Browsing by Subject "Genetic modifier"

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    Identification of a common polymorphism in COQ8B acting as a modifier of thoracic aortic aneurysm severity
    (Elsevier, 2022-01-13) Landis, Benjamin J.; Lai, Dongbing; Guo, Dong-Chuan; Corvera, Joel S.; Idrees, Muhammad T.; Stadler, Henry W.; Cuevas, Christian; Needler, Gavin U.; Vujakovich, Courtney E.; Milewicz, Dianna M.; Hinton, Robert B.; Ware, Stephanie M.; Pediatrics, School of Medicine
    Thoracic aortic aneurysm (TAA) predisposes to sudden, life-threatening aortic dissection. The factors that regulate interindividual variability in TAA severity are not well understood. Identifying a molecular basis for this variability has the potential to improve clinical risk stratification and advance mechanistic insight. We previously identified COQ8B, a gene important for biosynthesis of coenzyme Q, as a candidate genetic modifier of TAA severity. Here, we investigated the physiological role of COQ8B in human aortic smooth muscle cells (SMCs) and further tested its genetic association with TAA severity. We find COQ8B protein localizes to mitochondria in SMCs, and loss of mitochondrial COQ8B leads to increased oxidative stress, decreased mitochondrial respiration, and altered expression of SMC contractile genes. Oxidative stress and mitochondrial cristae defects were prevalent in the medial layer of human proximal aortic tissues in patients with TAA, and COQ8B expression was decreased in TAA SMCs compared with controls. A common single nucleotide polymorphism (SNP) rs3865452 in COQ8B (c.521A>G, p.H174R) was associated with decreased rate of aortic root dilation in young patients with TAA. In addition, the SNP was less frequent in a second cohort of early-onset thoracic aortic dissection cases compared with controls. COQ8B protein levels in aortic SMCs were increased in TAA patients homozygous for rs3865452 compared with those homozygous for the reference allele. Thus, COQ8B is important for aortic SMC metabolism, which is dysregulated in TAA, and rs3865452 may decrease TAA severity by increasing COQ8B level. Genotyping rs3865452 may be useful for clinical risk stratification and tailored aortopathy management.
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    TMEM106B is a genetic modifier of frontotemporal lobar degeneration with C9orf72 hexanucleotide repeat expansions
    (Springer, 2014) Gallagher, Michael D.; Suh, Eunran; Grossman, Murray; Elman, Lauren; McCluskey, Leo; Van Swieten, John C.; Al-Sarraj, Safa; Neumann, Manuela; Gelpi, Ellen; Ghetti, Bernardino; Rohrer, Jonathan D.; Halliday, Glenda; Van Broeckhoven, Christine; Seilhean, Danielle; Shaw, Pamela J.; Frosch, Matthew P.; International Collaboration for Frontotemporal Lobar Degeneration; Trojanowski, John Q.; Lee, Virginia M. Y.; Van Deerlin, Vivianna; Chen-Plotkin, Alice S.; Pathology and Laboratory Medicine, School of Medicine
    Hexanucleotide repeat expansions in chromosome 9 open reading frame 72 (C9orf72) have recently been linked to frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS), and may be the most common genetic cause of both neurodegenerative diseases. Genetic variants at TMEM106B influence risk for the most common neuropathological subtype of FTLD, characterized by inclusions of TAR DNA binding protein of 43kDa (FTLD-TDP). Previous reports have shown that TMEM106B is a genetic modifier of FTLD-TDP caused by progranulin (GRN) mutations, with the major (risk) allele of rs1990622 associating with earlier age at onset of disease. Here we report that rs1990622 genotype affects age at death in a single-site discovery cohort of FTLD patients with C9orf72 expansions (n=14), with the major allele correlated with later age at death (p=0.024). We replicate this modifier effect in a 30-site international neuropathological cohort of FTLD-TDP patients with C9orf72 expansions (n=75), again finding that the major allele associates with later age at death (p=0.016), as well as later age at onset (p=0.019). In contrast, TMEM106B genotype does not affect age at onset or death in 241 FTLD-TDP cases negative for GRN mutations or C9orf72 expansions. Thus, TMEM106B is a genetic modifier of FTLD with C9orf72 expansions. Intriguingly, the genotype that confers increased risk for developing FTLD-TDP (major, or T, allele of rs1990622) is associated with later age at onset and death in C9orf72 expansion carriers, providing an example of sign epistasis in human neurodegenerative disease.