De novo and biallelic DEAF1 variants cause a phenotypic spectrum.

PURPOSE: To investigate the effect of different DEAF1 variants on the phenotype of patients with autosomal dominant and recessive inheritance patterns and on DEAF1 activity in vitro. METHODS: We assembled a cohort of 23 patients with de novo and biallelic DEAF1 variants, described the genotype-phenotype correlation, and investigated the differential effect of de novo and recessive variants on transcription assays using DEAF1 and Eif4g3 promoter luciferase constructs. RESULTS: The proportion of the most prevalent phenotypic features, including intellectual disability, speech delay, motor delay, autism, sleep disturbances, and a high pain threshold, were not significantly different in patients with biallelic and pathogenic de novo DEAF1 variants. However, microcephaly was exclusively observed in patients with recessive variants (p < 0.0001). CONCLUSION: We propose that different variants in the DEAF1 gene result in a phenotypic spectrum centered around neurodevelopmental delay. While a pathogenic de novo dominant variant would also incapacitate the product of the wild-type allele and result in a dominant-negative effect, a combination of two recessive variants would result in a partial loss of function. Because the clinical picture can be nonspecific, detailed phenotype information, segregation, and functional analysis are fundamental to determine the pathogenicity of novel variants and to improve the care of these patients.

Cerebrofaciothoracic dysplasia: Four new patients with a recurrent TMCO1 pathogenic variant.

Biallelic loss of function variants in the TMCO1 gene have been previously demonstrated to result in cerebrofaciothoracic dysplasia (CFTD; MIM #213980). The phenotype of this condition includes severe intellectual disability, as well as distinctive craniofacial features, including brachycephaly, synophrys, arched eyebrows, "cupid's bow" upper lip, and microdontia. In addition, nonspecific skeletal anomalies are common, including bifid ribs, scoliosis, and spinal fusion. Only 19 molecularly confirmed patients have been previously described. Here, we present four patients with CFTD, including three brothers from a Pakistani background and an additional unrelated white Scottish patient. All share the characteristic craniofacial appearance, with severe intellectual disability and skeletal abnormalities. We further define the phenotype with comparison to the published literature, and present images to define the dysmorphic features in a previously unreported ethnic group. All of our patient series are homozygous for the same c.292_293del (p.Ser98*) TMCO1 pathogenic variant, which has been previously reported only in an isolated Amish population. Thus we provide evidence that CFTD may be more common than previously thought. The patients presented here further delineate the phenotypic spectrum of CFTD and provide evidence for a recurrent pathogenic variant in TMCO1.

Genome-wide association study of sporadic brain arteriovenous malformations.

BACKGROUND: The pathogenesis of sporadic brain arteriovenous malformations (BAVMs) remains unknown, but studies suggest a genetic component. We estimated the heritability of sporadic BAVM and performed a genome-wide association study (GWAS) to investigate association of common single nucleotide polymorphisms (SNPs) with risk of sporadic BAVM in the international, multicentre Genetics of Arteriovenous Malformation (GEN-AVM) consortium. METHODS: The Caucasian discovery cohort included 515 BAVM cases and 1191 controls genotyped using Affymetrix genome-wide SNP arrays. Genotype data were imputed to 1000 Genomes Project data, and well-imputed SNPs (>0.01 minor allele frequency) were analysed for association with BAVM. 57 top BAVM-associated SNPs (51 SNPs with p<10(-05) or p<10(-04) in candidate pathway genes, and 6 candidate BAVM SNPs) were tested in a replication cohort including 608 BAVM cases and 744 controls. RESULTS: The estimated heritability of BAVM was 17.6% (SE 8.9%, age and sex-adjusted p=0.015). None of the SNPs were significantly associated with BAVM in the replication cohort after correction for multiple testing. 6 SNPs had a nominal p<0.1 in the replication cohort and map to introns in EGFEM1P, SP4 and CDKAL1 or near JAG1 and BNC2. Of the 6 candidate SNPs, 2 in ACVRL1 and MMP3 had a nominal p<0.05 in the replication cohort. CONCLUSIONS: We performed the first GWAS of sporadic BAVM in the largest BAVM cohort assembled to date. No GWAS SNPs were replicated, suggesting that common SNPs do not contribute strongly to BAVM susceptibility. However, heritability estimates suggest a modest but significant genetic contribution.

Functionally distinct groups of inherited PTEN mutations in autism and tumour syndromes.

BACKGROUND: Germline mutations in the phosphatase PTEN are associated with diverse human pathologies, including tumour susceptibility, developmental abnormalities and autism, but any genotype-phenotype relationships are poorly understood. METHODS: We have studied the functional consequences of seven PTEN mutations identified in patients diagnosed with autism and macrocephaly and five mutations from severe tumour bearing sufferers of PTEN hamartoma tumour syndrome (PHTS). RESULTS: All seven autism-associated PTEN mutants investigated retained the ability to suppress cellular AKT signalling, although five were highly unstable. Observed effects on AKT also correlated with the ability to suppress soma size and the length and density of dendritic spines in primary neurons. Conversely, all five PTEN mutations from severe cases of PHTS appeared to directly and strongly disrupt the ability to inhibit AKT signalling. CONCLUSIONS: Our work implies that alleles causing incomplete loss of PTEN function are more commonly linked to autism than to severe PHTS cases.

Lifestyle changes in women at genetic risk of breast cancer: an observational study.

BACKGROUND: Lifestyle influences breast cancer risk. Women at increased familial risk may benefit from modifying behaviour, but it is not known to what extent they do so. PURPOSE: This study aims to measure changes that UK (Scottish) women make in response to increased familial risk of breast cancer and attitudes to a risk-reduction trial. METHODS: A questionnaire, completed by 140 "breast cancer family" clinic patients, generated data on habitual diet, alcohol consumption and exercise, changes made after learning of breast cancer risk and attitudes to possible further changes. Subgroups of patients were defined by criteria likely to influence changes in behaviour. Between-group differences were analysed by Fisher's exact test and overall correlations by linear regression. RESULTS: Thirty-six subjects (26 %) reported no behavioural change but, overall, around 25 % of diet, exercise and alcohol items had been changed. Women perceiving their lifetime cancer risk to be high (>50 %) and those who were obese (BMI >25) had made significantly more changes than others. Younger women (<40 years) and those with daughters had made fewer changes. Almost all suggested elements of a risk-reduction trial were strongly supported. CONCLUSIONS: Scottish women at increased risk of breast cancer have scope for protective changes in lifestyle and support a risk-reduction trial. The needs of younger women and of those with daughters should be addressed in its design.

Pathogenicity and Penetrance of Germline SDHA Variants in Pheochromocytoma and Paraganglioma (PPGL).

Germline SDHA mutations are reported in a minority of pheochromocytoma/paraganglioma (PPGL) cases but are associated with an increased risk of malignancy, leading some to advocate cascade genetic testing and surveillance screening of "at-risk" first-degree relatives. However, such approaches rely on accurate estimates of variant pathogenicity and disease penetrance, which may have been subject to ascertainment and reporting biases, although the recent provision of large population-based DNA sequence data sets may provide a potentially unbiased resource to aid variant interpretation. Thus, the aim of the current study was to evaluate the pathogenicity and penetrance of SDHA variants reported in literature-based PPGL cases by comparing their frequency to those occurring in the Genome Aggregation Database (GnomAD) data set, which provides high-quality DNA sequence data on 138,632 individuals. In total, 39 different missense or loss-of-function (LOF) SDHA variants were identified in 95 PPGL index cases. Notably, many of the PPGL-associated SDHA alleles were observed at an unexpectedly high frequency in the GnomAD cohort, with ~1% and ~0.1% of the background population harboring a rare missense or LOF variant, respectively. Although the pathogenicity of several SDHA alleles was supported by significant enrichment in PPGL cases relative to GnomAD controls, calculations of disease penetrance based on allele frequencies in the respective cohorts resulted in much lower estimates than previously reported, ranging from 0.1% to 4.9%. Thus, although this study provides support for the etiological role of SDHA in PPGL formation, it suggests that most variant carriers will not manifest PPGLs and are unlikely to benefit from periodic surveillance screening.

Assessing the effectiveness of NICE criteria for stratifying breast cancer risk in a UK cohort.

Breast cancer risk is a common indication for referral to clinical genetics services. UK National Institute of Health and Care Excellence (NICE) guidelines use family history (FH) to stratify by 10-year risk of breast cancer from age 40. Patients are stratified into population risk (PR, 10-year risk <3%), moderate (MR, 3-8%) and high risk (HR, >8%). Women at increased risk are offered screening at or prior to age 40. To assess the clinical effectiveness of current risk stratification, FH data were obtained for all unaffected women with a FH of breast cancer aged <50, referred to cancer genetics from 2000-2010. Patients were risk stratified by NICE criteria, identifying patients who subsequently developed breast cancer. A total of 1409 women had 15,414 patient years of follow-up. Thirty invasive breast cancers developed, 13 in MR and 13 in HR women. Kaplan-Meier analysis demonstrated no significant difference in the rate of breast cancer development between PR and MR women from ages 40 to 49 (Log rank p = 0.431). There was a significant difference between ages 40 and 49 years between PR and HR women (p = 0.036), but not on exclusion of BRCA mutation carriers (p = 0.136). NICE absolute 10-year risk thresholds between ages 40 and 49 were not met in any risk group, when risk was estimated using the guidelines (PR = 0.82%, MR = 1.68%, HR = 3.56%). Our data suggest that improved criteria are required for risk assessment prior to age 50 and screening resources may be best focussed on those with highly penetrant mutations in cancer risk genes.

Utility of Population-Level DNA Sequence Data in the Diagnosis of Hereditary Endocrine Disease.

CONTEXT: Genetic testing is increasingly used for clinical diagnosis, although variant interpretation presents a major challenge because of high background rates of rare coding-region variation, which may contribute to inaccurate estimates of variant pathogenicity and disease penetrance. OBJECTIVE: To use the Exome Aggregation Consortium (ExAC) data set to determine the background population frequencies of rare germline coding-region variants in genes associated with hereditary endocrine disease and to evaluate the clinical utility of these data. DESIGN SETTING PARTICIPANTS: Cumulative frequencies of rare nonsynonymous single-nucleotide variants were established for 38 endocrine disease genes in 60,706 unrelated control individuals. The utility of gene-level and variant-level metrics of tolerability was assessed, and the pathogenicity and penetrance of germline variants previously associated with endocrine disease evaluated. RESULTS: The frequency of rare coding-region variants differed markedly between genes and was correlated with the degree of evolutionary conservation. Genes associated with dominant monogenic endocrine disorders typically harbored fewer rare missense and/or loss-of-function variants than expected. In silico variant prediction tools demonstrated low clinical specificity. The frequency of several endocrine disease‒associated variants in the ExAC cohort far exceeded estimates of disease prevalence, indicating either misclassification or overestimation of disease penetrance. Finally, we illustrate how rare variant frequencies may be used to anticipate expected rates of background rare variation when performing disease-targeted genetic testing. CONCLUSIONS: Quantifying the frequency and spectrum of rare variation using population-level sequence data facilitates improved estimates of variant pathogenicity and penetrance and should be incorporated into the clinical decision-making algorithm when undertaking genetic testing.

Attenuated familial adenomatous polyposis manifests as autosomal dominant late-onset colorectal cancer.

Colorectal cancer (CRC) risk is well defined for families of patients with classical familial adenomatous polyposis (FAP). However, the risk for those with an attenuated form of FAP is less well characterised. In this study, we estimated CRC risks for carriers of a novel germline mutation in the APC gene that causes attenuated FAP (AFAP). We performed genetic testing on 53 individuals from seven AFAP families harbouring an identical APC:c.288T>A mutation. Using a modified segregation analysis, we estimated relative and absolute CRC risks for mutation carriers. Twenty-three individuals harboured the disease causing mutation. CRC occurred in 28 individuals (mean 61.7 years, range 32-80 years). The estimated CRC relative risks for mutation carriers aged 60-69 and ≥70 years were 19 (95% CI: 1.77-204.08) and 45 (95% CI: 11.32-180.10), respectively, while the absolute CRC lifetime risk for men was 94% (95% CI: 67.5-99.9%), and for women, 84% (95% CI: 50.9-99.0%). This study shows that AFAP can manifest as autosomal dominant late-onset CRC. These findings highlight a subgroup of inherited CRCs that require new criteria for identification and surveillance.

Germline FH mutations presenting with pheochromocytoma.

CONTEXT: At least a third of the patients with pheochromocytoma (PCC) or paraganglioma (PGL) harbor an underlying germline mutation in a known PCC/PGL gene. Mutations in genes (SDHB, SDHD, SDHC, and SDHA) encoding a component of the tricarboxylic acid cycle, succinate dehydrogenase (SDH), are a major cause of inherited PCC and PGL. SDHB mutations are also, albeit less frequently, associated with inherited renal cell carcinoma. Inactivation of SDH and another tricarboxylic acid cycle component, fumarate hydratase (FH), have both been associated with abnormalities of cellular metabolism, responsible for the activation of hypoxic gene response pathways and epigenetic alterations (eg, DNA methylation). However, the clinical phenotype of germline mutations in SDHx genes and FH is usually distinct, with FH mutations classically associated with hereditary cutaneous and uterine leiomyomatosis and renal cell carcinoma, although recently an association with PCC/PGL has been reported. OBJECTIVE AND DESIGN: To identify potential novel PCC/PGL predisposition genes, we initially undertook exome resequencing studies in a case of childhood PCC, and subsequently FH mutation analysis in a further 71 patients with PCC, PGL, or head and neck PGL. RESULTS: After identifying a candidate FH missense mutation in the exome study, we then detected a further candidate missense mutation (p.Glu53Lys) by candidate gene sequencing. In vitro analyses demonstrated that both missense mutations (p.Cys434Tyr and p.Glu53Lys) were catalytically inactive. CONCLUSIONS: These findings 1) confirm that germline FH mutations may present, albeit rarely with PCC or PGL; and 2) extend the clinical phenotype associated with FH mutations to pediatric PCC.

EXOSC3 mutations in pontocerebellar hypoplasia type 1: novel mutations and genotype-phenotype correlations.

BACKGROUND: Pontocerebellar hypoplasia (PCH) represents a group of neurodegenerative disorders with prenatal onset. Eight subtypes have been described thus far (PCH1-8) based on clinical and genetic features. Common characteristics include hypoplasia and atrophy of the cerebellum, variable pontine atrophy, and severe mental and motor impairments. PCH1 is distinctly characterized by the combination with degeneration of spinal motor neurons. Recently, mutations in the exosome component 3 gene (EXOSC3) have been identified in approximately half of the patients with PCH subtype 1. METHODS: We selected a cohort of 99 PCH patients (90 families) tested negative for mutations in the TSEN genes, RARS2, VRK1 and CASK. Patients in this cohort were referred with a tentative diagnose PCH type 1, 2, 4, 7 or unclassified PCH. Genetic analysis of the EXOSC3 gene was performed using Sanger sequencing. Clinical data, MR images and autopsy reports of patients positive for EXOSC3 mutations were analyzed. RESULTS: EXOSC3 mutations were found in twelve families with PCH subtype 1, and were not found in patients with other PCH subtypes. Identified mutations included a large deletion, nonsense and missense mutations. Examination of clinical data reveals a prolonged disease course in patients with a homozygous p.D132A mutation. MRI shows variable pontine hypoplasia in EXOSC3 mediated PCH, where the pons is largely preserved in patients with a homozygous p.D132A mutation, but attenuated in patients with other mutations. Additionally, bilateral cerebellar cysts were found in patients compound heterozygous for a p.D132A mutation and a nonsense allele. CONCLUSIONS: EXOSC3 mediated PCH shows clear genotype-phenotype correlations. A homozygous p.D132A mutation leads to PCH with possible survival into early puberty, and preservation of the pons. Compound heterozygosity for a p.D132A mutation and a nonsense or p.Y109N allele, a homozygous p.G31A mutation or a p.G135E mutation causes a more rapidly progressive course leading to death in infancy and attenuation of the ventral pons.Our findings imply a clear correlation between genetic mutation and clinical outcome in EXOSC3 mediated PCH, including variable involvement of the pons.

FGFR2 protein expression in breast cancer: nuclear localisation and correlation with patient genotype.

BACKGROUND: Single Nucleotide Polymorphisms (SNPs) in intron 2 of the Fibroblast Growth Factor Receptor Type 2 (FGFR2) gene, including rs2981582, contribute to multifactorial breast cancer susceptibility. The high risk polymorphism haplotype in the FGFR2 gene has been associated with increased mRNA transcription and altered transcription factor binding but the effect on FGFR2 protein expression is unknown. 40 breast tumours were identified from individuals with known rs2981582 genotype. Tumour sections were stained for FGFR2 protein expression, and scored for nuclear and cytoplasmic staining in tumour and surrounding normal tissue. FINDINGS: FGFR2 immunohistochemistry demonstrated variable nuclear staining in normal tissue and tumour tissue, as well as consistent cytoplasmic staining. We did not find an association between nuclear staining for FGFR2 and genotype, and there was no association between FGFR2 staining and estrogen or progestogen receptor status. There was an association between presence of nuclear staining for FGFR2 in normal tissue and presence of nuclear staining in the adjacent tumour (Fishers exact test, p = 0.002). CONCLUSIONS: Variable nuclear staining for FGFR2 in breast cancer, but an absence of correlation with rs2981582 genotype suggests that the mechanism of action of polymorphisms at the FGFR2 locus may be more complex than a direct effect on mRNA expression levels in the final cancer. The effect may relate to FGFR2 function or localisation during breast development or tumourigenesis. Nuclear localisation of FGFR2 suggests an important additional role for this protein in breast development and breast cancer, in addition to its function as a classical cell surface receptor.

Human retroviral gag- and gag-pol-like proteins interact with the transforming growth factor-beta receptor activin receptor-like kinase 1.

Mutations in activin receptor-like kinase 1 (ALK1), a transforming growth factor (TGF)-beta type I receptor, lead to the vascular disorder hereditary hemorrhagic telangiectasia caused by abnormal vascular remodeling. The underlying molecular cause of this disease is not well understood. Identifying binding partners for ALK1 will help to understand its cellular function. Using the two-hybrid system, we identified an ALK1-binding protein encoded by an ancient retroviral/retrotransposon element integrated as a single copy gene known as PEG10 on human chromosome 7q21. PEG10 contains two overlapping reading frames from which two proteins, PEG10-RF1 and PEG10-RF1/2, are translated by a typical retroviral -1 ribosomal frameshift mechanism. Reverse transcription-PCR and Northern blot analysis showed a broad range of PEG10 expression in different tissues and cell types, i.e. human placenta, brain, kidney, endothelial cells, lymphoblasts, and HepG2 and HEK293 cells. However, endogenous PEG10-RF1 and PEG10-RF1/2 proteins were only detected in HepG2 and HEK293 cells. PEG10-RF1, which is the major PEG10 protein product, represents a gag-like protein, and PEG10-RF1/2 represents a gag-pol-like protein. PEG10-RF1 also interacts with different members of TGF-beta superfamily type I and II receptors. PEG10-RF1 binding to ALK1 is mediated by a 200-amino acid domain with no recognized motif. PEG10-RF1 inhibits ALK1 as well as ALK5 signaling. Co-expression of ALK1 and PEG10-RF1 in different cell types induced morphological changes reminiscent of neuronal cells or sprouting cells. This is the first report of a human retroviral-like protein interacting with members of the TGF-beta receptor family.