Elisa Pisaneschi

Keppen-Lubinsky Syndrome Is Caused by Mutations in the Inwardly Rectifying K+ Channel Encoded by KCNJ6

Keppen-Lubinsky syndrome (KPLBS) is a rare disease mainly characterized by severe developmental delay and intellectual disability, microcephaly, large prominent eyes, a narrow nasal bridge, a tented upper lip, a high palate, an open mouth, tightly adherent skin, an aged appearance, and severe generalized lipodystrophy. We sequenced the exomes of three unrelated individuals affected by KPLBS and found de novo heterozygous mutations in KCNJ6 (GIRK2), which encodes an inwardly rectifying potassium channel and maps to the Down syndrome critical region between DIRK1A and DSCR4. In particular, two individuals shared an in-frame heterozygous deletion of three nucleotides (c.455_457del) leading to the loss of one amino acid (p.Thr152del). The third individual was heterozygous for a missense mutation (c.460G>A) which introduces an amino acid change from glycine to serine (p.Gly154Ser). In agreement with animal models, the present data suggest that these mutations severely impair the correct functioning of this potassium channel. Overall, these results establish KPLBS as a channelopathy and suggest that KCNJ6 (GIRK2) could also be a candidate gene for other lipodystrophies. We hope that these results will prompt investigations in this unexplored class of inwardly rectifying K(+) channels.

Diagnosis of Noonan syndrome and related disorders using target next generation sequencing

BackgroundNoonan syndrome is an autosomal dominant developmental disorder with a high phenotypic variability, which shares clinical features with other rare conditions, including LEOPARD syndrome, cardiofaciocutaneous syndrome, Noonan-like syndrome with loose anagen hair, and Costello syndrome. This group of related disorders, so-called RASopathies, is caused by germline mutations in distinct genes encoding for components of the RAS-MAPK signalling pathway. Due to high number of genes associated with these disorders, standard diagnostic testing requires expensive and time consuming approaches using Sanger sequencing. In this study we show how targeted Next Generation Sequencing (NGS) technique can enable accurate, faster and cost-effective diagnosis of RASopathies.MethodsIn this study we used a validation set of 10 patients (6 positive controls previously characterized by Sanger-sequencing and 4 negative controls) to assess the analytical sensitivity and specificity of the targeted NGS. As second step, a training set of 80 enrolled patients with a clinical suspect of RASopathies has been tested. Targeted NGS has been successfully applied over 92% of the regions of interest, including exons for the following genes: PTPN11, SOS1, RAF1, BRAF, HRAS, KRAS, NRAS, SHOC, MAP2K1, MAP2K2, CBL.ResultsAll expected variants in patients belonging to the validation set have been identified by targeted NGS providing a detection rate of 100%. Furthermore, all the newly detected mutations in patients from the training set have been confirmed by Sanger sequencing. Absence of any false negative event has been excluded by testing some of the negative patients, randomly selected, with Sanger sequencing.ConclusionHere we show how molecular testing of RASopathies by targeted NGS could allow an early and accurate diagnosis for all enrolled patients, enabling a prompt diagnosis especially for those patients with mild, non-specific or atypical features, in whom the detection of the causative mutation usually requires prolonged diagnostic timings when using standard routine. This approach strongly improved genetic counselling and clinical management.

Telomere shortening and telomere position effect in mild ring 17 syndrome

BackgroundRing chromosome 17 syndrome is a rare disease that arises from the breakage and reunion of the short and long arms of chromosome 17. Usually this abnormality results in deletion of genetic material, which explains the clinical features of the syndrome. Moreover, similar phenotypic features have been observed in cases with complete or partial loss of the telomeric repeats and conservation of the euchromatic regions. We studied two different cases of ring 17 syndrome, firstly, to clarify, by analyzing gene expression analysis using real-time qPCR, the role of the telomere absence in relationship with the clinical symptoms, and secondly, to look for a new model of the mechanism of ring chromosome transmission in a rare case of familial mosaicism, through cytomolecular and quantitative fluorescence in-situ hybridization (Q-FISH) investigations.ResultsThe results for the first case showed that the expression levels of genes selected, which were located close to the p and q ends of chromosome 17, were significantly downregulated in comparison with controls. Moreover, for the second case, we demonstrated that the telomeres were conserved, but were significantly shorter than those of age-matched controls; data from segregation analysis showed that the ring chromosome was transmitted only to the affected subjects of the family.ConclusionsSubtelomeric gene regulation is responsible for the phenotypic aspects of ring 17 syndrome; telomere shortening influences the phenotypic spectrum of this disease and strongly contributes to the familial transmission of the mosaic ring. Together, these results provide new insights into the genotype-phenotype relationships in mild ring 17 syndrome.

Kabuki syndrome: clinical and molecular diagnosis in the first year of life

Objective To review the clinical and molecular genetic characteristics of 16 patients presenting a suspected diagnosis of Kabuki syndrome (KS) in the first year of life, to evaluate the clinical handles leading to a prompt diagnosis of KS in newborns. Clinical diagnosis of KS can be challenging during the first year of life, as many diagnostic features become evident only in subsequent years. Methods All patients were clinically investigated by trained clinical geneticists. A literature review was performed using the Pubmed online database and diagnostic criteria suggested by DYSCERNE–Kabuki Syndrome Guidelines (2010) were used (a European Network of Centres of Expertise for Dysmorphology, funded by the European Commission Executive Agency for Health and Consumers (DG Sanco), Project 2006122). Molecular analysis of the known causative genes of KS, KMT2D/MLL2 and KDM6A, was performed through MiSeq-targeted sequencing platform. All mutations identified were validated by Sanger sequencing protocols. Results Mutations in KMT2D gene were identified in 10/16 (62%) of the patients, whereas none of the patients had KDM6A mutations. Facial dysmorphisms (94%), feeding difficulties (100%) and hypotonia (100%) suggested the clinical diagnosis of KS. No significative differences in terms of facial features were noticed between mutation positive and negative patients of the cohort. Brachydactyly, joint laxity and nail dysplasia were present in about 80% of the patients. Other congenital anomalies were most commonly present in the mutated group of patients, including left-sided cardiac abnormalities, skeletal, renal and anorectal malformations and hypertricosis. Conclusions We present an overview of patients with KS diagnosed during the first year of life. Early diagnosis is serviceable in terms of clinical management and for targeted genetic counselling.

Complete maternal isodisomy causing reduction to homozygosity for a novel LAMB3 mutation in Herlitz junctional epidermolysis bullosa

Herlitz junctional epidermolysis bullosa (HJEB) is a rare genodermatosis characterized by blister formation with tissue separation within the lamina lucida of the basement membrane zone and early lethality [1]. It is genetically heterogeneous, being caused by null mutations in the LAMA3 (18q11.2), LAMB3 (1q32), or LAMC2 (1q25—q31) genes encoding for the a3, b3 and g2 subunits of laminin 332, the major adhesion ligand of basal epithelial cells [2]. HJEB is inherited as an autosomal recessive trait from heterozygous healthy parents to 25% of their offspring. However, 4 HJEB sporadic patients have been described in whom the disease arose from reduction to homozygosity for a mutation carried by a single parent [3—6]. This phenomenon is ascribed to uniparental disomy (UPD), which is the exceptional derivation of a pair of the progeny chromosomes from one parent only [7]. In particular, UPD may present either as uniparental heterodisomy, which refers to the presence of a pair of chromosome homologues, or as uniparental isodisomy, when two identical copies of a single parental chromatid are found in the progeny [8]. By definition, only the latter phenomenon illustrates Mendelian recessive outlaws [9]. Here, we report an additional sporadic patient affected by HJEB due to a previously undescribed homozygous LAMB3 mutation resulting from complete maternal chromosome 1 isodisomy. The proband was a Bulgarian 10-month-old female, unique child of a 29-year-old mother and her non-consanguineous 31-year-old husband.

Role of molecular testing in the multidisciplinary diagnostic approach of ichthyosis.

BackgroundThe term ichthyosis describes a generalized disorder of cornification characterized by scaling and/or hyperkeratosis of different skin regions. Mutations in a broad group of genes related to keratinocyte differentiation and epidermal barrier function have been demonstrated to play a causative role in disease development. Ichthyosis may be classified in syndromic or non-syndromic forms based on the occurrence or absence of extracutaneous signs. In this setting, the diagnosis of ichthyosis is an integrated multistep process requiring a multidisciplinary approach in order to formulate the appropriate diagnostic hypothesis and to address the genetic testing.MethodsDue to the complex features of the different ichthyoses and the high number of genes involved we have investigated a group of 64 patients, affected by syndromic and non-syndromic diseases, using Next Generation Sequencing as a new tool for the molecular diagnosis.ResultsUsing this innovative molecular approach we were able to find pathogenic mutations in 53 out of 64 patients resulting in 82.8 % total detection rate. An interesting result from the analysis of the data is the high rate of novel sequence variations found compared to known mutations and the relevant rate of homozygous mutations.ConclusionsThe possibility to analyze a large number of genes associated with various diseases allows to study cases with phenotypes not well-determined, giving the opportunity to make new genotype-phenotype correlation. In some cases there were discrepancies between clinical features and histology or electron microscopy and only molecular analysis allowed to definitively resolve the diagnostic dilemma. The genetic diagnosis of ichthyosis leads to a more accurate and effective genetic counseling, allowing correct evaluation of the risk of recurrence, particularly in families with consanguineous background.

CHARGE syndrome due to deletion of region upstream of CHD7 gene START codon

AbstractBackgroundCHARGE syndrome is an autosomal dominant disorder, characterized by ocular Coloboma, congenital Heart defects, choanal Atresia, Retardation, Genital anomalies and Ear anomalies. Over 90 % of typical CHARGE patients are mutated in the CHD7 gene, 65 %–70 % of the cases for all typical and suspected cases combined. The gene encoding for a protein involved in chromatin organization. The mutational spectrum include nonsense, frameshift, splice site, and missense mutations. Large deletions and genomic rearrangements are rare.Case presentationWe report here on a 5.9 years old male of Moroccan origin displaying classic clinical features of CHARGE syndrome. Using CGH array and NGS analysis we detected a microdeletion (184 kb) involving the promoter region and exon 1 of CHD7 gene and the flanking RAB2 gene.ConclusionThe present observation suggests that deletion limited to the regulatory region of CHD7 is sufficient to cause the full blown CHARGE phenotype. Different size of deletions can result in different phenotypes, ranging from a milder to severe CHARGE syndrome; this is based on a combination of major and minor diagnostic characteristics, therefore to a more variable clinical features, likely due to the additive effect of other genetic imbalances. MLPA and CGH techniques should be considered in the diagnostic protocol of individuals with a clinical suspect of CHARGE syndrome

Novel PNPLA1 mutations in two Italian siblings with autosomal recessive congenital ichthyosis

Autosomal recessive congenital ichthyoses (ARCI) are a clinically and genetically heterogeneous group of non-syndromic ichthyoses due to mutations in at least 9 genes, including PNPLA1 (1). PNPLA1 (Patatin-Like Phospholipase Domain-Containing Protein 1) is strongly expressed in the epidermal granular cell layer (1), and has been recently shown to play a crucial role in epidermal ω-O-acylceramide biosynthesis and skin barrier integrity both in mice and humans (2-5). Concomitantly several ARCI families carrying PNPLA1 mutations have been described confirming that most mutations occur in the highly conserved patatin core domain (1, 5-10). We report the identification of two novel missense mutations in PNPLA1 in two Italian sisters affected with ARCI characterized by a cyclic disease course. This article is protected by copyright. All rights reserved.

Next-Generation Sequencing Identifies Different Genetic Defects in 2 Patients with Primary Adrenal Insufficiency and Gonadotropin-Independent Precocious Puberty

Background: The development of gonadotropin-independent (peripheral) precocious puberty in male children with primary adrenal insufficiency (PAI) is consistent with a defect in the genes encoding for the enzymes involved in steroid hormone biosynthesis. Methods: Two young boys presented with peripheral precocious puberty followed by PAI. In both patients, the analysis of CYP21A2 gene encoding 21-hydroxylase was normal. As a second step, a targeted next-generation sequencing (NGS) was performed in both patients using a customized panel of congenital endocrine disor ders. Results: Case 1 had a new homozygous variant in the CYP11B1 gene (c.1121+5G>A). Mutations of this gene cause congenital adrenal hyperplasia due to 11β-hydroxylase deficiency, an essential enzyme in the cortisol biosynthesis pathway. Case 2 showed a new hemizygous mutation in the NR0B1 gene (c.1091T>G), which encodes for DAX1 (dosage-sensitive sex reversal, adrenal hypoplasia congenita [AHC] and critical region on the X chromosome gene 1). NR0B1 mutations cause X-linked AHC and hypogonadotropic hypogonadism. Pathogenicity prediction software defined both mutations as probably damaging. Conclusions: Peripheral precocious puberty was the atypical presentation of 2 rare genetic diseases. The use of NGS made the characterization of these 2 cases with similar clinical phenotypes caused by 2 different genetic defects possible.

X-linked ichthyosis: Clinical and molecular findings in 35 Italian patients

Recessive X‐linked ichthyosis (XLI), the second most common ichthyosis, is caused by mutations in the STS gene encoding the steroid sulfatase enzyme. A complete deletion of the STS gene is found in 85%‐90% of cases. Rarely, larger deletions involving contiguous genes are detected in syndromic patients. We report the clinical and molecular genetic findings in a series of 35 consecutive Italian male patients. All patients underwent molecular testing by MLPA or aCGH, followed, in case of negative results, by next‐generation sequencing analysis. Neuropsychiatric, ophthalmological and paediatric evaluations were also performed. Our survey showed a frequent presence of disease manifestations at birth (42.8%). Fold and palmoplantar surfaces were involved in 18 (51%) and 7 (20%) patients, respectively. Fourteen patients (42%) presented neuropsychiatric symptoms, including attention‐deficit hyperactivity disorder and motor disabilities. In addition, two patients with mental retardation were shown to be affected by a contiguous gene syndrome. Twenty‐seven patients had a complete STS deletion, one a partial deletion and 7 carried missense mutations, two of which previously unreported. In addition, a de novo STS deletion was identified in a sporadic case. The frequent presence of palmoplantar and fold involvement in XLI should be taken into account when considering the differential diagnosis with ichthyosis vulgaris. Our findings also underline the relevance of involving the neuropsychiatrist in the multidisciplinary management of XLI. Finally, we report for the first time a de novo mutation which shows that STS deletion can also occur in oogenesis.