A RAB27A duplication in several cases of Griscelli syndrome type 2: An explanation for cases lacking a genetic diagnosis

Griscelli syndrome type 2 (GS2) is a rare and often fatal autosomal recessive, hyperinflammatory disorder. It is associated with hypopigmentation of the skin and the hair, resulting in the characteristic pigment accumulation and clumping in the hair shaft. Loss‐of‐function mutations in RAB27A, resulting from point mutations, short indel, or large deletions, account for all the cases reported to date. However, several GS2 cases originating from Saudi Arabia lack a genetic diagnosis. Here, we report on a new RAB27A genetic anomaly observed in seven Saudi Arabia families that had remained negative after extensive molecular genomic DNA testing. Linkage analysis and targeted sequencing of the RAB27A genomic region in several of these patients led to the identification of a common homozygous tandem duplication of 38 kb affecting exon 2–5 and resulting in a premature stop codon. The pathogenic effect of this duplication was confirmed by a cDNA analysis and functional assays. The identification of microhomology flanking the breakpoint site suggests a possible underlying mechanism.     

Analysis of RAB27A Gene in Griscelli Syndrome type 2: Novel Mutations Including a Deletion Hotspot

INTRODUCTION: Griscelli syndrome type 2 is an autosomal recessive disorder characterized by pigmentary dilution and occurrence of acute phases of hemophagocytosis. The disease is caused by mutations in RAB27A gene, coding a small GTPase involved in terminal phases of cytotoxic granule/melanosome exocytosis. MATERIALS AND METHODS: We describe the result of mutation analysis among nine patients from seven non-related Persian families. We present four novel mutations including a deletion hot spot (514del 5). CONCLUSION: This hot spot is flanked by "direct repeats" of nucleotides, which are previously shown to be associated with areas of recurrent small deletions.     

Functional Characterization and Rescue of a Deep Intronic Mutation in OCRL Gene Responsible for Lowe Syndrome

Dent‐2 disease and Lowe syndrome are two pathologies caused by mutations in inositol polyphosphate 5‐phosphatase OCRL gene. Both conditions share proximal tubulopathy evolving to chronic kidney failure. Lowe syndrome is in addition defined by a bilateral congenital cataract, intellectual disability, and hypotonia. The pathology evolves in two decades to a severe condition with renal complications and a fatal issue. We describe here a proof of principle for a targeted gene therapy on a mutation of the OCRL gene that is associated with Lowe syndrome. The affected patient bears a deep intronic mutation inducing a pseudo‐exon inclusion in the mRNA, leading to a OCRL‐1 protein loss. An exon‐skipping strategy was designed to correct the effect of the mutation in cultured cells. We show that a recombinant U7‐modified small RNA efficiently triggered the restoration of normal OCRL expression at mRNA and protein levels in patient's fibroblasts. Moreover, the PI(4,5)P2 accumulation and cellular alterations that are hallmark of OCRL‐1 dysfunction were also rescued. Altogether, we provide evidence that the restoration of OCRL‐1 protein, even at a reduced level, through RNA‐based therapy represents a potential therapeutic approach for patients with OCRL splice mutations.     

Familial Kallmann Syndrome: A Novel Splice Acceptor Mutation in the KAL Gene

Kallmann syndrome is an inherited disease which is characterised by anosmia (inability to smell) and hypogonadotropic hypogonadism both of which are thought to occur as a result of a failure of correct neuronal migration. To date the only genetic lesions identified are mutations in the X-linked gene, KAL. We conducted a mutation screen of the KAL gene in a family with Kallmann syndrome. This identified a new mutation in the KAL gene which removed an acceptor site at the junction of exon 6 /intron 5. Exon 6 of the KAL gene encodes the C-terminal portion of a fibronectin type III domain may be involved in axonal pathfinding. We presume that the described mutation would result in the removal of exon 6 resulting in a frame shift which terminates the protein prematurely. It has been proposed that both mental illness and vesico-ureteric reflux are associated with mutations in the KAL gene. However, results from the family presented here do not show an association between either trait and the KAL gene mutation.     

KCNH2 Gene Mutation: A Potential Link Between Epilepsy and Long QT-2 Syndrome

Long QT syndrome (LQTS) is closely associated with syncope, seizure, and sudden death but LQTS is frequently misdiagnosed as epilepsy. LQTS and epilepsy both belong to the group of ion channelopathies that manifest in the heart and brain. Therefore, genetic analysis of genes associated with potassium and sodium homeostasis and electrical disorders may reveal a link between epilepsy and lethal cardiac arrhythmia. Here, the authors report a young woman who suffered recurrent seizure episodes and syncopes that occurred while walking and also during rest. She showed electroencephalogram abnormalities and a pathological prolonged QTc interval in electrocardiogram. The patient and the patient's asymptomatic family members underwent genetic screening of the three genes most frequently associated with LQTS: KCNQ1, KCNH2, and SCN5A. The patient and the family members did not show DNA alterations in the genes KCNQ1 and SCN5A associated with LQT-1 and LQT-3, respectively. However, the patient showed a de novo mutation 2587T→C in exon 10 of KCNH2 gene associated with LQT-2. The mutation caused a stop codon substitution (R863X) in the HERG channel, leading to a 296–amino acid deletion. The patient's asymptomatic relatives did not show the KCNH2 gene mutation. R863X alteration in HERG channel may be involved in both prolonged QTc interval and epilepsy. This fact raises the possibility that R863X alteration in KCNH2-encoded potassium channel may confer susceptibility for epilepsy and cardiac LQT-2 arrhythmia.     

A Novel TAZ Gene Mutation and Mosaicism in a Polish Family with Barth Syndrome

Barth syndrome (BTHS) is an X‐linked recessive disease primarily affecting males. Clinically, the disease is characterized by hypertrophic or dilated cardiomyopathy, skeletal myopathy, chronic/cyclic neutropenia, 3‐methylglutaconic aciduria, growth retardation and respiratory chain dysfunction. It is caused by mutations in the TAZ gene coding for the tafazzin protein which is responsible for cardiolipin remodeling. In this work, we present a novel pathogenic TAZ mutation c.83T>A, p.Val28Glu, found in mosaic form in almost all female members of a Polish family. Sanger sequencing of DNA from peripheral blood and from epithelial cells showed female mosaicism in three generations. This appears to be a new mechanism of inheritance and further research is required in order to understand the mechanism of this mosaicism. We conclude that BTHS genetic testing should include two or more tissues for women that appear to be noncarriers when blood DNA is initially tested. The results of our study should not only be applicable to BTHS families, but also to families with other X‐linked diseases.     

Identification and Biochemical Characterization of a Novel Mutation in DDX11 Causing Warsaw Breakage Syndrome

Mutations in the gene encoding the iron–sulfur‐containing DNA helicase DDX11 (ChlR1) were recently identified as a cause of a new recessive cohesinopathy, Warsaw breakage syndrome (WABS), in a single patient with severe microcephaly, pre‐ and postnatal growth retardation, and abnormal skin pigmentation. Here, using homozygosity mapping in a Lebanese consanguineous family followed by exome sequencing, we identified a novel homozygous mutation (c.788G>A [p.R263Q]) in DDX11 in three affected siblings with severe intellectual disability and many of the congenital abnormalities reported in the WABS original case. Cultured lymphocytes from the patients showed increased mitomycin C‐induced chromosomal breakage, as found in WABS. Biochemical studies of purified recombinant DDX11 indicated that the p.R263Q mutation impaired DDX11 helicase activity by perturbing its DNA binding and DNA‐dependent ATP hydrolysis. Our findings thus confirm the involvement of DDX11 in WABS, describe its phenotypical spectrum, and provide novel insight into the structural requirement for DDX11 activity.     

Temporally Manipulated Rescue of Visual and Courtship Abnormalities Caused by a Nona Mutation in Drosophila

The no-on-transient-A gene was identified by independently isolated mutations causing visual-response abnormalities or courtship song defects. The nonA^diss mutant is abnormal for all of these phenotypes. The pleiotropic effects of this dissonance allele dovetail with the widespread tissue expression of the nonA products. This gene, which encodes a putative RNA-binding protein, is expressed at essentially all stages of the life cycle. To determine whether the behavioral and physiological abnormalities exhibited by nonA mutant adults have a developmental etiology or are the result of an impaired mature nervous (or perhaps neuro-muscular) system, a conditional form of this gene was constructed. Animals from the resulting hsp-nonA(cDNA) transgenic strain were subjected to heat-shock regimes such that the gene's coding sequences were activated during development only, solely in the imaginal stage, or both. Surprisingly, expression during any of these time periods effected rescue of the visual-response and the courtship-song defects.     

Structural,Functional, and Clinical Characterization of a Novel PTPN11 Mutation Cluster Underlying Noonan Syndrome

Germline mutations in PTPN11, the gene encoding the Src‐homology 2 (SH2) domain‐containing protein tyrosine phosphatase (SHP2), cause Noonan syndrome (NS), a relatively common, clinically variable, multisystem disorder. Here, we report on the identification of five different PTPN11 missense changes affecting residues Leu²⁶¹, Leu²⁶², and Arg²⁶⁵ in 16 unrelated individuals with clinical diagnosis of NS or with features suggestive for this disorder, specifying a novel disease‐causing mutation cluster. Expression of the mutant proteins in HEK293T cells documented their activating role on MAPK signaling. Structural data predicted a gain‐of‐function role of substitutions at residues Leu²⁶² and Arg²⁶⁵ exerted by disruption of the N‐SH2/PTP autoinhibitory interaction. Molecular dynamics simulations suggested a more complex behavior for changes affecting Leu²⁶¹, with possible impact on SHP2's catalytic activity/selectivity and proper interaction of the PTP domain with the regulatory SH2 domains. Consistent with that, biochemical data indicated that substitutions at codons 262 and 265 increased the catalytic activity of the phosphatase, while those affecting codon 261 were only moderately activating but impacted substrate specificity. Remarkably, these mutations underlie a relatively mild form of NS characterized by low prevalence of cardiac defects, short stature, and cognitive and behavioral issues, as well as less evident typical facial features.     

Mutations of the Imprinted CDKN1C Gene as a Cause of the Overgrowth Beckwith–Wiedemann Syndrome: Clinical Spectrum and Functional Characterization

Beckwith–Wiedemann syndrome (BWS) is an imprinting disorder associating macroglossia, abdominal wall defects, visceromegaly, and a high risk of childhood tumor. Molecular anomalies are mostly epigenetic; however, mutations of CDKN1C are implicated in 8% of cases, including both sporadic and familial forms. We aimed to describe the phenotype of BWS patients with CDKN1C mutations and develop a functional test for CDKN1C mutations. For each propositus, we sequenced the three exons and intron–exon boundaries of CDKN1C in patients presenting a BWS phenotype, including abdominal wall defects, without 11p15 methylation defects. We developed a functional test based on flow cytometry. We identified 37 mutations in 38 pedigrees (50 patients and seven fetuses). Analysis of parental samples when available showed that all mutations tested but one was inherited from the mother. The four missense mutations led to a less severe phenotype (lower frequency of exomphalos) than the other 33 mutations. The following four tumors occurred: one neuroblastoma, one ganglioneuroblastoma, one melanoma, and one acute lymphoid leukemia. Cases of BWS caused by CDKN1C mutations are not rare. CDKN1C sequencing should be performed for BWS patients presenting with abdominal wall defects or cleft palate without 11p15 methylation defects or body asymmetry, or in familial cases of BWS.     

A Novel Homozygous Nonsense Mutation in the PVRL4 Gene and Expansion of Clinical Spectrum of EDSS1

Ectodermal dysplasias (EDs) belong to a group of genetic diseases which result from alterations in ectoderm‐derived appendages including hair, nail, teeth and sweat glands. Ectodermal dysplasia syndactyly syndrome (EDSS1) is one of the rare forms of ED caused by mutations in nectin‐4, encoded by the PVRL4 gene. The present study described clinical investigation of the EDSS1 identified in a large consanguineous family. Furthermore, DNA sequence analysis revealed a novel homozygous nonsense mutation (181C>T, p.Asp61*) in the PVRL4 gene.     

IL-3、IL-6联合转基因的基质细胞促进异基因小鼠骨髓移植后的免疫重建

探讨转染IL 3和IL 6基因的骨髓基质细胞系QXMSC1对异基因骨髓移植 (BMT )小鼠免疫功能重建的促进作用。用逆转录病毒载体将小鼠IL 3和IL 6基因转染到骨髓基质细胞系QXMSC1(H 2 d) ,分别建立基质细胞系QXMSC1IL 3、QXMSC1IL 6及QXMSC1IL 3/IL 6 ,供体BALB/c(H 2 d)小鼠骨髓去除T细胞 ,致死量照射 (9 0Gy)受体小鼠C5 7BL/ 6 (H 2 b)后 ,输入供体骨髓细胞 (1× 10 5/只 )的同时输入基质细胞QXMSC1IL 3/IL 6 (5× 10 5/只 )。在骨髓移植后 30d、 6 0d ,检测BMT小鼠脾细胞对LPS、ConA的反应强度、脾细胞中辅助性T淋巴细胞前体频数 (HTLp )、杀伤性T淋巴细胞前体频数 (CTLp )、抗体生成细胞 (PFC )的能力及对迟发型超敏反应 (DTH )的能力来评价BMT后免疫功能的恢复情况。异基因BMT并输入基质细胞系QXMSC1IL 3/IL 6可明显增强BMT后淋巴细胞对LPS、ConA反应强度 ,小鼠对异基因小鼠脾细胞DTH反应增强 ,脾淋巴细胞HTLp、CTLp及PFC数明显增加。基质细胞QXMSC1可作为有效的基因载体明显促进异基因骨髓移植小鼠免疫功能重建。联合转入IL 3和IL 6对BMT后免疫功能的恢复有协同作用     

Mutation spectrum in children with primary hemophagocytic lymphohistiocytosis: molecular and functional analyses of PRF1, UNC13D, STX11, and RAB27A

Familial hemophagocytic lymphohistiocytosis (FHL) is an autosomal-recessive disease that affects young children. It presents as a severe hyperinflammatory syndrome with activated macrophages and T lymphocytes. Mutations in the perforin 1 gene (PRF1) were found in FHL-2 in 15-50% of all cases. Defective granule exocytosis caused by mutations in the hMunc13-4 gene (UNC13D) has been described in FHL-3. FHL-4 patients have mutations in STX11, a t-SNARE involved in intracellular trafficking. We analyzed a large group of 63 unrelated patients with FHL of different geographic origins (Turkey:32; Germany:23; others:8) for mutations in STX11, PRF1, and UNC13D. We identified mutations in 38 samples (20 in PRF1, 12 in UNC13D, and six in STX11). Of 32 patients from Turkey, 14 had mutations in PRF1, six had mutations in UNC13D, and six had mutations in STX11. The mutation Trp374X in PRF1 was found in 12 patients from Turkey and was associated with a very early onset of the disease below the age of 3 months in all cases. In contrast, three of 23 and four of 23 patients from Germany, and three of eight and two of eight from other origins showed mutations in PRF1 and UNC13D, respectively, but none in STX11. Thus, FHL-2, FHL-3, and FHL-4 account for 80% of the HLH cases of Turkish origin, and for 30% of German patients. Furthermore, we identified mutations in RAB27A in three patients with FHL-related Griscelli syndrome type 2. In functional studies using a mammalian two-hybrid system we found that missense mutations Ala87Pro in Rab27a and Leu403Pro in hMunc13-4 each prevented the formation of a stable hMunc13-4/Rab27a complex in vitro. Our findings demonstrate extensive genetic and allelic heterogeneity in FHL and delineate an approach for functionally characterizing missense mutations in RAB27A and UNC13D.     

Association of Gene Polymorphism of the Fat Mass and Obesity Associated Gene with Metabolic Syndrome: A Retrospective Cohort Study in Japanese Workers

To investigate whether gene polymorphism of the fat mass and obesity associated gene(FTO) is associated with metabolic syndrome (MS), we used two MS criteria, the NationalCholesterol Education Program-Adult Treatment panel III (NCEP-ATPIII) definition in 2003and the Japanese definition in 2005. Subjects were respectively 859 and 865 Japaneseworkers at a company in Shimane Prefecture, Japan. They were non-MS individuals in 1998and had regular health checkups between 1998 and 2006. The Cox proportional hazardregression was used to predict MS. Three SNPs in the FTO, rs9939609, rs1121980 andrs1558902, were genotyped by the TaqMan PCR assay and a retrospective study was performed.The three SNPs in the FTO were significantly associated with body mass index, andrs1121980 and rs1558902 were associated with fasting plasma glucose. MS defined by theNCEP-ATPIII definition was significantly associated with additive and dominant models ofrs9939609 and rs1121980, and the dominant model of rs1558902, even after adjusting forconfounding factors such as age, sex and lifestyle. MS defined by the Japanese definitionwas significantly associated with the additive model of rs1121980 and additive anddominant models of rs1558902 in multivariate analysis. These results suggested that FTOgene polymorphisms, rs9939609, rs1121980 and rs1558902, were associated with an increasedrisk of MS among Japanese workers.     

Uptake Rate of Risk-Reducing Salpingo-Oophorectomy and Surgical Outcomes of Female Germline BRCA1/2 Mutation Carriers: A Retrospective Cohort Study

PurposeThis study investigated the uptake rate of risk-reducing salpingo-oophorectomy (RRSO) and surgical outcomes of germline BRCA1/2 mutation carriers at Seoul National University Hospital (SNUH).Materials and MethodsWe examined the records of 824 women who underwent germline BRCA1/2 gene testing at SNUH between 2005 and 2020. Among them, we identified women with a pathogenic mutation on either the BRCA1 or the BRCA2 gene, and excluded ovarian cancer patients. Characteristics of participants who underwent RRSO (RRSO group) were compared to those who did not (non-RRSO group). Surgical outcomes and pathologic results were investigated in the RRSO group.ResultsThere were 117 BRCA1/2 mutation carriers included in the analysis. The uptake rate of RRSO was 70.1% (82/117). Older age (mean: 48.8 years vs. 42.1 years; p=0.002) and higher employment rate (65.9% vs. 14.3%; p<0.001) were observed in the RRSO group compared to the non-RRSO group. However, no differences in other factors, such as personal and family history of breast cancer, were observed between the two groups. In the RRSO group, the median time interval between the genetic test and RRSO was 10.0 months, and there were three (3.7%) incidental cases of high-grade serous carcinoma. However, one patient in the non-RRSO group developed primary peritoneal cancer after 103.8 months of surveillance.ConclusionThe uptake rate of RRSO in BRCA1/2 mutation carriers was about 70%. Considering incidental cancer cases in women without abnormal findings on preoperative evaluation, BRCA1/2-mutated women might refrain from the delayed implementation of RRSO after the genetic test.     

HLA loss variants of a B27+ lymphoblastoid cell line: Genetic and cellular characterization

Variants of a lymphoblastoid cell line, LCL 526 (SB3 MB1 DR1 B44 C5 A2/SB4 MT4 DR4 B27 C2 A24), which lost various HLA specificities were selected with monoclonal antibodies and complement using a method developed by Kavathas et al. (PNAS 77:4251, 1980). Using αB27 monoclonals, 8 B27 only loss mutants and 4 B27 haplotype multiple loss mutants were generated. The parental LCL 526 and two of the B27^? mutants were used to select αB27 CTLs. The selection of six A2 loss, one A2-C5 loss, and 14 A2 haplotype multiple loss variants as well as secondary selection on haplotype loss variants to obtain A null, B null, DR null, and total A,B,C, null variants is also described. The usefulness of these mutants for the study of the relationship between B27 and disease and as two new haplotypes for immunologic, genetic, and molecular research is discussed. These mutants are available to other researchers.     

Novel A219P Mutation of Hydroxymethylbilane Synthase Identified in a Chinese Woman with Acute Intermittent Porphyria and Syndrome of Inappropriate Antidiuretic Hormone

Acute intermittent porphyria (AIP) is an autosomal dominant metabolic disorder caused by deficiency of the heme biosynthetic enzyme hydroxymethylbilane synthase (approved gene symbol HMBS), also known as porphobilinogen deaminase (PBGD). AIP is characterised by intermittent attacks of abdominal pain, vomiting, and neurological complaints. The highly variable symptomatic presentation of AIP causes confusion with other diseases and results in a high misdiagnosis rate (68% in China) and delayed effective treatments. Based on biochemical and genetic analysis of two Chinese families, a new and a previously reported HMBS mutation were identified in patients with AIP and syndrome of inappropriate antidiuretic hormone (SIADH). The novel HMBS mutation is the 655G>C point mutation (A219P). In addition, the 973C>T point mutation (R325X), which had been previously reported in two Danish families, was identified.     

Analysis of SWAP-70 as a Candidate Gene for Non-X-Linked Hyper IgM Syndrome and Common Variable Immunodeficiency

SWAP-70 is a recently identified protein that functions as the only B cell-specific component of an isotype switch recombination complex called SWAP. The SWAP complex has specificity for the switch regions upstream of the constant region immunoglobulin genes and it facilitates the transfer of DNA between switch regions. These features suggested that mutations in the gene encoding SWAP-70 might result in humoral immunodeficiency. To test this hypothesis we determined the genomic structure of this gene and used single-stranded conformational polymorphism (SSCP) analysis to screen DNA from 38 patients with either non-X-linked hyper IgM syndrome or common variable immunodeficiency. The results demonstrated that SWAP-70 consists of 12 exons spread over 89 kb at chromosome 11p15.2. SSCP analysis of the patient population revealed five polymorphic variants in the gene, one of which (Q505E) is an amino acid substitution in the putative nuclear export signal of SWAP-70. However, none of the alterations appeared to be associated with disease in the patients screened.