Penetrance estimation of PRRT2 variants in paroxysmal kinesigenic dyskinesia and infantile convulsions / 医学前沿

Proline-rich transmembrane protein 2 (PRRT2) is the leading cause of paroxysmal kinesigenic dyskinesia (PKD), benign familial infantile epilepsy (BFIE), and infantile convulsions with choreoathetosis (ICCA). Reduced penetrance of PRRT2 has been observed in previous studies, whereas the exact penetrance has not been evaluated well. The objective of this study was to estimate the penetrance of PRRT2 and determine its influencing factors. We screened 222 PKD index patients and their available relatives, identified 39 families with pathogenic or likely pathogenic (P/LP) PRRT2 variants via Sanger sequencing, and obtained 184 PKD/BFIE/ICCA families with P/LP PRRT2 variants from the literature. Penetrance was estimated as the proportion of affected variant carriers. PRRT2 penetrance estimate was 77.6% (95% confidence interval (CI) 74.5%-80.7%) in relatives and 74.5% (95% CI 70.2%-78.8%) in obligate carriers. In addition, we first observed that penetrance was higher in truncated than in non-truncated variants (75.8% versus 50.0%, P = 0.01), higher in Asian than in Caucasian carriers (81.5% versus 68.5%, P = 0.004), and exhibited no difference in gender or parental transmission. Our results are meaningful for genetic counseling, implying that approximately three-quarters of PRRT2 variant carriers will develop PRRT2-related disorders, with patients from Asia or carrying truncated variants at a higher risk.

Early-Life Stress in D2 Heterozygous Mice Promotes Autistic-like Behaviors through the Downregulation of the BDNF-TrkB Pathway in the Dorsal Striatum

A number of specific genetic variants including gene mutations and single nucleotide variations have been identified in genomewide association studies of autism spectrum disorder (ASD). ASD phenotypes in individuals carrying specific genetic variations are manifest mostly in a heterozygous state. Furthermore, individuals with most genetic variants show incomplete penetrance and phenotypic variability, suggesting that non-genetic factors are also involved in developing ASD. However, the mechanisms of how genetic and environmental factors interactively promote ASD are not clearly understood. In the present study, we investigated whether early-life stress (ELS) in D2 dopamine receptor heterozygous knockout (D2(+/−)) mice induces ASD-like symptoms. To address that, we exposed D2 heterozygous pups to maternal separation stress for 3 h daily for 13 days beginning on postnatal day 2. D2(+/−) adult mice that had experienced ELS exhibited impaired sociability in the three-chamber test and home-cage social interaction test and increased grooming behavior, whereas wildtype littermates exposed to ELS did not show those phenotypes. ELS-exposed D2(+/−) mice had decreased levels of BDNF, TrkB, phospho-ERK1/2 and phospho-CREB in the dorsal striatum. Administration of the TrkB agonist 7,8-dihydroxyflavone (7,8-DHF) to ELS-exposed D2(+/−) mice rescued the sociability deficits and repetitive behavior. In contrast, behavioral rescue by 7,8-DHF in ELS-exposed D2(+/−) mice was blocked when TrkB expression in the dorsal striatum was locally inhibited by the injection of TrkB-siRNA. Together, our results suggest that the interaction between ELS and defective D2 gene function promotes autistic-like behaviors by downregulating the BDNF-TrkB pathway in the dorsal striatum.

Clinical and Genetic Characteristics of BRCA1/2 Mutation in Korean Ovarian Cancer Patients: A Multicenter Study and Literature Review / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: We investigated the clinical relevance and spectrum of BRCA1/2 mutations in Korean ovarian cancer (KoOC) patients. MATERIALS AND METHODS: Two hundred seventy-nine KoOC patients were enrolled from three university hospitals between 2012 and 2017. Their peripheral blood samples were obtained for BRCA1/2 mutation analysis by direct sequencing. Clinicopathological characteristics were retrospectively reviewed, and spectrum analyses of BRCA1/2 mutation were assessed by systematic literature review. RESULTS: Frequency of BRCA1/2 mutations was 16.5% in KoOC patients. BRCA1/2 mutations were significantly associated with family history of breast/ovarian cancer (pT of BRCA2 in KoBC). CONCLUSION: The clinical relevance of BRCA1/2 mutations in KoOC patients was confirmed but that of early age-of-onset was not. Possible inconsistency in the ratio of BRCA1-to-BRCA2 mutations and the most common mutation between KoOC and KoBC may probably suggest presence of mutation sequence-associated penetrance tendency in hereditary Korean breast and ovarian cancer. These data may provide insights for optimal genetic counseling and prophylactic treatment for at-risk relatives of KoOC patients.

Síndrome de Lynch: aspectos genéticos, clínicos y diagnósticos / Lynch syndrome: genetic, clinical and diagnostic aspects

Esta revisión tiene como objetivo dar a conocer los aspectos genéticos, clínicos y diagnósticos del síndrome de Lynch, además de brindar la información más relevante acerca de la asesoría genética en estos pacientes y las recomendaciones actuales para su seguimiento.

This review aims to present the genetic, clinical and diagnostic aspects of Lynch syndrome, as well as providing the most relevant information about genetic counseling in these patients and the current recommendations for their surveillance.

Clinical Presentation with High Penetrance in a Korean Family with Pulmonary Arterial Hypertension Associated with a BMPR2 Intron 3 Splice Site Pathogenic Variant

Pathogenic variants of bone morphogenic protein receptor type 2 gene (BMPR2) are related to the majority of cases of heritable pulmonary arterial hypertension (PAH). Over 400 pathogenic variants have been identified. However, clinical characterization of PAH is still incomplete. We present a case of heritable PAH in a Korean family showing serious clinical presentation with high penetrance. Genetic sequencing revealed a known heterozygous BMPR2 pathogenic variant, c.418+5G>A, at a splice site of intron 3. Serious clinical presentation with high penetrance suggested that the interplay of other factors with pathologic variants might be in genotype-phenotype correlation. Further studies are needed to clarify these issues for the development of personalized medicine approaches for PAH.

Novel Mutation in PTHLH Related to Brachydactyly Type E2 Initially Confused with Unclassical Pseudopseudohypoparathyroidism

BACKGROUND: Autosomal-dominant brachydactyly type E is a congenital abnormality characterized by small hands and feet, which is a consequence of shortened metacarpals and metatarsals. We recently encountered a young gentleman exhibiting shortening of 4th and 5th fingers and toes. Initially, we suspected him having pseudopseudohypoparathyroidism (PPHP) because of normal biochemical parameters, including electrolyte, Ca, P, and parathyroid hormone (PTH) levels; however, his mother and maternal grandmother had the same conditions in their hands and feet. Furthermore, his mother showed normal biochemical parameters. To the best of our knowledge, PPHP is inherited via a mutated paternal allele, owing to the paternal imprinting of GNAS (guanine nucleotide binding protein, alpha stimulating) in the renal proximal tubule. Therefore, we decided to further analyze the genetic background in this family. METHODS: Whole exome sequencing was performed using genomic DNA from the affected mother, son, and the unaffected father as a negative control. RESULTS: We selected the intersection between 45,490 variants from the mother and 45,646 variants from the son and excluded 27,512 overlapping variants identified from the father. By excluding homogenous and compound heterozygous variants and removing all previously reported variants, 147 variants were identified to be shared by the mother and son. Variants that had least proximities among species were excluded and finally 23 variants remained. CONCLUSION: Among them, we identified a defect in parathyroid hormone like hormone (PTHLH), encoding the PTH-related protein, to be disease-causative. Herein, we report a family affected with brachydactyly type E2 caused by a novel PTHLH mutation, which was confused with PPHP with unclassical genetic penetrance.

1q21.1 microdeletion identified by chromosomal microarray in a newborn with upper airway obstruction

A 1q21.1 microdeletion is an extremely rare chromosomal abnormality that results in phenotypic diversity and incomplete penetrance. Patients with a 1q21.1 microdeletion exhibit neurological-psychiatric problems, microcephaly, epilepsy, facial dysmorphism, cataract, and thrombocytopenia absent radius syndrome. We reported a neonate with confirmed intrauterine growth restriction (IUGR), micrognathia, glossoptosis, upper airway obstruction, facial dysmorphism, and eye abnormality at birth as well as developmental delay at the age of 1 year. These clinical manifestations, except for the IUGR and upper airway obstruction, in the neonate indicated a 1q21.1 microdeletion. Here, we report a rare case of a 1q21.1 microdeletion obtained via paternal inheritance in a newborn with upper airway obstruction caused by glossoptosis and tracheal stenosis.

Pedigree Analysis and Audiological Investigations of Otosclerosis: An Extended Family Based Study

BACKGROUND AND OBJECTIVES: To analyse the audiometric profile and the pedigree of a large family with otosclerosis to understand the inheritance pattern and its implication in clinical management of the disease. SUBJECTS AND METHODS: Pedigree analysis was performed on the basis of family history and audiometric tests. Pure tone audiometry, tympanometry, and acoustic reflexes were evaluated for the family members. Audiometric analysis was also carried out for the individuals who have already underwent corrective surgery at the time of study. RESULTS: Out of 112 family members, 17 were affected individuals, and 11 of them were surgically confirmed. Hearing loss (HL) started unilaterally and progressed to bilateral form. Otosclerosis was presented in early 20’s in the first and second generations but it was delayed to mid-late 30’s in the fourth generation. An affected female was diagnosed with otosclerosis during her pregnancy. Though the disease was familial, a mother of four affected offspring in this family did not develop otosclerosis until she died at the age of 84. CONCLUSIONS: The five-generation family, which was analysed in the present study, exhibited autosomal dominant inheritance of otosclerosis with reduced penetrance. Bilateral HL and pregnancy-aggravated otosclerosis were observed in this family. It was found for the first time that the age of onset of the disease delayed in the successive generations. The current study indicated the importance of detailed pedigree analysis for better clinical management of otosclerosis.

[Fibrodysplasia ossificans progressive: a case report]

Fibrodysplasia ossificans progressiva [FOP] is an extremely rare autosomal dominant disorder having variable expressivity with complete penetrance. FOP incidence has been estimated to be 1 per 2 million. FOP caused by mutations in ACVR1 gene encoding bone morphogenetic protein type-1 receptor. To date, 15 types of mutations have been reported. The majority of cases were determined to be the rsult of a new mutation occuring sporadically. Here we report a 20 years old girl who's suffering FOP for 11 years

Genetic Markers for Adolescent Idiopathic Scoliosis on Chromosome 19p13.3 among Saudi Arabian Girls

STUDY DESIGN: Prospective case-controlled study. PURPOSE: This study aimed to assess genetic influence in Saudi Arabian children with adolescent idiopathic scoliosis (AIS). OVERVIEW OF LITERATURE: The genetic locus linked to chromosome 19p for idiopathic scoliosis has been described. A pilot study conducted at King Fahd Hospital of the University, Al-Khobar showed that three microsatellite markers (D19S216, D19S894, and DS1034) of chromosome 19p13.3 were significant in Saudi Arabian females compared with healthy subjects. METHODS: A total of 100 unrelated Saudi Arabian girls treated for AIS, their parents, healthy siblings, and healthy subjects were recruited for genetic analysis of markers on chromosome 19p13.3. After informed consent was obtained from their parents, blood samples were collected and parametric and nonparametric linkage analyses were performed using GENEHUNTER ver. 2.1. Multipoint linkage analysis was used to specify an autosomal dominant trait with a gene frequency of 0.01 and an estimated penetrance of 80% at the genotypic and allelic levels. RESULTS: Five hundred blood samples were collected and analyzed for microsatellite markers (D19S216, D19S894, and DS1034) of chromosome 19p13.3. Comparison among patients, family members, and healthy subjects revealed no significant association between markers and scoliosis at the genotypic level: D19S216 (p=0.21), D19S894 (p=0.37), and DS1034 (p=0.25). However, at the allelic level, a statistically significant association was observed for marker DS1034 (p=0.008), and marker D19S216 showed significance between fathers and patients (p<0.001) compared with patients and mothers. The other two markers, D19S216 (p=0.25) and D19S894 (p=0.17), showed no significant association between patients and mothers. CONCLUSIONS: At the allelic level, marker DS1034 was significantly associated with AIS patients and their fathers. This allelic marker on chromosome 19p13.3 appears to be important in AIS etiology.

Genetic Screening for Spinocerebellar Ataxia Genes in a Japanese Single-Hospital Cohort

OBJECTIVE: Diagnosis of sporadic cerebellar ataxia is a challenge for neurologists. A wide range of potential causes exist, including chronic alcohol use, multiple system atrophy of cerebellar type (MSA-C), and sporadic late cortical cerebellar atrophy. Recently, an autosomal-dominant spinocerebellar ataxia (SCA) mutation was identified in a cohort of patients with non-MSA-C sporadic cerebellar ataxia. The aim of this study is to genetically screen genes involved in SCA in a Japanese single-hospital cohort. METHODS: Over an 8-year period, 140 patients with cerebellar ataxia were observed. There were 109 patients with sporadic cerebellar ataxia (no family history for at least four generations, 73 patients with MSA-C, and 36 patients with non-MSA-C sporadic cerebellar ataxia) and 31 patients with familial cerebellar ataxia. We performed gene analysis comprising SCA1, 2, 3, 6, 7, 8, 12, 17, 31, and dentatorubro-pallidoluysian atrophy (DRPLA) in 28 of 31 non-MSA-C sporadic patients who requested the test. Familial patients served as a control. RESULTS: Gene abnormalities were found in 57% of non-MSA-C sporadic cerebellar ataxia cases. Among patients with sporadic cerebellar ataxia, abnormalities in SCA6 were the most common (36%), followed by abnormalities in SCA1 (7.1%), SCA2 (3.6%), SCA3 (3.6%), SCA8 (3.6%), and DRPLA (3.6%). In contrast, gene abnormalities were found in 75% of familial cerebellar ataxia cases, with abnormalities in SCA6 being the most common (29%). For sporadic versus familial cases for those with SCA6 abnormalities, the age of onset was older (69 years vs. 59 years, respectively), and CAG repeat length was shorter (23 vs. 25, respectively) in the former than in the latter (not statistically significant). CONCLUSION: Autosomal-dominant mutations in SCA genes, particularly in SCA6, are not rare in sporadic cerebellar ataxia. The reason for the frequency of mutations in SCA6 remains unclear; however, the reason may reflect a higher age at onset and variable penetrance of SCA6 mutations.

Familial Pancreatic Cancer and the Future of Directed Screening

Pancreatic cancer (PC) is the third most common cause of cancer-related death in the United States and the 12th most common worldwide. Mortality is high, largely due to late stage of presentation and suboptimal treatment regimens. Approximately 10% of PC cases have a familial basis. The major genetic defect has yet to be identified but may be inherited by an autosomal dominant pattern with reduced penetrance. Several known hereditary syndromes or genes are associated with an increased risk of developing PC and account for approximately 2% of PCs. These syndromes include the hereditary breast-ovarian cancer syndrome, Peutz-Jeghers syndrome, familial atypical multiple mole melanoma, Lynch syndrome, familial polyposis, ataxia-telangiectasia, and hereditary pancreatitis. Appropriate screening using methods such as biomarkers or imaging, with endoscopic ultrasound and magnetic resonance imaging, may assist in the early detection of neoplastic lesions in the high-risk population. If these lesions are detected and treated before the development of invasive carcinoma, PC disease morbidity and mortality may be improved. This review will focus on familial PC and other hereditary syndromes implicated in the increased risk of PC; it will also highlight current screening methods and the future of new screening modalities.

Surgical Treatment of Axial Polysyndactyly and Postaxial Polydactyly of The Hand in Korean: A Clinical Analysis of 24 Cases

PURPOSE: Non-preaxial polydactyly of the hand refers to axial polysyndactyly involving the 2nd, 3rd, or 4th finger and postaxial polydactyly involving the 5th finger. It has a much lower incidence and a higher genetic penetrance than preaxial type. METHODS: Medical records of the patients who had operation for their polydactyly between July 1997 and July 2015 were retrospectively reviewed. The clinical data of the patients were investigated regarding demographics, clinical findings of the involved digits, foot involvement, and genetic penetrance. Through postoperative follow-up based on physical and radiologic examinations, we assessed functional and aesthetic outcomes, postoperative complications, and reoperation rate. RESULTS: Twenty-four patients (17 males and 7 females) underwent surgery for non-preaxial polydactyly of the hand. There were 15 postaxial type polydactyly, and 9 axial type polysyndactyly. Thirteen patients had bilateral involvement (54.2%), while 5 patients (20.8%) were right-sided and 6 patients (25%) were left-sided. In the axial type, 4th finger was the most frequently involved in 8 patients, followed by the 3rd finger in 1 patient. Thirteen patients (54.2%) had concurrent congenital foot anomalies. One patient (4.2%) had a family history of congenital hand anomaly. Patients with axial type polysyndactyly had poorer postoperative outcome than those with postaxial type, regarding reoperation rate. CONCLUSION: Non-preaxial polydactyly is a very rare congenital hand anomaly and the surgical outcome is not always promising especially in the axial type. Therefore, it is necessary to provide a sufficient preoperative counseling and to perform a meticulous surgery.

A case of Alagille syndrome presenting with chronic cholestasis in an adult

Alagille syndrome (AGS) is a complex multisystem disorder that involves mainly the liver, heart, eyes, face, and skeleton. The main associated clinical features are chronic cholestasis due to a paucity of intrahepatic bile ducts, congenital heart disease primarily affecting pulmonary arteries, vertebral abnormalities, ocular embryotoxon, and peculiar facies. The manifestations generally become evident at a pediatric age. AGS is caused by defects in the Notch signaling pathway due to mutations in JAG1 or NOTCH2. It is inherited in an autosomal dominant pattern with a high degree of penetrance, but variable expressivity results in a wide range of clinical features. Here we report on a 31-year-old male patient who presented with elevated serum alkaline phosphatase and gamma-glutamyl transpeptidase, and was diagnosed with AGS associated with the JAG1 mutation after a comprehensive workup.

Analysis of COL1A1 gene mutation in an ethnic Han Chinese family from Henan affected with osteogenesis imperfecta / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To identify potential mutation of COL1A1 gene in an ethnic Han Chinese family from Henan affected with osteogenesis imperfecta (OI).</p><p><b>METHODS</b>Peripheral blood samples were collected from all 11 members of the family and 50 healthy adults for the extraction of genomic DNA. All exons and introns of the COL1A1 gene were amplified by polymerase chain reaction and subjected to direct sequencing. Mutations found in the proband were analyzed through comparison with other members of the family, 50 healthy individuals and sequence from the GenBank.</p><p><b>RESULTS</b>Fifteen sequence variants were discovered, which included 1 missense mutation, 1 synonymous mutation and 13 intronic mutations. All of the 4 patients from the family were detected as having carried a novel heterozygous missense mutation (c.4193T>G, p.I1398S) in exon 50 of the COL1A1 gene. The father of the proband has carried the same mutation but had a normal phenotype. The same mutation was not found in other healthy members of the family.</p><p><b>CONCLUSION</b>The OI type of this family may have been autosomal dominant with incomplete penetrance or autosomal recessive associated with COL1A1 gene mutations.</p>

Moyamoya Disease: Cardiologist's Perspectives

Moyamoya disease (MMD) is a steno-occlusive disease of the cerebral artery around the circle of Willis. It was first described in 1957 in Japan and named because the characteristic appearance of the basal collaterals in cerebral angiography looks like “a puff of smoke” (moyamoya in Japanese). MMD is one of the major causes of stroke in children worldwide, however most common in Korea, Japan and China. In 2011 the ring finger protein 213 gene (RNF213) was identified as a susceptibility gene for MMD. The RNF213 R4810K variant is an Asian founder mutation common to above nations with carrier rates of 0.5-2% of the general population but a 1/150 penetrance of clinical MMD. MMD patients in Korea and Japan harbors RNF213 R4810K variant in 70-90%. In MMD arterial stenosis was found to occur systematically, not only in the intracranial cerebral arteries but also in renal, coronary, pulmonary arteries, suggesting that MMD is a systemic vasculopathy. These extracranial vasculopathy (ECV) is rare but important as a cause of renovascular hypertension, ischemic heart disease, and pulmonary hypertension especially in children with MMD or family members of MMD. Clinical features of ECV will be reviewed in this article.

Neurofibromatosis tipo 1 (NF1) y su diagnóstico molecular como estrategia del diagnóstico diferencial y a edades tempranas / Molecular diagnosis as a strategy for differential diagnosis and at early ages of neurofibromatosis type 1 (NF1)

Neurofibromatosis type 1 (NF1), is a haploinsufficient and multisystemic disease, caused by inherited or sporadic mutations in the NF1 gene. Its incidence is one in 2,500 to 3,000 individuals, it has an autosomal dominant pattern of inheritance, high clinical variability, complete penetrance and age-dependent complications. Neurofibromin is the product of the NF1 gene and is believed to act as a tumor suppressor since the loss of its function has been associated with benign and malignant tumors in neural crest-derived tissues. Only two correlations between clinical phenotype and mutant alleles in the NF1 gene have been observed. The established criteria for disease diagnosis are very efficient in adults and children older than 3 years of age, but not for children under this age. Mutational analysis is therefore recommended to confirm the disease in young children with a negative family history. A pathogenic mutation in the NF1 should be added to the list of diagnostic criteria. Mutational analysis is also recommended for differential diagnosis and for prenatal or pre-implantation genetic diagnosis, taking into consideration the family history and the type of method to be applied. Molecular studies of this disease using different complimentary molecular techniques and bioinformatics tools have characterized NF1 gene mutations at both the DNA and mRNA levels, increasing the mutational spectrum. Consequently, about 1,289 defects have been reported to date, mainly nonsense/missense mutations, deletions and splice site defects.

Multiple Ruptured Cerebral Aneurysms as a Presenting Feature of Pheochromocytoma in a Patient with Neurofibromatosis 1 / 대한내과학회지

Neurofibromatosis 1 (NF-1) shows an autosomal dominant pattern of inheritance with complete penetrance and variable expression. Vascular abnormalities are frequently associated with NF-1. Pheochromocytoma occurs in 0.1-5.7% of patients with NF-1. Spontaneous intracerebral hemorrhage in patients with NF-1-related pheochromocytoma is very rare. Herein, we report a case of subarachnoid hemorrhage caused by multiple ruptured cerebral aneurysms in a patient with concurrent NF-1 and pheochromocytoma. Coil embolization of the aneurysms and subsequent adrenalectomy for pheochromocytoma were successfully performed, and the patient remained normotensive thereafter. This case demonstrates the importance of a careful search for a remediable cause of episodic hypertension in patients with NF-1, who are predisposed to cerebral hemorrhage from fluctuating blood pressure.

Reduced penetrance in human inherited disease

For many inherited diseases, the same mutation is not always expressed in all persons who care it, moreover, when the mutation is expressed, it is not always expressed in the same way. These findings are the basis for the concepts of penetrance and expressivity. Understanding the factors that control penetrance of disease genes will provide insight into the fundamental disease processes and will help in genetic counselling. With the advancement of molecular genetics over the last few years, some of the underlying mechanisms of reduced penetrance have been elucidated. These include, mutation type, allelic variations in gene expression, epigenetic factors, gene-environment interplay, influence of age and sex, allele dosage, oligogenic and modifier genes, copy number variations as well as the influence of additional gene variants and the effect of single nucleotide polymorphisms. The aim of this review is to clarify factors affecting gene penetrance as well as some of the underlying molecular mechanisms in some genetic disorders

Long QT Syndrome: a Korean Single Center Study

The long QT syndrome (LQTS) is a rare hereditary disorder in which affected individuals have a possibility of ventricular tachyarrhythmia and sudden cardiac death. We investigated 62 LQTS (QTc > or = 0.47 sec) and 19 family members whose genetic study revealed mutation of LQT gene. In the proband group, the modes of presentation were ECG abnormality (38.7%), aborted cardiac arrest (24.2%), and syncope or seizure (19.4%). Median age of initial symptom development was 10.5 yr. Genetic studies were performed in 61; and mutations were found in 40 cases (KCNQ1 in 19, KCNH2 in 10, SCN5A in 7, KCNJ2 in 3, and CACNA1C in 1). In the family group, the penetrance of LQT gene mutation was 57.9%. QTc was longer as patients had the history of syncope (P = 0.001), ventricular tachycardia (P = 0.017) and aborted arrest (P = 0.010). QTc longer than 0.508 sec could be a cut-off value for major cardiac events (sensitivity 0.806, specificity 0.600). Beta-blocker was frequently applied for treatment and had significant effects on reducing QTc (P = 0.007). Implantable cardioverter defibrillators were applied in 6 patients. Congenital LQTS is a potentially lethal disease. It shows various genetic mutations with low penetrance in Korean patients.