一中国脑海绵状血管瘤家系中发现krit1基因新的缺失突变

脑海绵状血管瘤（CCM）是多定位于中枢神经系统的一种脑部血管异常,少数在皮肤和视网膜处有并发症。依据致病基因在染色体上的不同位置分为CCM1、CCM2和CCM33种类型。目前,CCM1、CCM2和CCM3的致病基因已经被克隆,分别为krit1、MGC4607和细胞程序性死亡10基因（PDCD10）。利用连锁分析发现内蒙古的一个家系属于CCM1,突变检测发现患者CCM1基因（krit1）第9内含子和第10外显子拼接位点处存在一“GTA”缺失,该突变导致终止密码子提前出现,产生截短蛋白。实验结果支持krit1为CCM1致病基因。     

A Patient with Posterior Cortical Atrophy Possesses a Novel Mutation in the Presenilin 1 Gene

Posterior cortical atrophy is a dementia syndrome with symptoms of cortical visual dysfunction, associated with amyloid plaques and neurofibrillary tangles predominantly affecting visual association cortex. Most patients diagnosed with posterior cortical atrophy will finally develop a typical Alzheimer''s disease. However, there are a variety of neuropathological processes, which could lead towards a clinical presentation of posterior cortical atrophy. Mutations in the presenilin 1 gene, affecting the function of γ-secretase, are the most common genetic cause of familial, early-onset Alzheimer''s disease. Here we present a patient with a clinical diagnosis of posterior cortical atrophy who harbors a novel Presenilin 1 mutation (I211M). In silico analysis predicts that the mutation could influence the interaction between presenilin 1 and presenilin1 enhancer-2 protein, a protein partner within the γ-secretase complex. These findings along with published literature support the inclusion of posterior cortical atrophy on the Alzheimer''s disease spectrum.     

A Novel Deletion Mutation in CCM1 Gene (krit1) is Detected in a Chinese Family with Cerebral Cavernous Malformations

Cerebral Cavernous Malformations (CCM) are vascular malformations that are mostly located in the central nervous system (CNS) and occasionally within the skin and retina, which are classified into three types (CCM1, CCM2 and CCM3) by being located at different loci on chromosomes. At present, CCM1 (7q21), CCM2 (7p13-p15) and CCM3 (3q25.2-q27) are respectively linked to krit1 (Krev interaction trapped gene 1), MGC4607 and PDCD10 (programmed cell death 10). In this work, we identified a novel “GTA” deletion mutation at the acceptor splicing site of intron9/exon 10 on krit1. The mutation results in an abnormally spliced protein by creating a premature termination code at the 23rd amino acid downstream from the sequence alteration. Our results are consistent with previous research on krit1 mutations and confirm the conclusion that KR1T1 haploinsufficiency may be the underlying mechanism of CCM1.     

Mutation and Expression of Gene YY1 in Pancreatic Neuroendocrine Tumors and Its Clinical Significance

ObjectiveThe clinical significance of the YY1 gene mutation and expression in pancreatic neuroendocrine tumors (PNETs) remains unknown. Therefore, this study aimed to comprehensively analyze the somatic mutation of YY1 in the different subtypes of PNETs.MethodsA total of 143 PNETs were assessed by Sanger sequencing to identify the somatic mutation of YY1 gene in various subtypes of PNETs. YY1 protein expression was examined in 103 PNETs by immunohistochemical staining and western blot. Gene mutation and its protein expression were correlated with clinicopathologic features.ResultsA recurrent mutation (chr14:100743807C>G) in the YY1 gene was identified in 15 of 83 insulinomas (18%) and in only 1 of 60 noninsulinoma PNETs (1.7%) (P = .0045). The YY1 mutation was not found in MEN1-associated insulinomas. The YY1 mutation in insulinomas was correlated with older age and lower serum glucose levels (age, 57 vs 42.5 years, P = .006; blood glucose, 25.2 vs 33.6 mg/dL, P = .008). YY1 protein expression was found in 100 of 103 PNETs, although expression was weaker in metastases than in localized tumors (P = .036). The stronger expression of YY1 protein was associated with favorable disease-free survival of patients with PNETs (log-rank, P = .011; n = 70). Multivariable statistical analysis showed that YY1 protein expression could be an independent predictor of prognosis.ConclusionThe hotspot YY1 mutation mostly occurred in insulinomas and rarely in noninsulinoma PNETs. The stronger YY1 protein expression was correlated with the better prognosis of PNETs patients.     

Identification of a Novel Mutation in the COL2A1 Gene in a Chinese Family with Spondyloepiphyseal Dysplasia Congenita

Spondyloepiphyseal dysplasia congenita (SEDC) is an autosomal dominant chondrodysplasia characterized by disproportionate short-trunk dwarfism, skeletal and vertebral deformities. Exome sequencing and Sanger sequencing were performed in a Chinese Han family with typical SEDC, and a novel mutation, c.620G>A (p.Gly207Glu), in the collagen type II alpha-1 gene (COL2A1) was identified. The mutation may impair protein stability, and lead to dysfunction of type II collagen. Family-based study suggested that the mutation is a de novo mutation. Our study extends the mutation spectrum of SEDC and confirms genotype-phenotype relationship between mutations at glycine in the triple helix of the alpha-1(II) chains of the COL2A1 and clinical findings of SEDC, which may be helpful in the genetic counseling of patients with SEDC.     

一性连锁Alport综合征中国家系COL4A5基因新突变位点的检测

通过PCR和直接测序的方法,对一性连锁Alport综合征家系17个受检个体的COL4A5基因所有51个外显子及其相邻内含子的DNA序列进行检测。结果发现,在第26外显子2240位点,男患者存在C碱基缺失(2240delc),女患者存在杂合缺失,同时对女患者相应的PCR产物进行克隆和测序以验证PCR测序结果的可靠性,而在正常家系成员和80例对照中均未发现此位点异常,说明2240delc为引起该家系临床病变的突变位点,不是多态性位点。在性连锁Alport综合征中,COL4A5基因的这个单碱基缺失突变位点为首次报道。     

Analysis of POFUT1 Gene Mutation in a Chinese Family with Dowling-Degos Disease

Dowling-Degos disease (DDD) is an autosomal dominant genodermatosis characterized by reticular pigmented anomaly mainly affecting flexures. Though KRT5 has been identified to be the causal gene of DDD, the heterogeneity of this disease was displayed: for example, POFUT1 and POGLUT1 were recently identified and confirmed to be additional pathogenic genes of DDD. To identify other DDD causative genes, we performed genome-wide linkage and exome sequencing analyses in a multiplex Chinese DDD family, in which the KRT5 mutation was absent. Only a novel 1-bp deletion (c.246+5delG) in POFUT1 was found. No other novel mutation or this deletion was detected in POFUT1 in a second DDD family and a sporadic DDD case by Sanger Sequencing. The result shows the genetic-heterogeneity and complexity of DDD and will contribute to the further understanding of DDD genotype/phenotype correlations and to the pathogenesis of this disease.     

A Novel Cysteine-Sparing NOTCH3 Mutation in a Chinese Family with CADASIL

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an adult onset cerebral small vessel disorder caused by the mutations of the neurogenic locus notch homolog protein 3 (NOTCH3) gene. The extracellular part of NOTCH3 is composed of 34 epidermal growth factor-like (EGF-like) repeat domains. Each EGF-like domain is rich of cysteine and glycine to produce three loops that are essential for high-affinity binding to its ligand. Nearly all reported CADASIL-associated mutations result in gain or loss of a cysteine residue within the EGF-like domains. Only a few cysteine-sparing NOTCH3 mutations have been documented in the patients with CADASIL to date. Here, we reported a Chinese CADASIL family with a cysteine-sparing NOTCH3 mutation. In this family, affected patients had dizziness, memory loss, gait instability, or hemiplegia. Brain magnetic resonance imaging (MRI) showed diffuse leukoencephalopathy with confluent signal abnormalities in the periventricular white matter, basal ganglia, and centrum semiovale bilaterally. By screening the entire coding region of NOTCH3, a novel missense mutation p.G149V (c.446G>T) was found. This mutation was not detected in 400 normal controls. Considering the critical position of glycine within the C-loop of EGF-like domain and its high conservation through evolution, p.G149V mutation could be a potential pathogenic cause for CADASIL.     

Identification and Functional Analysis of a Novel MIP Gene Mutation Associated with Congenital Cataract in a Chinese Family

Congenital cataracts are major cause of visual impairment and blindness in children and previous studies have shown about 1/3 of non-syndromic congenital cataracts are inherited. Major intrinsic protein of the lens (MIP), also known as AQP0, plays a critical role in transparency and development of the lens. To date, more than 10 mutations in MIP have been linked to hereditary cataracts in humans. In this study, we investigated the genetic and functional defects underlying a four-generation Chinese family affected with congenital progressive cortical punctate cataract. Mutation screening of the candidate genes revealed a missense mutation at position 448 (c.448G>C) of MIP, which resulted in the substitution of a conserved aspartic acid with histidine at codon 150 (p.D150H). By linkage and haplotype analysis, we obtained positive multipoint logarithm of odds (LOD) scores at microsatellite markers D12S1632 (Z_max = 1.804 at α = 1.000) and D12S1691 (Z_max = 1.806 at α = 1.000), which flanked the candidate locus. The prediction results of PolyPhen-2 and SIFT indicated that the p.D150H mutation was likely to damage to the structure and function of AQP0. The wild type and p.D150H mutant AQP0 were expressed in HeLa cells separately and the immunofluorescence results showed that the WT-AQP0 distributed at the plasma membrane and in cytoplasm, while AQP0-D150H failed to reach the plasma membrane and was mainly retained in the Golgi apparatus. Moreover, protein levels of AQP0-D150H were significantly lower than those of wide type AQP0 in membrane-enriched lysates when the HEK-293T cells were transfected with the same amount of wild type and mutant plasmids individually. Taken together, our data suggest the p.D150H mutation is a novel disease-causing mutation in MIP, which leads to congenital progressive cortical punctate cataract by impairing the trafficking mechanism of AQP0.     

Variable Myopathic Presentation in a Single Family with Novel Skeletal RYR1 Mutation

We describe an autosomal recessive heterogeneous congenital myopathy in a large consanguineous family. The disease is characterized by variable severity, progressive course in 3 of 4 patients, myopathic face without ophthalmoplegia and proximal muscle weakness. Absence of cores was noted in all patients. Genome wide linkage analysis revealed a single locus on chromosome 19q13 with Zmax = 3.86 at θ = 0.0 and homozygosity of the polymorphic markers at this locus in patients. Direct sequencing of the main candidate gene within the candidate region, RYR1, was performed. A novel homozygous A to G nucleotide substitution (p.Y3016C) within exon 60 of the RYR1 gene was found in patients. ARMS PCR was used to screen for the mutation in all available family members and in an additional 150 healthy individuals. This procedure confirmed sequence analysis and did not reveal the A to G mutation (p.Y3016C) in 300 chromosomes from healthy individuals. Functional analysis on EBV immortalized cell lines showed no effect of the mutation on RyR1 pharmacological activation or the content of intracellular Ca²⁺ stores. Western blot analysis demonstrated a significant reduction of the RyR1 protein in the patient’s muscle concomitant with a reduction of the DHPRα1.1 protein. This novel mutation resulting in RyR1 protein decrease causes heterogeneous clinical presentation, including slow progression course and absence of centrally localized cores on muscle biopsy. We suggest that RYR1 related myopathy should be considered in a wide variety of clinical and pathological presentation in childhood myopathies.     

A Novel Nonsense Mutation in the MIP Gene Linked to Congenital Posterior Polar Cataracts in a Chinese Family

Purpose

To detect the causative mutation for congenital posterior polar cataracts in a five-generation Chinese family and further explore the potential pathogenesis of this disease.

Methods

Coding exons, with flanking sequences of five candidate genes, were screened using direct DNA sequencing. The identified mutations were confirmed by restriction fragment length polymorphism (RFLP) analysis. A full-length wild-type or an Y219* mutant aquaporin0 (AQP0) fused with an N-terminal FLAG tag, was transfected into HEK293T cells. For co-localization studies, FLAG-WT-AQP0 and Myc-Y219*-AQP0 constructs were co-transfected. Quantitative real-time RT-PCR, western blotting and immunofluorescence studies were performed to determine protein expression levels and sub-cellular localization, respectively.

Results

We identified a novel nonsense mutation in MIP (c.657 C>G; p.Y219*) (major intrinsic protein gene) that segregates with congenital posterior polar cataract in a Chinese family. This mutation altered a highly conserved tyrosine to a stop codon (Y219*) within AQP0.When FLAG-WT-AQP0 and FLAG-Y219*-AQP0 expression constructs were singly transfected into HEK 293T cells, mRNA expression showed no significant difference between the wild-type and the mutant, while Y219*-AQP0 protein expression was significantly lower than that of wild-type AQP0. Wild-type AQP0 predominantly localized to the plasma membrane, while the mutated protein was abundant within the cytoplasm of HEK293T cells. However, when FLAG-WT-AQP0 andMyc-MU-AQP0were co-expressed, both proteins showed high fluorescence in the cytoplasm.

Conclusions

The novel nonsense mutation in the MIP gene (c.657 C>G) identified in a Chinese family may cause posterior polar cataracts. The dominant negative effect of the mutated protein on the wild-type protein interfered with the trafficking of wild-type protein to the cell membrane and both the mutant and wild-type protein were trapped in the cytoplasm. Consequently, both wild-type and mutant protein lost their function as a water channel on the cell membrane, and may result in a cataract phenotype. Our data also expands the spectrum of known MIP mutations.     

Clinical and Functional Characterization of a Novel Mutation in Lamin A/C Gene in a Multigenerational Family with Arrhythmogenic Cardiac Laminopathy

Mutations in the lamin A/C gene (LMNA) were associated with dilated cardiomyopathy (DCM) and, recently, were related to severe forms of arrhythmogenic right ventricular cardiomyopathy (ARVC). Both genetic and phenotypic overlap between DCM and ARVC was observed; molecular pathomechanisms leading to the cardiac phenotypes caused by LMNA mutations are not yet fully elucidated. This study involved a large Italian family, spanning 4 generations, with arrhythmogenic cardiomyopathy of different phenotypes, including ARVC, DCM, system conduction defects, ventricular arrhythmias, and sudden cardiac death. Mutation screening of LMNA and ARVC-related genes PKP2, DSP, DSG2, DSC2, JUP, and CTNNA3 was performed. We identified a novel heterozygous mutation (c.418_438dup) in LMNA gene exon 2, occurring in a highly conserved protein domain across several species. This newly identified variant was not found in 250 ethnically-matched control subjects. Genotype-phenotype correlation studies suggested a co-segregation of the LMNA mutation with the disease phenotype and an incomplete and age-related penetrance. Based on clinical, pedigree, and molecular genetic data, this mutation was considered likely disease-causing. To clarify its potential pathophysiologic impact, functional characterization of this LMNA mutant was performed in cultured cardiomyocytes expressing EGFP-tagged wild-type and mutated LMNA constructs, and indicated an increased nuclear envelope fragility, leading to stress-induced apoptosis as the main pathogenetic mechanism. This study further expands the role of the LMNA gene in the pathogenesis of cardiac laminopathies, suggesting that LMNA should be included in mutation screening of patients with suspected arrhythmogenic cardiomyopathy, particularly when they have ECG evidence for conduction defects. The combination of clinical, genetic, and functional data contribute insights into the pathogenesis of this form of life-threatening arrhythmogenic cardiac laminopathy.     

Somatic Mutations in Exocrine Pancreatic Tumors: Association with Patient Survival

KRAS mutations are major factors involved in initiation and maintenance of pancreatic tumors. The impact of different mutations on patient survival has not been clearly defined. We screened tumors from 171 pancreatic cancer patients for mutations in KRAS and CDKN2A genes. Mutations in KRAS were detected in 134 tumors, with 131 in codon 12 and only 3 in codon 61. The GGT>GAT (G12D) was the most frequent mutation and was present in 60% (80/134). Deletions and mutations in CDKN2A were detected in 43 tumors. Analysis showed that KRAS mutations were associated with reduced patient survival in both malignant exocrine and ductal adenocarcinomas (PDAC). Patients with PDACs that had KRAS mutations showed a median survival of 17 months compared to 30 months for those without mutations (log-rank P = 0.07) with a multivariate hazard ratio (HR) of 2.19 (95%CI 1.09–4.42). The patients with G12D mutation showed a median survival of 16 months (log-rank-test P = 0.03) and an associated multivariate HR 2.42 (95%CI 1.14–2.67). Although, the association of survival in PDAC patients with CDKN2A aberrations in tumors was not statistically significant, the sub-group of patients with concomitant KRAS mutations and CDKN2A alterations in tumors were associated with a median survival of 13.5 months compared to 22 months without mutation (log-rank-test P = 0.02) and a corresponding HR of 3.07 (95%CI 1.33–7.10). Our results are indicative of an association between mutational status and survival in PDAC patients, which if confirmed in subsequent studies can have potential clinical application.     

一个中国Gilbert综合征家系的遗传学分析

对一个中国汉族Gilbert综合征遗传家系致病基因突变位点进行鉴定,以期了解该病的分子遗传学基础。首先提取先证者基因组DNA,PCR扩增尿苷二磷酸葡萄糖醛酸转移酶UGT1A1基因的5个外显子,以琼脂糖电泳鉴定PCR产物,纯化后直接测序鉴定。基因扫描显示,与血清胆红素水平密切相关的UGT1A1基因在第1和第5外显子存在纯合突变,而 UGT1A1基因启动子区域和内含子/外显子剪接边界位点序列未检测到突变。进一步对其他家系成员该基因的相应位点进行突变检测,结果显示他们在第1和第5外显子也存在杂合突变,其中还有两个成员在启动子区域检测到(TA)插入突变。对家系成员未抗凝新鲜血液进行生化检测证实了基因突变分析的结果。综合以上结果发现该家系三种突变并存,致病因素为第1和/或第5外显子突变,为显性遗传,两种突变位点纯合导致先证者出现严重胆红素代谢功能障碍。该家系因此成为Gilbert综合征突变位点及其致病机理研究的一个典型临床病例。     

A Sporadic Case of Pseudohypoparathyroidism Type 1 and Idiopathic Primary Adrenal Insufficiency Associated with a Novel Mutation in the Gnas1 Gene

ObjectiveWe report an atypical association of primary adrenal insufficiency and pseudohypoparathyroidism (PHP) and a novel GNAS1 gene mutation in a Caucasian female who initially presented with adrenal crisis.MethodsA case report and literature review.ResultsA 37-year-old female presented with shock at 11 years of age, and investigations revealed primary adrenal insufficiency and pseudohypoparathyroidism (PHP). She had typical features of Albright hereditary osteodystrophy (AHO) and evidence of thyroid-stimulating hormone (TSH), growth-hormone-releasing hormone (GHRH), and gonadotrophin resistance fitting with the diagnosis of PHP type 1a/1c. She did not have a family history of any autoimmune disease or PHP. Her mother was phenotypically normal. Genomic DNA sequencing of those GNAS exons and adjacent intronic regions that encode the stimulatory guanine nucleotide-binding protein Gsαrevealed a novel heterozygous mutation in exon 11, c.857-858delCT.ConclusionThe association of primary adrenal insufficiency and PHP has not been reported in literature and may prove an area for further research. The novel mutation in this case adds to the spectrum of mutations associated with these disorders. (Endocr Pract. 2014;20:e202-e206)     

A Novel Large In-Frame Deletion within the CACNA1F Gene Associates with a Cone-Rod Dystrophy 3-Like Phenotype

Cone-rod dystrophies (CORDs) represent a heterogeneous group of monogenic diseases leading to early impairment of vision. The majority of CORD entities show autosomal modes of inheritance and X-linked traits are comparably rare. So far, three X-chromosomal entities were reported (CORDX1, -X2 and -X3). In this study, we analysed a large family of German origin with solely affected males over three generations showing a CORDX-like phenotype. Due to the heterogeneity of cone-rod dystrophies, we performed a combined linkage and X-exome sequencing approach and identified a novel large intragenic in-frame deletion encompassing exons 18 to 26 within the CACNA1F gene. CACNA1F is described causative for CORDX3 in a single family originating from Finland and alterations in this gene have not yet been reported in other CORDX pedigrees. Our data independently confirm CACNA1F as the causative gene for CORDX3-like phenotypes and detailed clinical characterization of the family expands the knowledge about the phenotypic spectrum of deleterious CACNA1F alterations.