Future of Dutch NGS-Based Newborn Screening: Exploring the Technical Possibilities and Assessment of a Variant Classification Strategy.

In this study, we compare next-generation sequencing (NGS) approaches (targeted panel (tNGS), whole exome sequencing (WES), and whole genome sequencing (WGS)) for application in newborn screening (NBS). DNA was extracted from dried blood spots (DBS) from 50 patients with genetically confirmed inherited metabolic disorders (IMDs) and 50 control samples. One hundred IMD-related genes were analyzed. Two data-filtering strategies were applied: one to detect only (likely) pathogenic ((L)P) variants, and one to detect (L)P variants in combination with variants of unknown significance (VUS). The variants were filtered and interpreted, defining true/false positives (TP/FP) and true/false negatives (TN/FN). The variant filtering strategies were assessed in a background cohort (BC) of 4833 individuals. Reliable results were obtained within 5 days. TP results (47 patient samples) for tNGS, WES, and WGS results were 33, 31, and 30, respectively, using the (L)P filtering, and 40, 40, and 38, respectively, when including VUS. FN results were 11, 13, and 14, respectively, excluding VUS, and 4, 4, and 6, when including VUS. The remaining FN were mainly samples with a homozygous VUS. All controls were TN. Three BC individuals showed a homozygous (L)P variant, all related to a variable, mild phenotype. The use of NGS-based workflows in NBS seems promising, although more knowledge of data handling, automated variant interpretation, and costs is needed before implementation.

Dual association of a TRKA polymorphism with schizophrenia.

OBJECTIVE: An interaction between predisposing genes and environmental stressors is thought to underlie the neurodevelopmental disorder schizophrenia. In a targeted gene screening, we previously found that the minor allele of the single nucleotide polymorphism (SNP) rs6336 in the neurotrophic tyrosine kinase receptor 1 (NTRK1/TRKA) gene is associated with schizophrenia as a risk factor. METHODS: We genotyped the TRKA SNP in a total of eight independent Caucasian schizophrenia case-control groups. RESULT: Remarkably, although in five of the groups a higher frequency of the risk allele was indeed found in the patients compared with the controls, in the three other groups the SNP acted as a protective factor. CONCLUSION: An intriguing possibility is that this dual character of the TRKA SNP is caused by its interaction with endophenotypic and/or epistatic factors.

Dopamine susceptibility of APO-SUS rats is not per se coupled to HPA-axis activity.

A synergistic relationship is thought to exist between hypothalamic-pituitary-adrenal (HPA) axis activity and dopamine neurotransmission. To test whether a high response to dopamine indeed implies a hyperactive HPA-axis, we here used Wistar rats that were selected twice independently (original and replicate lines) for a high or low susceptibility to the dopamine receptor agonist apomorphine (so-called APO-SUS and APO-UNSUS rats, respectively). The APO-SUS rats from the original line displayed a hyperactive HPA-axis in that higher basal and stress-induced adrenocorticotropic hormone (ACTH) levels, and lower basal free-corticosterone levels were observed than those found in the original APO-UNSUS rats. In contrast, the activity of the HPA-axis in the APO-SUS rats from the replicate line did not differ from that in the replicate APO-UNSUS rats. Thus, in the APO-SUS/APO-UNSUS rat model the level of HPA-axis activity is not necessarily causally linked to dopamine responsiveness, implying that a hyperactive HPA-axis is not a prerequisite for a high dopaminergic response.

Gene expression profiling in brain regions of a rat model displaying schizophrenia-related features.

Animal models allow insights into complex neurodevelopmental disorders. Apomorphine-susceptible rats (so-called APO-SUS rats) provide a model that displays a complex phenotype with schizophrenia-related features and together with its phenotypic counterpart (APO-UNSUS rats) has been independently generated twice (original and replicate rat lines). To understand the molecular basis underlying this phenotype, we here performed mRNA expression profiling in various APO-SUS and APO-UNSUS rat brain regions. The expression of only the previously reported Aph-1b and the newly discovered KCnIP1 (a member of the potassium channel-interacting protein family that is known to modulate neuronal channel activity) was significantly different in the APO-SUS and APO-UNSUS rats from both the original and replicate rat lines. Thus, KCnIP1 may constitute a novel candidate gene playing a role in the complex phenotype of the APO-SUS/APO-UNSUS rat model and further studies on this gene are warranted.

Vascular damage in testicular cancer patients: a study on endothelial activation by bleomycin and cisplatin in vitro.

Following treatment with bleomycin- and cisplatin-containing chemotherapy, testicular cancer patients frequently develop vascular complications, which may result from damage to endothelial cells. Understanding bleomycin- and cisplatin-induced endothelial alterations may help to develop strategies to prevent or reduce vascular toxicity. The effects of bleomycin and cisplatin on proliferation and apoptosis of the human dermal microvascular endothelial cell line HMEC-1 were determined. In addition, modulation of drug-induced cytotoxicity by the free radical scavenger amifostine, the low molecular weight heparin dalteparin, the iron-chelator dexrazoxane, the HMG-CoA reductase inhibitor rosuvastatin and the PPAR agonist troglitazone was tested. Furthermore, the effects of bleomycin and cisplatin on endothelial activation measured by the expression of the intercellular adhesion molecule-1 (ICAM-1) and on two main proteins involved in fibrinolysis, tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor type 1 (PAI-1), were measured. Decreased endothelial cell survival induced by bleomycin and cisplatin coincided with the induction of apoptosis. Only troglitazone was able to protect the endothelial cells from both bleomycin- and cisplatin-induced cytotoxicity. At high concentrations, amifostine and dexrazoxane also protected HMEC-1 from drug-induced cytotoxicity. However, due to the required high (toxic) concentrations of both modulators no absolute cell survival benefit could be achieved. Both bleomycin and cisplatin induced up-regulation of ICAM-1, tPA and PAI-1. Summarizing, bleomycin and cisplatin induce alterations in the function of endothelial cells regarding proliferation, inflammation and fibrinolysis in vitro. Strategies aimed at these functions should be developed in order to ameliorate or prevent cytostatic agent-induced vascular damage.

Correlation between HIV-1 seropositivity and prevalence of a gamma-secretase polymorphism in two distinct ethnic populations.

Susceptibility for human immunodeficiency virus type 1 (HIV-1) infection may be influenced by host genetics. Recent findings with a Wistar rat model raised the possibility that the gamma-secretase pathway may be associated with an individual's susceptibility to infection. A functional single-nucleotide polymorphism (SNP) in the gamma-secretase component APH1B (Phe217Leu; rs1047552) was therefore analyzed for association with HIV-1 infection. The SNP showed a tendency for association with HIV-1 infection in a Xhosa indigenous South African Bantu study (P = 0.087), and associated significantly in a Caucasian Dutch study (P = 0.049). Together, the results suggest a role for the gamma-secretase pathway in susceptibility to HIV-1 infection.

Three-cohort targeted gene screening reveals a non-synonymous TRKA polymorphism associated with schizophrenia.

Schizophrenia is a complex neurodevelopmental disorder that is thought to be induced by an interaction between predisposing genes and environmental stressors. To identify predisposing genetic factors, we performed a targeted (mostly neurodevelopmental) gene approach involving the screening of 396 selected non-synonymous single-nucleotide polymorphisms (SNPs) in three independent Caucasian schizophrenia case-control cohorts (USA, Denmark and Norway). A meta-analysis revealed ten non-synonymous SNPs that were nominally associated with schizophrenia, nine of which have not been previously linked to the disorder. Risk alleles are in TRKA (rs6336), BARD1 (rs28997576), LAMA5 (rs3810548), DKK2 (rs7037102), NOD2 (rs2066844) and RELN (rs2229860), whereas protective alleles are in NOD2 (rs2066845), NRG1 (rs10503929), ADAM7 (rs13259668) and TNR (rs859427). Following correction for multiple testing, the most attractive candidate for further study concerns SNP rs6336 (q=0.12) that causes the substitution of an evolutionarily highly conserved amino acid residue in the kinase domain of the neurodevelopmentally important receptor TRKA. Thus, TRKA signaling may represent a novel susceptibility pathway for schizophrenia.

Male-specific association between a gamma-secretase polymorphism and premature coronary atherosclerosis.

BACKGROUND: Atherosclerosis is a common multifactorial disease resulting from an interaction between susceptibility genes and environmental factors. The causative genes that contribute to atherosclerosis are elusive. Based on recent findings with a Wistar rat model, we speculated that the gamma-secretase pathway may be associated with atherosclerosis. METHODOLOGY/PRINCIPAL FINDINGS: We have tested for association of premature coronary atherosclerosis with a non-synonymous single-nucleotide polymorphism (SNP) in the gamma-secretase component APH1B (Phe217Leu; rs1047552), a SNP previously linked to Alzheimer's disease. Analysis of a Dutch Caucasian cohort (780 cases; 1414 controls) showed a higher prevalence of the risk allele in the patients (odds ratio (OR) = 1.35), albeit not statistically different from the control population. Intriguingly, after gender stratification, the difference was significant in males (OR = 1.63; p = 0.033), but not in females (OR = 0.50; p = 0.20). Since Phe217Leu-mutated APH1B showed reduced gamma-secretase activity in mouse embryonic fibroblasts, the genetic variation is likely functional. CONCLUSION/SIGNIFICANCE: We conclude that, in a male-specific manner, disturbed gamma-secretase signalling may play a role in the susceptibility for premature coronary atherosclerosis.

Genetic variation in the bleomycin hydrolase gene and bleomycin-induced pulmonary toxicity in germ cell cancer patients.

OBJECTIVE: Use of bleomycin as a cytotoxic agent is limited by its pulmonary toxicity. Bleomycin is mainly excreted by the kidneys, but can also be inactivated by bleomycin hydrolase (BMH). An 1450A>G polymorphic site in the BMH gene results in an amino acid substitution in the C-terminal domain of the protein. Deletion of this domain, including the polymorphic site, reduces enzymatic activity. We investigated the relation between the BMH genotype and the risk of bleomycin-induced pneumonitis (BIP). METHODS: From male germ cell cancer patients, treated with bleomycin-containing chemotherapy at the University Hospital Groningen, The Netherlands, between 1977 and 2003, data were collected on age, cumulative bleomycin dose, pretreatment creatinine clearance, pulmonary metastases, lung function parameters, and occurrence of BIP. BIP was defined as: death due to BIP, or presence of clinical and/or radiographic signs of BIP during or following treatment. Polymerase chain reaction and restriction fragment length polymorphism were used to determine the BMH genotype. RESULTS: BIP developed in 38 (11%) of 340 patients; four of these cases were fatal. BMH genotype distribution did not differ between patients with and those without BIP. Patients with BIP were older and had a lower pretreatment creatinine clearance. Changes in pulmonary function tests were similar in patients with different genotypes. CONCLUSIONS: The BMH genotype was not associated with the development of BIP nor with changes in pulmonary function tests. Since renal function is important for bleomycin pharmacokinetics, variations in renal clearance may have obscured significant effects of the BMH genotype.