BACKGROUND: The ventricular septal defect (VSD), a hole between the ventricles of the heart, is the most common birth defect. Despite its commonality, little is known about related in utero functional deficits. Furthermore, although about 80% of clinical VSD resolve within a year, the long-term effects after their resolution are unknown due to lack of clinical follow-up. Chemical treatment was used to induce VSD in the rat and to investigate their functional consequences both in utero and postnatally. METHODS: Pregnant Sprague-Dawley rats were administered six 300mg/kg doses of dimethadione (DMO) by oral gavage every 12 hours beginning at 19h00 on gestational day (GD) 8 (Weston et al., 2011). DMO is the N-demethylated metabolite of the anticonvulsant trimethadione, a potent inducer of VSDs clinically and in laboratory animals. Fetal heart structure and function were examined with high-resolution ultrasound on GD 14, 15, 16, 17, and 21. A separate cohort of rats was dosed using the described paradigm, but offspring were allowed to reach parturition and mature naturally. Postnatal heart structure and function were assessed using telemetry (70 days postnatally), high-resolution ultrasound, and electrocardiography (ECG) (one year postnatally). RESULTS: Relative to controls, DMO-treated fetal rats had structural defects including VSD, an increased incidence of bradycardia (23 vs. 45%) and dysrhythmia (1.2 vs. 11%), and a reduction in cardiac output, stroke volume, and mean heart rate. Adult rats exposed to DMO in utero were more physically active, had elevated blood pressure, and had a higher incidence of dysrhythmia associated with ECG disturbances compared to controls. Both in utero and postnatal functional deficits occurred independent of septum patency. CONCLUSIONS: Gestational exposure to DMO disrupted cardiac function both in utero and postnatally, even in the absence of gross structural defects, indicating chemical exposures in utero may have permanent pathophysiological consequences on the heart. / Thesis (Master, Pharmacology & Toxicology) -- Queen's University, 2012-05-30 17:19:35.529

Understanding the molecular basis of Mendelian disorders featuring joint dislocation can enhance the knowledge of genetic or cellular pathways required in joint development, and provide candidate genes for studying related complex disorders, such as developmental dysplasia of the hip. Two strategies were employed in this project to investigate Mendelian contributors to congenital joint dislocation. The first strategy was to investigate in-depth a gene known to be associated with joint dislocation. Missense mutations or small in-frame deletions in FLNB, encoding filamin B, have previously been associated with a spectrum of osteochondrodysplasias. Screening a larger cohort established FLNB as the sole underlying disease gene for atelosteogenesis type I and III and also boomerang dysplasia, which was previously thought clinically to be allelic to AOI. Mutations in FLNB cause a large proportion of Larsen syndrome cases with phenotypes reminiscent of the early case series reported. Atypical or "recessive" Larsen syndrome may therefore be due to a different underlying genetic aberration. The disease-associated amino acid substitutions or in-frame deletion/insertions cluster to two main regions of the filamin B protein: the calponin homology 2 domain of the actin-binding domain, and repeats 13-17 of the rod domain. To analyse the functions of these regions, yeast two-hybrid analyses were performed. No interactors were identified with the calponin homology 2 domain, which suggests the amino acid substitutions may disrupt actin binding or the regulation thereof. A candidate interactor, centromere protein J, was identified that binds to repeats 13-15, and could suggest a model for aberrant cell division seen in growth plates of bones of individuals with atelosteogenesis types I and III and boomerang dysplasia. The second strategy used in this project was to investigate the genetic cause of a novel syndrome featuring joint dislocation. A neurocutaneous phenotype segregated in a consanguineous New Zealand family, and through a genetic mapping strategy, a significantly linked locus was identified at 10q23 (Z = 3.63), in which segregation of a common ancestral haplotype fits the linkage hypothesis of homozygosity by descent. Candidate gene analysis and subsequent screening identified a missense mutation 2350C>T in ALDH18A1, which predicts the substitution H784Y in the encoded protein [Delta]�-pyrroline-5-carboxylate synthase (P5CS). The known function of P5CS in proline and ornithine biosynthesis was not affected by the presence of H784Y in an indirect assay, and therefore the hypothesis proposed was that a novel, unknown moonlighting function of P5CS is perturbed causing the phenotype segregating in the family. As an initial exploration of functions of P5CS in the cell, yeast two-hybrid analysis was undertaken. This project examined the contribution of two genes, FLNB and ALDH18A1, to Mendelian congenital joint dislocations. How the cellular functions of the encoded proteins in the cytoskeleton, metabolism, or signal transduction, are critical for joint development is ill understood. Future investigations aimed at identifying candidate genes that confer susceptibility to developmental dysplasia of the hip should consider candidate genes that encode proteins related in function to the products of the FLNB and ALDH18A1 genes.

Congenital heart disease is the most common form of birth defect, affecting approximately 1% of liveborn babies. Secundum atrial septal defect (ASD) is the second most common form of congenital heart disease (CHD). Most cases have no known cause. Chromosomal, syndromal and teratogenic causes account for a minority of cases. The hypothesis that mutations in the ASD genes NKX2-5 and GATA4 may cause apparently sporadic ASD was tested by sequencing them in unrelated probands with ASD. In this study, 1/102 individuals with ASD had an NKX2-5 mutation, and 1/129 had a deletion of the GATA4 gene. The cardiac transcription factor TBX20 interacts with other ASD genes but had not previously been associated with human disease. Of 352 individuals with CHD, including 175 with ASD, 2 individuals, each with a family history of CHD, had pathogenic mutations in TBX20. Phenotypes included ASD, VSD, valvular abnormalities and dilated cardiomyopathy. These studies of NKX2-5, GATA4 and TBX20 indicate that dominant ASD genes account for a small minority of cases of ASD, and emphasize the considerable genetic heterogeneity in dominant ASD (also caused by mutations in MYH6 and ACTC). A new syndrome of dominant ASD and the Marcus Gunn jaw winking phenomenon is reported. Linkage to known loci was excluded, extending this heterogeneity, but a whole genome scan did not identify a candidate locus for this disorder. Previous studies of inbred laboratory mice showed an association between patent foramen ovale (PFO) and measures of atrial septal morphology, particularly septum primum length (???flap valve length??? or FVL). In humans, PFO is associated with cryptogenic stroke and migraine, and is regarded as being in a pathological contiuum with ASD. Twelve inbred strains, including 129T2/SvEms and QSi5, were studied, with generation of [129T2/SvEms x QSi5] F1, F2 and F14 mice. Studies of atrial morphology in 3017 mice confirmed the relationship between FVL and PFO but revealed considerable complexity. An F2 mapping study identified 7 significant and 6 suggestive quantitative trait loci (QTL), affecting FVL and two other traits, foramen ovale width (FOW) and crescent width (CRW). Binary analysis of PFO supported four of these.

Thesis (M.A.)--Northern Kentucky University, 2007. / Made available through ProQuest. Publication number: AAT 1447123. ProQuest document ID: 1414126941. Includes bibliographical references (p. 30-31)

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 5 uppsatser.

Thesis--Copenhagen. / Summary in Danish. Bibliography: p. 219-235.

Thesis--Copenhagen. / Summary in Danish. Bibliography: p. 219-235.

Thesis (M.Med.Sc.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 25-30). Also available in print.

Thesis (doctoral)--University of Uppsala, 1983. / Includes bibliographical references (p. 17-19).