Christian Munch Hagen

Objective To determine whether mitochondrial haplogroups function as disease-modifiers or as susceptibility factors in preeclampsia using a traditional haplogroup association model. Methods This retrospective study haplotyped 235 control and 78 preeclamptic pregnancies from Denmark using either real-time PCR or Sanger sequencing depending on the rarity of the haplogroup. Results No significant association between haplogroups and the risk of preeclampsia was found, nor was any role for haplogroups in disease severity uncovered. Conclusion Mitochondrial haplogroups are not associated with preeclampsia or the severity of preeclampsia in the Danish population. However, this study cannot exclude a role for less common mtDNA variation. Models that can examine these should be applied in preeclamptic patients.

Background: Maternal obesity has been positively associated with increased risk of congenital heart defects in the offspring. However, none of the large studies have included the considerable proportion of congenital heart defects that are identified due to improvements in prenatal diagnostics and terminated in pregnancy. The mechanism behind the association is poorly understood, and a relation to interpregnancy weight changes is to be investigated. Objectives: To evaluate the association between maternal obesity and congenital heart defects in the offspring when including all pregnancies and to investigate if interpregnancy weight change between the first and second pregnancy influences risk of fetal congenital heart defects. Study Design: A nationwide cohort study of all singleton pregnancies in Denmark from 2008 to 2018. All data on maternal and offspring characteristics were retrieved from the Danish Fetal Medicine Database. The database included data on postnatal diagnoses of congenital heart defects in live births and prenatal diagnoses of congenital heart defects from ultrasound examinations during pregnancy resulting in live birth, stillbirth, spontaneous abortion after gestational week 12 or termination of pregnancies after gestational week 12. As this cohort encompassed all pregnancies over a 10-year period, it was possible for women to experience multiple pregnancies. Congenital heart defects and severe congenital heart defects were grouped according to European Surveillance of Congenital Anomalies’ definitions. Children or fetuses with chromosomal aberrations were excluded. Relative risks were calculated using log-linear Poisson models for congenital heart defects overall, severe congenital heart defects and for five of the most prevalent subtypes of congenital heart defects. Results: Of the 547 178 pregnancies included in the cohort, 5 498 had congenital heart defects (1.0%). Risk of congenital heart defects became gradually higher with higher maternal BMI; for BMI 30-34.9 kg/m ² , adjusted relative risk = 1.23 (95% confidence interval 1.12-1.36), for BMI 35-39.9 kg/m ² , adjusted relative risk = 1.26 (95% confidence interval 1.09-1.46) and for BMI ≥ 40 kg/m ² , adjusted relative risk = 1.81 (95% confidence interval 1.50-2.15). Data was adjusted for maternal age, smoking status and year of estimated due date. The same pattern was seen for the subgroup of severe congenital heart defects. Among the atrioventricular septal defects (n = 245), a particularly strong association with maternal BMI ≥ 40 kg/m ² was seen, adjusted relative risk = 4.19 (95% confidence interval 2.13-7.42). 107 627 women were identified with their first and second pregnancies in the cohort. Interpregnancy BMI change was positively, albeit not statistically significant, associated with risk of congenital heart defects in the second pregnancy when adjusting for maternal age and BMI, with an adjusted relative risk = 1.27 (95% confidence interval 0.96-1.64) among persons with a BMI increase of ≥ 4 kg/m ² . Conclusions: When including both pre- and postnatally diagnosed congenital heart defects, this study showed a positive dose-response association between maternal BMI and risk of congenital heart defects in the offspring. However, only a non-significant trend was seen between interpregnancy BMI changes and risk of congenital heart defects in the second pregnancies. Condensation: Tweetable statement: The risk of fetal congenital heart defect is associated with high maternal BMI, and it may also be affected by a substantial weight gain between pregnancies. AJOG at a Glance: A. Why was this study conducted? None of the large cohort studies on the association between maternal BMI and congenital heart defects (CHDs) have included the proportion of CHDs that are identified in terminated pregnancies. No previous studies have investigated the association between interpregnancy weight changes and CHDs. B. What are the key findings? Risk of CHDs became gradually higher with higher maternal BMI when including live births, stillbirths, abortions and terminated pregnancies. A trend was found between interpregnancy weight gain and risk of CHDs. C. What does this study add to what is already known? The association between high maternal BMI and risk of CHDs are not caused by a lower detection rate of fetal CHDs in pregnant women with obesity.

Mitochondrial DNA (mtDNA) haplogroups (hgs) are evolutionarily conserved sets of mtDNA SNP-haplotypes with characteristic geographical distribution. Associations of hgs with disease and physiological characteristics have been reported, but have frequently not been reproducible. Using 418 mtDNA SNPs on the PsychChip (Illumina), we assessed the spatio-temporal distribution of mtDNA hgs in Denmark from DNA isolated from 24,642 geographically un-biased dried blood spots (DBS), collected from 1981 to 2005 through the Danish National Neonatal Screening program. ADMIXTURE was used to establish the genomic ancestry of all samples using a reference of 100K+ autosomal SNPs in 2,248 individuals from nine populations. Median-joining analysis determined that the hgs were highly variable, despite being typically Northern European in origin, suggesting multiple founder events. Furthermore, considerable heterogeneity and variation in nuclear genomic ancestry was observed. Thus, individuals with hg H exhibited 95%, and U hgs 38.2% - 92.5%, Danish ancestry. Significant clines between geographical regions and rural and metropolitan populations were found. Over 25 years, macro-hg L increased from 0.2% to 1.2% (p = 1.1*E-10), and M from 1% to 2.4% (p = 3.7*E-8). Hg U increased among the R macro-hg from 14.1% to 16.5% (p = 1.9*E-3). Genomic ancestry, geographical skewedness, and sub-hg distribution suggested that the L, M and U increases are due to immigration. The complex spatio-temporal dynamics and genomic ancestry of mtDNA in the Danish population reflect repeated migratory events and, in later years, net immigration. Such complexity may explain the often contradictory and population-specific reports of mito-genomic association with disease.

Mitochondria play a significant role in human diseases. However, disease associations with mitochondrial DNA (mtDNA) SNPs have proven difficult to replicate. An analysis of eight schizophrenia-associated mtDNA SNPs, in 23,743 Danes without a psychiatric diagnosis and 2,538 schizophrenia patients, revealed marked inter-allelic differences in mitochondrial haplogroup affiliation and nuclear ancestry. This bi-genomic dependence could entail population stratification. Only two mitochondrial SNPs, m.15043A and m.15218G, were significantly associated with schizophrenia. However, these associations disappeared when corrected for haplogroup affiliation and nuclear ancestry. The extensive bi-genomic dependence documented here is a major concern when interpreting historic, as well as designing future, mtDNA association studies.

Mitochondria play a significant role in human diseases. However, disease associations with mitochondrial DNA (mtDNA) SNPs have proven difficult to replicate. A reanalysis of eight schizophrenia-associated mtDNA SNPs, in 23,743 normal Danes and 2,538 schizophrenia patients, revealed marked inter-allelic differences in haplogroup affiliation and nuclear ancestry, genogeophraphic affinity (GGA). This bi-genomic linkage disequilibrium (2GLD) could entail population stratification. Only two mitochondrial SNPs, m. 15043A and m. 15218G, were significantly associated with schizophrenia. However, these associations disappeared when corrected for haplogroup affiliation. The extensive 2GLD documented is a major concern when interpreting historic as well as designing future mtDNA association studies.

Mitochondrial DNA (mtDNA) haplogroups (hgs) are evolutionarily conserved sets of mtDNA SNP-haplotypes with characteristic geographical distribution. Associations of hgs with disease and physiological characteristics have been reported, but have frequently not been reproducible. Using 418 mtDNA SNPs on the PsychChip (Illumina), we assessed the spatio-temporal distribution of mtDNA hgs in Denmark in DNA isolated from 24,642 geographically un-biased dried blood spots (DBS), collected from 1981 to 2005 through the Danish National Neonatal Screening program. Geno-geographic affinity (ancestry background) was established with ADMIXTURE using a reference of 100K+ autosomal SNPs in 2,248 individuals from nine populations. The hg distribution was typically Northern European, and hgs were highly variable based on median-joining analysis, suggesting multiple founder events. Considerable heterogeneity and variation in autosomal geno-geographic affinity was observed. Thus, individuals with hg H exhibited 95 %, and U hgs 38.2 % - 92.5 %, Danish ancestry. Significant clines between geographical regions and rural and metropolitan populations were found. Over 25 years, macro-hg L increased from 0.2 % to 1.2 % (p = 1.1*E-10), and M from 1 % to 2.4 % (p = 3.7*E-8). Hg U increased among the R macro-hg from 14.1 % to 16.5 % (p = 1.9*E-3). Geno-geographic affinity, geographical skewedness, and sub-hg distribution suggested that the L, M and U increases are due to immigration. The complex spatio-temporal dynamics and geno-geographic heterogeneity of mtDNA in the Danish population reflect repeated migratory events and, in later years, net immigration. Such complexity may explain the often contradictory and population-specific reports of mito-genomic association with disease.

Congenital long QT syndrome (LQTS) is a hereditary cardiac channelopathy characterized by delayed ventricular repolarization, syncope, torsades de pointes and sudden cardiac death. Thirty-three members of five apparently 'unrelated' Danish families carry the KCNH2:c.87C> A; p.F29L founder mutation. Linkage disequilibrium mapping with microsatellites around KCNH2 enabled us to estimate the age of the founder mutation to be approximately 22 generations, corresponding to around 550 years. Neighbouring-Joining analysis disclosed one early and three later nodes. The median QTc time of the carriers was 490 ms (range: 415-589 ms) and no difference was seen between the different branches of the family. The mutation is malignant with a penetrance of 73%. Ten F29L carriers received implantable defibrillators (ICDs) (median age at implant 20 years), and of those four individuals experienced eight appropriate shocks. Patch-clamp analysis in HEK 293 cells, performed at 34°C disclosed a loss-of-function phenotype with fast deactivation, reduced steady-state inactivation current density and a positive voltage shift in inactivation. Western blotting of HEK 293 cells transfected with KCNH2:WT and KCNH2:c.87C> A revealed a reduced fraction of fully glycosylated hERG:p.F29L suggesting that this mutation results in defective trafficking. The altered channel gating kinetics in combination with defective trafficking of mutated channels is expected to result in reduced repolarizing current density and, thus, a LQTS phenotype.