Broad Phenotypic Variability Research Articles

Further evidence for POMK as candidate gene for WWS with meningoencephalocele

BackgroundWalker-Warburg syndrome (WWS) is a rare form of alpha-dystroglycanopathy characterized by muscular dystrophy and severe malformations of the CNS and eyes. Bi-allelic pathogenic variants in POMK are the cause of a broad spectrum of alpha-dystroglycanopathies. POMK encodes protein-O-mannose kinase, which is required for proper glycosylation and function of the dystroglycan complex and is crucial for extracellular matrix composition.ResultsHere, we report on male monozygotic twins with severe CNS malformations (hydrocephalus, cortical malformation, hypoplastic cerebellum, and most prominently occipital meningocele), eye malformations and highly elevated creatine kinase, indicating the clinical diagnosis of a congenital muscular dystrophy (alpha-dystroglycanopathy). Both twins were found to harbor a homozygous nonsense mutation c.640C>T, p.214* in POMK, confirming the clinical diagnosis and supporting the concept that POMK mutations can be causative of WWS.ConclusionOur combined data suggest a more important role for POMK in the pathogenesis of meningoencephalocele. Only eight different pathogenic POMK variants have been published so far, detected in eight families; only five showed the severe WWS phenotype, suggesting that POMK-associated WWS is an extremely rare disease. We expand the phenotypic and mutational spectrum of POMK-associated WWS and provide evidence of the broad phenotypic variability of POMK-associated disease.

The role of 5-HTTLPR in autism spectrum disorder: New evidence and a meta-analysis of this polymorphism in Latin American population with psychiatric disorders.

The autism spectrum disorder (ASD) is a complex disorder encompassing a broad phenotypic and genotypic variability. The short (S)/long (L) 5-HTTLPR polymorphism has a functional role in the regulation of extracellular serotonin levels and both alleles have been associated to ASD. Most studies including European, American, and Asian populations have suggested an ethnical heterogeneity of this polymorphism; however, the short/long frequencies from Latin American population have been under-studied in recent meta-analysis. Here, we evaluated the 5-HTTLPR polymorphism in Colombian individuals with idiopathic ASD and reported a non-preferential S or L transmission and a non-association with ASD risk or symptom severity. Moreover, to recognize the allelic frequencies of an under-represented population we also recovered genetic studies from Latin American individuals and compared these frequencies with frequencies from other ethnicities. Results from meta-analysis suggest that short/long frequencies in Latin American are similar to those reported in Caucasian population but different to African and Asian regions.

Genetic variability in Rubus ellipticus collections assessed by morphological traits and EST-SSR markers

Rubus ellipticus Smith. commonly known as ‘Yellow Himalayan raspberry’ is an important member of Rosaceae family with high medicinal importance having antioxidant and antibacterial properties. This study was done with the objective of characterizing 21 R. ellipticus collections from different regions of India, based on morphological descriptors and expressed sequence tags-simple sequence repeat (EST-SSR) markers. Broad phenotypic variability among the R. ellipticus collections was detected by using morphological descriptors. The Euclidian distance matrix discriminated two groups, based on morphological characters. A set of 68 EST-SSR markers were developed based on 7777 unigenes generated by us from ‘Kumarhatti-1’ collection of R. ellipticus using assembled pair—end sequences from Illumina NextSeq 500. The ESTs containing simple sequence repeat motifs were extracted using Microsatellite identification tool and primers were designed. Out of 68 EST-SSRs polymorphism was detected using 61 (89.7%) primer pairs, indicating high genetic variability in the R. ellipticus collections. Effective multiplex ratio, marker index and polymorphism information content were 0.43, 0.24 and 0.50, respectively. The unweighted pair group method with arithmetic mean coincided with the bootstrap analysis and two groups were formed, separating the collections Uttrakhand from the other. Morphological descriptors along with EST-SSR markers proved efficient in detecting the levels of genetic variability among the collections maintained in the field. These results can be used as an additional source of exploitation in R. ellipticus breeding programs.

Homozygosity mapping and whole exome sequencing provide exact diagnosis of Cohen syndrome in a Saudi family

BackgroundCohen syndrome (CS) is a rare multi-system autosomal recessive disorder with a high prevalence in the Finnish population. Clinical features of Finnish-type CS are homogeneous, however, in non-Finnish populations, CS diagnosis is challenging due to broad phenotypic variability. MethodsWe studied a consanguineous family having three affected individuals with clinical features of severe intellectual disability and global developmental delay. Clinical diagnosis of the phenotype could not be established based on the features. Therefore, whole genome SNP genotyping and whole exome sequencing (WES) were performed on DNA samples from affected and unaffected family members. ResultsHomozygosity mapping identified a shared loss of heterozygosity region on chromosome 8q22.1-q22.3 and WES data analysis revealed an insertion-deletion (indel) mutation (c.11519_11521delCAAinsT) in the VPS13B gene. The indel is predicted to cause a frameshift resulting in a premature termination of the VPS13B protein (NP_060360.3:p.Pro3840Leufs*2). ConclusionVPS13B encodes a giant transmembrane protein called vacuolar protein sorting 13 homolog B. VPS13B is known to play a role in the glycosylation of Golgi proteins and in endosomal-lysosomal trafficking. Moreover, it is thought to function in vesicle mediated transport and sorting of proteins within the cell. The mechanism by which abnormalities of the VPS13B protein lead to the phenotype of CS is currently unknown. Here, in this study, we successfully established a clinical diagnosis of CS cases from a family using genomic analyses. Clinical re-examination of the patients revealed characteristic ocular abnormalities.

Clinical features and genetic characteristics of hereditary diffuse leukoencephalopathy with spheroids due to CSF1R mutation: a case report and literature review.

Hereditary diffuse leukoencephalopathy with spheroid (HDLS) is an autosomal dominant white matter disease characterized by adult-onset cognitive impairment, behavioral or emotional changes, paresis, Parkinsonism, and seizures. Mutations in the gene encoding colony-stimulating factor 1 receptor (CSF1R) have been identified as the cause of HDLS. Detail medical history, clinical features and brain imaging of a patient with adult-onset leukoencephalopathy, cognitive impairment and motor dysfunction was reviewed and next generation sequencing was performed. An extensive literature research was then performed to identify all patients with HDLS previously reported. The clinical characteristics, brain imaging and genetic features of patients with HDLS were reviewed. A novel CSF1R mutation, c.1952G>A p.G651E was identified in the patient. Extensive review showed that HDLS typically presents with broad phenotypic variability. The most common symptoms of HDLS were cognitive impairment, followed by psychiatric symptoms, Parkinsonism, gait disorder, and dysphagia. The most common brain imaging findings of HDLS were bilateral white matter lesion, mostly around the ventricles, frontal lobe, and parietal lobe. Calcifications in white matter on CT, cerebral atrophy and thinning of corpus callosum were also common features. Although HDLS demonstrates an autosomal dominant pattern, sporadic cases are not uncommon. Early recognition of clinical and neuroradiographical characteristics of HDLS is key for the correct diagnosis of the disease.

Prenatal Diagnosis of 4q Terminal Deletion and Review of the Literature

Terminal deletion of chromosome 4 (4q deletion syndrome) is a rare genetic condition that is characterized by a broad clinical spectrum and phenotypic variability. Diagnosis of the distinct condition can be identified by conventional chromosome analysis and small deletions by novel molecular cytogenetic methods such as microarray comparative genome hybridization (aCGH). Prenatal diagnosis is challenging; to date 10 cases have been described. We report a prenatally diagnosed case of de novo 4q deletion syndrome confirmed by conventional karyotyping and FISH due to an elevated combined risk for Down syndrome and prenatal ultrasound findings. aCGH validated the diagnosis and offered exact characterization of the disorder. Cytogenetic and microarray results described a 4q32.1qter terminal deletion of the fetus. Prenatal ultrasound detected multiple nonstructural findings (micrognathia, choroid plexus cysts, echogenic fetal bowel, short femur, and cardiac axis deviation). Pregnancy was terminated at 20 weeks. In addition to the index patient, we reviewed the 10 prenatally published cases of 4q deletion syndrome in the literature and compared these with our results. We summarize the patients' characteristics and prenatal clinical findings. Alterations of maternal serum biochemical factors, an elevated combined risk for trisomies, and distinct ultrasonographic findings can often be observed in cases of prenatal 4q deletion syndrome and may facilitate the otherwise difficult prenatal diagnosis.

Further corroboration of distinct functional features in SCN2A variants causing intellectual disability or epileptic phenotypes

BackgroundDeleterious variants in the voltage-gated sodium channel type 2 (Nav1.2) lead to a broad spectrum of phenotypes ranging from benign familial neonatal-infantile epilepsy (BFNIE), severe developmental and epileptic encephalopathy (DEE) and intellectual disability (ID) to autism spectrum disorders (ASD). Yet, the underlying mechanisms are still incompletely understood.MethodsTo further elucidate the genotype-phenotype correlation of SCN2A variants we investigated the functional effects of six variants representing the phenotypic spectrum by whole-cell patch-clamp studies in transfected HEK293T cells and in-silico structural modeling.ResultsThe two variants p.L1342P and p.E1803G detected in patients with early onset epileptic encephalopathy (EE) showed profound and complex changes in channel gating, whereas the BFNIE variant p.L1563V exhibited only a small gain of channel function. The three variants identified in ID patients without seizures, p.R937C, p.L611Vfs*35 and p.W1716*, did not produce measurable currents. Homology modeling of the missense variants predicted structural impairments consistent with the electrophysiological findings.ConclusionsOur findings support the hypothesis that complete loss-of-function variants lead to ID without seizures, small gain-of-function variants cause BFNIE and EE variants exhibit variable but profound Nav1.2 gating changes. Moreover, structural modeling was able to predict the severity of the variant impact, supporting a potential role of structural modeling as a prognostic tool. Our study on the functional consequences of SCN2A variants causing the distinct phenotypes of EE, BFNIE and ID contributes to the elucidation of mechanisms underlying the broad phenotypic variability reported for SCN2A variants.

Spectrum of Movement Disorders in 18p Deletion Syndrome.

Deletion of the short arm of chromosome 18 leads to 18p deletion syndrome. Clinical features include short stature, facial dysmorphism, mental retardation, and several types of movement disorders. The 18p deletion syndrome in our patient was diagnosed using karyotype analysis and confirmed by genome-wide single-nucleotide polymorphism array. We have performed a literature search and summarized all previously reported patients with 18p deletion syndrome and movement disorders. We present a 41-year-old male patient with childhood-onset generalized dystonia. Dystonia is the most prevalent movement disorder in 18p deletion patients, with onset ranging from childhood to adulthood. Chorea, myoclonus, tremor, tics, and ataxia have been reported in a minority of these patients. Dystonia is commonly observed in 18p deletion syndrome. The variable size of the deletion on 18p is probably responsible for the broad phenotypic variability of movement disorders in this syndrome.

Familial Treacher Collins Syndrome: Report of 3 Cases

Treacher Collins syndrome (TCS) is a craniofacial developmental disorder of the first and second pharyngeal arches, with a high penetrance and variable expressivity related to malfunctions in migration of facial structures during embryonic development and TCOF1 gene mutation in approximately 90% of the cases. A 26-year-old man (patient 1) presented with bilateral hypoplasia of the zygomatic bone, palpebral fissures with lower eyelid coloboma, bilateral microtia, severe mandible micrognathia, and a convex facial profile. Further familial investigation led to patients 2 (34 years old) and 3 (38 years old), exhibiting mild but similar clinical features, indicating a broad phenotypic variability among the patients. These evidences clearly show an autosomal dominant familial pattern of TCS and its varied expression. The patients are currently being followed up by the local basic health unit.

Genetic variability in Brazilian Capsicum baccatum germplasm collection assessed by morphological fruit traits and AFLP markers.

Capsicum baccatum is one of the main pepper species grown and consumed in South America. In Brazil, it is commonly cultivated by family farmers, using mostly the genotypes bishop's hat genotypes (locally cambuci) and red chili pepper (dedo-de-moça). This study had the objective of characterizing 116 C. baccatum accessions from different regions of Brazil, based on morphological fruit descriptors and AFLP (Amplified Fragment Length Polymorphisms) markers. Broad phenotypic variability among the C. baccatum accessions was detected when using morphological fruit descriptors. The Ward modified location model (Ward-MLM) discriminated five groups, based mainly on fruit shape. Six combinations of AFLP primers detected polymorphism in 97.93% of the 2466 identified bands, indicating the high genetic variability in the accessions. The UPGMA coincided with the Bayesian clustering analysis and three large groups were formed, separating the wild variety C. baccatum var. praetermissum from the other accessions. There was no relation between genetic distance and geographical origin of the accessions, probably due to the intense exchange of fruits and seeds between farmers. Morphological descriptors used together with AFLP markers proved efficient in detecting the levels of genetic variability among the accessions maintained in the germplasm collections. These results can be used as an additional source of helpful information to be exploited in C. baccatum breeding programs.

Clinique et génétique de l’albinisme

Albinism is a genetic disease affecting 1/17,000 person worldwide. It constitutes the second cause of congenital loss of visual acuity after optic atrophy. Albinism is heterogeneous both at the clinical and genetic levels. It is characterized by ocular development anomalies and by a variable degree of hypopigmentation. Clinically, three forms of the disease are described: oculocutaneous, ocular and syndromic (Hermansky-Pudlak syndrome, Chediak-Higashi syndrome). Nineteen genes involved in the different types of albinism have been described so far. The broad phenotypic variability between the different forms but also within a particular form renders the establishment of phenotype-genotype correlations impossible. A genetic test exploring all 19 genes is necessary to establish the diagnosis and to distinguish between syndromic and non-syndromic forms. We present the creation of an albinism-dedicated Day Hospital at the University Hospital of Bordeaux.

Genetic defects in pediatric-onset adrenal insufficiency in Japan.

Most patients with pediatric-onset primary adrenal insufficiency (PAI), such as 21-hydroxylase deficiency, can be diagnosed by measuring the urine or serum levels of steroid metabolites. However, the etiology is often difficult to determine in a subset of patients lacking characteristic biochemical findings. To assess the frequency of genetic defects in Japanese children with biochemically uncharacterized PAI and characterize the phenotypes of mutation-carrying patients. We enrolled 63 Japanese children (59 families) with biochemically uncharacterized PAI, and sequenced 12 PAI-associated genes. The pathogenicities of rare variants were assessed based on in silico analyses and structural modeling. We calculated the proportion of mutation-carrying patients according to demographic characteristics. We identified genetic defects in 50 (85%) families: STAR in 19, NR0B1 in 18, SAMD9 in seven, AAAS in two, NNT in two, MC2R in one and CDKN1C in one. NR0B1 defects were identified in 78% of the male patients that received both glucocorticoid and mineralocorticoid replacement therapy and had normal male external genitalia. STAR defects were identified in 67% of female and 9% of male patients. Seven of the 19 patients with STAR defects developed PAI at age two or older, out of whom, five did not have mineralocorticoid deficiency. Molecular testing elucidated the etiologies of most biochemically uncharacterized PAI patients. Genetic defects such as NR0B1 defects are presumed based on phenotypes, while others with broad phenotypic variability, such as STAR defects, are difficult to diagnose. Molecular testing is a rational approach to diagnosis in biochemically uncharacterized PAI patients.

Cellular Hydration and Oxidation As Phenotype Modifiers in Sickle Cell Anemia

Although Sickle Cell Anemia (SCA) is caused by a single nucleotide mutation in the beta globin gene, there is broad phenotypic variability in affected individuals. It would be highly advantageous to be able to predict which SCA patients are most likely to suffer severe complications and which are likely to benefit from specific treatments. Since two of the major pathologic mechanisms in SCA are erythrocyte dehydration and chronic inflammation, alterations in the expression and/or function of proteins affecting these processes may be responsible for heterogeneity in SCA phenotype. We have developed a 23-gene Next-Generation sequencing panel to identify variants in genes involved in erythrocyte hydration and in reactive oxygen species (ROS) generation and reduction in patients with SCA. We have collected blood samples from an initial cohort of 18 SCA patients with severe phenotype, defined by history of stroke or abnormal transcranial Doppler velocities, and 13 SCA patients with mild phenotype for DNA preparation and for specialized testing to evaluate erythrocyte hydration status and ROS generation.Advia Automated Cell Counter results provided the clearest indications of erythrocyte dehydration in patient blood samples. The ability to examine reticulocyte parameters made it possible to evaluate hydration regardless of the frequency of transfusion. Reticulocyte CHCM, MCV, and percent hyperdense cells were significantly different between the two groups and indicative of a greater degree of dehydration in the severe phenotype group.Osmoscans (using a LoRRca ektacytometer) demonstrated a highly significant left shift indicative of erythrocyte dehydration in both mild and severe groups relative to controls (O min and O hyper values significantly decreased). Both phenotypic groups also demonstrated a significantly lower EI max in relation to controls, indicating decreased deformability of sickle erythrocytes. Deformability scans revealed significant increases in SS ½ and decreases in EI max in both groups in relation to the controls. There were significant differences between mild and severe phenotype groups in osmoscan O min and O hyper values and in deformability assay SS ½ and EI max values. The severe group had values closer to the normal values, most likely due to the contribution of transfused blood in the severe phenotype group. There were no significant differences between the mild and severe SCA phenotype groups in intracellular cation levels (K+ and Na+) measured by flame emission spectroscopy, although both groups had significantly higher intracellular Na+ compared to normal controls.Erythrocyte ROS detection was performed using a flow cytometry DCFDA assay. Both mild and severe phenotype groups demonstrated a highly significant increase in ROS compared to controls. However there was not a significant difference in erythrocyte ROS between the mild and severe phenotype groups.DNA from patient blood samples has been sequenced using the Haloplex target enrichment system and Illumina high-throughput sequencing. We analyzed 23 genes that are likely candidates to be involved in erythrocyte hydration (ABCB6, ABCG5, ABCG8, AQP1, AQP3, ATP2B4, KCNN4, PIEZO1, RHAG, SLC9A1, SLC12A4, SLC12A6, SLC12A7, SLC2A1, SLC4A1, STOM, TRPC6, XK) or in ROS production or reduction (G6PD, NOX1, CYBB, NOX4, NOX5). At least 19 variants classified as possibly damaging have been detected in 10 of the genes. Future study will be directed toward exploring the phenotypic implications of identified variants.Results of this study should further our understanding of the pathogenesis of SCD and help identify biomarkers of disease severity which may ultimately help guide clinical management for individual patients. They may also suggest novel targets for development of new therapies for SCD based on the modulation of erythrocyte hydration and inflammation. DisclosuresQuinn:Amgen: Research Funding; Eli Lilly: Research Funding; Silver Lake Research Corporation: Consultancy. Joiner:Global Blood Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees.

Clinical and genetic heterogeneity in Slovenian patients with BEST disease.

To determine the spectrum of BEST1 mutations and to study the phenotype in Slovenian families with Best vitelliform macular dystrophy (BVMD) to identify genotype-phenotype correlations. Twenty patients from five families underwent the ophthalmological examination including electrooculogram (EOG; N=17), fundus autofluorescence imaging (N=16) and optical coherence tomography (N=14). Mutational screening was performed by direct DNA sequencing of the BEST1 gene. Mutation c.43G>C (p.Gly15Arg) was detected in three patients from family M presenting with different clinical stages of Best disease. Mutation c.313G>C (p.Arg105Gly) was found in families K, ST, S, B and was associated with incomplete clinical penetrance and variable retinal changes, including extramacular and multifocal lesions. In three patients from family K, an atypical form of BVMD was observed; there were additional peripheral lesions outside of the vascular arcades in addition to the typical macular lesions. Multiple alterations between the vitelliruptive and pseudohypopyon stages over a period of 11years were seen in one patient. Two previously unreported disease-associated variants in the BEST1 gene (p.Gly15Arg and p.Arg105Gly) were found in Slovenian patients with Best disease. Our data expand the mutation spectrum of the BEST1 gene and further support the broad phenotypic variability observed clinically and with optical coherence tomography (OCT) and AF imaging.

Variable White Matter Atrophy and Intellectual Development in a Family With X-linked Creatine Transporter Deficiency Despite Genotypic Homogeneity

BackgroundThe X-linked creatine transporter deficiency (CRTD) caused by an SLC6A8 mutation represents the second most common cause of X-linked intellectual disability. The clinical phenotype ranges from mild to severe intellectual disability, epilepsy, short stature, poor language skills, and autism spectrum disorders. The objective of this study was to investigate phenotypic variability in the context of genotype, cerebral creatine concentration, and volumetric analysis in a family with CRTD. Patients and MethodsThe clinical phenotype and manifestations of epilepsy were assessed in a Caucasian family with CRTD. DNA sequencing and creatine metabolism analysis confirmed the diagnosis. Cerebral magnetic resonance imaging (cMRI) with voxel-based morphometry and magnetic resonance spectroscopy was performed in all family members. ResultsAn SLC6A8 missense mutation (c.1169C>T; p.Pro390Leu, exon 8) was detected in four of five individuals. Both male siblings were hemizygous, the mother and the affected sister heterozygous for the mutation. Structural cMRI was normal, whereas voxel-based morphometry analysis showed reduced white matter volume below the first percentile of the reference population of 290 subjects in the more severely affected boy compared with family members and controls. Normalized creatine concentration differed significantly between the individuals (P < 0.005). ConclusionsThere is a broad phenotypic variability in CRTD even in family members with the same mutation. Differences in mental development could be related to atrophy of the subcortical white matter.

Update on the Diagnosis and Management of Progressive Supranuclear Palsy

Progressive supranuclear palsy (PSP) is an adult-onset neurodegenerative disease clinically characterized by a variable combination of symmetrical parkinsonism, early postural instability and falls, vertical supranuclear ophthalmoparesis, and cognitive decline. PSP is a disorder of 4-repeat tau protein aggregation, belonging to the family of tauopathies. A broad phenotypic variability has been recognized, and specific clinical diagnostic criteria are available. Several ancillary tests are helpful for diagnosis; however, there are no diagnostic biomarkers, and definite diagnosis still requires histopathological confirmation. Symptomatic management of PSP patients is limited, but recent advances in the understanding of its pathophysiology might lead us to disease-modifying treatments. A multidisciplinary approach is essential in managing the symptom complexity of a progressive condition such as PSP.

Eight Novel Mutations Confirm the Role of AAGAB in Punctate Palmoplantar Keratoderma Type 1 (Buschke-Fischer-Brauer) and Show Broad Phenotypic Variability.

Punctate palmoplantar keratoderma (PPKP1; Buschke-Fischer-Brauer) is a rare autosomal dominant inherited skin disease characterized by multiple hyperkeratotic papules involving the palms and soles. Mutations have been found at 2 loci, on chromosomes 15q22-15q24 and 8q24.13-8q24.21. We recently identified mutations in 3 families, in the AAGAB gene on 15q, which encodes the alpha- and gamma-adaptin-binding protein p34. The current study examined 14 additional families, comprising a total of 26 affected individuals and identified 8 novel mutations in 9 families. In one family a mutation that was present only in the affected individuals was found, and in 4 other families, previously reported mutations were found (1, 2). These results confirm the role of AAGAB in PPKP1. Our findings suggest that there is no correlation with age, but with mechanical factors. No additional obvious genotype-phenotype correlation was observed, even when comparing different types of mutations. Rather, identical genotypes presented a very broad interfamilial and intrafamilial variability of phenotypes.

LRH-1 May Rescue SF-1 Deficiency for Steroidogenesis: An in vitro and in vivo Study

Steroidogenic factor 1 (NR5A1/SF-1) mutations usually manifest in 46,XY individuals with variable degrees of disordered sex development and in 46,XX women with ovarian insufficiency. So far, there is no genotype-phenotype correlation. The broad spectrum of phenotype with NR5A1 mutations may be due to a second hit in a gene with similar function to NR5A1/SF-1. Liver receptor homologue-1 (LRH-1/NR5A2) might be a good candidate. We performed in vitro studies for the interplay between SF-1, LRH-1 and DAX-1, expression profiles in human steroidogenic tissues, and NR5A2 genetic studies in a cohort (11 patients, 8 relatives, 11 families) harboring heterozygote NR5A1/SF-1 mutations. LRH-1 isoforms transactivate the CYP17A1 and HSD3B2 promoters similarly to SF-1 and compensate for SF-1 deficiency. DAX-1 inhibits SF-1- and LRH-1-mediated transactivation. LRH-1 is found expressed in human adult and fetal adrenals and testes. However, no NR5A2/LRH-1 mutations were detected in 14 individuals with heterozygote NR5A1/SF-1 mutations. These findings demonstrate that in vitro LRH-1 can act like SF-1 and compensate for its deficiency. Expression of LRH-1 in fetal testis suggests a role in male gonadal development. However, as we found no NR5A2/LRH-1 mutations, the ‘second genetic hit' in SF-1 patients explaining the broad phenotypic variability remains elusive.

Phenotypic variability of TRPV4 related neuropathies

Mutations in the transient receptor potential vanilloid 4 (TRPV4) gene have been associated with autosomal dominant skeletal dysplasias and peripheral nervous system syndromes (PNSS). PNSS include Charcot–Marie–Tooth disease (CMT) type 2C, congenital spinal muscular atrophy and arthrogryposis and scapuloperoneal spinal muscular atrophy. We report the clinical, electrophysiological and muscle biopsy findings in two unrelated patients with two novel heterozygous missense mutations in the TRPV4 gene. Whole exome sequencing was carried out on genomic DNA using Illumina TruseqTM 62Mb exome capture. Patient 1 harbours a de novo c.805C > T (p.Arg269Cys) mutation. Clinically, this patient shows signs of both scapuloperoneal spinal muscular atrophy and skeletal dysplasia. Patient 2 harbours a novel c.184G > A (p.Asp62Asn) mutation. While the clinical phenotype is compatible with CMT type 2C with the patient's muscle harbours basophilic inclusions. Mutations in the TRPV4 gene have a broad phenotypic variability and disease severity and may share a similar pathogenic mechanism with Heat Shock Protein related neuropathies.

Broad phenotypic variability in patients with complex I deficiency due to mutations in NDUFS1 and NDUFV1

We report clinical, metabolic, genetic and neuroradiological findings in five patients from three different families with isolated complex I deficiency. Genetic analysis revealed mutations in NDUFS1 in three patients and in NDUFV1 in two patients. Four of the mutations are novel and affect amino acid residues that either are invariant among species or conserved in their properties. The presented clinical courses are characterized by leukoencephalopathy or early death and expand the already heterogeneous phenotypic spectrum. A literature review was performed, showing that patients with mutations in NDUFS1 in general have a worse prognosis than patients with mutations in NDUFV1.