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In the light of modern molecular technologies, the understanding of the complexity of the numerous genotype-phenotype correlations regarding Dravet syndrome is mandatory. Motivated by 2 patients, whose whole-exome sequencing revealed novel mutations that exemplify the phenotypic and genetic heterogeneities associated with typical and atypical Dravet syndrome presentations, the authors discuss the existence of a broader spectrum of Dravet syndrome. The first patient is a 4-year-old boy with fairly typical Dravet syndrome and a novel sodium channel α1 subunit gene mutation of high-predicted combined pathogenicity likelihood. The second patient is a 15-year-old boy with some atypical features of Dravet syndrome, harboring a novel mutation of the γ-aminobutyric acid receptor α1 subunit gene, whose role in this syndrome pathogenesis has recently been highlighted. A brief review of the literature reveals that none of the current diagnostic criteria is thoroughly predictive of the disease, and phenotypic discrepancies are common among patients carrying atypical Dravet syndrome mutations. The authors conclude that the discussion of a Dravet syndrome spectrum is relevant., Competing Interests: Declaration of Conflicting Interests: The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Fetal malformations detected through routine prenatal ultrasound examination comprise a heterogeneous group potentially associated with genetic disorders where the underlying cause is difficult to establish. We present the prenatal diagnosis of a rare X-linked myopathy involving a new VMA21 gene mutation, detected through a novel prenatal exome sequencing-based approach.

Background: Although several studies in various countries have indicated that the presence of the E4 allele of the apolipoprotein-E (APOE) gene is a risk factor for ischemic cerebrovascular disease, the strength of this association still remains a matter of debate., Objectives: The aim of the study was to determine the frequency of the APOE E4 allele and various other gene polymorphisms in in a well-characterized sample of Greek patients and to evaluate the potential associations with the risk of ischemic stroke (IS) and coronary heart disease (CHD)., Material and Methods: A total of nine gene variants/polymorphisms - F5 (Leiden - R5 06Q, rs6025), F2 (20210G > A, rs1799963), F13A1 (V34L, rs5985), MTHFR (677C > T - A222V, rs1801133), MTHFR (1298A > C - E429A, rs1801131), FGB (-455G > A -c.-463G > A; rs1800790), SERPINE1 (PAI14G/5G - rs1799889), ACE (ACE I/D, rs1799752), ITGB3 (GPIIIa L33P, rs5918) and the APOE E2/E3/E4 alleles (rs7412, rs429358) - were genotyped in 200 newly diagnosed ischemic stroke (IS) patients, 165 patients with ischemic coronary heart disease (CHD) and 159 controls with no cerebroor cardiovascular disease (non-CVD). A statistical analysis was performed using univariate and multivariate logistic regression models., Results: No significant association was found regarding most gene polymorphisms and the presence of IS or CHD in the patient cohort. However, the APOE E4 allele frequency was significantly higher (p = 0.02) among patients with ischemic stroke (IS) or IS + CHD (12.7%) when compared to the controls (5.1%). More accurately, E4 carriers had 2.66 and 2.71 times greater likelihood of IS or IS + CHD than non-carriers, respectively (OR = 2.66, 95% CI 1.39-5.07, OR = 2.71, 95% CI 0.98-7.48)., Conclusions: In contrast to some previous studies, these results support the role of the APOE E4 allele as an independent risk factor for ischemic stroke and ischemic coronary heart disease among Greek patients.

Background. Fetal malformations and other structural abnormalities are relatively frequent findings in the course of routine prenatal ultrasonographic examination. Due to their considerable genetic and clinical heterogeneity, the underlying genetic cause is often elusive and the resulting inability to provide a precise diagnosis precludes proper reproductive and fetal risk assessment. We report the development and first applications of an expanded exome sequencing-based test, coupled to a bioinformatics-driven prioritization algorithm, targeting gene disorders presenting with abnormal prenatal ultrasound findings. Methods. We applied the testing strategy to14 euploid fetuses, from 11 on-going pregnancies and three products of abortion, all with various abnormalities or malformations detected through prenatal ultrasound examination. Whole exome sequencing (WES) was followed by variant prioritization, utilizing a custom analysis pipeline (Fetalis algorithm), targeting 758 genes associated with genetic disorders which may present with abnormal fetal ultrasound findings. Results. A definitive or highly-likely diagnosis was made in 6 of 14 cases (43%), of which 3 were abortuses (Ellis-van Creveld syndrome, Ehlers-Danlos syndrome and Nemaline myopathy 2) and 3 involved on-going pregnancies (Citrullinemia, Noonan syndrome, PROKR2-related Kallmann syndrome). In the remaining eight on-going pregnancy cases (57%), a ZIC1 variant of unknown clinical significance was detected in one case, while in seven cases testing did not reveal any pathogenic variant(s). Pregnancies were followed-up to birth, resulting in one neonate harboring the PROKR2 mutation, presenting with isolated minor structural cardiac abnormalities, and in seven apparently healthy neonates. Discussion. The expanded targeted exome sequencing-based approach described herein (Fetalis), provides strong evidence suggesting a definite and beneficial increase in our diagnostic capabilities in prenatal diagnosis of otherwise chromosomally balanced fetuses with troubling ultrasound abnormalities. Furthermore, the proposed targeted exome sequencing strategy, designed primarily as a diagnostic rather than a research discovery tool, overcomes many of the problems and limitations associated with clinical wide-scale WES testing in a prenatal setting.

Introduction: The aim of this article is to provide a perspective of prenatal chromosomal diagnosis (PCD) derived from a single center's evolving experience from ∼90,000 consecutive prenatal cases and to highlight important issues and current dilemmas., Materials and Methods: Prenatal cases in this study (1985-2013) were referred for various indications, and PCD was performed by standard karyotype in 84,255 cases, multiplex ligation-dependent probe amplification (MLPA) panel in 3,010 cases and standalone array comparative genomic hybridization (aCGH) in 3,122 cases., Results: Classic karyotype revealed 1.7 and 7.9% of pathological cases in amniotic fluid and CVS samples, respectively, with common aneuploidies accounting for 59.6 and 64.3% of the total abnormal. Molecular approaches increased the diagnostic yield by 0.6% for MLPA and 1.6% for aCGH, uncovering pathogenic chromosomal abnormalities undetectable by karyotype analysis., Conclusions: Current molecular diagnostic capabilities and the recent introduction of noninvasive prenatal testing (NIPT) point to one current major dilemma in PCD, with serious implications in genetic counseling, relating on the one hand to reaping the benefits from the high detection rate afforded through aCGH but accepting an invasive risk, and on the other hand, offering a lower detection rate practically only for Down syndrome, with minimal invasive risk., (© 2015 S. Karger AG, Basel.)

Objective: The presence of numerical and/or structural chromosomal abnormalities is a frequent finding in clonal hematopoietic malignant disease, typically diagnosed through routine karyotyping and/or fluorescent in situ hybridization (FISH) analysis. Recently, the application of array comparative genomic hybridization (aCGH) has uncovered many new cryptic genomic copy number imbalances, most of which are now recognized as clinically useful markers of haematological malignancies. In view of the limitations of both FISH and aCGH techniques, in terms of their routine application as a first line screening test, we designed a new multiple ligation-dependent probe amplification (MLPA) probemix for use in addition to classic karyotype analysis., Methods: A novel MLPA probemix was developed to interrogate copy number changes involving chromosomal regions: 2p23-24 (MYCN, ALK), 5q32-34 (MIR145A, EBF1, MIR146A), 6q21-27, 7p12.2 (IKZF1), 7q21-36, 8q24.21 (MYC), 9p24 (JAK2 V617F point mutation), 9p21.3 (CDKN2A/2B), 9p13.2 (PAX5), 10q23 (PTEN), 11q22.3 (ATM), 12p13.2 (ETV6), 13q14 (RB1, MIR15A, DLEU2, DLEU1), 17p13.1 (TP53), and 21q22.1 (RUNX1/AML1) and was applied to DNA extracted from 313 consecutive bone marrow patient samples, referred for routine karyotype analysis., Results: More than half of the samples originated from newly investigated patients. We discovered clinically relevant genomic aberrations, involving a total of 24 patients (8%) all with a normal karyotype, which would have remained undiagnosed., Discussion: Our data clearly indicate that routine application of this MLPA screening panel, as an adjunct to karyotype analysis, provides a sensitive, robust, rapid and low-cost approach for uncovering clinically important genomic abnormalities, which would have otherwise remained undetected.

A 33-year-old adult male of Greek ethnicity, with hematological indices suggesting β(0)-thalassemia (β(0)-thal) trait, was investigated for HBB gene mutations in the course of preparation for preimplantation genetic diagnosis (PGD). Application of a routine diagnostic protocol, consisting of sequence analysis of the HBB gene, coupled to multiplex ligation-dependent probe amplification (MLPA), identified a single nucleotide deletion (-T) at codon 72 [HBB: c.216delT], leading to a novel pathogenic frameshift and protein-truncating β(0)-thal mutation (p.Phe72LeufsX18).

Objective: To present the application of multiplex ligation-dependent probe amplification (MLPA)-based screening approach in 1550 typical prenatal cases, for the simultaneous targeted detection of 23 recurrent microdeletion syndromes as well as subtelomeric copy number assessment for all chromosomes and discuss the implications in routine prenatal chromosomal diagnosis (PCD)., Methods: Following amniocentesis or chorionic villus sampling, samples were processed for routine karyotype analysis while DNA was extracted in parallel for MLPA analysis. When necessary, parental samples were analyzed to determine the inheritance of the detected aberrations., Results: This panel has been applied since 2006 in 1550 prenatal samples, referred for routine karyotype analysis, with (16.1%) or without (77.7%) ultrasound (US) findings. We identified eight fetuses with pathological genomic abnormalities (approximately 1 in 193), five of which had as sole indication advanced maternal age (1 in 240). In two cases an abnormality was suspected from karyotype analysis, while the remaining six cases would have otherwise remained totally undetected., Conclusions: Our data represent the largest published series involving this type of genomic analysis in routine prenatal diagnosis, without indication bias. The panel increases significantly the diagnostic yield of conventional PCD and does not pose interpretation problems., (Copyright © 2011 John Wiley & Sons, Ltd.)

A cDNA clone complementary to the mRNA encoding the rabbit erythrocyte specific carbonic anhydrase, CAI, has been used as probe for human CAI sequences in the analysis of DNA from panels of rodent/human somatic cell hybrids. The presence of the human CAI gene in all hybrids correlates with the presence of chromosome 8. Together with published mapping data, this assignment indicates that three CA loci are situated on chromosome 8.