduction/loss of very long chain PUFAs (VLC-PUFAs) due to mutations in the ELOngase of very long chain fatty acid-4 (ELOVL4) protein contributes to retinal degeneration in autosomal dominant Stargardt-like macular dystrophy (STGD3) and age-related macular degeneration; hence, increasing VLC-PUFA in the retina of these patients could provide some therapeutic benefits. Thus, we tested the efficiency of elongation of C20-C22 PUFA by the ELOVL4 protein to determine which substrates are the best precursors for biosynthesis of VLC-PUFA. The ELOVL4 protein was expressed in pheochromocytoma cells, while green fluorescent protein-expressing and nontransduced cells served as controls. The cells were treated with 20:5n3, 22:6n3, and 20:4n6, either individually or in equal combinations. Both transduced and control cells internalized and elongated the supplemented FAs to C22-C26 precursors. Only ELOVL4-expressing cells synthesized C28-C38 VLC-PUFA from these precursors. In general, 20:5n3 was more efficiently elongated to VLC-PUFA in the ELOVL4-expressing cells, regardless of whether it was in combination with 22:6n3 or with 20:4n6. In each FA treatment group, C34 and C36 VLC-PUFAs were the predominant VLC-PUFAs in the ELOVL4-expressing cells. In summary, 20:5n3, followed by 20:4n6, seems to be the best precursor for boosting the synthesis of VLC-PUFA by ELOVL4 protein.

P2-13-02: Parent of Origin of BRCA Mutation May Determine Age at Breast Cancer Diagnosis.

Abstract Background: Genetic diseases may display parent-of-origin effects. In such cases, the risk depends on the specific parent or origin allele. Imprinting effect is evident in autosomal dominant hereditary paraganglioma leads to tumors only if inherited from paternal germline. Cancer penetrance in mutations carriers may be determined by the parent origin of BRCA mutation. Methods: From 2007–2010 we analyzed 1889 consecutive (136 ovarian + 1753 breast) breast (BrCa) or ovarian cancer (OvCa) patients presenting for treatment at our outpatient facility. In 130 patients with BRCA 1 or 2 mutations the parent of origin for the mutation was known. Of the 130 patients 2 had both BRCA1 and BRCA2 mutated paternally inherited and were excluded from this analysis. Of the breast cancer patients: 28 patients had paternal and 29 had maternal BRCA1 mutations, 24 had paternal and 21 had maternal BRCA 2 mutations. Of the ovarian cancer patients 6 had paternal and 10 had maternal BRCA1 mutations, 7 had paternal and 3 had maternal BRCA2 mutations. In carriers of BRCA mutations the mean age at diagnosis for ovarian cancer was 51 (range 21–70) and for breast cancer was 43 (range 24–78). Two-sample t-test was used to compare the mean age at diagnosis in patients with BRCA 1 or 2 mutations of paternal or maternal inheritance. For breast cancer maternal allele versus paternal allele 2-sample t-test and p-value were compared for the age at first diagnosis. For breast cancer patients BRCA1 maternal inheritance (mean+SD yrs) 45.73+11.22 versus paternal inheritance 38.04+7.14 2-sample t-test p-value p&amp;lt;0.0020. For breast cancer BRCA2 maternal inheritance (mean+SD yrs) 50.65+10.44 versus paternal inheritance 41.68+6.16, 2-sample t-test p-value p&amp;lt;0.0008. Results: Significantly younger age at breast cancer diagnosis was observed in paternal vs. maternal inheritance of BRCA1 mutation (38 vs 46, respectively, p&amp;lt;0.0020) and BRCA2 mutation (42 vs 51 respectively, p&amp;lt;0.0008). There was no significant difference between paternal and maternal age of ovarian cancer diagnosis of BRCA1 (p&amp;lt;0.1415) or BRCA2 mutation (p&amp;lt;0.3470). Conclusion: The restrospective nature of the study may introduce ascertainment bias. However, the breast and ovarian cancers cases in BRCA1 &amp; 2 carriers with maternal or paternal inheritance mirror the Mendelian autosomal dominant pattern in our unselected consecutive cohort of patients. Maternal and paternal inherited BRCA alleles may not be exchangeable. Women with paternally inherited mutations in BRCA gene mutations develop breast cancer at younger age compared with women who inherit the gene mutations from their mothers. In this small sample, clear differences at age of cancer diagnosis are apparent in paternal inheritance of BRCA gene mutation. If this observation duplicates in larger cohorts results will have important implications for recommendation of surgical risk reduction in BRCA mutation carriers. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-13-02.

Digenic Inheritance of Mutations in the Coproporphyrinogen Oxidase and Protoporphyrinogen Oxidase Genes in a Unique Type of Porphyria

The simultaneous dysfunction of two enzymes within the heme biosynthetic pathway in a single patient is rare. Not more than 15 cases have been reported. A woman with a transient episode of severe photosensitivity showed a biochemical porphyrin profile suggestive of hereditary coproporphyria (HCP), whereas some of her relatives had a profile that was suggestive of variegate porphyria (VP). HCP and VP result from a partial enzymatic deficiency of coproporphyrinogen oxidase (CPOX) and protoporphyrinogen oxidase (PPOX), respectively. DNA analysis in the index patient revealed mutations in both the CPOX and PPOX genes, designated as c.557-15C>G and c.1289dupT, respectively. The CPOX mutation leads to a cryptic splice site resulting in retention of 14 nucleotides from intron 1 in the mRNA transcript. Both mutations encode null alleles and were associated with nonsense-mediated mRNA decay. Given the digenic inheritance of these null mutations, coupled with the fact that both HCP and VP can manifest with life-threatening acute neurovisceral attacks, the unusual aspect of this case is a relatively mild clinical phenotype restricted to dermal photosensitivity.