Genetic studies of neurodevelopmental disorders

Neurodevelopmental disorders (NDDs) constitute a heterogeneous group of disorders that adversely impacts a child’s behavioural and learning processes. Developmental delay (DD) and mental retardation are included among the NDDs and are frequently associated with a wide range of accompanying disabilities such as multiple congenital anomalies and dysmorphic features. Despite extensive clinical and laboratory investigation, the cause of the patient’s symptoms remains unknown in approximately half of the cases. For the children’s families this is often frustrating since an aetiological diagnosis not only gives an explanation of why the child has symptoms but may also provide better prognosis evaluation, adequate genetic counselling and enable prenatal diagnosis. In approximately 20% of patients, a clear genetic cause can be found, including both single-gene disorders and chromosomal disorders. In paper I a NIPBL and SMC1L1 mutation screening by direct sequencing and MLPA was performed in a group of nine index patients diagnosed with Cornelia de Lange syndrome (CdLS), which is characterized by severe mental and growth retardation and distinctive dysmorphic facial features. We identified seven NIPBL mutations and showed that a splice-site mutation lead to skipping of an exon. A clear genotype-phenotype correlation was not found. In paper II sequencing and MLPA analysis revealed 18 CHD7 mutations in 28 index patients with CHARGE syndrome. In addition, inherited variants were identified and clinical interpretation of these are discussed. Our results indicate that hypoplastic semicircular canals is not obligatory for a CHD7 mutation, although we agree that it is the most frequent and specific sign of CHARGE syndrome. A CHD7 mutation was found in a patient not fulfilling clinical criteria showing that also atypical patients benefit from testing. Paper I and II confirm that NIPBL and CHD7 are the main causative genes for CdLS and CHARGE syndrome respectively. However, in >30% of our patients no causal mutation could be detected. Whole genome-/exome sequencing might find new causative genes and/or mutations in non-coding sequences of known genes. The patient described in paper III had an 18.2 Mb de novo deletion of chromosome 11q13.4-q14.3. By comparing his phenotype to the few previously described patients, we show that a common phenotype for patients with deletions in this region might be emerging, comprising mild-moderate DD, a sociable personality and dysmorphic facial features. The implementation of high-resolution array-CGH over the last decade has enabled the genome-wide identification of submicroscopic copy number variations (CNVs) in patients with NDDs. In study IV we wanted to evaluate array-CGH as a diagnostic tool in our clinical laboratory. In the 160 investigated patients, 21 (13,1%) causal CNVs and 15 (9.4%) CNVs of unclear clinical significance were detected. Standard karyotyping had in seven cases failed to detect causal CNVs ≥5 Mb, five of which were ≥10Mb, emphasizing that more reliable methods were needed to exclude CNVs in these patients. Array-CGH proved to be very useful and became recommended as the first step investigation for patients with idiopathic DD. However, increasing the resolution of a whole genome screen in the diagnostic setting has its drawback of detecting an increased number of CNVs of unclear clinical significance. In paper V we report on the clinical and molecular characterization of 16 individuals with distal 22q11.2 duplications. The patients displayed a variable phenotype, and many of the duplications were inherited (83%). The possible pathogenicity of these duplications is discussed and we conclude that it is likely that distal 22q11.2 duplications represent a susceptibility/risk locus for NDDs rather than being causal variants. Additional genetic, epigenetic or environmental factors are likely required to cause a phenotype. Five patients had additional CVNs of unclear clinical significance making a 2-hit event plausible. Paper IV and V illustrate that the identification of CNVs of uncertain clinical significance puts new demands on genetic counselling and continuous research and submission of cases to databases are still important. Future challenges include how to deal with the interpretation of multiple rare variants in one individual and to find ways to estimate how great a risk factor certain CNVs, such as distal 22q11.2 duplications, actually are for a phenotypic effect

Positive Attitudes towards Non-Invasive Prenatal Testing (NIPT) in a Swedish Cohort of 1,003 Pregnant Women

OBJECTIVE: The clinical utilization of non-invasive prenatal testing (NIPT) for identification of fetal aneuploidies is expanding worldwide. The aim of this study was to gain an increased understanding of pregnant women's awareness, attitudes, preferences for risk information and decision-making concerning prenatal examinations with emphasis on NIPT, before its introduction into Swedish healthcare. METHOD: Pregnant women were recruited to fill in a questionnaire, including multiple-choice questions and Likert scales, at nine maternity clinics located in different areas of Stockholm, Sweden. RESULTS: In total, 1,003 women participated in the study (86% consent rate). The vast majority (90.7%) considered examinations aiming to detect fetal abnormalities to be good. Regarding NIPT, 59.8% stated that they had heard about the method previously, yet 74.0% would like to use the test if available. The main factor affecting the women's decision to undergo prenatal chromosomal screening was worry about the baby's health (82.5%), followed by the urge to have as much information as possible about the fetus (54.5%). Most women (79.9%) preferred to receive NIPT information orally. CONCLUSION: The overwhelming majority of a cohort of 1,003 pregnant women considered prenatal examinations good. Moreover, the majority had a positive attitude towards NIPT and would like to use the test if available

The risk of cholesteatoma in individuals with first-degree relatives surgically treated for the disease

IMPORTANCE:  Cholesteatoma in the middle ear is not regarded as a hereditary disease, but case reports of familial clustering exist in the literature, as well as observed familial cases in the clinical work. However, the knowledge regarding cholesteatoma as a hereditary disease is lacking in the literature. OBJECTIVE To assess the risk of cholesteatoma in individuals with a first-degree relative surgically treated for the same disease. DESIGN, SETTING, AND PARTICIPANTS: In this nested case-control study in the Swedish population between 1987 and 2018 of first-time cholesteatoma surgery identified from the Swedish National Patient Register, 2 controls per case were randomly selected from the population register through incidence density sampling, and all first-degree relatives for cases and controls were identified. Data were received in April 2022, and analyses were conducted between April and September 2022. EXPOSURE: Cholesteatoma surgery in a first-degree relative. MAIN OUTCOMES AND MEASURES: The main outcome was first-time cholesteatoma surgery. The association between having a first-degree relative with cholesteatoma and the risk of cholesteatoma surgery in the index persons was estimated by odds ratios (ORs) and 95% CIs through conditional logistic regression analysis. RESULTS: Between 1987 and 2018, 10 618 individuals with a first-time cholesteatoma surgery (mean [SD] age at surgery, 35.6 [21.5] years; 6302 [59.4%] men) were identified in the Swedish National Patient Register. The risk of having a cholesteatoma surgery was almost 4 times higher in individuals having a first-degree relative surgically treated for the disease (OR, 3.9; 95% CI, 3.1-4.8), but few cases were exposed overall. Among the 10 105 cases with at least 1 control included in the main analysis, 227 (2.2%) had at least 1 first-degree relative treated for cholesteatoma, while the corresponding numbers for controls were 118 of 19 553 control patients (0.6%). The association was stronger for individuals under the age of 20 years at first surgery (OR, 5.2; 95% CI, 3.6-7.6) and for a surgery involving the atticus and/or mastoid region (OR, 4.8; 95% CI, 3.4-6.2). There was no difference in the prevalence of having a partner with cholesteatoma between cases and controls (10 cases [0.3%] and 16 controls [0.3%]; OR, 0.92; 95% CI, 0.41-2.05), which implies that increased awareness does not explain the association. CONCLUSIONS AND RELEVANCE:  In this Swedish case-control study using nationwide register data with high coverage and completeness, the findings suggest that the risk of cholesteatoma in the middle ear is strongly associated with a family history of the condition. Family history was nevertheless quite rare and can therefore only explain a limited number of all cases; these families could be an important source for information regarding the genetic background for cholesteatoma disease

Pregnant women’s attitudes towards prenatal examinations.

<p>Pregnant women’s attitudes towards prenatal examinations.</p

Pregnant women’s attitudes towards specific prenatal examination methods.

<p>Pregnant women’s attitudes towards specific prenatal examination methods.</p

Proportion of pregnant women’s perception of what they consider a high probability of having a child with a chromosomal abnormality (A) and the perception of their risk of having a child with a chromosomal abnormality (B).

<p>The women answered the question by selecting one of the answers displayed on the x-axis. In B, women who had performed the first trimester combined test or invasive testing were excluded.</p

A Missense Variant in PDK1 Associated with Severe Neurodevelopmental Delay and Epilepsy

The pyruvate dehydrogenase complex (PDC) is responsible for the conversion of pyruvate into acetyl-CoA, which is used for energy conversion in cells. PDC activity is regulated by phosphorylation via kinases and phosphatases (PDK/PDP). Variants in all subunits of the PDC and in PDK3 have been reported, with varying phenotypes including lactic acidosis, neurodevelopmental delay, peripheral neuropathy, or seizures. Here, we report a de novo heterozygous missense variant in PDK1 (c.1139G &gt; A; p.G380D) in a girl with developmental delay and early onset severe epilepsy. To investigate the role of PDK1G380D in energy metabolism and neuronal development, we used a zebrafish model. In zebrafish embryos we show a reduced number of cells with mitochondria with membrane potential, reduced movements, and a delay in neuronal development. Furthermore, we observe a reduction in the phosphorylation of PDH-E1&alpha; by PDKG380D, which suggests a disruption in the regulation of PDC activity. Finally, in patient fibroblasts, a mild reduction in the ratio of phosphorylated PDH over total PDH-E1&alpha; was detected. In summary, our findings support the notion that this aberrant PDK1 activity is the cause of clinical symptoms in the patient

Characteristics of 1,003 pregnant women recruited to answer a questionnaire about prenatal examinations.

<p>Characteristics of 1,003 pregnant women recruited to answer a questionnaire about prenatal examinations.</p

Pregnant women’s opinions about what affects their decision to undergo chromosomal screening on their fetus.

<p>Pregnant women’s opinions about what affects their decision to undergo chromosomal screening on their fetus.</p

Pregnant women’s information preferences after undergoing NIPT.

<p>Pregnant women’s information preferences after undergoing NIPT.</p