OMIM Number Research Articles

Epidermolytic Hyperkeratosis Type 1 with a New Heterozygous Mutation in KRT1 Gene: A Case Report

Background: Epidermolytic hyperkeratosis (EHK) formerly known as bullous ichthyosiform erythroderma, is a rare autosomal dominant inheritance condition with a prevalence ranging from 1:200,000 to 1:300,000. The underlying etiology of which is a mutation in the genes responsible for keratin proteins synthesis, primarily in KRT1 and KRT10 genes, cataloged under OMIM number 113800. Clinicopathological presentations include blistering in the neonatal period followed by ichthyotic hyperkeratosis in childhood and adolescence, characterized by the hallmark features of generalized dry skin, scaling, hyperkeratosis, and frequently associated with erythroderma. EHK may present with or without palmoplantar keratoderma involvement, depending on the keratin gene variant. Case report: A 24-year-old male of Arab descent was born with diffuse skin hyperkeratotic plates featuring erythematous fissures, covering his entire body, resembling a collodion baby. His birth was full-term via cesarean section without complications, although he later developed developmental dysplasia of the hip. By the time he started primary school, he began experiencing severe thickening of the skin around his joints, reducing flexibility and leading to contractures and significant disfigurement. He is undergoing treatment with acitretin. Genetic testing using Next-Generation Sequencing (NGS) was performed to identify the responsible gene, revealing a novel heterozygous variant in the KRT1 gene (OMIM 139350), while no variant was detected in the KRT10 gene. Conclusion: EHK type 1 manifests with a new heterozygous variant in the KRT1 gene. This rare disorder, associated with variant in genes related to keratin production such as KRT1 and KRT10, results in distinctive skin features present from birth, as well as joint problems and fungal foot infections. Genetic testing has confirmed the presence of a variant in the KRT1 gene.

Assessment of myogenic potency in patient-derived fibroblasts with c.1289-2A>G Desmin mutation

Abstract Objectives The ultra-rare DES c.1289-2A>G mutation, resulting in a 48-base pair insertion in the Desmin tail domain, is associated with late-onset MFM1 (myofibrillar myopathy-1; OMIM number; 601419) and exhibits distinctive pathological features. Despite sustained expression and cytoskeletal integrity, muscle biopsies reveal dystrophic characteristics through an unidentified mechanism. A deeper understanding of the molecular mechanisms underlying Desmin-related MFM1 could enhance our perspective and comprehension of the disease’s pathophysiology. In this study, we aimed to investigate the pathological phenotype by assessing the myogenic potency of MyoD-induced patient-derived fibroblasts. Methods Following the immortalization and myoconversion of unaffected and patient-derived fibroblast cells, we analyzed the myogenic potency of the mutant and control groups on day 5 post-differentiation. This analysis involved staining cells with MF20 antibody and DAPI after MyoD induction. Results Employing six parameters to quantify extra nuclei and myotube properties, we unveil impaired myogenic differentiation in c.1289-2A>G mutant cells, as evidenced by a compromised fusion index and distinctive myogenic features. In summary, our preliminary findings indicate phenotypic abnormalities and suggest an association between the DES c.1289-2A>G mutation and delayed maturation and MFM in affected individuals. Conclusions Our results indicate a significant involvement of Desmin in the myogenic maturation of muscle cells. Further investigation is required to understand the changes in the transcriptome during the myoconversion of patient-derived fibroblasts.

An Unexpected Diagnosis of MAGT1 Deficiency in a Patient with CVID-like Features, Molluscum Contagiosum and Atopy

Case DescriptionA 6-year-old boy presented to the immunology clinic with recurrent infections. He started to have recurrent otitis media at the age of 18 months. He also had multiple sinus infections and 3–4 episodes of pneumonia. Immunologic evaluation revealed an IgG of 498 (ref 608–1229 mg/dL), an IgA of 20.8 (ref 33–200 mg/dL) and an impaired response to the Streptococcus pneumoniae vaccine. T and B lymphocyte counts were normal. He was started on subcutaneous immunoglobulin replacement therapy after which his IgG level normalized and his frequency of sinopulmonary infections improved. He also has a history of eczema, chronic cough and environmental allergies for which he receives allergen-specific subcutaneous immunotherapy in addition to treatment with an inhaled corticosteroid and omalizumab. The patient also had persistent skin warts on his hands and extensive molluscum contagiosum lesions. He underwent targeted genetic testing for a primary immunodeficiency which revealed a hemizygous pathogenic variant in the magnesium transporter 1 (MAGT1) gene (c.580dup; p.Ser194Phefs*3). This variant is a duplication at nucleotide position 580 that creates a premature stop codon 3 amino acids downstream from this location. The patient subsequently underwent a carbohydrate deficient transferrin test (CDT) for congenital disorders of glycosylation (CDG) that revealed moderately elevated transferrin mono-oligosaccharide to di-oligosaccharide and Apo CIII-1/Apo CIII-2 ratios, consistent with the diagnosis of MAGT1-CDG (XMEN; X-linked immunodeficiency with magnesium defect, EBV infection, and neoplasia). Additionally, NKG2D surface expression was reduced by ~90% on the CD8T cells, and by ~85% on the NK cells in the patient sample compared to the control sample assessed in parallel. The patient continues to test negative for EBV infection by PCR. ConclusionXMEN disease (OMIM number 300853) is a rare, combined immunodeficiency resulting from a mutation in the magnesium transporter 1 gene (MAGT1) located on the X chromosome. Only 36 patients have been reported to have this disease thus far. While the clinical phenotype is variable, the disease is often associated with EBV infection. This case is unique in that the patient was diagnosed due to a history of severe warts, atopy, and hypogammaglobulinemia in the absence of EBV infection.

A Novel Homozygous Nonsense Variant in the DYM Underlies Dyggve-Melchior-Clausen Syndrome in Large Consanguineous Family.

(1) Background: Dyggve-Melchior-Clausen Syndrome is a skeletal dysplasia caused by a defect in the DYM gene (OMIM number 607461). Pathogenic variants in the gene have been reported to cause Dyggve-Melchior-Clausen (DMC; OMIM 223800) dysplasia and Smith-McCort (SMC; OMIM 607326) dysplasia. (2) Methods: In the present study, large consanguineous families with five affected individuals with osteochondrodysplasia phenotypes were recruited. The family members were analyzed by polymerase chain reaction for homozygosity mapping using highly polymorphic microsatellite markers. Subsequent to linkage analysis, the coding exons and exon intron border of the DYM gene were amplified. The amplified products were then sent for Sanger sequencing. The structural effect of the pathogenic variant was analyzed by different bioinformatics tools. (3) Results: Homozygosity mapping revealed a 9 Mb homozygous region on chromosome 18q21.1 harboring DYM shared by all available affected individuals. Sanger sequencing of the coding exons and exon intron borders of the DYM gene revealed a novel homozygous nonsense variant [DYM (NM_017653.6):c.1205T>A, p.(Leu402Ter)] in affected individuals. All the available unaffected individuals were either heterozygous or wild type for the identified variant. The identified mutation results in loss of protein stability and weekend interactions with other proteins making them pathogenic (4) Conclusions: This is the second nonsense mutation reported in a Pakistani population causing DMC. The study presented would be helpful in prenatal screening, genetic counseling, and carrier testing of other members in the Pakistani community.

Cafe-au-lait spots as a clinical sign of syndromes

Several studies describe the frequent association of cafe-au-lait spots with neurofibromatosis. However, many other genetic diseases might be associated with the presence of café-au-lait spots. Several genetic diseases are rare. In most cases, syndromes present themselves as a set of signs and symptoms that may present varied penetrance, therefore largely reducing the percentage of final diagnosis. Exploration of clinical symptomatology is essential for the understanding and diagnosis of syndromes. In this review, we conduct an extensive literature search looking for research that investigated diseases that may be present simultaneously with the cafe-au-lait spots. A total of 60 genetic diseases were found, all of them rare. These syndromes were evaluated based on their most relevant features and described in a summary of the typical, general, and head and neck findings. The available OMIM number, mode of inheritance, chromosome, mutated genes, and affected proteins were also listed. The considerable variety of diseases associated with the presence of cafe-au-lait spots and the fact that many of these conditions affect various organ systems with diverse phenotypic presentations is a diagnostic and therapeutic challenge. The objective of this study was to provide health professionals with an instrument containing a broad spectrum of genetic diseases coincident with the presence of cafe-au-lait spots in order to facilitate the differential and final diagnosis of these syndromes.

A case of autosomal recessive hypercholesterolemia with a novel mutation in the LDLRAP1 gene.

Familial hypercholesterolemia (FH, OMIM number #143890), a life-threatening monogenic disorder characterized by high levels of low-density lipoprotein cholesterol (LDL-C), is classified into dominant and recessive types (1). The dominant form of FH may result from mutations in the LDLR, APOB, and PCSK9 genes (2). However, mutations in the low-density lipoprotein receptor (LDLR) adaptor protein-1 (LDLRAP1) gene cause an autosomal recessive inheritance pattern of FH called autosomal recessive hypercholesterolemia (ARH, OMIM number #603813). The LDLRAP1 protein, encoded by the LDLRAP1 gene, is required for receptor-mediated endocytosis of LDL-C (2). ARH is a rare disorder with an estimated prevalence of less than 1 in a population of one million. This disease is considered a phenocopy of the most severe form of FH, homozygous familial hypercholesterolemia (HoFH; OMIM number 143890). Hence, most ARH patients are clinically indiscernible from HoFH, which is caused by two defective LDLR genes with an approximate prevalence of one individual per million (8). Considering that ARH patients may develop aggressive and premature atherosclerotic cardiovascular disease (ASCVD) due to hypercholesterolemia during early adulthood, lipid-lowering therapy must be initiated during childhood (3). Early identification of ARH patients through genetic analysis of the proband and their relatives can provide prognosis and subsequently appropriate, timely treatment. In this report, we describe a novel variant, c.649G>T, p.Glu217Ter, in the homozygous state in exon 7 of the LDLRAP1 gene, causing severe ARH.

Progressive Osseous Heteroplasia is not an Autosomal Dominant Trait but Reflects Superimposed Mosaicism in Different GNAS Inactivation Disorders.

Progressive osseous heteroplasia (POH) is a rarely occurring genetic condition characterized by severe segmental ossification involving the skin and deep connective tissues including the muscles. So far, the disorder is generally described as an autosomal dominant trait. By contrast, the following arguments are in favor of the alternative concept that POH should rather be taken as a non-specific segmental manifestation of different GNAS inactivation disorders such as Albright hereditary osteodystrophy (AHO) with hormone resistance, AHO without hormone resistance, and osteomatosis cutis. Presently, POH has got its own OMIM number 166350 but this is obviously wrong because the disorder does not reflect heterozygosity for a GNAS mutation. Conversely, the disorder is most likely due to an early event of postzygotic loss of heterozygosity with loss of the corresponding wild-type allele. This alternative concept, as proposed in 2016, offers a plausible explanation for the following features of POH. Familial occurrence is usually absent. POH is usually observed in families with one of the three GNAS inactivation disorders as mentioned above. Mosaicism is suggested by the pronounced segmental manifestation of POH and by its lateralization. Some patients have, in addition to POH, bilaterally disseminated features of osteomatosis cutis or AHO, and other patients have family members with one of these nonsegmental disorders. Remarkably, POH tends to appear much earlier than the nonsegmental GNAS inactivation disorders. – Molecular support of the concept was documented in a superficial variant of POH called 'plate-like osteoma cutis'. In several other autosomal dominant skin disorders, molecular corroboration of the theory of superimposed mosaicism has been provided. – For all of these reasons, it is unlikely that POH can further be taken as a distinct autosomal dominant trait. Generation of more molecular data in multiple cases of POH occurring in GNAS inactivation disorders will be crucial to corroborate the proposed concept.

Activation of Naturally Occurring Lecithin:Cholesterol Acyltransferase Mutants by a Novel Activator Compound.

Lecithin:cholesterol acyltransferase (LCAT) is a unique plasma enzyme able to esterify cholesterol, and it plays an important role in HDL maturation and promotion of reverse cholesterol transport. Familial LCAT deficiency (FLD; OMIM number 245900) is a rare recessive disease that results from loss-of-function mutations in the LCAT gene and has no cure. In this study, we assessed the in vitro efficacy of a novel small-molecule LCAT activator. Cholesterol esterification rate (CER) and LCAT activity were tested in plasma from six controls and five FLD homozygous carriers of various LCAT mutations at different doses of the compound (0.1, 1, and 10 µg/ml). In control plasma, the compound significantly increased both CER (P < 0.001) and LCAT activity (P = 0.007) in a dose-dependent manner. Both CER and LCAT activity increased by 4- to 5-fold, reaching maximum activation at the dose of 1 µg/ml. Interestingly, Daiichi Sankyo compound produced an increase in CER in two of the five tested LCAT mutants (Leu372--Arg and Val309--Met), while LCAT activity increased in three LCAT mutants (Arg147--Trp, Thr274--Ile and Leu372--Arg); mutant Pro254--Ser was not activated at any of the tested doses. The present findings form the basis for personalized therapeutic interventions in FLD carriers and support the potential LCAT activation in secondary LCAT defects. SIGNIFICANCE STATEMENT: We characterized the pharmacology of a novel small-molecule LCAT activator in vitro on a subset of naturally occurring LCAT mutants. Our findings form the basis for personalized therapeutic interventions for familial LCAT deficiency carriers, who can face severe complications and for whom no cure exists.

A Japanese case of familial hypercholesterolemia with a novel mutation in the LDLR gene.

Familial hypercholesterolemia (FH, OMIM number #143890) is an autosomal dominant disorder, resulting in low-density lipoprotein (LDL) receptor dysfunction. The prevalence of FH is estimated to be approximately, 1 in 200 and 1 in 170,000 among heterozygotes and homozygotes, respectively (1). Since FH patients develop severe coronary-artery disease (CAD) due to hypercholesterolemia in early adult life, lipid-lowering treatments must be started at childhood (2). Although pediatric FH is clinically diagnosed based on the serum LDL cholesterol (LDL-C) levels and a family history of hypercholesterolemia, genetic analysis is useful for a definitive diagnosis, as it can predict the risk stratification of CAD (3, 4) and assist in early diagnosis and intervention, leading to improved prognosis. Here, we present a novel mutation in the LDLR gene, in a patient with heterozygous FH (HeFH).

Cenani-Lenz syndrome and other related syndactyly disorders due to variants in LRP4, GREM1/FMN1, and APC: Insight into the pathogenesis and the relationship to polyposis through the WNT and BMP antagonistic pathways.

Cenani-Lenz (C-L) syndrome is characterized by oligosyndactyly, metacarpal synostosis, phalangeal disorganization, and other variable facial and systemic features. Most cases are caused by homozygous and compound heterozygous missense and splice mutations of the LRP4 gene. Currently, the syndrome carries one OMIM number (212780). However, C-L syndrome-like phenotypes as well as other syndactyly disorders with or without metacarpal synostosis/phalangeal disorganization are also known to be associated with specific LRP4 mutations, adenomatous polyposis coli (APC) truncating mutations, genomic rearrangements of the GREM1-FMN1 locus, as well as FMN1 mutations. Surprisingly, patients with C-L syndrome-like phenotype caused by APC truncating mutations have no polyposis despite the increased levels of β catenin. The LRP4 and APC proteins act on the WNT (wingless-type integration site family) canonical pathway, whereas the GREM-1 and FMN1 proteins act on the bone morphogenetic protein (BMP) pathway. In this review, we discuss the different mutations associated with C-L syndrome, classify its clinical features, review familial adenomatous polyposis caused by truncating APC mutations and compare these mutations to the splicing APC mutation associated with syndactyly, and finally, explore the pathophysiology through a review of the cross talks between the WNT canonical and the BMP antagonistic pathways.

Signs indicating dementia in Down, Williams and Fragile X syndromes

BackgroundIntellectual disability (ID) and dementia reflect disturbed cortical function during and after developmental age, respectively. Due to the wide heterogeneity of ID population the decline in cognitive and adaptive skills may be different in distinct genetic subgroups.MethodsUsing the British Present Psychiatric State–learning Disabilities assessment (PPS‐LD) questionnaire the dementia signs were screened in 62, 22 and 44 individuals (> 35 year of age) with Down (DS, OMIM number 190685), Williams (WS, OMIM number, 194050), and Fragile X syndrome (FXS, OMIM number 309550), respectively. The median age of those with FXS (59 years) was higher than of those with DS (50 years) and WS (53 years).ResultsMost study participants with DS (80%) and FXS (89%) were or had been moderately or severely intellectually disabled while most participants with WS (73%) were or had been mildly or moderately disabled at adolescent age. The adolescent (premorbid) level of ID did not correlate with the dementia score. The median scores were 11/27, 1/27, and 0/27 in DS, WS, and FXS subgroups, respectively. Dementia that was confirmed by brain imaging, manifested as Alzheimer disease and as moya‐moya disease associated vascular dementia in DS and as vascular dementia in WS.ConclusionsThis survey suggests that the risk of dementia varies depending on the cause of ID and that the severity of ID in adolescence does not predict the development of dementia at a later age. Consequently, the ID and dementia should be understood as separate clinical entities that need to be taken into account in the health management of intellectually disabled people. This is important for the arrangement of appropriate and timely interventions, which can be expected to delay the need for institutionalization.

Genetic Diagnosis if a Lethal Form of Autosomal Recessive Polycystic Kidney Disease

Background Autosomal recessive polycystic kidney disease (ARPKD; OMIM number 263200) is a severe early onset hereditary form of polycystic kidney and liver disease. Case Report In the current study, we present a consanguineous couple with a history of an affected son with polycystic kidney disease (PKD), hepatic failure and epileptic seizures who died at the age of 8 months. Both parents were heterozygote for a missense mutation in PKHD1 gene (NM_170724, c.9107T>G, p.V3036G). Conclusion Unlike previous studies which showed the association between missense mutations of PKHD1 gene and mild phenotype of ARPKD, we have demonstrated the presence of a certain heterozygote missense mutation in parents of a patient affected with lethal form of disorder. Such phenotypic variations should be considered in genetic counseling of families especially those seeking prenatal diagnosis.

Idiopathic Infantile Arterial Calcification: A Case Report

Idiopathic infantile arterial calcificationI (IIAC) is a rare disorder characterized by calcium deposition in the internal elastica lamina of medium and large arteries and it has been defined in term of molecular genetics. It is usually fatal, approximately 85% of all patients die within the first months of life owing to ischemia of vital organs. Death from myocardial infarction usually occurs in the first 6 months. Calcification in a peripheral artery with electrocardiogram (ECG) changes of occlusive coronary artery disease suggests the diagnosis. It is caused by mutations in the ENPP1 gene localized on chromosome 6q22 and has OMIM number 208000. A case with fatal evolution at the end of the first month is presented.

Clinical Phenotypes of Hyper-IgM Syndromes

The primary immunodeficiency (PID) diseases comprise a heterogeneous group of inherited disorders of immune function. Technical advancements in whole-genome, whole-exome, and RNA-sequencing have seen the explosion of genetic discoveries in the field of PIDs. The present review aims to focus on a group of immunodeficiency disorders associated with elevated levels of IgM (hyper IgM; HIGM) and provides a clinical differential diagnosis. Most patients present for evaluation of immunodeficiency due to recurrent infections, and laboratory studies show either a clear isolated elevation of serum immunoglobulin M (IgM) with low or absent IgG, IgA, and IgE. Alternatively, IgM levels may be normal or moderately elevated while other serum immunoglobulins are reported below the norms for age but not absent. Mechanistically, these disorders are recognized as defects in immunoglobulin (Ig) class switch recombination (CSR). Importantly, to safeguard genetic stability, CSR utilizes elements of the DNA repair machinery including multi-protein complexes involved in mismatch repair (MMR). Therefore, it is not uncommon for defects in the DNA repair machinery, to present with laboratory findings of HIGM. This review will discuss clinical phenotypes associated with congenital defects associated with HIGM. Clinical manifestations, relevant immunologic testing, inheritance pattern, molecular diagnosis, presumed pathogenesis, and OMIM number, when annotated are compiled. Accepted therapeutic options, when available, are reviewed for each condition discussed.

Incidental Finding of a Homozygous p.M348K Asymptomatic Italian Patient Confirms the Many Faces of Cystic Fibrosis.

Cystic fibrosis (CF; OMIM number 219700) is an autosomal recessive disease caused by mutations in the CFTR (cystic fibrosis transmembrane conductance regulator) gene, which results in abnormal viscous mucoid secretions in multiple organs and whose main clinical features are pancreatic insufficiency, chronic endobronchial infection, and male infertility. We report the case of a 47-year-old apparently normal male resulting in homozygosity for the mutation p.M348K from nonconsanguineous parents. The proband was screened using a standard panel of 70 different tested on NanoChip 400 platform. The massive parallel pyrosequencing on 454 JS machine allowed the second level analysis. The patient was firstly screened with two different platforms available in our laboratory, obtaining an ambiguous signal for the p.R347P mutation. For this reason we decided to clarify the discordant result of CFTR status by Next Generation Sequencing (NGS) using 454 Junior instrument. The patient is resulted no carrier of the p.R347P mutation, but NGS highlighted a homozygous substitution from T>A at position 1043 in the coding region, causing an amino acid substitution from methionine to lysine (p.M348K). Casual finding of p.M348K homozygote mutation in an individual, without any feature of classical or nonclassical CF form, allowed us to confirm that p.M348K is a benign rare polymorphism.

Teeth anomalies and genetics, including genetic syndromes

This book by Professor Bloch-Zupan and co-workers, Professors Sedano and Scully, is clear and easy to read. The objectives are to present the background of genetic dental and orofacial anomalies from their clinical to biological (genetic) perspectives. This volume is edited by Elsevier in the Elsevier Insights Series. It reviews and synthesizes the known data on these rare syndromes associated with tooth anomalies. This is interesting as there are very few specific books on this topic. The first chapter is a short contribution to odontogenesis (tooth development) and to pathways involved in dental development, including signal transduction and transcription factors. The other seven chapters are dedicated to the description of genetic syndromes associated with tooth anomalies, classified by the dental phenotype (missing teeth (ie, hypodontia and oligodontia), supernumerary teeth, abnormalities of tooth shape and size, anomalies in structure of teeth (two contributions: dentine and enamel), anomalies of teeth eruption and/or resorption, pathology and dental anomalies). There are a total of 68 described syndromes in the seven chapters of this book. Every syndrome is approached to the same projection: definition, synonyms, OMIM number, prevalence, inheritance, etiology/molecular basis/gene, animal models/main features, clinical description (main features, cranio-oro-dental features), management/oral health, references, pictures illustrating the oro-dental features. The authors have compiled a lot of data regarding teeth anomalies in genetic syndromes. The book adds a lot of details. One can notice that every animal (mouse) model is noted. The volume is well illustrated with oral (dental) clinical pictures and/or teeth panoramic radiographs, showing specific dental anomalies in each disease. There is also a huge bibliography added (1242 references). In conclusion, this book is interesting and will be useful for clinical geneticists, for dentists, and for other medical specialists (facial surgeons…). It will help to recognize specific genetic syndromes for dentists, and to recognize specific dental features for clinical geneticists. This volume, available in hardback and in electronic format, is recommended to those interested in the oral cavity and in the craniofacial development.

P heno DB : A New Web‐Based Tool for the Collection, Storage, and Analysis of Phenotypic Features

To interpret whole exome/genome sequence data for clinical and research purposes, comprehensive phenotypic information, knowledge of pedigree structure, and results of previous clinical testing are essential. With these requirements in mind and to meet the needs of the Centers for Mendelian Genomics project, we have developed PhenoDB (http://phenodb.net), a secure, Web-based portal for entry, storage, and analysis of phenotypic and other clinical information. The phenotypic features are organized hierarchically according to the major headings and subheadings of the Online Mendelian Inheritance in Man (OMIM®) clinical synopses, with further subdivisions according to structure and function. Every string allows for a free-text entry. All of the approximately 2,900 features use the preferred term from Elements of Morphology and are fully searchable and mapped to the Human Phenotype Ontology and Elements of Morphology. The PhenoDB allows for ascertainment of relevant information from a case in a family or cohort, which is then searchable by family, OMIM number, phenotypic feature, mode of inheritance, genes screened, and so on. The database can also be used to format phenotypic data for submission to dbGaP for appropriately consented individuals. PhenoDB was built using Django, an open source Web development tool, and is freely available through the Johns Hopkins McKusick-Nathans Institute of Genetic Medicine (http://phenodb.net).

Reassessing the role of mitochondrial DNA mutations in autism spectrum disorder

BackgroundThere is increasing evidence that impairment of mitochondrial energy metabolism plays an important role in the pathophysiology of autism spectrum disorders (ASD; OMIM number: 209850). A significant proportion of ASD cases display biochemical alterations suggestive of mitochondrial dysfunction and several studies have reported that mutations in the mitochondrial DNA (mtDNA) molecule could be involved in the disease phenotype.MethodsWe analysed a cohort of 148 patients with idiopathic ASD for a number of mutations proposed in the literature as pathogenic in ASD. We also carried out a case control association study for the most common European haplogroups (hgs) and their diagnostic single nucleotide polymorphisms (SNPs) by comparing cases with 753 healthy and ethnically matched controls.ResultsWe did not find statistical support for an association between mtDNA mutations or polymorphisms and ASD.ConclusionsOur results are compatible with the idea that mtDNA mutations are not a relevant cause of ASD and the frequent observation of concomitant mitochondrial dysfunction and ASD could be due to nuclear factors influencing mitochondrion functions or to a more complex interplay between the nucleus and the mitochondrion/mtDNA.

Disorders of the genome architecture: a review

Genetic diseases are recognized to be one of the major categories of human disease. Traditionally genetic diseases are subdivided into chromosomal (numerical or structural aberrations), monogenic or Mendelian diseases, multifactorial/polygenic complex diseases and mitochondrial genetic disorders. A large proportion of these conditions occur sporadically. With the advent of newer molecular techniques, a number of new disorders and dysmorphic syndromes are delineated in detail. Some of these conditions do not conform to the conventional inheritance patterns and mechanisms are often complex and unique. Examples include submicroscopic microdeletions or microduplications, trinucleotide repeat disorders, epigenetic disorders due to genomic imprinting, defective transcription or translation due to abnormal RNA patterning and pathogenic association with single nucleotide polymorphisms and copy number variations. Among these several apparently monogenic disorders result from non-allelic homologous recombination associated with the presence of low copy number repeats on either side of the critical locus or gene cluster. The term 'disorders of genome architecture' is alternatively used to highlight these disorders, for example Charcot-Marie-Tooth type IA, Smith-Magenis syndrome, Neurofibromatosis type 1 and many more with an assigned OMIM number. Many of these so called genomic disorders occur sporadically resulting from largely non-recurrent de novo genomic rearrangements. Locus-specific mutation rates for genomic rearrangements appear to be two to four times greater than nucleotide-specific rates for base substitutions. Recent studies on several disease-associated recombination hotspots in male-germ cells indicate an excess of genomic rearrangements resulting in microduplications that are clinically underdiagnosed compared to microdeletion syndromes. Widespread application of high-resolution genome analyses may offer to detect more sporadic phenotypes resulting from genomic rearrangements involving de novo copy number variation.

Endoplasmic Reticulum Stress Increases the Expression of Methylenetetrahydrofolate Reductase through the IRE1 Transducer

Methylenetetrahydrofolate reductase (MTHFR), an enzyme in folate and homocysteine metabolism, influences many cellular processes including methionine and nucleotide synthesis, methylation reactions, and maintenance of homocysteine at nontoxic levels. Mild deficiency of MTHFR is common in many populations and modifies risk for several complex traits including vascular disease, birth defects, and cancer. We recently demonstrated that MTHFR can be up-regulated by NF-kappaB, an important mediator of cell survival that is activated by endoplasmic reticulum (ER) stress. This observation, coupled with the reports that homocysteine can induce ER stress, prompted us to examine the possible regulation of MTHFR by ER stress. We found that several well characterized stress inducers (tunicamycin, thapsigargin, and A23187) as well as homocysteine could increase Mthfr mRNA and protein in Neuro-2a cells. The induction of MTHFR was also observed after overexpression of inositol-requiring enzyme-1 (IRE1) and was inhibited by a dominant-negative mutant of IRE1. Because IRE1 triggers c-Jun signaling, we examined the possible involvement of c-Jun in up-regulation of MTHFR. Transfection of c-Jun and two activators of c-Jun (LiCl and sodium valproate) increased MTHFR expression, whereas a reported inhibitor of c-Jun (SP600125) and a dominant-negative derivative of c-Jun N-terminal kinase-1 reduced MTHFR activation. We conclude that ER stress increases MTHFR expression and that IRE1 and c-Jun mediate this activation. These findings provide a novel mechanism by which the ER can regulate homeostasis and allude to an important role for MTHFR in cell survival.