This thesis focusses on the further unravelling of one of the mechanisms involved in developing Parkinson's disease: the GBA1 gene, encoding the lysosomal enzyme GCase. Several questions are... Show moreThis thesis focusses on the further unravelling of one of the mechanisms involved in developing Parkinson's disease: the GBA1 gene, encoding the lysosomal enzyme GCase. Several questions are addressed: How prevalent are mutations in this gene in the Netherlands and does it affect disease onset (chapter 2 and 5)? What methodological challenges accompany the sequencing of this gene (chapter 3 and 4)? What biomarkers may be used in clinical trials targeting GCase (chapter 6)? And what are the effects of the novel GCase activator LTI-291, when first administered to healthy volunteers (chapter 7) and to GBA-PD patients (chapter 8)? Show less
Retinal vasculopathy with cerebral leukoencephalopathy and systemic manifestations (RVCL-S) is a rare, underrecognized, systemic small vessel disease caused by heterozygous C-terminal truncating T...Show moreRetinal vasculopathy with cerebral leukoencephalopathy and systemic manifestations (RVCL-S) is a rare, underrecognized, systemic small vessel disease caused by heterozygous C-terminal truncating TREX1 mutations. The disease is characterized by vascular retinopathy, focal neurological complaints, cognitive decline and a wide range of systemic manifestations, including Raynaud's phenomenon, anemia and liver and kidney disease. Eventually, RVCL-S leads to premature death. The underlying pathological finding in RVCL-S is a nonatherosclerotic, amyloid-negative angiopathy involving small arteries and capillaries. However, the exact mechanisms by which the truncated TREX1 protein causes angiopathy remains unknown. Timely recognition of this disease is important to slow down and treat complications of the disorder, but also to prevent unnecessary (invasive) diagnostic or therapeutic procedures. As we move forward, translational research combining basic science advances and clinical findings as well as studies focusing on natural history following RVCL-S patients at different disease stages, will be critical to help elucidate RVCL-S pathophysiology. These studies will also provide the tools to identify appropriate biomarkers and therapeutic agent options for RVCL-S patients. Show less
A family history of breast cancer is one of the most important risk factors for the disease. Over the last decades many genetic loci associated with breast cancer risk have been discovered. In... Show moreA family history of breast cancer is one of the most important risk factors for the disease. Over the last decades many genetic loci associated with breast cancer risk have been discovered. In spite of this, only approximately half of the familial relative risk (FRR) for breast cancer can be explained by the currently known genetic risk factor. In this thesis we have explored the role of rare genetic variants in familial breast cancer with the help of next generation sequencing. Through this approach we have not been able to identify any novel high-risk breast cancer susceptibility alleles. Although there are likely still several extremely rare risk alleles to be discovered and the presence of high-risk alleles outside of protein-coding regions cannot be excluded, it seems presently unlikely that these will explain a substantial proportion of familial breast cancer. Both our work and that of others has suggested that most non BRCA1/2 familial breast cancer cases are likely explained by a combination of low-, and moderate-risk susceptibility alleles. Show less
Early-onset breast cancer may be due to Li-Fraumeni Syndrome (LFS). Current national and international guidelines recommend that TP53 genetic testing should be considered for women with breast... Show moreEarly-onset breast cancer may be due to Li-Fraumeni Syndrome (LFS). Current national and international guidelines recommend that TP53 genetic testing should be considered for women with breast cancer diagnosed before the age of 31years. However, large studies investigating TP53 mutation prevalence in this population are scarce. We collected nationwide laboratory records for all young breast cancer patients tested for TP53 mutations in the Netherlands. Between 2005 and 2016, 370 women diagnosed with breast cancer younger than 30years of age were tested for TP53 germline mutations, and eight (2.2%) were found to carry a (likely) pathogenic TP53 sequence variant. Among BRCA1/BRCA2 mutation negative women without a family history suggestive of LFS or a personal history of multiple LFS-related tumours, the TP53 mutation frequency was <1% (2/233). Taking into consideration that TP53 mutation prevalence was comparable or even higher in some studies selecting patients with breast cancer onset at older ages or HER2-positive breast cancers, raises the question of whether a very early age of onset is an appropriate single TP53 genetic testing criterion. Show less
