👤 Laura E Gibbons

BackgroundOthers have examined heterogeneity in Alzheimer's disease (AD); however, few have used longitudinal data while accounting for variation in disease stage. We used latent classes to model heterogeneity in the trajectories of three cognitive domains (memory, language, and executive functioning) starting at AD dementia diagnosis.ObjectiveOur aim was to describe the patterns of heterogeneity in cognitive decline across cognitive domains during the course of AD and to contextualize our findings by assessing associations with demographic factors and neuropathological measures.MethodsWe used cognitive data from the Religious Orders Study, the Rush Memory and Aging Project, and the Minority Aging Research Study in a multi-dimensional joint latent class mixed model, which allowed us to estimate cognitive trajectories that varied across cognitive domains and latent classes. We accounted for the uncertainty in latent class assignment and corrected for multiple hypotheses when assessing the association of the latent classes with demographic and neuropathological variables.ResultsWe identified five latent classes differentiated by level of impairment (high to low) and rate of decline (slow to fast). Within each latent class, the pattern of decline did not differ substantially across cognitive domains. Classes were associated with Show less

People with mild cognitive impairment (MCI) are candidates for early intervention, but not all progress to Alzheimer's disease (AD) dementia. Identifying a subgroup at highest risk may improve treatment targeting. We analyzed data from participants with MCI enrolled in the Alzheimer's Disease Neuroimaging Initiative (ADNI). Cognitive domains included memory, executive functioning, language, and visuospatial abilities. We evaluated baseline performance and 6-month change scores, using proportional hazards models to estimate associations with time to conversion to AD dementia. The strength of association varied by domain, but in general both baseline performance and 6-month change were associated with conversion. The strongest effects observed for memory and language. Observed associations were largely independent of established risk biomarkers, including APOE genotype, structural MRI measures, and CSF biomarkers. 6-month change scores on cognitive tests may help identify a high-risk subgroup of persons with MCI likely to progress to AD dementia. Systematic review. The authors reviewed the literature using traditional (e.g. PubMed) sources. There is a modest literature on change scores in the context of the AD clinical spectrum, but few investigations have evaluated whether short-term changes may be able to identify a high-risk subgroup of people with MCI. The authors have published a systematic review of this literature (Jutten et al. 2020) and appropriately refer to relevant citations here.Interpretation: Our findings suggest that short-term changes in cognition may be useful as part of a strategy to identify subsets of people with MCI who are at highest risk of conversion. Findings were clearest for memory and language. Domain-specific changes appeared to be independent from other biomarkers used to identify people at highest risk. Domain-specific changes did not appear to be better than changes in global cognition as measured by the MMSE or the CDR-sum of boxes.Future directions: Short-term changes in cognition may be useful to help identify a subgroup of people with MCI at highest risk of conversion to AD dementia. Future work could consider time frames shorter than the 6-month data we had available, better characterizing changes with more than 2 time points, or developing strategies that combine changes in cognition with other biomarkers to identify a subgroup of people with MCI to target for treatment. Show less

Alzheimer's disease (AD) is characterized by the presence of tau protein inclusions and amyloid beta (Aβ) plaques in the brain, with Aβ peptides generated by cleavage of the amyloid precursor protein (APP) by BACE1 and γ-secretase. We previously described a primary rat neuron assay in which tau inclusions form from endogenous rat tau after seeding cells with insoluble tau isolated from the human AD brain. Here, we used this assay to screen an annotated library of ∼8700 biologically active small molecules for their ability to reduce immuno-stained neuronal tau inclusions. Compounds causing ≥30% inhibition of tau aggregates with <25% loss of DAPI-positive cell nuclei underwent further confirmation testing and assessment of neurotoxicity, and non-neurotoxic hits were subsequently analyzed for inhibitory activity in an orthogonal ELISA that quantified multimeric rat tau species. Of the 173 compounds meeting all criteria, a subset of 55 inhibitors underwent concentration-response testing and 46 elicited a concentration-dependent reduction of neuronal tau inclusions that were distinct from measures of toxicity. Among the confirmed inhibitors of tau pathology were BACE1 inhibitors, several of which, along with γ-secretase inhibitors/modulators, caused a concentration-dependent lowering of neuronal tau inclusions and a reduction of insoluble tau by immunoblotting, although they did not decrease soluble phosphorylated tau species. In conclusion, we have identified a diverse set of small molecules and related targets that reduce neuronal tau inclusions. Notably, these include BACE1 and γ-secretase inhibitors, suggesting that a cleavage product from a shared substrate, such as APP, might affect tau pathology. Show less

Myeloid/lymphoid neoplasm with fibroblast growth factor 1 rearrangements (MLN-FGFR1) represents a rare group of hematologic neoplasms, with approximately 100 cases reported to date. A 69-year-old woman with a history of polycythemia and leukocytosis, with negative molecular testing for JAK2, CALR, and MPL, presented with diffuse adenopathy. A lymph node (LN) biopsy revealed effacement by T-lymphoblasts, consistent with T-cell acute lymphoblastic lymphoma (T-ALL). A staging bone marrow (BM) biopsy demonstrated trilineage hyperplasia, which, taken together with the patient's elevated hemoglobin and low serum erythropoietin level, fulfilled diagnostic criteria for polycythemia vera. Karyotype and fluorescence in situ hybridization on both the BM and LN demonstrated a FGFR1 rearrangement due to t(8;13), consistent with MLN-FGFR1. Whole genome sequencing on the LN additionally identified a pathogenic frameshift mutation of ASXL1 NC₀₀₀₀₂₀.11:g32434646dup NM₀₁₅₃₃₈.6(ASXL1):c.1934dup p.(Gly646Trpfs) predicted to result in loss of protein function, a finding also observed in 8.1% of BM reads. Both the BM and LN harbored missense variants in HDAC4 NM₀₀₁₃₇₈₄₁₄.1(HDAC4):c.[2763G>A]; [2763=] p.(Met921Ile) and CHEK2 NM₀₀₇₁₉₄.4(CHEK2):c.[538C>T];[538=] p.(Arg180Cys), with an unknown significance. Despite initial response to Mini-CVD + venetoclax, the patient subsequently experienced rapid clinical deterioration and death. We report the second case of MLN-FGFR1 with an ASXL1 mutation and the first case with HDAC4 and CHEK2 variants. Show less

In just over a decade, advances in genome-wide association studies (GWAS) have offered an approach to stratify individuals based on genetic risk for disease. Using recent Alzheimer's disease (AD) GWAS results as the base data, we determined each individual's polygenic risk score (PRS) in the UK Biobank dataset. Using individuals within the extreme risk distribution, we performed a GWAS that is agnostic of AD phenotype and is instead based on known genetic risk for disease. To interpret the functions of the new risk factors, we conducted phenotype analyses, including a phenome-wide association study. We identified 246 loci surpassing the significance threshold of which 229 were not reported in the base AD GWAS. These include loci that showed suggestive levels of association in the base GWAS and loci not previously suspected to be associated with AD. Among these, there are loci, such as IL34 and KANSL1, that have since been shown to be associated with AD in recent studies. We also show highly significant genetic correlations with multiple health-related outcomes that provide insights into prodromal symptoms and comorbidities. This is the first study to utilize PRS as a phenotype-agnostic group classification in AD genetic studies. We identify potential new loci for AD and detail phenotypic analysis of these PRS extremes. Show less

Ribosomes are essential intracellular machines composed of proteins and RNA molecules. The DNA sequences (rDNA) encoding ribosomal RNAs (rRNAs) are tandemly repeated and give origin to the nucleolus. Here we develop a computational method for estimating rDNA dosage (copy number) and mitochondrial DNA abundance using whole-genome short-read DNA sequencing. We estimate these attributes across hundreds of human genomes and their association with global gene expression. The analyses uncover abundant variation in rDNA dosage that is coupled with the expression of hundreds of functionally coherent gene sets. These include associations with genes coding for chromatin components that target the nucleolus, including CTCF and HP1β. Finally, the data show an inverse association between rDNA dosage and mitochondrial DNA abundance that is manifested across genotypes. Our findings uncover a novel and cryptic source of hypervariable genomic diversity with global regulatory consequences (ribosomal eQTL) in humans. The variation provides a mechanism for cellular homeostasis and for rapid and reversible adaptation. Show less

The mRNA expression of lipogenic genes Scd-1 and Fas is regulated partly by the insulin-sensitive transcription factor SREBP-1c and liver X receptor alpha (LXRalpha). Compared with normal mice, the increase in the mRNA expression of hepatic Scd-1, Fas, and Srebp-1c was severely attenuated in peroxisome proliferator-activated receptor alpha (PPARalpha)-deficient mice during the transition from the starved to the re-fed states. The concentration of the membrane-bound form of SREBP-1c was also lower in the livers of the PPARalpha-deficient mice during re-feeding but there was little difference in the concentration of the active, nuclear form, or in the abundance of Insig-2a mRNA. The response of plasma insulin to starvation and re-feeding was normal in the PPARalpha-deficient mice. Rat hepatocytes transfected with an adenovirus encoding a dominant negative form of PPARalpha were resistant to the stimulatory effects of insulin on Fas and Scd-1 mRNA expression in vitro. When LXRalpha was activated in vivo by inclusion of a non-steroidal ligand in the diet, the expression of the mRNA for hepatic Srebp-1c, Fas, and Scd-1 was increased severalfold in mice of both genotypes and resistance associated with PPARalpha deficiency was abolished during re-feeding. However, although re-feeding the LXRalpha ligand induced the immature form of SREBP-1c equally in the livers of both genotypes, the concentration of the nuclear form remained relatively low in the livers of the PPARalpha-deficient mice. We conclude that intact PPARalpha is required to mediate the response of Scd-1 and Fas gene expression to insulin and that this is normally achieved directly by activation of LXRalpha. Show less