Risks and Recommendations in Prenatally Detected De Novo Balanced Chromosomal Rearrangements from Assessment of Long-Term Outcomes.

The 6%-9% risk of an untoward outcome previously established by Warburton for prenatally detected de novo balanced chromosomal rearrangements (BCRs) does not account for long-term morbidity. We performed long-term follow-up (mean 17 years) of a registry-based nationwide cohort of 41 individuals carrying a prenatally detected de novo BCR with normal first trimester screening/ultrasound scan. We observed a significantly higher frequency of neurodevelopmental and/or neuropsychiatric disorders than in a matched control group (19.5% versus 8.3%, p = 0.04), which was increased to 26.8% upon clinical follow-up. Chromosomal microarray of 32 carriers revealed no pathogenic imbalances, illustrating a low prognostic value when fetal ultrasound scan is normal. In contrast, mate-pair sequencing revealed disrupted genes (ARID1B, NPAS3, CELF4), regulatory domains of known developmental genes (ZEB2, HOXC), and complex BCRs associated with adverse outcomes. Seven unmappable autosomal-autosomal BCRs with breakpoints involving pericentromeric/heterochromatic regions may represent a low-risk group. We performed independent phenotype-aware and blinded interpretation, which accurately predicted benign outcomes (specificity = 100%) but demonstrated relatively low sensitivity for prediction of the clinical outcome in affected carriers (sensitivity = 45%-55%). This sensitivity emphasizes the challenges associated with prenatal risk prediction for long-term morbidity in the absence of phenotypic data given the still immature annotation of the morbidity genome and poorly understood long-range regulatory mechanisms. In conclusion, we upwardly revise the previous estimates of Warburton to a morbidity risk of 27% and recommend sequencing of the chromosomal breakpoints as the first-tier diagnostic test in pregnancies with a de novo BCR.

Recurrence of congenital heart defects in families.

BACKGROUND: Knowledge of the familial contribution to congenital heart diseases (CHD) on an individual and population level is sparse. We estimated an individual's risk of CHD given a family history of CHD, as well as the contribution of CHD family history to the total number of CHD cases in the population. METHODS AND RESULTS: In a national cohort study, we linked all Danish residents to the National Patient Register, the Causes of Death Register, the Danish Central Cytogenetic Register, and the Danish Family Relations Database, yielding 1 763 591 persons born in Denmark between 1977 and 2005, of whom 18 708 had CHD. Individuals with CHD were classified by phenotype. We estimated recurrence risk ratios and population-attributable risk. Among first-degree relatives, the recurrence risk ratio was 79.1 (95% confidence interval [CI] 32.9 to 190) for heterotaxia, 11.7 (95% CI, 8.0 to 17.0) for conotruncal defects, 24.3 (95% CI,12.2 to 48.7) for atrioventricular septal defect, 12.9 (95% CI, 7.48 to 22.2) for left ventricular outflow tract obstruction, 48.6 (95% CI, 27.5 to 85.6) for right ventricular outflow tract obstruction, 7.1 (95% CI, 4.5 to 11.1) for isolated atrial septal defect, and 3.4 (95% CI, 2.2 to 5.3) for isolated ventricular septal defect. The overall recurrence risk ratio for the same defect was 8.15 (95% CI, 6.95 to 9.55), whereas it was 2.68 (95% CI, 2.43 to 2.97) for different heart defects. Only 2.2% of heart defect cases in the population (4.2% after the exclusion of chromosomal aberrations) were attributed to CHD family history in first-degree relatives. CONCLUSIONS: Specific CHDs showed highly variable but strong familial clustering in first-degree relatives, ranging from 3-fold to 80-fold compared with the population prevalence, whereas the crossover risks between dissimilar cases of CHD were weaker. Family history of any CHD among first-degree relatives accounted for a small proportion of CHD cases in the population.

National time trends in congenital heart defects, Denmark, 1977-2005.

BACKGROUND: Time trends in congenital heart defects (CHD) by specific phenotype and with long follow-up time are rarely available for an entire population. We present trends in national CHD prevalences over the past 3 decades. METHODS: We linked information from the National Patient Register, the Causes of Death Register, and the Danish Cytogenetic Central Register for all persons born in Denmark, 1977 to 2005, and registered in the Civil Registration System, yielding a cohort of 1,763,591 persons-18,207 with CHD. Individuals with CHDs were classified by phenotype (heterotaxia, conotruncal defect, atrioventricular septal defect, anomalous pulmonary venous return, left and right ventricular outflow tract obstructions, septal defects, complex defects, associations, patent ductus arteriosus, unspecified, and other specified) by combining International Classification of Diseases codes using a hierarchical approach. RESULTS: From 1977 to 2005, the overall CHD birth prevalence increased from 73 to 113 per 10,000 live births. Generally, prevalence increased for defects diagnosed in infancy, until 1996-1997, and then stabilized. For each 5-year interval, isolated septal defects and severe defects increased by 22% (95% CI, 20%-25%) and 5% (95% CI, 4%-7%), respectively. Among the severe defects, conotruncal defects and atrioventricular septal defect showed the largest prevalence increases. Women had a lower prevalence of severe defects during the 1980s. The CHD prevalence increase was unchanged when persons with extracardiac defects or chromosomal aberrations were excluded. CONCLUSIONS: CHD birth prevalence increased from the beginning of the 1980s but stabilized in the late 1990s.

Systematic re-examination of carriers of balanced reciprocal translocations: a strategy to search for candidate regions for common and complex diseases.

Balanced reciprocal translocations associated with genetic disorders have facilitated the identification of a variety of genes for early-onset monogenic disorders, but only rarely the genes associated with common and complex disorders. To assess the potential of chromosomal breakpoints associated with common/ complex disorders, we investigated the full spectrum of diseases in 731 carriers of balanced reciprocal translocations without known early-onset disorders in a nation-wide questionnaire-based re-examination. In 42 families, one of the breakpoints at the cytogenetic level concurred with known linkage data and/or the translocation co-segregated with the reported phenotype, for example, we found a significant linkage (lod score=2.1) of dyslexia and a co-segregating translocation with a breakpoint in a previously confirmed locus for dyslexia. Furthermore, we identified 441 instances of at least two unrelated carriers with concordant breakpoints and traits. If applied to other populations, re-examination of translocation carriers may identify additional genotype-phenotype associations, some of which may be novel and others that may coincide with and provide additional support of data presented here.

Low frequency of large genomic rearrangements of BRCA1 and BRCA2 in western Denmark.

Germline mutations in BRCA1 and BRCA2 predispose female carriers to breast and ovarian cancer. The majority of mutations identified are small deletions or insertions or are nonsense mutations. Large genomic rearrangements in BRCA1 are found with varying frequencies in different populations, but BRCA2 rearrangements have not been investigated thoroughly. The objective in this study was to determine the frequency of large genomic rearrangements in BRCA1 and BRCA2 in a large group of Danish families with increased risk of breast and ovarian cancer. A total of 617 families previously tested negative for mutations involving few bases were screened with multiplex ligation-dependent probe amplification (MLPA). Two deletions in BRCA1 were identified in three families; no large rearrangements were detected in BRCA2. The large deletions constitute 3.8% of the BRCA1 mutations identified, which is low compared to several other populations.

A missense mutation in exon 13 in BRCA2, c.7235G>A, results in skipping of exon 13.

We report here the functional characterisation of a missense mutation c.7235G>A in BRCA2. By reverse transcriptase polymerase chain reaction the mutation is demonstrated to cause skipping of exon 13. We conclude that the mutation is most likely deleterious.

[Monogenic hereditary diseases]. / Monogent arvelige sygdomme.

Monogenic disorders are caused by the inheritance of single gene mutations; alternatively, a monogenic disorder arises as a consequence of a de novo mutation in either the paternal or maternal germ line. The exponential increase in our understanding of the human genome has resulted in the localisation and cloning of a vast number of disease genes which has enabled the precise characterization of the underlying molecular defect in many of these disorders. Single nucleotide substitutions and microdeletions are the major types of disease-related mutations, but more complex mutations have also been described.

Recurrence of discordant congenital heart defects in families.

BACKGROUND: Variation within a single gene might produce different congenital heart defects (CHDs) within a family, which could explain the previously reported familial aggregation of discordant CHDs. We investigated whether certain groups of discordant CHDs are more common in families than others. METHODS AND RESULTS: Using Danish national population and health registers, we identified CHDs among all singletons born in Denmark during 1977-2005 and their first-degree relatives. In a cohort of 1 711 641 persons, 16 777 had CHDs, which we classified into 14 phenotypes. We estimated relative risks of discordant CHDs by history of specific CHDs in first-degree relatives. The relative risk of any dissimilar CHD given the specified CHD in first-degree relatives was as follows: heterotaxia, 2.00 (95% CI, 0.96 to 4.17); conotruncal defects, 2.78 (95% CI, 2.12 to 3.66); atrioventricular septal defects, 2.25 (95% CI, 1.39 to 3.66); anomalous pulmonary venous return, 1.76 (95% CI, 0.66 to 4.64); left- and right-ventricular outflow tract obstruction, 2.55 (95% CI, 1.87 to 3.48) and 3.09 (95% CI, 2.03 to 4.71), respectively; isolated atrial septal defects, 2.76 (95% CI, 2.11 to 3.61); isolated ventricular septal defects, 2.27 (95% CI, 1.75 to 2.94); persistent ductus arteriosus, 1.92 (95% CI, 1.32 to 2.79); other specified CHDs, 3.29 (95% CI, 2.51 to 4.32); and unspecified CHDs, 2.30 (95% CI, 1.76 to 3.00). Relative risks for all pairwise combinations of discordant CHD phenotypes gave no indications that certain constellations of CHDs cluster more in families than others. CONCLUSIONS: We documented strong familial aggregation of discordant CHD phenotypes. However, we observed no excess clustering of specific CHD phenotypes among the first-degree relatives.

No signature of Y chromosomal resemblance between possible descendants of the Cimbri in Denmark and Northern Italy.

Two European populations are believed to be related to the ancient Germanic tribe Cimbri: one living in Northern Italy, the other living in Jutland, Denmark. The people called Cimbri are documented in the ancient Roman historical record. Arriving from the far north their movements can be tracked from successive battles with the Romans. The Cimbri finally entered Italy from the northeast and were defeated at Vercellae (present day Vercelli) in 101 BC by Gaius Marius and his professional legions. Classical sources from the first centuries AD relate the homeland of the Cimbri to the coasts around the Elb estuary (northern Germany) or specifically towards the north (Himmerland in northern Jutland). In the alpine parts of Veneto, northeast of the historical battlefield, local traditions dating back to late medieval time, identify a local population as Cimbri living in Terra dei Cimbri. They are considered the descendents of the Germanic combatants that fled the battlefield at Vercelli. As the defeated Cimbri that possibly fled to the mountains of Northern Italy most likely would have been male (warriors), the present study investigated the possible Y chromosomal diversity of the two present populations using microsatellite markers and single nucleotide polymorphisms. While Cimbri from Himmerland resembled their geographical neighbors from Denmark for the Y-chromosome markers, Cimbri from Italy were significantly differentiated both from Cimbri from Himmerland and from Danes. Therefore, we were not able to show any biological relationship for uniparentally transmitted markers.

Functional testing of keratin 14 mutant proteins associated with the three major subtypes of epidermolysis bullosa simplex.

Epidermolysis bullosa simplex (EBS) is a group of autosomal dominantly inherited skin disorders characterized by the development of intra-epidermal skin blisters on mild mechanical trauma. The three major clinical subtypes (Weber-Cockayne, Koebner and Dowling-Meara) are all caused by mutations in either the keratin 5 (KRT5) or keratin 14 (KRT14) gene. Previously, we identified three novel KRT14 missense mutations in Danish EBS patients associated with the three different forms of EBS (1). The identified KRT14 mutations represent the full spectrum of the classical EBS subtypes. In the present study we investigated these mutations in a cellular expression system in order to analyse their effects on the keratin cytoskeleton. KRT14 expression vectors were constructed by fusing the nucleotide sequence encoding the FLAG reporter peptide to the 3' end of the KRT14 cDNA sequences. The expression vectors were transiently transfected into normal human primary keratinocytes (NHK), HaCaT or HeLa cells in order to analyze the ability of the mutant K14 proteins to integrate into the existing endogenous keratin filament network (KFN). No effect on the keratin cytoskeleton was observed upon transfection of NHK with the various K14 constructs neither with nor without a subsequently induced heat-stress. In contrast, all constructs, including wild-type K14, caused collapse of the endogenous KFN in a small fraction of the transfected HeLa and HaCaT cells. However, overexpression of the mutation associated with the most severe form of the disease, EBS Dowling-Meara, resulted in a higher number of transfected HaCaT cells with KFN collapse (P < 0.001). Thus, although a background KFN perturbance was observed upon transfection with the wild-type K14 construct, the mutant protein associated with the most severe form of EBS worsened the KFN perturbation significantly compared with the mutant proteins associated with the milder forms of the disease and the normal K14 protein. This shows that the clinical severity of disease-associated mutations identified in patients can be tested using this expression system, although it can not at present be used to discriminate between the milder forms. Assessment of the endogenous K14 protein expression in NHK and HaCaT cells indicated that the higher level of endogenous keratin expression in NHK might make these cells more resistant to perturbation of the keratin cytoskeleton by overexpressed K14 protein than HaCaT cells.