[Genetic counselling and testing in pulmonary arterial hypertension - A consensus statement on behalf of the International Consortium for Genetic Studies in PAH - French version]. / Conseil génétique et dépistage de l'hypertension artérielle pulmonaire ­ consensus du Consortium international pour les études génétiques dans l'HTAP ­ version française.

Pulmonary arterial hypertension (PAH) is a rare disease that can be caused by (likely) pathogenic germline genomic variants. In addition to the most prevalent disease gene, BMPR2 (bone morphogenetic protein receptor 2), several genes, some belonging to distinct functional classes, are also now known to predispose to the development of PAH. As a consequence, specialist and non-specialist clinicians and healthcare professionals are increasingly faced with a range of questions regarding the need for, approaches to and benefits/risks of genetic testing for PAH patients and/or related family members. We provide a consensus-based approach to recommendations for genetic counselling and assessment of current best practice for disease gene testing. We provide a framework and the type of information to be provided to patients and relatives through the process of genetic counselling, and describe the presently known disease causal genes to be analysed. Benefits of including molecular genetic testing within the management protocol of patients with PAH include the identification of individuals misclassified by other diagnostic approaches, the optimisation of phenotypic characterisation for aggregation of outcome data, including in clinical trials, and importantly through cascade screening, the detection of healthy causal variant carriers, to whom regular assessment should be offered.

Somatic mutational landscape of extracranial arteriovenous malformations and phenotypic correlations.

BACKGROUND: Somatic genetic variants may be the cause of extracranial arteriovenous malformations, but few studies have explored these genetic anomalies, and no genotype-phenotype correlations have been identified. OBJECTIVES: The aim of the study was to characterize the somatic genetic landscape of extracranial arteriovenous malformations and correlate these findings with the phenotypic characteristics of these lesions. METHODS: This study included twenty-three patients with extracranial arteriovenous malformations that were confirmed clinically and treated by surgical resection, and for whom frozen tissue samples were available. Targeted next-generation sequencing analysis of tissues was performed using a gene panel that included vascular disease-related genes and tumour-related genes. RESULTS: We identified a pathogenic variant in 18 out of 23 samples (78.3%). Pathogenic variants were mainly located in MAP2K1 (n = 7) and KRAS (n = 6), and more rarely in BRAF (n = 2) and RASA1 (n = 3). KRAS variants were significantly (P < 0.005) associated with severe extended facial arteriovenous malformations, for which relapse after surgical resection is frequently observed, while MAP2K1 variants were significantly (P < 0.005) associated with less severe, limited arteriovenous malformations located on the lips. CONCLUSIONS: Our study highlights a high prevalence of pathogenic somatic variants, predominantly in MAP2K1 and KRAS, in extracranial arteriovenous malformations. In addition, our study identifies for the first time a correlation between the genotype, clinical severity and angiographic characteristics of extracranial arteriovenous malformations. The RAS/MAPK variants identified in this study are known to be associated with malignant tumours for which targeted therapies have already been developed. Thus, identification of these somatic variants could lead to new therapeutic options to improve the management of patients with extracranial arteriovenous malformations.

Lack of referral for genetic counseling and testing in BRCA1/2 and Lynch syndromes: a nationwide study based on 240,134 consultations and 134,652 genetic tests.

Based on nationwide data from the French national cancer institute (INCa), we analyzed the evolution of cancer genetics consultations and testing over time, and the uptake of targeted tests in relatives of families with BRCA1/2 or MMR genes mutation. Genetic testing and consultations for familial high-risk individuals are exclusively funded and monitored by the INCa in France. All nationwide cancer genetics centers reported annually standardized parameters of activity from 2003 to 2011. The analysis included a total of 240,134 consultations and 134,652 genetic tests enabling to identify 32,494 mutation carriers. Referral for hereditary breast and ovarian cancer (HBOC) or colorectal cancer predisposition syndromes represented 59 % (141,639) and 23.2 % (55,698) consultations, respectively. From 2003 to 2011, we found a dramatic and steady increase of tests performed for BRCA1/2 (from 2,095 to 7,393 tests/year, P < 0.0001) but not for MMR genes (from 1,144 to 1,635/year, P = NS). The overall percentage of deleterious mutations identified in the probands tested was 13.8 and 20.9 % in HBOC and Lynch syndromes, respectively. Pooled analysis for BRCA1/2 and Lynch syndrome tests showed an inverse relationship between the percentage of mutation detected and the absolute number of tests performed over the time (overall Cochran-Armitage test for trend: P < 0.001). In families with BRCA1/2 or MMR identified mutations, there was an average number of 2.94 and 3.28 relatives performing targeted tests, respectively. This nationwide study shows a lack of referral and genetic testing in Lynch as compared to HBOC syndromes. Only a third of relatives of a proband with a predisposing mutation performed a targeted test. Enhanced information about benefit of genetic testing should be given to clinicians and patients for Lynch syndrome and relatives of a proband carrying an identified predisposing mutation.

Germline RAD51C mutations in ovarian cancer susceptibility.

Several genes might explain BRCA1/2 negative breast and ovarian family cases. Deleterious mutations in few genes involved in the Fanconi complex are responsible for Fanconi anemia at the homozygous state and breast cancer (BC) susceptibility at the heterozygous state (BRCA2, PALB2, BRIP1). RAD51C plays an important role in the double-strand break repair pathway and a biallelic missense mutation in the RAD51C gene was found in a Fanconi anemia-like disorder. Subsequently, six monoallelic pathogenic mutations were identified after screening 480 BRCA1/2 negative breast and ovarian cancer (BC/OC) pedigrees. Several reports were unsuccessful to replicate these results. To investigate whether germline mutations in RAD51C are associated with an increased risk of developing BC/OC, we screened, by Sanger sequencing of the coding sequence, 117 index cases of breast and ovarian families from French or European origin, and negative for BRCA1/2 mutations. In our study, we found 3 pathogenic mutations among 117 families screened which corresponds to a 2.6% frequency. Our results confirm that RAD51C is a susceptibility gene for ovarian and BC and that this gene should be screened for mutations in families with multiple BC/OC.

[Medical care of brain malformative vascular diseases discovered during the pre- or neonatal period]. / Prise en charge des malformations vasculaires cérébrales découvertes en période ante- ou néonatale.

Three types of brain arteriovenous vascular malformations can be found during the neonatal period, according to their anatomical location. Vein of Galen malformations are the most common. The others are pial arteriovenous malformations or dural arteriovenous malformations, which include dural sinus malformations. They can be asymptomatic, but most often they are associated with different symptoms, related to their angioarchitecture or their effect on the brain. High-flow arteriovenous malformations can thus be responsible for heart failure. Local or regional venous hyperpressure exposes the patient to subacute or chronic brain lesions, or to hydrovenous disorders such as hydrocephalus. Some types of venous reflux can expose patients to brain hemorrhage. The treatment chosen for these vascular malformations and their consequences is transarterial or transvenous embolization, depending on the angioarchitecture and type of lesion. The schedule for the treatment will be determined according to the malformation type and its local or general effects on the brain. The aim of this article is to present the recommendations of the French National Referral Center for neurovascular malformations in children, in order to help clinicians and radiologists treat these patients during pre- or neonatal period.

Molecular genetics and clinical features of Chinese idiopathic and heritable pulmonary arterial hypertension patients.

Mutations of the bone morphogenetic protein type II receptor (BMPR2) gene predispose to pulmonary arterial hypertension (PAH). 290 idiopathic (I)PAH patients and 15 heritable (H)PAH were screened to determine the spectrum and rate of BMPR2 mutations in a large Chinese patient group. Gene sequencing and multiplex ligation-dependent probe amplification (MLPA®) were used to detect sequence mutations and large rearrangements (RGTs). Total mutation rate was 14.5% (n = 42 out of 290) in Chinese IPAH patients, and 53.3% (n = 8 out of 15) in HPAH patients. RGT mutation rate was 3.1% (n = 7 out of 229) and represented 14% (n = 7 out of 50) of all identified mutations. 25 BMPR2 mutations were newly identified. Patients in this study were younger than other reported PAH subjects. BMPR2 mutation carriers were ~6 yrs younger at diagnosis than noncarriers (p = 0.002), but this relationship was significant only in the female group, which was larger. The proportion of females carrying a BMPR2 mutation was half that of males (12.8% versus 25.3%; p = 0.008). Our results indicate that the overall genetics of Chinese PAH patients is similar to that of other populations, but the clinical picture differs by the precocity of the disease in the whole patient group, and the lower proportion of females found to carry a BMPR2 mutation.

ACVRL1 germinal mosaic with two mutant alleles in hereditary hemorrhagic telangiectasia associated with pulmonary arterial hypertension.

Germline mutations in genes encoding members of the transforming growth factor-ß (TGF-ß)/bone morphogenetic protein (BMP) superfamily are causal for two hereditary vascular disorders, hereditary hemorrhagic telangiectasia (HHT) and heritable pulmonary arterial hypertension (PAH). When the two diseases coexist, activin A receptor type II-like kinase-1 (ACVRL1) gene mutations are usually identified. We report a remarkable ACVRL1 germinal and somatic mosaicism characterized by the presence of two distinct mutant alleles and a non-mutant ACVRL1 allele in a woman diagnosed with PAH at the age 40. She also met the Curaçao diagnostic criteria for HHT based on additional findings of telangiectases, epistaxis and arteriovenous malformations. Mutation analysis of ACVRL1 identified two adjacent heterozygous deleterious mutations within exon 10: c.1388del (p.Gly463fsX2) and c.1390del (p.Leu464X) in a region enriched by mutation-associated DNA motifs. The mother transmitted the c.1388del to one child and the c.1390del to two children confirming germinal mosaicism. Allele-specific polymerase chain reaction analysis showed that c.1388del is the predominant mutation in lymphocytes of the index case. Haplotype analysis revealed that both mutant alleles have a common chromosomal origin which is distinct from that of the mother's non-mutant ACVRL1 allele. These distinct mutant alleles in tissues and germline could have arisen by DNA structure-mediated events occurring in the early stages of the mother's embryogenesis, prior to the segregation of her germline, which ultimately led to the independent transmission of each allele. These highlight the complexity of genomic events occurring during early embryogenesis and the consequences of mutational mosaicism upon pathogenic variability.

Unexplained polyposis: a challenge for geneticists, pathologists and gastroenterologists.

Two main colorectal polyposis syndromes have been described, familial adenomatous polyposis and MUTYH-associated polyposis syndromes. Some polyposis remains unexplained: 20% of adenomatous polyposis and serrated polyposis. The aim of this study was to evaluate in a cohort of patients with unexplained polyposis whether a genetic defect could be detected. Individuals presenting polyposis with more than 40 adenomas or more than 20 serrated polyps (hyperplastic, sessile serrated and mixed), without causative mutation identified, were included. Complementary explorations on APC or MUTYH were performed: search for APC mosaicism, splicing-affecting mutations, large genomic rearrangement of MUTYH. Four genes of Wnt pathway (AXIN2, PPP2R1B, WIF1, SFRP1) and two genes of transforming growth factor-ß (TGF-ß) pathway (SMAD4, BMPR1A) were screened for germline mutation. Twenty-five patients had an unexplained adenomatous polyposis (familial or sporadic). Five pathogenic mutations were found: four in APC gene (with one case of mosaicism) and one in BMPR1A gene. The exploration of APC mosaicism was better performed from adenoma DNA with high-resolution melting. The screening of the candidate genes did not find any causative mutation. Thirteen individuals had an unexplained serrated polyposis and a frameshift on SMAD4 gene was identified. All mutations were identified in familial cases of polyposis. After new pathological examination, both BMPR1A and SMAD4 cases were found to be associated with a juvenile polyposis while the polyposis was initially described as adenomatous or undetermined. In 17% (6/38) of the patients the causative mutation of the polyposis was identified. Genetic causes were heterogeneous. Sporadic polyposis patients must be considered as potential APC mosaicism. The histological classification of polyposis is strongly important in direct genetic exploration.

Frequent mutation in North African patients with MUTYH-associated polyposis.

MUTYH-associated polyposis (MAP) has been characterized as an autosomal recessive disease predisposing to a variable number of colorectal adenomas with a high risk of cancer. Numerous studies have indicated that two missense mutations (Y179C and G396D) account for about 80% of MUTYH allelic variants in Europeans. Ethnic and geographic differences in the mutation spectrum have been observed. The aim of this study was to report mutations in patients from North Africa, determine the incidence of the c.1227_1228dup mutation in our cohort of MUTYH patients and to evaluate the existence of a founder effect. Within a group of 36 families with MAP, 11 were shown to have a homozygous c.1227_1228dup mutation. These families came from Algeria (n = 5), Tunisia (n = 4), Morocco (n = 1) and Portugal (n = 1). Probands belonging to families of North African origin showed a significantly higher frequency of c.1227_1228dup (78.6% vs 4.5%, p < 0.0001). Haplotype analyses were performed using 10 microsatellite markers surrounding the MUTYH gene spanning a region of 4.4 cM. We identified a common haplotype of at least 1.3 cM in all families suggesting a founder effect for this mutation.

[Modalities for the functionning of a Care Center for women at high risk for breast and ovarian cancers: The French experience of Tenon Hospital]. / Modalités de fonctionnement d'un centre de suivi des femmes à haut risque de cancer du sein et de l'ovaire : une expérience à l'hôpital Tenon.

High risk may be defined as either an absolute risk greater than 20 % or a relative risk greater than 4. Concerning breast and ovarian cancer, high risk patients include carriers of a constitutive deleterious mutation of BRCA1 or BRCA2 genes, patients with a significant family history of breast or ovarian cancer, and patients who have been diagnosed a benign breast lesion with a high risk of degeneration, i.e. atypical hyperplasia. Following up such patients relies on specific strategies. A center including a large panel of physicians involved in the various modalities for patients' management (geneticians, radiologists, gynecologists, plastic surgeons, pathologists, endocrinologists, psychologists, medical oncologists) has been created at Tenon Hospital with this purpose. The collaboration of these different specialists with the referent physician of the patient allows for the definition and the implementation of a patient-centered follow-up continuously updated to take into account the different periods of a woman's life, according to best practices recommendations and the evolving state-of-the art.

[Unexpected in vitro fertilization failure in patients with normal sperm: a proteomic analysis]. / Infertilité masculine chez les patients normospermiques : analyse protéomique des spermes normaux non fécondants en fécondation in vitro classique.

OBJECTIVE: Despite normal sperm parameters, 5% of in vitro fertilization (IVF) attempts result in an unpredictable failure of fertilization. In 56% of the cases, there is no obvious oocyte anomaly, but lack of sperm binding to the zona pellucida. This study aims to contribute to clarify the male molecular causes of failures in IVF, which are undetected by classical sperm analysis. PATIENTS AND METHODS: The spermatic proteomic profiles of patients, with a complete failure of fertilization and no spermatozoa bound to the zona pellucida, is compared to controls (patients with normal fertilization and cleavage rates after a classical IVF for tubal indication). All samples are analysed by 2 Dimensional Electrophoresis-Differential In Gel Electrophoresis (2DE-DIGE) after being divided into three fractions according to their isoelectric point (acid, intermediate and basic). RESULTS: Fourteen proteins differentially expressed between all the cases and all the controls were highlighted. Twelve of these proteins were identified by mass spectrometry (six from the acid fraction and six from the basic fraction). Two of these proteins may have an interest in gametic interaction: the laminin receptor LR67 and the L-xylulose reductase. DISCUSSION AND CONCLUSION: More investigation is needed to understand the involvement of the identified proteins in the IVF fertilization failure of the infertile patients in this study.

The TP53 Arg72Pro and MDM2 309G>T polymorphisms are not associated with breast cancer risk in BRCA1 and BRCA2 mutation carriers.

BACKGROUND: The TP53 pathway, in which TP53 and its negative regulator MDM2 are the central elements, has an important role in carcinogenesis, particularly in BRCA1- and BRCA2-mediated carcinogenesis. A single nucleotide polymorphism (SNP) in the promoter region of MDM2 (309T>G, rs2279744) and a coding SNP of TP53 (Arg72Pro, rs1042522) have been shown to be of functional significance. METHODS: To investigate whether these SNPs modify breast cancer risk for BRCA1 and BRCA2 mutation carriers, we pooled genotype data on the TP53 Arg72Pro SNP in 7011 mutation carriers and on the MDM2 309T>G SNP in 2222 mutation carriers from the Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA). Data were analysed using a Cox proportional hazards model within a retrospective likelihood framework. RESULTS: No association was found between these SNPs and breast cancer risk for BRCA1 (TP53: per-allele hazard ratio (HR)=1.01, 95% confidence interval (CI): 0.93-1.10, P(trend)=0.77; MDM2: HR=0.96, 95%CI: 0.84-1.09, P(trend)=0.54) or for BRCA2 mutation carriers (TP53: HR=0.99, 95%CI: 0.87-1.12, P(trend)=0.83; MDM2: HR=0.98, 95%CI: 0.80-1.21, P(trend)=0.88). We also evaluated the potential combined effects of both SNPs on breast cancer risk, however, none of their combined genotypes showed any evidence of association. CONCLUSION: There was no evidence that TP53 Arg72Pro or MDM2 309T>G, either singly or in combination, influence breast cancer risk in BRCA1 or BRCA2 mutation carriers.

No evidence of the APC D1822V missense variant's pathogenicity in Tunisian patients with sporadic colorectal cancer.

OBJECTIVES: Sporadic colorectal cancer is influenced by numerous single nucleotide polymorphisms (SNPs), each with minor effects on the cancer risk. This study seeks to determine whether there is any association of the I1307K, E1317Q and D1822V variants within the Adenomatous polyposis coli gene (APC) and risk to develop colorectal cancer in Tunisian population. METHODS: Direct sequencing was used to investigate three SNPs in the APC in 48 Tunisian sporadic colorectal cancer cases and 63 controls. RESULTS: There was no statistically significant association between the I1307K, E1317Q and D1822V variants investigated and colorectal cancer risk. CONCLUSION: The lack of association may show that these variants selected for this study are not involved in the colorectal carcinogenic process. Otherwise, the eventual biological effect is so little to go undetected, unless increasing the sample size.

Pulmonary arterial hypertension associated with fenfluramine exposure: report of 109 cases.

The aim of the present study was to describe a large cohort of fenfluramine-associated pulmonary arterial hypertension (fen-PAH) and its possible prognostic markers. The records of all patients with a diagnosis of fen-PAH evaluated at the present authors' centre from 1986-2004 were retrospectively studied. Baseline clinical and haemodynamic data were collected, as well as survival times. The median duration of fenfluramine exposure was 6 months, with a median of 4.5 yrs between exposure and onset of symptoms. Nine (22.5%) out of 40 patients evaluated resulted positive for the presence of germline bone morphogenetic protein receptor (BMPR) type 2 mutations. In these patients, the duration of exposure to fenfluramine was significantly lower than in patients without mutation. The median survival was 6.4 yrs, without significant difference between fen-PAH and a control group of idiopathic and familial pulmonary arterial hypertension patients referred to the present authors' centre during the same time frame and treated identically. Duration of fenfluramine exposure showed no relation to survival, while cardiac index was the only independent predictor of multivariate analysis. Fenfluramine-associated pulmonary arterial hypertension shares clinical, functional, haemodynamic and genetic features with idiopathic pulmonary arterial hypertension, as well as overall survival rates. Therefore, the present authors conclude that fenfluramine exposure characterises a potent trigger for pulmonary arterial hypertension without influencing its clinical course.

Altered endothelial gene expression associated with hereditary haemorrhagic telangiectasia.

BACKGROUND: Mutations in endoglin (ENG) and activin receptor-like kinase 1 (ALK-1 or ACVRL1) genes are the underlying basis of hereditary haemorrhagic telangiectasia (HHT) types 1 and 2, respectively. Both genes belong to the transforming growth factor-beta (TGF-beta) receptors superfamily and are expressed in endothelial cells. The current model for HHT is that ENG or ALK-1 haplo-insufficiency affects angiogenesis and predisposes to vascular dysplasia and arteriovenous malformations. MATERIALS AND METHODS: Using microarray technology, we compared human umbilical vein endothelial cells (HUVEC) from newborns with ENG or ALK-1 mutations to control cells to search for gene profiles associated with early stages of the disease. Real-time polymerase chain reaction and Western blot analysis were used to validate a subset of the modulated genes and functionally related genes. RESULTS: Our results indicate that HHT endothelial cells in vitro display several gene expression disturbances, including genes associated with the activation phase of angiogenesis, with cell guidance and intercellular connections, and also with the TGF-beta pathway. Hierarchical clustering using modulated genes enables discrimination between affected and non-affected samples. CONCLUSION: HHT HUVECs display gene modulations which can suggest that ENG and ALK-1 haplo-insufficiency induces compensatory regulatory mechanisms at the expression levels.

The contribution of germline rearrangements to the spectrum of BRCA2 mutations.

BACKGROUND: Few germline BRCA2 rearrangements have been described compared with the large number of germline rearrangements reported in the BRCA1 gene. However, some BRCA2 rearrangements have been reported in families that included at least one case of male breast cancer. OBJECTIVE: To estimate the contribution of large genomic rearrangements to the spectrum of BRCA2 defects. METHODS: Quantitative multiplex PCR of short fluorescent fragments (QMPSF) was used to screen the BRCA2 gene for germline rearrangements in highly selected families. QMPSF was previously used to detect heterozygous deletions/duplications in many genes including BRCA1 and BRCA2. RESULTS: We selected a subgroup of 194 high risk families with four or more breast cancers with an average age at diagnosis of < or = 50 years, who were recruited through 14 genetic counselling centres in France and one centre in Switzerland. BRCA2 mutations were detected in 18.6% (36 index cases) and BRCA1 mutations in 12.4% (24 index cases) of these families. Of the 134 BRCA1/2 negative index cases in this subgroup, 120 were screened for large rearrangements of BRCA2 using QMPSF. Novel and distinct BRCA2 deletions were detected in three families and their boundaries were determined. We found that genomic rearrangements represent 7.7% (95% confidence interval 0% to 16%) of the BRCA2 mutation spectrum. CONCLUSION: The molecular diagnosis of breast cancer predisposition should include screening for BRCA2 rearrangements, at least in families with a high probability of BRCA2 defects.

Improvement of pCOR plasmid copy number for pharmaceutical applications.

Production of pharmaceutical-grade plasmid DNA is becoming important as the demand for clinical batches is steadily growing. pCOR plasmids have been specifically designed and used for gene delivery into humans, and have been produced by high cell-density fermentation with a yield of 100 mg/l. This yield could probably be increased as long as the release specifications of bulk plasmid remain the same, particularly in terms of plasmid sequence. We report here the use of genetic approaches in Escherichia coli to increase the copy number of pCOR. The bacterial gene encoding the pi initiator-protein, which plays a pivotal role in pCOR replication, was mutagenized. A fluorescence-based screening methodology in E. coli was used to identify novel copy-up mutations. A particular combination of copy-up mutations translated into a 3-5-fold increase in monomer pCOR plasmid DNA per biomass unit.

Endoglin germline mutation in a patient with hereditary haemorrhagic telangiectasia and dexfenfluramine associated pulmonary arterial hypertension.

Dexfenfluramine associated pulmonary arterial hypertension occurring in a patient with hereditary haemorrhagic telangiectasia related to a mutation within the endoglin gene is described. This report highlights the critical role of the TGF-beta signalling pathway in this condition.

No evidence for point mutations of the calcium-sensing receptor in familial idiopathic hypercalciuria.

BACKGROUND: Idiopathic hypercalciuria (IH) is frequently associated with nephrolithiasis. As 40% of patients have a positive familial history of IH, an autosomal dominant mode of inheritance has been suggested. Numerous genes have been studied in this regard but none have been found to be linked to IH. Mutation of the calcium-sensing receptor (CaR) has never been studied. Therefore, we conducted a study to detect such mutations. METHODS: Seven families with IH and nephrolithiasis were recruited in a prospective study. Forty-two family members underwent 24-h urine calcium measurement. Twenty-five of them with 24-h hypercalciuria also underwent extensive metabolic evaluation. Blood samples were collected in one or two affected family members in each family and exons 2-7 of the CaR gene were sequenced. RESULTS: In the seven families, at least one parent and more than half of the children had hypercalciuria (21/30), consistent with autosomal dominant inheritance. Among the nine affected family members whose CaR gene has been studied, all nine had absorptive hypercalciuria, three also had fasting hypercalciuria, and one had renal phosphorous leak. No mutation of the CaR gene was detected in these seven families. Two previously reported polymorphisms were detected, each of them in five families: A986S and C-to-T change at -60 in intron 5. CONCLUSION: In these seven families, IH is not related to the CaR gene mutation. Although we cannot exclude that point mutations can be found in other families, familial IH does not seem to be generally associated with CaR mutation.

Point mutation in the stalk of angiotensin-converting enzyme causes a dramatic increase in serum angiotensin-converting enzyme but no cardiovascular disease.

BACKGROUND: Angiotensin-converting enzyme (ACE) metabolizes many small peptides and plays a key role in blood pressure regulation. Elevated serum ACE is claimed to be associated with an increased risk for cardiovascular disease. Previously, two families with dramatically increased serum ACE were described, but no systematic survey of affected individuals was performed, and the molecular background of this trait is unknown. METHODS AND RESULTS: Eight families were identified with autosomal dominant inheritance of a dramatic (5-fold) increase of serum ACE activity. Strikingly, no clinical abnormalities were apparent in the affected subjects. Isolated blood cells were used for genetic and biochemical analysis. The level of ACE expression on the blood leukocytes and dendritic cells and total cell-associated ACE of the affected individuals was similar to that in nonaffected relatives; however membrane-bound mutant ACE was much more efficiently clipped from the cell surface compared with its wild-type counterpart. A point mutation causing Pro1199Leu in the stalk region of the ACE molecule cosegregates with the increase in serum ACE (LOD score, 6.63). CONCLUSIONS: A point mutation in the stalk region of the ACE protein causes increased shedding, leading to increased serum ACE, whereas cell-bound ACE is unaltered, and affected individuals exhibit no clinical abnormalities. These findings qualify the importance of serum ACE and establish a new determinant of ACE solubilization.