👤 Eric Gauthier

It is unclear whether the different Alzheimer's disease (AD) progression trajectories of apolipoprotein E (APOE) ɛ4 carriers is reflected by blood phosphorylated tau (p-tau) analytes. We assessed longitudinal trajectories in plasma p-tau181, 217, and 231, in amyloid beta-positive (A+) and negative (A-) APOE ɛ4 carriers (E+) or non-carriers (E-). We included 2039 participants from the observational Translational Biomarkers in Aging and Dementia (TRIAD) and Alzheimer's Disease Neuroimaging Initiative cohorts, categorized into 840 A-E-, 251 A-E+, 386 A+E4-, and 616 A+E4+. Longitudinal data were available for 1045 participants. In TRIAD, ALZpath p-tau217 (β = 0.45, p = 0.02) and p-tau217+ These findings suggest p-tau217 as a marker of faster progression in APOE ɛ4 carriers, highlighting its potential in disease stratification. Blood phosphorylated tau (p-tau)217 increases faster in apolipoprotein E (APOE) ɛ4 carriers with amyloid pathology. p-tau181 and p-tau231 do not increase faster in APOE ɛ4 carriers. APOE ɛ4 carriership does not change p-tau in individuals without amyloid pathology. Show less

The apolipoprotein E4 (APOE4) allele is the strongest genetic risk factor for Alzheimer's disease (AD) and is linked to poorer cerebrovascular health. Cerebrovascular reactivity (CVR), an indicator of vascular reserve, and cerebral pulsatility (CP), a marker of vascular stiffness, are sensitive biomarkers of early vascular dysfunction associated with aging and AD. However, the relationship between APOE4 status and these cerebrovascular metrics remains unclear. This study investigated whether the APOE genotype influences longitudinal changes in CVR and CP, and their association with cognitive performance in cognitively unimpaired individuals. We utilized the PREVENT-AD cohort, including 101 APOE4 carriers (30 males and 71 females) and 152 non-APOE4 carriers (48 males and 104 females) aged 55 and older. Relative CVR and CP were derived from resting state functional magnetic resonance imaging data, with regional values extracted from cerebral arterial territories. Results indicated significant interactions between APOE4 status and relative CVR in the left middle cerebral artery and left posterior cerebral artery (PCA) territories. APOE4 status disaggregated analyses revealed that APOE4 carriers uniquely presented a significant decline in relative CVR within the left PCA. Furthermore, sex-specific effects were identified, with female APOE4 carriers having lower relative CVR in the right anterior cerebral artery territory compared to female non-carriers. Importantly, higher relative CVR was positively associated with better cognitive performance in APOE4 carriers. No significant effects of APOE4 status on CP were found. Together, these findings suggest that relative CVR may be an important early measure of cerebrovascular health and cognition in cognitively intact APOE4 carriers. Show less

To identify gene alterations in circulating tumor DNA (ctDNA) from palbociclib-treated patients with advanced or metastatic breast cancer (ABC) in POLARIS to identify potential mutagenic drivers of resistance. POLARIS was a prospective, real-world study of palbociclib in patients with hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) ABC in the United States and Canada. Patients who received ≥1 palbociclib dose and had ≥1 ctDNA measurement were included in the biomarker analysis. ctDNA samples were analyzed using the Guardant360 platform (73 genes) at baseline, cycle 2 day 1 (C2D1), and end of treatment (EOT). Cox proportional hazard models were used to estimate hazard ratios (HRs) and 95% CIs. A total of 344 patients were included in the biomarker analysis. Gene alterations were detected in 85% (286 of 336) of baseline samples, 72% (201 of 278) of C2D1 samples, and 85% (88 of 104) of EOT samples. The most frequently mutated genes were Patients without altered Show less

Cell identity is specified by a core transcriptional regulatory circuitry (CoRC), typically limited to a small set of interconnected cell-specific transcription factors (TFs). By mining global hepatic TF regulons, we reveal a more complex organization of the transcriptional regulatory network controlling hepatocyte identity. We show that tight functional interconnections controlling hepatocyte identity extend to non-cell-specific TFs beyond the CoRC, which we call hepatocyte identity (Hep-ID) Show less

VPS13 protein family members VPS13A through VPS13C have been associated with various recessive movement disorders. We describe the first disease association of rare recessive VPS13D variants including frameshift, missense, and partial duplication mutations with a novel complex, hyperkinetic neurological disorder. The clinical features include developmental delay, a childhood onset movement disorder (chorea, dystonia, or tremor), and progressive spastic ataxia or paraparesis. Characteristic brain magnetic resonance imaging shows basal ganglia or diffuse white matter T2 hyperintensities as seen in Leigh syndrome and choreoacanthocytosis. Muscle biopsy in 1 case showed mitochondrial aggregates and lipidosis, suggesting mitochondrial dysfunction. These findings underline the importance of the VPS13 complex in neurological diseases and a possible role in mitochondrial function. Ann Neurol 2018;83:1089-1095. Show less

Growing genetic evidence is converging in favor of common pathogenic mechanisms for autism spectrum disorders (ASD), intellectual disability (ID or mental retardation) and schizophrenia (SCZ), three neurodevelopmental disorders affecting cognition and behavior. Copy number variations and deleterious mutations in synaptic organizing proteins including NRXN1 have been associated with these neurodevelopmental disorders, but no such associations have been reported for NRXN2 or NRXN3. From resequencing the three neurexin genes in individuals affected by ASD (n = 142), SCZ (n = 143) or non-syndromic ID (n = 94), we identified a truncating mutation in NRXN2 in a patient with ASD inherited from a father with severe language delay and family history of SCZ. We also identified a de novo truncating mutation in NRXN1 in a patient with SCZ, and other potential pathogenic ASD mutations. These truncating mutations result in proteins that fail to promote synaptic differentiation in neuron coculture and fail to bind either of the established postsynaptic binding partners LRRTM2 or NLGN2 in cell binding assays. Our findings link NRXN2 disruption to the pathogenesis of ASD for the first time and further strengthen the involvement of NRXN1 in SCZ, supporting the notion of a common genetic mechanism in these disorders. Show less

Thyroid hormone (TR) and liver X (LXR) receptors are transcription factors involved in lipogenesis. Both receptors recognize the same consensus DNA-response element in vitro. It was previously shown that their signaling pathways interact in the control of cholesterol elimination in the liver. In the present study, carbohydrate-response element-binding protein (ChREBP), a major transcription factor controlling the activation of glucose-induced lipogenesis in liver, is characterized as a direct target of thyroid hormones (TH) in liver and white adipose tissue (WAT), the two main lipogenic tissues in mice. Using genetic and molecular approaches, ChREBP is shown to be specifically regulated by TRbeta but not by TRalpha in vivo, even in WAT where both TR isoforms are expressed. However, this isotype specificity is not found in vitro. This TRbeta specific regulation correlates with the loss of TH-induced lipogenesis in TRbeta(-/-) mice. Fasting/refeeding experiments show that TRbeta is not required for the activation of ChREBP expression particularly marked in WAT following refeeding. However, TH can stimulate ChREBP expression in WAT even under fasting conditions, suggesting completely independent pathways. Because ChREBP has been described as an LXR target, the interaction of LXR and TRbeta in ChREBP regulation was assayed both in vitro and in vivo. Each receptor recognizes a different response element on the ChREBP promoter, located only 8 bp apart. There is a cross-talk between LXR and TRbeta signaling on the ChREBP promoter in liver but not in WAT where LXR does not regulate ChREBP expression. The molecular basis for this cross-talk has been determined in in vitro systems. Show less