Genotype-phenotype of autosomal dominant polycystic kidney disease in Malta.

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is characterized by the development of multiple renal cysts causing kidney enlargement and end-stage renal disease (ESRD) in half the patients by 60 years of age. The aim of the study was to determine the genetic aetiology in Maltese patients clinically diagnosed with ADPKD and correlate the clinical features. METHODS: A total of 60 patients over 18 years of age clinically diagnosed with ADPKD were studied using a customized panel of genes that had sufficient evidence of disease diagnosis using next generation sequencing (NGS). The genes studied were PKD1, PKD2, GANAB, DNAJB11, PKHD1 and DZIP1L. Selected variants were confirmed by bidirectional Sanger sequencing with specifically designed primers. Cases where no clinically significant variant was identified by the customized gene panel were then studied by Whole Exome Sequencing (WES). Microsatellite analysis was performed to determine the origin of an identified recurrent variant in the PKD2 gene. Clinical features were studied for statistical correlation with genetic results. RESULTS: Genetic diagnosis was reached in 49 (82%) of cases studied. Pathogenic/likely pathogenic variants PKD1 and PKD2 gene were found in 25 and in 23 cases respectively. The relative proportion of genetically diagnosed PKD1:PKD2 cases was 42:38. A pathogenic variant in the GANAB gene was identified in 1 (2%) case. A potentially significant heterozygous likely pathogenic variant was identified in PKHD1 in 1 (2%) case. Potentially significant variants of uncertain significance were seen in 4 (7%) cases of the study cohort. No variants in DNAJB11 and DZIP1L were observed. Whole exome sequencing (WES) added the diagnostic yield by 10% over the gene panel analysis. Overall no clinically significant variant was detected in 6 (10%) cases of the study population by a customized gene panel and WES. One recurrent variant the PKD2 c.709+1G > A was observed in 19 (32%) cases. Microsatellite analysis showed that all variant cases shared the same haplotype indicating that their families may have originated from a common ancestor and confirmed it to be a founder variant in the Maltese population. The rate of decline in eGFR was steeper and progression to ESRD was earlier in cases with PKD1 variants when compared to cases with PKD2 variants. Cases segregating truncating variants in PKD1 showed a significantly earlier onset of ESRD and this was significantly worse in cases with frameshift variants. Overall extrarenal manifestations were commoner in cases segregating truncating variants in PKD1. CONCLUSIONS: This study helps to show that a customized gene panel is the first-line method of choice for studying patients with ADPKD followed by WES which increased the detection of variants present in the PKD1 pseudogene region. A founder variant in the PKD2 gene was identified in our Maltese cohort with ADPKD. Phenotype of patients with ADPKD is significantly related to the genotype confirming the important role of molecular investigations in the diagnosis and prognosis of polycystic kidney disease. Moreover, the findings also highlight the variability in the clinical phenotype and indicate that other factors including epigenetic and environmental maybe be important determinants in Autosomal Dominant Polycystic Kidney Disease.

Expanding the genetic and phenotypic spectrum of CHD2-related disease: From early neurodevelopmental disorders to adult-onset epilepsy.

CHD2 encodes the chromodomain helicase DNA-binding protein 2, an ATP-dependent enzyme that acts as a chromatin remodeler. CHD2 pathogenic variants have been associated with various early onset phenotypes including developmental and epileptic encephalopathy, self-limiting or pharmacoresponsive epilepsies and neurodevelopmental disorders without epilepsy. We reviewed 84 previously reported patients carrying 76 different CHD2 pathogenic or likely pathogenic variants and describe 18 unreported patients carrying 12 novel pathogenic or likely pathogenic variants, two recurrent likely pathogenic variants (in two patients each), three previously reported pathogenic variants, one gross deletion. We also describe a novel phenotype of adult-onset pharmacoresistant epilepsy, associated with a novel CHD2 missense likely pathogenic variant, located in an interdomain region. A combined review of previously published and our own observations indicates that although most patients (72.5%) carry truncating CHD2 pathogenic variants, CHD2-related phenotypes encompass a wide spectrum of conditions with developmental delay/intellectual disability (ID), including prominent language impairment, attention deficit hyperactivity disorder and autistic spectrum disorder. Epilepsy is present in 92% of patients with a median age at seizure onset of 2 years and 6 months. Generalized epilepsy types are prevalent and account for 75.5% of all epilepsies, with photosensitivity being a common feature and adult-onset nonsyndromic epilepsy a rare presentation. No clear genotype-phenotype correlation has emerged.

Missense mutations in small muscle protein X-linked (SMPX) cause distal myopathy with protein inclusions.

Using deep phenotyping and high-throughput sequencing, we have identified a novel type of distal myopathy caused by mutations in the Small muscle protein X-linked (SMPX) gene. Four different missense mutations were identified in ten patients from nine families in five different countries, suggesting that this disease could be prevalent in other populations as well. Haplotype analysis of patients with similar ancestry revealed two different founder mutations in Southern Europe and France, indicating that the prevalence in these populations may be higher. In our study all patients presented with highly similar clinical features: adult-onset, usually distal more than proximal limb muscle weakness, slowly progressing over decades with preserved walking. Lower limb muscle imaging showed a characteristic pattern of muscle involvement and fatty degeneration. Histopathological and electron microscopic analysis of patient muscle biopsies revealed myopathic findings with rimmed vacuoles and the presence of sarcoplasmic inclusions, some with amyloid-like characteristics. In silico predictions and subsequent cell culture studies showed that the missense mutations increase aggregation propensity of the SMPX protein. In cell culture studies, overexpressed SMPX localized to stress granules and slowed down their clearance.

Progressive myoclonus epilepsies-Residual unsolved cases have marked genetic heterogeneity including dolichol-dependent protein glycosylation pathway genes.

Progressive myoclonus epilepsies (PMEs) comprise a group of clinically and genetically heterogeneous rare diseases. Over 70% of PME cases can now be molecularly solved. Known PME genes encode a variety of proteins, many involved in lysosomal and endosomal function. We performed whole-exome sequencing (WES) in 84 (78 unrelated) unsolved PME-affected individuals, with or without additional family members, to discover novel causes. We identified likely disease-causing variants in 24 out of 78 (31%) unrelated individuals, despite previous genetic analyses. The diagnostic yield was significantly higher for individuals studied as trios or families (14/28) versus singletons (10/50) (OR = 3.9, p value = 0.01, Fisher's exact test). The 24 likely solved cases of PME involved 18 genes. First, we found and functionally validated five heterozygous variants in NUS1 and DHDDS and a homozygous variant in ALG10, with no previous disease associations. All three genes are involved in dolichol-dependent protein glycosylation, a pathway not previously implicated in PME. Second, we independently validate SEMA6B as a dominant PME gene in two unrelated individuals. Third, in five families, we identified variants in established PME genes; three with intronic or copy-number changes (CLN6, GBA, NEU1) and two very rare causes (ASAH1, CERS1). Fourth, we found a group of genes usually associated with developmental and epileptic encephalopathies, but here, remarkably, presenting as PME, with or without prior developmental delay. Our systematic analysis of these cases suggests that the small residuum of unsolved cases will most likely be a collection of very rare, genetically heterogeneous etiologies.

International consensus recommendations on the diagnostic work-up for malformations of cortical development.

Malformations of cortical development (MCDs) are neurodevelopmental disorders that result from abnormal development of the cerebral cortex in utero. MCDs place a substantial burden on affected individuals, their families and societies worldwide, as these individuals can experience lifelong drug-resistant epilepsy, cerebral palsy, feeding difficulties, intellectual disability and other neurological and behavioural anomalies. The diagnostic pathway for MCDs is complex owing to wide variations in presentation and aetiology, thereby hampering timely and adequate management. In this article, the international MCD network Neuro-MIG provides consensus recommendations to aid both expert and non-expert clinicians in the diagnostic work-up of MCDs with the aim of improving patient management worldwide. We reviewed the literature on clinical presentation, aetiology and diagnostic approaches for the main MCD subtypes and collected data on current practices and recommendations from clinicians and diagnostic laboratories within Neuro-MIG. We reached consensus by 42 professionals from 20 countries, using expert discussions and a Delphi consensus process. We present a diagnostic workflow that can be applied to any individual with MCD and a comprehensive list of MCD-related genes with their associated phenotypes. The workflow is designed to maximize the diagnostic yield and increase the number of patients receiving personalized care and counselling on prognosis and recurrence risk.

Correction: DPH1 syndrome: two novel variants and structural and functional analyses of seven missense variants identified in syndromic patients.

Following the publication of the article, it was noted that the last column in Table 1, the total % should have read 5/8 (62.5) for the 'Epilepsy' row, and not 5.7 (71.4). This has now been amended in the HTML and PDF of the original article.

DPH1 syndrome: two novel variants and structural and functional analyses of seven missense variants identified in syndromic patients.

DPH1 variants have been associated with an ultra-rare and severe neurodevelopmental disorder, mainly characterized by variable developmental delay, short stature, dysmorphic features, and sparse hair. We have identified four new patients (from two different families) carrying novel variants in DPH1, enriching the clinical delineation of the DPH1 syndrome. Using a diphtheria toxin ADP-ribosylation assay, we have analyzed the activity of seven identified variants and demonstrated compromised function for five of them [p.(Leu234Pro); p.(Ala411Argfs*91); p.(Leu164Pro); p.(Leu125Pro); and p.(Tyr112Cys)]. We have built a homology model of the human DPH1-DPH2 heterodimer and have performed molecular dynamics simulations to study the effect of these variants on the catalytic sites as well as on the interactions between subunits of the heterodimer. The results show correlation between loss of activity, reduced size of the opening to the catalytic site, and changes in the size of the catalytic site with clinical severity. This is the first report of functional tests of DPH1 variants associated with the DPH1 syndrome. We demonstrate that the in vitro assay for DPH1 protein activity, together with structural modeling, are useful tools for assessing the effect of the variants on DPH1 function and may be used for predicting patient outcomes and prognoses.

Infantile Hypertrophic Pyloric Stenosis: An Epidemiological Review.

Infantile hypertrophic pyloric stenosis (IHPS) is the most common gastrointestinal disease among infants. IHPS occurs as an isolated condition or together with other congenital anomalies. Association with genetic and environmental factors, bottle feeding, younger maternal age, maternal smoking, and erythromycin administration in the first two weeks of life has been shown. Familial aggregation has been described and a family history is seen in 47.9 percent of siblings. Infants typically present with projectile vomiting associated with symptoms of failure to thrive. An olive-like mass palpable in the right upper abdominal quadrant is being reported less frequently because of earlier diagnosis by ultrasound. IHPS is generally corrected through laparoscopic pyloromyotomy. Endoscopic pyloric balloon dilation is a novel alternative. Further studies on different populations, the general population, and familial segregation to determine the prevalence, influence, and mode of familial aggregation and correlation with environmental factors are needed to determine the etiology of IHPS.

Survival beyond the perinatal period expands the phenotypes caused by mutations in GLE1.

Mutations in GLE1 underlie Lethal Congenital Contracture syndrome (LCCS) and Lethal Arthrogryposis with Anterior Horn Cell Disease (LAAHD). Both LCCS and LAAHD are characterized by reduced fetal movements, congenital contractures, and a severe form of motor neuron disease that results in fetal death or death in the perinatal period, respectively. We identified bi-allelic mutations in GLE1 in two unrelated individuals with motor delays, feeding difficulties, and respiratory insufficiency who survived beyond the perinatal period. Each affected child had missense variants predicted to result in amino acid substitutions near the C-terminus of GLE1 that are predicted to disrupt protein-protein interaction or GLE1 protein targeting. We hypothesize that mutations that preserve function of the coiled-coil domain of GLE1 cause LAAHD whereas mutations that abolish the function of the coiled-coil domain cause LCCS. The phenotype of LAAHD is now expanded to include multiple individuals surviving into childhood suggesting that LAAHD is a misnomer and should be re-named Arthrogryposis with Anterior Horn Cell Disease (AAHD).

Diagnosis and management of Silver-Russell syndrome: first international consensus statement.

This Consensus Statement summarizes recommendations for clinical diagnosis, investigation and management of patients with Silver-Russell syndrome (SRS), an imprinting disorder that causes prenatal and postnatal growth retardation. Considerable overlap exists between the care of individuals born small for gestational age and those with SRS. However, many specific management issues exist and evidence from controlled trials remains limited. SRS is primarily a clinical diagnosis; however, molecular testing enables confirmation of the clinical diagnosis and defines the subtype. A 'normal' result from a molecular test does not exclude the diagnosis of SRS. The management of children with SRS requires an experienced, multidisciplinary approach. Specific issues include growth failure, severe feeding difficulties, gastrointestinal problems, hypoglycaemia, body asymmetry, scoliosis, motor and speech delay and psychosocial challenges. An early emphasis on adequate nutritional status is important, with awareness that rapid postnatal weight gain might lead to subsequent increased risk of metabolic disorders. The benefits of treating patients with SRS with growth hormone include improved body composition, motor development and appetite, reduced risk of hypoglycaemia and increased height. Clinicians should be aware of possible premature adrenarche, fairly early and rapid central puberty and insulin resistance. Treatment with gonadotropin-releasing hormone analogues can delay progression of central puberty and preserve adult height potential. Long-term follow up is essential to determine the natural history and optimal management in adulthood.

EPG5-related Vici syndrome: a paradigm of neurodevelopmental disorders with defective autophagy.

Vici syndrome is a progressive neurodevelopmental multisystem disorder due to recessive mutations in the key autophagy gene EPG5. We report genetic, clinical, neuroradiological, and neuropathological features of 50 children from 30 families, as well as the neuronal phenotype of EPG5 knock-down in Drosophila melanogaster. We identified 39 different EPG5 mutations, most of them truncating and predicted to result in reduced EPG5 protein. Most mutations were private, but three recurrent mutations (p.Met2242Cysfs*5, p.Arg417*, and p.Gln336Arg) indicated possible founder effects. Presentation was mainly neonatal, with marked hypotonia and feeding difficulties. In addition to the five principal features (callosal agenesis, cataracts, hypopigmentation, cardiomyopathy, and immune dysfunction), we identified three equally consistent features (profound developmental delay, progressive microcephaly, and failure to thrive). The manifestation of all eight of these features has a specificity of 97%, and a sensitivity of 89% for the presence of an EPG5 mutation and will allow informed decisions about genetic testing. Clinical progression was relentless and many children died in infancy. Survival analysis demonstrated a median survival time of 24 months (95% confidence interval 0-49 months), with only a 10th of patients surviving to 5 years of age. Survival outcomes were significantly better in patients with compound heterozygous mutations (P = 0.046), as well as in patients with the recurrent p.Gln336Arg mutation. Acquired microcephaly and regression of skills in long-term survivors suggests a neurodegenerative component superimposed on the principal neurodevelopmental defect. Two-thirds of patients had a severe seizure disorder, placing EPG5 within the rapidly expanding group of genes associated with early-onset epileptic encephalopathies. Consistent neuroradiological features comprised structural abnormalities, in particular callosal agenesis and pontine hypoplasia, delayed myelination and, less frequently, thalamic signal intensity changes evolving over time. Typical muscle biopsy features included fibre size variability, central/internal nuclei, abnormal glycogen storage, presence of autophagic vacuoles and secondary mitochondrial abnormalities. Nerve biopsy performed in one case revealed subtotal absence of myelinated axons. Post-mortem examinations in three patients confirmed neurodevelopmental and neurodegenerative features and multisystem involvement. Finally, downregulation of epg5 (CG14299) in Drosophila resulted in autophagic abnormalities and progressive neurodegeneration. We conclude that EPG5-related Vici syndrome defines a novel group of neurodevelopmental disorders that should be considered in patients with suggestive features in whom mitochondrial, glycogen, or lysosomal storage disorders have been excluded. Neurological progression over time indicates an intriguing link between neurodevelopment and neurodegeneration, also supported by neurodegenerative features in epg5-deficient Drosophila, and recent implication of other autophagy regulators in late-onset neurodegenerative disease.

A case of true hermaphroditism presenting as a testicular tumour.

True hermaphroditism represents only 5% cases of all of disorders of sexual differentiation (DSD) and usually present in early childhood with ambiguous genitalia. Occasionally, cases might present later on in adolescence with problems of sexual maturation. Our case report presents a true hermaphrodite with normal male phenotype that presented as a left testicular mass, two years after being diagnosed with Sertoli cell only syndrome in the contralateral testis. Histological examination of the left testis showed ovarian, fallopian tube, myometrial, endometrial, and epididymal tissue. This combination of findings is found in approximately one-third of true hermaphrodites, but it is very rare to present clinically as an inguinoscrotal mass.

A recurrent de novo mutation in KCNC1 causes progressive myoclonus epilepsy.

Progressive myoclonus epilepsies (PMEs) are a group of rare, inherited disorders manifesting with action myoclonus, tonic-clonic seizures and ataxia. We sequenced the exomes of 84 unrelated individuals with PME of unknown cause and molecularly solved 26 cases (31%). Remarkably, a recurrent de novo mutation, c.959G>A (p.Arg320His), in KCNC1 was identified as a new major cause for PME. Eleven unrelated exome-sequenced (13%) and two affected individuals in a secondary cohort (7%) had this mutation. KCNC1 encodes KV3.1, a subunit of the KV3 voltage-gated potassium ion channels, which are major determinants of high-frequency neuronal firing. Functional analysis of the Arg320His mutant channel showed a dominant-negative loss-of-function effect. Ten cases had pathogenic mutations in known PME-associated genes (NEU1, NHLRC1, AFG3L2, EPM2A, CLN6 and SERPINI1). Identification of mutations in PRNP, SACS and TBC1D24 expand their phenotypic spectra to PME. These findings provide insights into the molecular genetic basis of PME and show the role of de novo mutations in this disease entity.

Vici syndrome--a rapidly progressive neurodegenerative disorder with hypopigmentation, immunodeficiency and myopathic changes on muscle biopsy.

Since its first description by Vici et al. [1988], further reports have continued to broaden the clinical phenotype of this rare multisystem disorder. Main features of agenesis of corpus callosum (ACC), hypopigmentation, immunodeficiency/recurrent infections, cataracts, severe failure to thrive, and profound psychomotor delay have been reported in all cases. An additional feature is the recent evidence for neuromuscular involvement. We describe a female infant with the above core features in whom an initial rapid neurological deterioration and associated transient left ventricular hypertrophy and liver dysfunction was followed by relative clinical stability after ten months of age. This case further underlines the clinical phenotype of Vici syndrome as an early onset neurodegenerative disorder with hypopimentation, recurrent infections and muscle findings indicating myopathic and neurogenic features.

Toriello-Carey syndrome with a 6Mb interstitial deletion at 22q12 detected by array CGH.

Toriello-Carey syndrome is a rare multiple congenital anomaly syndrome comprising agenesis of the corpus callosum, telecanthus, short palpebral fissures, abnormal ears, Pierre Robin sequence, and cardiac anomaly. Autosomal recessive inheritance has been hypothesized and chromosome abnormalities have been reported. The present case is a girl with agenesis of the corpus callosum, a large cleft palate, telecanthus, hypertelorism, atrial septal defect, ventricular septal defect, and patent ductus arteriosus. A routine karyotype and fluorescence in situ hybridization subtelomeric analysis were normal. Array comparative genomic hybridization (CGH) identified a de novo 6 Mb interstitial deletion at 22q12.1→22q12.2. These findings support recent findings of chromosomal abnormalities in patients with the Toriello-Carey phenotype. We suggest that the clinical features described in some cases with Toriello-Carey syndrome might be due to cryptic chromosomal rearrangements and that array CGH should be considered in any case presenting with clinical features of Toriello-Carey.

Screening of ARHSP-TCC patients expands the spectrum of SPG11 mutations and includes a large scale gene deletion.

Autosomal recessive spastic paraplegia with thinning of corpus callosum (ARHSP-TCC) is a complex form of HSP initially described in Japan but subsequently reported to have a worldwide distribution with a particular high frequency in multiple families from the Mediterranean basin. We recently showed that ARHSP-TCC is commonly associated with mutations in SPG11/KIAA1840 on chromosome 15q. We have now screened a collection of new patients mainly originating from Italy and Brazil, in order to further ascertain the spectrum of mutations in SPG11, enlarge the ethnic origin of SPG11 patients, determine the relative frequency at the level of single Countries (i.e., Italy), and establish whether there is one or more common mutation. In 25 index cases we identified 32 mutations; 22 are novel, including 9 nonsense, 3 small deletions, 4 insertions, 1 in/del, 1 small duplication, 1 missense, 2 splice-site, and for the first time a large genomic rearrangement. This brings the total number of SPG11 mutated patients in the SPATAX collection to 111 cases in 44 families and in 17 isolated cases, from 16 Countries, all assessed using homogeneous clinical criteria. While expanding the spectrum of mutations in SPG11, this larger series also corroborated the notion that even within apparently homogeneous population a molecular diagnosis cannot be achieved without full gene sequencing.

Eight previously unidentified mutations found in the OA1 ocular albinism gene.

BACKGROUND: Ocular albinism type 1 (OA1) is an X-linked ocular disorder characterized by a severe reduction in visual acuity, nystagmus, hypopigmentation of the retinal pigmented epithelium, foveal hypoplasia, macromelanosomes in pigmented skin and eye cells, and misrouting of the optical tracts. This disease is primarily caused by mutations in the OA1 gene. METHODS: The ophthalmologic phenotype of the patients and their family members was characterized. We screened for mutations in the OA1 gene by direct sequencing of the nine PCR-amplified exons, and for genomic deletions by PCR-amplification of large DNA fragments. RESULTS: We sequenced the nine exons of the OA1 gene in 72 individuals and found ten different mutations in seven unrelated families and three sporadic cases. The ten mutations include an amino acid substitution and a premature stop codon previously reported by our team, and eight previously unidentified mutations: three amino acid substitutions, a duplication, a deletion, an insertion and two splice-site mutations. The use of a novel Taq polymerase enabled us to amplify large genomic fragments covering the OA1 gene. and to detect very likely six distinct large deletions. Furthermore, we were able to confirm that there was no deletion in twenty one patients where no mutation had been found. CONCLUSION: The identified mutations affect highly conserved amino acids, cause frameshifts or alternative splicing, thus affecting folding of the OA1 G protein coupled receptor, interactions of OA1 with its G protein and/or binding with its ligand.

Defect in dorso-ventral patterning, asplenia, and conotruncus in a spontaneously aborted fetus.

We describe a very unusual combination, and previously unreported, of malformations in an 18-week, spontaneously aborted male fetus. The fetus had a reversed dorsoventral positioning of the head and upper limbs relative to the body axis with the head and both upper limbs directed dorsally, and an abrupt rotation of the vertebral bones at the level of CZ The fetus also had asplenia, single ventricle, and conotruncus. The fetus also had flexion deformities at the wrist, reduction deformity of the left second digit, anomalies in ossification of the bones of the left hand, and bilateral talipes calcaneovalgus. The major malformations in this fetus were all blastogenetic in origin and consisted of dorsoventral patterning defect involving structures cranial to C7, a laterality, and a septation defect of the ventricle and outflow tract of the heart. The defects are interpreted as being the result of abnormal coordination of the molecular signaling involved in dorsoventral axis formation and laterality of the limbs and trunk, and possibly also in cardiac septation.