Large Pedigree Research Articles

Strategies for phasing and imputation in a population isolate.

In the search for genetic associations with complex traits, population isolates offer the advantage of reduced genetic and environmental heterogeneity. In addition, cost-efficient next-generation association approaches have been proposed in these populations where only a subsample of representative individuals is sequenced and then genotypes are imputed into the rest of the population. Gene mapping in such populations thus requires high-quality genetic imputation and preliminary phasing. To identify an effective study design, we compare by simulation a range of phasing and imputation software and strategies. We simulated 1,115,604 variants on chromosome 10 for 477 members of the large complex pedigree of Campora, a village within the established isolate of Cilento in southern Italy. We assessed the phasing performance of identical by descent based software ALPHAPHASE and SLRP, LD-based software SHAPEIT2, SHAPEIT3, and BEAGLE, and new software EAGLE that combines both methodologies. For imputation we compared IMPUTE2, IMPUTE4, MINIMAC3, BEAGLE, and new software PBWT. Genotyping errors and missing genotypes were simulated to observe their effects on the performance of each software. Highly accurate phased data were achieved by all software with SHAPEIT2, SHAPEIT3, and EAGLE2 providing the most accurate results. MINIMAC3, IMPUTE4, and IMPUTE2 all performed strongly as imputation software and our study highlights the considerable gain in imputation accuracy provided by a genome sequenced reference panel specific to the population isolate.

Identification of a novel locus in a large pedigree with Parkinson’s disease

Identification of a novel locus in a large pedigree with Parkinson’s disease

Rare Coding Variants in ANGPTL6 Are Associated with Familial Forms of Intracranial Aneurysm

Intracranial aneurysms (IAs) are acquired cerebrovascular abnormalities characterized by localized dilation and wall thinning in intracranial arteries, possibly leading to subarachnoid hemorrhage and severe outcome in case of rupture. Here, we identified one rare nonsense variant (c.1378A>T) in the last exon of ANGPTL6 (Angiopoietin-Like 6)-which encodes a circulating pro-angiogenic factor mainly secreted from the liver-shared by the four tested affected members of a large pedigree with multiple IA-affected case subjects. We showed a 50% reduction of ANGPTL6 serum concentration in individuals heterozygous for the c.1378A>T allele (p.Lys460Ter) compared to relatives homozygous for the normal allele, probably due to the non-secretion of the truncated protein produced by the c.1378A>T transcripts. Sequencing ANGPTL6 in a series of 94 additional index case subjects with familial IA identified three other rare coding variants in five case subjects. Overall, we detected a significant enrichment (p = 0.023) in rare coding variants within this gene among the 95 index case subjects with familial IA, compared to a reference population of 404 individuals with French ancestry. Among the 6 recruited families, 12 out of 13 (92%) individuals carrying IA also carry such variants in ANGPTL6, versus 15 out of 41 (37%) unaffected ones. We observed a higher rate of individuals with a history of high blood pressure among affected versus healthy individuals carrying ANGPTL6 variants, suggesting that ANGPTL6 could trigger cerebrovascular lesions when combined with other risk factors such as hypertension. Altogether, our results indicate that rare coding variants in ANGPTL6 are causally related to familial forms of IA.

Autosomal Recessive Limb Girdle Muscular Dystrophy In A Complex Consanguineous Family: The First Cases Series In Indonesia

ABSTRACTBackground: Limb girdle muscular dystrophy (LGMD) is a neuromuscular abnormality with clinical heterogeneity and various severity, where over 30 subtypes have been identified. Meanwhile, molecular diagnosis of LGMD is not commonly carried out in Indonesia. We present a large pedigree of familial LGMD, with over 14 years of follow-up.Case Presentation: A 12-year old female patient came with muscle weakness. She had toe walking since age of 6, followed by calf hypertrophy for over three years. Family history revealed complex consanguinity. Her younger sister and her parents’ cousin had similar condition, with the latter was already bedridden.Physical examination results were waddling gait, lordotic spine, and absent deep tendon reflexes. Muscle biopsy showed sign of dystrophic process. Immunoperoxidase staining of some proteins resulted normal. Single nucleotide polymorphism (SNP) array in two siblings revealed homozygosity on chromosome 15 containing CAPN3 gene of LGMD2A subtype.Recently, the patient is wheelchair bound and undergoes rehabilitation. Her sister is still able to walk with abnormal gait, while her parents’ cousin had passed away in age 55. From the multiple consanguinity, it could be concluded as autosomal recessive type LGMD.Conclusion: A large family with LGMD from Indonesia was presented with more than 14 years of care. Clinical diagnosis was made based on physical and additional examination, however molecular analysis for establishing definitive diagnosis is still limited. Further studies such as targeted or whole exome sequencing is warranted to elucidate the cause of disease. Long-term evaluation and supportive care, in addition to proper counseling may increase quality of life.

Evaluating the contribution of rare variants to type 2 diabetes and related traits using pedigrees

A major challenge in evaluating the contribution of rare variants to complex disease is identifying enough copies of the rare alleles to permit informative statistical analysis. To investigate the contribution of rare variants to the risk of type 2 diabetes (T2D) and related traits, we performed deep whole-genome analysis of 1,034 members of 20 large Mexican-American families with high prevalence of T2D. If rare variants of large effect accounted for much of the diabetes risk in these families, our experiment was powered to detect association. Using gene expression data on 21,677 transcripts for 643 pedigree members, we identified evidence for large-effect rare-variant cis-expression quantitative trait loci that could not be detected in population studies, validating our approach. However, we did not identify any rare variants of large effect associated with T2D, or the related traits of fasting glucose and insulin, suggesting that large-effect rare variants account for only a modest fraction of the genetic risk of these traits in this sample of families. Reliable identification of large-effect rare variants will require larger samples of extended pedigrees or different study designs that further enrich for such variants.

GIGI-Quick: a fast approach to impute missing genotypes in genome-wide association family data.

Genome-wide association studies have become common over the last ten years, with a shift towards targeting rare variants, especially in pedigree-data. Despite lower costs, sequencing for rare variants still remains expensive. To have a relatively large sample with acceptable cost, imputation approaches may be used, such as GIGI for pedigree data. GIGI is an imputation method that handles large pedigrees and is particularly good for rare variant imputation. GIGI requires a subset of individuals in a pedigree to be fully sequenced, while other individuals are sequenced only at relevant markers. The imputation will infer the missing genotypes at untyped markers. Running GIGI on large pedigrees for large numbers of markers can be very time consuming. We present GIGI-Quick as a method to efficiently split GIGI's input, run GIGI in parallel and efficiently merge the output to reduce the runtime with the number of cores. This allows obtaining imputation results faster, and therefore all subsequent association analyses. GIGI-Quick is open source and publicly available via: https://cse-git.qcri.org/Imputation/GIGI-Quick. msaad@hbku.edu.qa. Supplementary data are available at Bioinformatics online.

A novel missense mutation in HSF4 causes autosomal-dominant congenital lamellar cataract in a British family.

PurposeInherited cataract, opacification of the lens, is the most common worldwide cause of blindness in children. We aimed to identify the genetic cause of isolated autosomal-dominant lamellar cataract in a five-generation British family.MethodsWhole exome sequencing (WES) was performed on two affected individuals of the family and further validated by direct sequencing in family members.ResultsA novel missense mutation NM_001040667.2:c.190A>G;p.K64E was identified in the DNA-binding-domain of heat-shock transcription factor 4 (HSF4) and found to co-segregate with disease.ConclusionWe have identified a novel mutation in HSF4 in a large British pedigree causing dominant congenital lamellar cataract. This is the second mutation in this gene found in the British population. This mutation is likely to be dominant negative and affect the DNA-binding affinity of HSF4.

Common founder effects of hereditary hemochromatosis, Wilson\xb4s disease, the long QT syndrome and autosomal recessive deafness caused by two novel mutations in the WHRN and TMC1 genes

BackgroundGenealogy and molecular genetic studies of a Swedish river valley population resulted in a large pedigree, showing that the hereditary hemochromatosis (HH) HFE/p.C282Y mutation is inherited with other recessive disorders such as Wilson´s disease (WND), a rare recessive disorder of copper overload. The population also contain individuals with the Swedish long QT syndrome (LQTS1) founder mutation (KCNQ1/p.Y111C) which in homozygotes causes the Jervell & Lange Nielsen syndrome (JLNS) and hearing loss (HL).Aims of the study were to test whether the Swedish long QT founder mutation originated in an ancestral HFE family and if carriers had an increased risk for hemochromatosis (HH), a treatable disorder. We also aimed to identify the pathogenic mutation causing the hearing loss disorder segregating in the pedigree.MethodsLQTS patients were asked about their ancestry and possible origin in a HH family. They were also offered a predictive testing for the HFE genotype. Church books were screened for families with hearing loss. One HH family had two members with hearing loss, who underwent molecular genetic analysis of the LQTS founder mutation, connexin 26 and thereafter exome sequencing. Another family with hearing loss in repeat generations was also analyzed for connexin 26 and underwent exome sequencing.ResultsOf nine LQTS patients studied, four carried a HFE mutation (two p.C282Y, two p.H63D), none was homozygous. Three LQTS patients confirmed origin in a female founder ( b 1694, identical to AJ b 1694, a HFE pedigree member from the Fax river. Her descent of 44 HH families, included also 29 families with hearing loss (HL) suggesting JLNS. Eleven LQTS probands confirmed origin in a second founder couple (b 1614/1605) in which the woman b 1605 was identical to a HFE pedigree member from the Fjällsjö river. In her descent there were not only 64 HH, six WND families, one JLNS, but also 48 hearing loss families. Most hearing loss was non syndromic and caused by founder effects of the late 16th century. One was of Swedish origin carrying the WHRN, c.1977delC, (p.S660Afs*30) mutation, the other was a TMC1(NM_138691),c.1814T>C,(p.L605P) mutation, possibly of Finnish origin.ConclusionsDeep human HFE genealogies show HFE to be associated with other genetic disorders like Wilson´s disease, LQTS, JLNS, and autosomal recessive hearing loss. Two new homozygous HL mutations in WHRN/p.S660Afs*30 and TMC1/p.L605P were identified,none of them previously reported from Scandinavia. The rarity of JLNS was possibly caused by miscarriage or intrauterine death. Most hearing loss (81.7%) was seen after 1844 when first cousin marriages were permitted. However, only 10 (10.3%) came from 1st cousin unions and only 2 (2.0 %) was born out of wedlock.

A fast indirect method to compute functions of genomic relationships concerning genotyped and ungenotyped individuals, for diversity management

BackgroundPedigree-based management of genetic diversity in populations, e.g., using optimal contributions, involves computation of the {mathbf{Ax}} type yielding elements (relationships) or functions (usually averages) of relationship matrices. For pedigree-based relationships {mathbf{A}}, a very efficient method exists. When all the individuals of interest are genotyped, genomic management can be addressed using the genomic relationship matrix {mathbf{G}}; however, to date, the computational problem of efficiently computing {mathbf{Gx}} has not been well studied. When some individuals of interest are not genotyped, genomic management should consider the relationship matrix {mathbf{H}} that combines genotyped and ungenotyped individuals; however, direct computation of {mathbf{Hx}} is computationally very demanding, because construction of a possibly huge matrix is required. Our work presents efficient ways of computing {mathbf{Gx}} and {mathbf{Hx}}, with applications on real data from dairy sheep and dairy goat breeding schemes.ResultsFor genomic relationships, an efficient indirect computation with quadratic instead of cubic cost is {mathbf{x}} = {mathbf{Z}}left( {{mathbf{Z^{prime}x}}} right)/k, where Z is a matrix relating animals to genotypes. For the relationship matrix {mathbf{H}}, we propose an indirect method based on the difference between vectors {mathbf{Hx}} - {mathbf{Ax}}, which involves computation of {mathbf{Ax}} and of products such as {mathbf{Gw}} and {mathbf{A}}_{22}^{ - 1} {mathbf{w}}, where {mathbf{w}} is a working vector derived from {mathbf{x}}. The latter computation is the most demanding but can be done using sparse Cholesky decompositions of matrix {mathbf{A}}^{ - 1}, which allows handling very large genomic and pedigree data files. Studies based on simulations reported in the literature show that the trends of average relationships in {mathbf{H}} and {mathbf{A}} differ as genomic selection proceeds. When selection is based on genomic relationships but management is based on pedigree data, the true genetic diversity is overestimated. However, our tests on real data from sheep and goat obtained before genomic selection started do not show this.ConclusionsWe present efficient methods to compute elements and statistics of the genomic relationships {mathbf{G}} and of matrix {mathbf{H}} that combines ungenotyped and genotyped individuals. These methods should be useful to monitor and handle genomic diversity.

The unique clinical spectrum of maturity onset diabetes of the young type 3

Phenotypic variability in maturity-onset diabetes of the young (MODY) makes screening criteria for genomic analysis challenging. We describe the clinical spectrum in a large pedigree with HNF1A-MODY; as generations progressed, the course and outcome became poorer. Although uncommon, pancreatic autoantibodies and diabetes ketoacidosis should not exclude the diagnosis of MODY.

Dysfunction of Myosin Light‐Chain 4 (MYL4) Leads to Heritable Atrial Cardiomyopathy With Electrical, Contractile, and Structural Components: Evidence From Genetically‐Engineered Rats

BackgroundThere is increasing interest in the concept of atrial cardiomyopathy, but the underlying molecular and mechanistic determinants remain poorly defined. We identified a family with heritable atrial cardiomyopathy manifesting as progressive atrial‐selective electromechanical dysfunction, tachyarrhythmias, and bradyarrhythmias requiring pacemaker implantation. Myosin light‐chain 4 (MYL4), encoding the atrial‐selective essential myosin light chain, was identified as a candidate gene. We used genetically modified rat models to investigate the role of MYL4 in atrial cardiomyopathy.Methods and ResultsExome sequencing and systematic bioinformatic analyses identified a rare missense variant of MYL4 (c.31G>A [p.E11K]) in a large multiplex atrial cardiomyopathy family pedigree. The mutation cosegregated with atrial standstill (selected as the principal presenting trait) with a logarithm of the odds score of 5.3. The phenotype of rats with MYL4 mutation knock‐in confirmed the causative role of the mutation. MYL4 knockout rats showed a similar atrial cardiomyopathy phenotype, whereas rats with an adjacent 4‐amino‐acid deletion showed no phenotype. Both MYL4 p.E11K knock‐in rats and MYL4 knockout rats showed progressive atrial electrophysiological, contractile, and fibrotic abnormalities, similar to affected patients. Biochemical analyses of MYL4 p.E11K mutation rats showed activation of proapoptotic and profibrotic signaling, along with increased atrial‐cardiomyocyte terminal deoxynucleotidyl transferase dUTP nick end labeling staining, suggesting enhanced apoptotic cell death, findings that were mimicked by in vitro adenoviral transfer of the mutant gene to neonatal‐rat cardiomyocytes.ConclusionsLoss‐of‐function MYL4 gene variants cause progressive atrial cardiomyopathy in humans and rats. Our findings identify MYL4 as a key gene required for atrial contractile, electrical and structural integrity. These results improve our understanding of the molecular basis of atrial cardiomyopathy and introduce new models for further mechanistic analysis.

The identification of molecular-genetic background of familial atypical parkinsonism in "Hornacko", a specific region of the South-Eastern Moravia, Czech Republic

Background: Increased prevalence of parkinsonism was detected in a small region of south-eastern Czech Republic. Three large pedigrees were identified.

235 Genotype-phenotype correlation in vascular Ehlers-Danlos syndrome: Novel duplication mutation of COL3A1 gene in a large pedigree

235 Genotype-phenotype correlation in vascular Ehlers-Danlos syndrome: Novel duplication mutation of COL3A1 gene in a large pedigree

Variation in Recombination Rate and Its Genetic Determinism in Sheep Populations.

Recombination is a complex biological process that results from a cascade of multiple events during meiosis. Understanding the genetic determinism of recombination can help to understand if and how these events are interacting. To tackle this question, we studied the patterns of recombination in sheep, using multiple approaches and data sets. We constructed male recombination maps in a dairy breed from the south of France (the Lacaune breed) at a fine scale by combining meiotic recombination rates from a large pedigree genotyped with a 50K SNP array and historical recombination rates from a sample of unrelated individuals genotyped with a 600K SNP array. This analysis revealed recombination patterns in sheep similar to other mammals but also genome regions that have likely been affected by directional and diversifying selection. We estimated the average recombination rate of Lacaune sheep at 1.5 cM/Mb, identified ∼50,000 crossover hotspots on the genome, and found a high correlation between historical and meiotic recombination rate estimates. A genome-wide association study revealed two major loci affecting interindividual variation in recombination rate in Lacaune, including the RNF212 and HEI10 genes and possibly two other loci of smaller effects including the KCNJ15 and FSHR genes. The comparison of these new results to those obtained previously in a distantly related population of domestic sheep (the Soay) revealed that Soay and Lacaune males have a very similar distribution of recombination along the genome. The two data sets were thus combined to create more precise male meiotic recombination maps in Sheep. However, despite their similar recombination maps, Soay and Lacaune males were found to exhibit different heritabilities and QTL effects for interindividual variation in genome-wide recombination rates. This highlights the robustness of recombination patterns to underlying variation in their genetic determinism.

Mutation detection and prenatal diagnosis of XLHED pedigree.

BackgroundThe phenotypic characters of X -linked Hypohidrotic Ectodermal Dysplasia (XLHED) are the dysplasia of epithelial- and mesenchymal-derived organs. Ectodysplasin (EDA) is the causative gene of XLHED.MethodsThe current study reported a large Chinese XLHED pedigree. The genomic DNA of adult and fetus was extracted from peripheral blood and shed chorion cell respectively. The nucleotide variation in EDA gene was screened through direct sequencing the coding sequence. The methylation state of EDA gene’s promoter was evaluated by pyrosequencing.ResultsThis Chinese XLHED family had two male patients and three carriers. All of them were with a novel EDA frameshift mutation. The mutation, c.172-173insGG, which leads to an immediate premature stop codon in exon one caused severe structural changes of EDA. Prenatal diagnosis suggested that the fetus was a female carrier. The follow-up observation of this child indicated that she had mild hypodontia of deciduous teeth at age six. The methylation level of EDA gene’s promoter was not related to carriers’ phenotype changes in this family.DiscussionWe reported a new frameshift mutation of EDA gene in a Chinese family. Prenatal diagnosis can help to predict the disease status of the fetus.

Whole Exome Sequencing Identified a Novel IGFBP6 Variant in a Disc Degeneration Pedigree.

To identify the likely causal mutation that results in disc degeneration in a pedigree with a high incidence of disc degeneration. A large pedigree with a high incidence of disc degeneration was recruited for this study. Exome sequencing was completed on four family members with disc degeneration to screen for potential causal gene variants. Detected variants were filtered against the 1000 Genomes Project, the Short Genetic Variations database (dbSNP), and the Beijing Genomics Institute (BGI) in-house database. After removing synonymous variants, Sanger sequencing was used to verify the lack of the candidate single nucleotide polymorphism (SNP) in five healthy subjects of the study family. We identified a novel SNP variant, Chr12:g.53494591T>C. c.T430C (p.S144P) in the insulin-like growth factor binding protein-6 (IGFBP6) gene. This variant was shared by all four affected family members, but not by five unaffected members in the same pedigree. Furthermore, this variant was not detected in 200 unrelated healthy people. The c.T430C (p.S144P) variant of IGFBP6 was identified as the likely causal variant associated with increased risk of familial disc degeneration in the studied pedigree.

The practical use of genome sequencing data in the management of a feline colony pedigree

BackgroundA higher prevalence of inherited disorders among companion animals are often rooted in their historical restricted artificial selection for a variety of observed phenotypes that eventually decreased genetic diversity. Cats have been afflicted with many inherited diseases due to domestication and intense breed selection. Advances in sequencing technology have generated a more comprehensive way to access genetic information from an individual, allowing identification of putative disease-causing variants and in practice a means to avoid their spread and thus better pedigree management. We examine variants in three domestic shorthair cats and then calculated overall genetic diversity to extrapolate the benefits of this data for breeding programs within a feline colony.ResultsWe generated whole genome sequence (WGS) data for three related cats that belong to a large feline pedigree colony. Genome-wide coverage ranged from 27-32X, from which we identified 18 million variants in total. Previously known disease-causing variants were screened in our cats, but none carry any of these known disease alleles. Loss of function (LoF) variants, that are in genes associated with a detrimental phenotype in human or mice were chosen for further evaluation on the comparative impact inferred. A set of LoF variants were observed in four genes, each with predicted detrimental phenotypes as a result. However, none of our cats displayed the expected disease phenotypes. Inbreeding coefficients and runs of homozygosity were also evaluated as a measure of genetic diversity. We find low inbreeding coefficients and total runs of homozygosity, thus suggesting pedigree management of genetic relatedness is acceptable.ConclusionsThe use of WGS of a small sampling among a large feline colony has enabled us to identify possible disease-causing variants, their genotype state and measure pedigree management of genetic diversity. We contend a limited but strategic sampling of feline colony individuals using WGS can inform veterinarians of future health anomalies and guide breeding practices to ensure healthy genetic diversity.

Benchmarking Relatedness Inference Methods with Genome-Wide Data from Thousands of Relatives.

Inferring relatedness from genomic data is an essential component of genetic association studies, population genetics, forensics, and genealogy. While numerous methods exist for inferring relatedness, thorough evaluation of these approaches in real data has been lacking. Here, we report an assessment of 12 state-of-the-art pairwise relatedness inference methods using a data set with 2485 individuals contained in several large pedigrees that span up to six generations. We find that all methods have high accuracy (92-99%) when detecting first- and second-degree relationships, but their accuracy dwindles to <43% for seventh-degree relationships. However, most identical by descent (IBD) segment-based methods inferred seventh-degree relatives correct to within one relatedness degree for >76% of relative pairs. Overall, the most accurate methods are Estimation of Recent Shared Ancestry (ERSA) and approaches that compute total IBD sharing using the output from GERMLINE and Refined IBD to infer relatedness. Combining information from the most accurate methods provides little accuracy improvement, indicating that novel approaches, such as new methods that leverage relatedness signals from multiple samples, are needed to achieve a sizeable jump in performance.

Abstract 440: A Lamin A/C Haploinsufficiency Model of Cardiomyopathy Using Patient-Specific iPSC Derived Cardiomyocytes Demonstrates Impaired Contractility

Background: Lamin A/C (LMNA) mutations are the second most common cause of familial dilated cardiomyopathy (DCM). LMNA encodes nuclear lamins which are intermediate filaments of the inner nuclear membrane. Patients with LMNA DCM present with early signs of arrhythmias and often display a rapid deterioration in cardiac function. Previous induced pluripotent derived stem cell (iPSC) modeling of cardiac laminopathy did not demonstrate defects in cardiomyocyte (CM) contractility nor provide evidence of arrhythmogenesis. Developing a robust human model that recapitulates disease manifestations of LMNA cardiomyopathy is a critical step for understanding CM-intrinsic defects contributing to disease pathogenesis. Purpose: As such, our lab hypothesized that iPSC-CMs derived from a laminopathy patient would recapitulate the contractile dysfunction of the disease if studied in monolayer using flexible matrigel substrate. Methods: Patients with symptomology indicative of LMNA DCM were recruited for clinical testing. Peripheral blood mononuclear cells were isolated and reprogrammed into iPSCs. CMs were generated using a chemical differentiation method and then subjected to molecular and functional assessment. Cardioexcyte96 based detection of impedance was utilized for analysis of contractility of iPSC-CMs in a monolayer. Results/Conclusions: We identified a large pedigree with DCM in which affected individuals had a putatively pathogenic mutation within LMNA. Western blot analyses demonstrated that lamin A/C can be detected in iPSC-CMs with reduced expression in mutant cells. Mutant iPSC-CMs in a monolayer demonstrate both increased time for contraction (+55.1 msec P&lt;.0001) and relaxation (+44.8 msec P&lt;.0001) compared to control. Our results are the first to provide evidence for contractile dysfunction in an iPSC-CM model of cardiac laminopathy. In addition, this work highlights the utility of impedance based measurement of contractility as a robust outcome that can be applied to high throughput discovery of therapeutic interventions in this disease model.

A large Chinese pedigree of multiple endocrine neoplasia type 2A with a novel C634Y/D707E germline mutation in RET exon 11.

The present study identified the clinical features of the largest multiple endocrine neoplasia type 2 (MEN2) A pedigree from China, with a novel double missense rearranged during transfection (RET) mutation (C634Y/D707E). To the best of our knowledge, the D707E mutation has not been identified to date. In the present study, a total of 101 family members who originated from a large pedigree (134 members in total) underwent RET mutation screening by next-generation sequencing and polymerase chain reaction (PCR) amplification, followed by direct bidirectional DNA sequencing. The clinical features of this pedigree were carefully reviewed retrospectively, and statistical analyses were conducted using SPSS software. A total of 33 (32.67%) carriers were identified to exhibit the C634Y/D707E RET germline mutation. The mean age of the patients with medullary thyroid carcinoma (MTC) identified by RET screening was 38.4±16.5 years (n=11; range, 14–65 years). Only 4 patients with pheochromocytoma with a median age of 37 years were identified. No hyperparathyroidism was diagnosed. Persistent or recurrent disease developed in the patients of the present study who underwent inappropriate initial thyroid surgeries that were performed in previous decades (III10, III23, III24, III27 and IV46, as they had undergone two surgeries prior to the present study). A total of 66.70% (6/9) of patients, following thyroidectomy, continued to develop persistent or recurrent disease during the present screening study. In total, 3 patients succumbed to MTC or distant metastasis in the present study. The increase in carcinoembryonic antigen (CEA) levels correlated with the increase in basal serum calcitonin (Ct) levels according to Pearson correlation analysis in patients with MTC without surgery. Ct and CEA levels were also significantly correlated with tumor volumes. To the best of our knowledge, the present study is the first to identify a novel double RET missense mutation in the largest MEN2A pedigree from China. Additional in-depth study is necessary to elucidate the molecular mechanisms of the D707E mutation and its potential joint effects with the other C634Y mutation in the pedigree of the present study.