Genetic Epidemiology of Amyotrophic Lateral Sclerosis

Het doel van dit proefschrift was met epidemiologische onderzoeks methoden een gezamelijke genetische predispositie voor amyotro.sche lateraal sclerose (ALS), dementie en parkinsonisme, en de invloed van omgevingsfactoren te bestuderen. Hiervoor werd een patient-controle studie verricht van 1989 to 1991 op het Neurological Institute van het Columbia University Medical Center in New York. De onderzoekspopulatie bestond uit 151 patienten bij wie recent de diagnose ALS was gesteld en 140 controle patienten, met andere neurologische aandoeningen, die dezelfde leeftijd (+ 5 jaar) en geslacht hadden als de ALS patienten, en die in dezelfde klasse medisch verzekerd waren. Tot ver in de twintigste eeuw was men zich nauwelijks bewust van de erfelijke vormen van amyotro.sche lateral sclerose (ALS). Hierin kwam geleidelijk verandering na de publicatie van Kurland en Mulder in 1955, waarin zij een overzicht gaven van achtien families met ALS, die in de afgelopen 100 jaar in de literatuur werden beschreven. In hoofdstuk 2 wordt de huidige kennis over de relatie tussen ALS, dementie en parkinsonisme samengevat. Zoals in het overzichtsartikel (hoofdstuk 3) wordt beschreven heeft de groeiende belangstelling voor en onderzoek naar familiaire ALS er inmiddels toe geleid dat nu bekend is dat bij ongeveer 5 tot 10 procent van de ALS patienten een erfelijke vorm van de ziekte met een mendeliaans overervingspatroon voorkomt. Pas in het afgelopen decennium kon met de toepassing van moderne moleculaire onderzoekstechnieken het gen of de locatie van verschillende - maar lang nog niet alle- mendeliaans overervende vormen van ALS worden geidenti.ceerd. Inmiddels kennen we zes autosomaal dominant overervende en drie autosomaal recessief overervende erfelijke vormen van ALS. Bovendien worden in rap tempo steeds meer genen ontdekt, die het voorkomen van combinaties van ALS, frontaalkwab dementie en/of parkinsonisme in families verklaren. Ook worden, ondanks dat bij het merendeel (90%) van de ALS patienten de ziekte niet in de familie voorkomt, nu ook bij sporadische patienten veschillende genmutaties of ­polymorphismen waargenomen. Vermoedelijk bestaat er ook bij sporadische patienten een wisselwerking tussen predispositie genen en schadelijke omgevingsfactoren, die ieder opzich onvoldoende penetrant zijn om ALS te veroorzaken.This thesis aims to use epidemiologic methods to investigate genetic and environmental factors playing a role in ALS. We conducted a case control study between 1989-1991 at the Neurological Institute Columbia University Medical Center in New York. The study population consisted of 151 newly diagnosed ALS patients and 140 neurologic controls, matched for age (+ 5 years), gender (83 pairs of men and 57 pairs of women) and insurance status. In chapter 2 the current insights in the relation of ALS, dementia and parkinsonism is summarized. As described in the review (chapter 3) until the 1960s, ALS was considered to be a non-hereditary neurologic disease. In a land-mark report in 1955, Kurland and Mulder described 18 families with hereditary ALS from a 100-year review of the world literature. Only in the past decade, genetic analysis of familial forms of ALS led to the identi.cation of several mendelian inherited forms of ALS. These familial forms comprise 5-10% of all cases. Thus far six autosomal dominant and three autosomal recessive forms were found to be associated with familial ALS. In addition, a growing number of genetic defects are being associated with syndromes featuring familial recurrence of ALS, frontotemporal dementia and parkinsonism. In the 90% of cases were ALS is sporadic, changes in various genes have been linked to an increased risk for ALS, so called susceptibility genes. Susceptibility genes are thought to interact with other low penetrant genes and/or with environmental risk factors. In chapter 4 of this thesis we used epidemiologic methods to .nd evidence for a shared genetic susceptibility for ALS, dementia and parkinsonism. To do so, we investigated familial aggregation of these three disorders in families of ALS patients. In the case­control study we compared the family histories of ALS patients and controls. A semi­structured questionnaire was used to ascertain valid information on neurologic conditions for each sibling, parent and grandparent, individually. The data showed familial recurrence of ALS in .ve percent of the patients and not in controls. We found that the risk (cumulative incidence) of dementia was twofold increased for relatives of ALS patients

The role of renin-angiotensin-aldosterone system polymorphisms in phenotypic expression of MYBPC3-related hypertrophic cardiomyopathy

The phenotypic variability of hypertrophic cardiomyopathy (HCM) in patients with identical pathogenic mutations suggests additional modifiers. In view of the regulatory role in cardiac function, blood pressure, and electrolyte homeostasis, polymorphisms in the renin-angiotensin-aldosterone system (RAAS) are candidates for modifying phenotypic expression. In order to investigate whether RAAS polymorphisms modulate HCM phenotype, we selected a large cohort of carriers of one of the three functionally equivalent truncating mutations in the MYBPC3 gene. Family-based association analysis was performed to analyze the effects of five candidate RAAS polymorphisms (ACE, rs4646994; AGTR1, rs5186; CMA, rs1800875; AGT, rs699; CYP11B2, rs1799998) in 368 subjects carrying one of the three mutations in the MYBPC3 gene. Interventricular septum (IVS) thickness and Wigle score were assessed by 2D-echocardiography. SNPs in the RAAS system were analyzed separately and combined as a pro-left ventricular hypertrophy (LVH) score for effects on the HCM phenotype. Analyzing the five polymorphisms separately for effects on IVS thickness and Wigle score detected two modest associations. Carriers of the CC genotype in the AGT gene had less pronounced IVS thickness compared with CT and TT genotype carriers. The DD polymorphism in the ACE gene was associated with a high Wigle score (P=0.01). No association was detected between the pro-LVH score and IVS thickness or Wigle score. In conclusion, in contrast to previous studies, in our large study population of HCM patients with functionally equivalent mutations in the MYBPC3 gene we did not find major effects of genetic variation within the genes of the RAAS system on phenotypic expression of HCM

Cardiac b-myosin heavy chain defects in two families with non-compaction cardiomyopathy: linking non-compaction to hypertrophic, restrictive, and dilated cardiomyopathies

Cardiomyopathies are classified according to distinct morphological characteristics. They occur relatively frequent and are an important cause of mortality and morbidity. Isolated ventricular noncompaction or non-compaction cardiomyopathy (NCCM) is characterized by an excessively thickened endocardial layer with deep intertrabecular recesses, reminiscent of the myocardium during early embryogenesis. Aims Autosomal-dominant as well as X-linked inheritance for NCCM has been described and several loci have been associated with the disease. Nevertheless, a major genetic cause for familial NCCM remains to be identified. Methods and Results We describe, in two separate autosomal-dominant NCCM families, the identification of mutations in the sarcomeric cardiac b-myosin heavy chain gene (MYH7), known to be associated with hypertrophic cardiomyopathy (HCM), restricted cardiomyopathy (RCM), and dilated cardiomyopathy (DCM). Conclusion These results confirm the genetic heterogeneity of NCCM and suggest that the molecular classification of cardiomyopathies includes an MYH7-associated spectrum of NCCM with HCM, RCM, and DCM

Avian influenza a virus in wild birds in highly urbanized areas

Avian influenza virus (AIV) surveillance studies in wild birds are usually conducted in rural areas and nature reserves. Less is known of avian influenza virus prevalence in wild birds located in densely populated urban areas, while these birds are more likely to be in close contact with humans. Influenza virus prevalence was investigated in 6059 wild birds sampled in cities in the Netherlands between 2006 and 2009, and compared with parallel AIV surveillance data from low urbanized areas in the Netherlands. Viral prevalence varied with the level of urbanization, with highest prevalence in low urbanized areas. Within cities virus was detected in 0.5% of birds, while seroprevalence exceeded 50%. Ring recoveries of urban wild birds sampled for virus detection demonstrated that most birds were sighted within the same city, while few were sighted in other cities or migrated up to 2659 km away from the sample location in the Netherlands. Here we show that urban birds were infected with AIVs and that urban birds were not separated completely from populations of long-distance migrants. The latter suggests that wild birds in cities may play a role in the introduction of AIVs into cities. Thus, urban bird populations should not be excluded as a human-animal interface for influenza viruses

Contraction pressure analysis using optical imaging in normal and MYBPC3-mutated hiPSC-derived cardiomyocytes grown on matrices with tunable stiffness

Current in vivo disease models and analysis methods for cardiac drug development have been insufficient in providing accurate and reliable predictions of drug efficacy and safety. Here, we propose a custom optical flow-based analysis method to quantitatively measure recordings of contracting cardiomyocytes on polydimethylsiloxane (PDMS), compatible with medium-throughput systems. Movement of the PDMS was examined by covalently bound fluorescent beads on the PDMS surface, differences caused by increased substrate stiffness were compared, and cells were stimulated with β-agonist. We further validated the system using cardiomyocytes treated with endothelin-1 and compared their contractions against control and cells incubated with receptor antagonist bosentan. After validation we examined two MYBPC3-mutant patient-derived cell lines. Recordings showed that higher substrate stiffness resulted in higher contractile pressure, while beating frequency remained similar to control. β-agonist stimulation resulted in both higher beating frequency as well as higher pressure values during contraction and relaxation. Cells treated with endothelin-1 showed an increased beating frequency, but a lower contraction pressure. Cells treated with both endothelin-1 and bosentan remained at control level of beating frequency and pressure. Lastly, both MYBPC3-mutant lines showed a higher beating frequency and lower contraction pressure. Our validated method is capable of automatically quantifying contraction of hiPSC-derived cardiomyocytes on a PDMS substrate of known shear modulus, returning an absolute value. Our method could have major benefits in a medium-throughput setting.</p

First genetic analysis of aneurysm genes in familial and sporadic abdominal aortic aneurysm

Genetic causes for abdominal aortic aneurysm (AAA) have not been identified and the role of genes associated with familial thoracic aneurysms in AAA has not been explored. We analyzed nine genes associated with familial thoracic aortic aneurysms, the vascular Ehlers–Danlos gene COL3A1 and the MTHFR p.Ala222Val variant in 155 AAA patients. The thoracic aneurysm genes selected for this study were the transforming growth factor-beta pathway genes EFEMP2, FBN1, SMAD3, TGBF2, TGFBR1, TGFBR2, and the smooth muscle cells genes ACTA2, MYH11 and MYLK. Sanger sequencing of all coding exons and exon–intron boundaries of these genes was performed. Patients with at least one first-degree relative with an aortic aneurysm were classified as familial AAA (n = 99), the others as sporadic AAA. We found 47 different rare heterozygous variants in eight genes: two pathogenic, one likely pathogenic, twenty-one variants of unknown significance (VUS) and twenty-three unlikely pathogenic variants. In familial AAA we found one pathogenic and segregating variant (COL3A1 p.Arg491X), one likely pathogenic and segregating (MYH11 p.Arg254Cys), and fifteen VUS. In sporadic patients we found one pathogenic (TGFBR2 p.Ile525Phefs*18) and seven VUS. Thirteen patients had two or more variants. These results show a previously unknown association and overlapping genetic defects between AAA and familial thoracic aneurysms, indicating that genetic testing may help to identify the cause of familial and sporadic AAA. In this view, genetic testing of these genes specifically or in a genome-wide approach may help to identify the cause of familial and sporadic AAA