New insights into the genetic etiology of Alzheimer's disease and related dementias

Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele

Chromosome Xq23 is associated with lower atherogenic lipid concentrations and favorable cardiometabolic indices

AbstractAutosomal genetic analyses of blood lipids have yielded key insights for coronary heart disease (CHD). However, X chromosome genetic variation is understudied for blood lipids in large sample sizes. We now analyze genetic and blood lipid data in a high-coverage whole X chromosome sequencing study of 65,322 multi-ancestry participants and perform replication among 456,893 European participants. Common alleles on chromosome Xq23 are strongly associated with reduced total cholesterol, LDL cholesterol, and triglycerides (min P = 8.5 × 10−72), with similar effects for males and females. Chromosome Xq23 lipid-lowering alleles are associated with reduced odds for CHD among 42,545 cases and 591,247 controls (P = 1.7 × 10−4), and reduced odds for diabetes mellitus type 2 among 54,095 cases and 573,885 controls (P = 1.4 × 10−5). Although we observe an association with increased BMI, waist-to-hip ratio adjusted for BMI is reduced, bioimpedance analyses indicate increased gluteofemoral fat, and abdominal MRI analyses indicate reduced visceral adiposity. Co-localization analyses strongly correlate increased CHRDL1 gene expression, particularly in adipose tissue, with reduced concentrations of blood lipids.Abstract Autosomal genetic analyses of blood lipids have yielded key insights for coronary heart disease (CHD). However, X chromosome genetic variation is understudied for blood lipids in large sample sizes. We now analyze genetic and blood lipid data in a high-coverage whole X chromosome sequencing study of 65,322 multi-ancestry participants and perform replication among 456,893 European participants. Common alleles on chromosome Xq23 are strongly associated with reduced total cholesterol, LDL cholesterol, and triglycerides (min P = 8.5 × 10−72), with similar effects for males and females. Chromosome Xq23 lipid-lowering alleles are associated with reduced odds for CHD among 42,545 cases and 591,247 controls (P = 1.7 × 10−4), and reduced odds for diabetes mellitus type 2 among 54,095 cases and 573,885 controls (P = 1.4 × 10−5). Although we observe an association with increased BMI, waist-to-hip ratio adjusted for BMI is reduced, bioimpedance analyses indicate increased gluteofemoral fat, and abdominal MRI analyses indicate reduced visceral adiposity. Co-localization analyses strongly correlate increased CHRDL1 gene expression, particularly in adipose tissue, with reduced concentrations of blood lipids

Genetic architecture of human plasma lipidome and its link to cardiovascular disease

Understanding genetic architecture of plasma lipidome could provide better insights into lipid metabolism and its link to cardiovascular diseases (CVDs). Here, we perform genome-wide association analyses of 141 lipid species (n = 2,181 individuals), followed by phenome-wide scans with 25 CVD related phenotypes (n = 511,700 individuals). We identify 35 lipid-species-associated loci (P <5 x10(-8)), 10 of which associate with CVD risk including five new loci-COL5A1, GLTPD2, SPTLC3, MBOAT7 and GALNT16 (false discovery rate<0.05). We identify loci for lipid species that are shown to predict CVD e.g., SPTLC3 for CER(d18:1/24:1). We show that lipoprotein lipase (LPL) may more efficiently hydrolyze medium length triacylglycerides (TAGs) than others. Polyunsaturated lipids have highest heritability and genetic correlations, suggesting considerable genetic regulation at fatty acids levels. We find low genetic correlations between traditional lipids and lipid species. Our results show that lipidomic profiles capture information beyond traditional lipids and identify genetic variants modifying lipid levels and risk of CVD

Evaluation of Gallium-68 tris(2-mercaptobenzyl)amine: a complex with brain and myocardial uptake

Previous research into development of a gallium-radiolabeled agent that crosses the blood-brain barrier has met with limited success. In this study, we focused our attention on a Ga(III) complex of a 4-coordinate amine trithiolate tripod ligand, tris(2-mercaptobenzyl) amine (S3N). The Ga(III) S3N complex is small, neutral, and lipophilic, meeting the requirements for a potential brain imaging agent. The Ga-68 complex was easily formed with a radiochemical purity of >95%. In vitro stability of the Ga-S3N complex, determined in rat serum incubated at 37 degrees C, was greater than 95% intact at 2 h by silica gel and reversed-phase radio-thin layer chromatography, Biodistribution studies conducted in female Sprague-Dawley rats showed the complex cleared rapidly from the blood with initial high liver uptake followed by rapid washout. Significant uptake was observed in the brain, with brain:blood ratios increasing from 0.11 at 2 min postinjection to 3.8 at 60 min postinjection. Uptake was also observed in the heart going from a heart:blood ratio of 2.3 at 2 min postinjection to 11 at 60 min postinjection. Molecular mechanics were used to determine the coordination number, and demonstrated that the Ga(III) complex prefers to be di-coordinate, Imaging studies with Ga-68-S3N in a Nemestrina macaque showed significant brain uptake, similar to other lipophilic agents. The extraction of Ga-68-S3N into the brains of both rodents and primates, higher than any Ga-68 agent reported in the literature, suggests that this compound may have potential as a brain imaging agent for positron emission tomography

Factors influencing the in vivo behavior of In(III)S3N and Ga(III)S3N

Proceedings of the XIIth International Symposium on Radiopharmaceutical Chemistr

Identification of Recurrent Genomic Alterations in the Apoptotic Machinery in CLL Patients Treated with Venetoclax Monotherapy

Background: Venetoclax (VEN) monotherapy in patients (pts) with relapsed or refractory (R/R) chronic lymphocytic leukemia (CLL) has been efficacious with a complete remission rate of 16% and also durable with median time to progression of 33.2 months (Roberts et al., 2019). Despite these responses, many pts eventually relapse. To investigate possible mechanisms of resistance to VEN monotherapy, we performed a genome-wide CRISPR screen to identify genes whose loss of expression leads to reduction in drug sensitivity. To determine whether similar genomic alterations occur in pts treated with VEN, we analyzed the DNA and RNA of pre- and post-therapy specimens from CLL pts enrolled in two VEN monotherapy trials (NCT01328626 and NCT01889186). Methods: CRISPR screen was performed in lymphoma SUDHL4 cell line using Brunello library. Peripheral blood or bone marrow specimens were collected pre-dose and after VEN discontinuation; CLL cells were enriched via CD19-positive (CD19+) selection using magnetic beads. DNA from 43 pts was analyzed by whole exome and two targeted sequencing panels. RNA-seq analysis was performed on paired pre- and post-therapy CD19+ samples from 24 pts. Results: The CRISPR screen identified genes whose loss of expression led to resistance to VEN. Several members of the pro-apoptotic machinery were among the strongest hits, including BAX, BCL2L11 (BIM) and PMAIP1 (NOXA). Outside of the apoptotic pathway, loss of ID3 or NFKBIA also led to decreased VEN sensitivity, suggesting multiple possible mechanisms of resistance. To compare these results to the potential mechanisms of resistance in pts treated with VEN, we sequenced the DNA from CD19+ B cells extracted before treatment initiation or upon treatment discontinuation. Of the 37 pts with disease progression, 15 acquired mutations in BCL2 at progression (N=14 CLL, N=1 Richters); 6 pts had a single mutation and 9 pts acquired 2-4 distinct BCL2 mutations. The prevalence of mutations increased with time on VEN therapy; mutations were observed in 12 pts progressing between 22 and 59 months and in only 3 pts progressing between 6 and 16 months. BCL2 mutations at G101V and D103 (E/Y/V) as previously described (Blombery et al., 2019; Tausch et al., 2019) were identified in 13/15 pts. Additionally, our analysis identified 1 patient with a mutation at F104L and 3 pts with mutations at A113G. These F104L and A113G mutations were previously identified in a preclinical NHL model of VEN resistance (Tahir et al., 2017) and in DLBLCL pts, respectively, but have not been previously reported in CLL pts. Two novel mutations in BCL2: a 4 amino acid insertion at position 110 and a substitution at V156(D) were acquired at CLL progression in 3 and 4 pts, respectively. Most BCL-2 mutations were subclonal (VAF &amp;lt;2%), with only 4 of the 15pts having VAF &amp;gt; 10%. In accordance with the CRISPR screen, we identified mutations in other pro-apoptotic genes including PMAIP1 (N=4), BAX (N=2) and BAD (N=1). In contrast to the acquired BCL2 mutations, mutations in these BCL-2 family members occurred with high allelic frequency in 4 of the 7 pts (27-35%). Interestingly, 4 pts had a mutation in BCL2 in addition to another member of the apoptotic machinery. In each case, allele frequency suggested that the mutations were found in different clones. Comparison of mRNA expression pre- and post-VEN treatment demonstrated increased expression at the time of progression of key apoptotic genes BCL2L1 (BCL-XL), MCL1 and BCL2A1, all of which are known resistance factors to VEN. Concomitant decreases in BCL2 and HRK expression, and to a lesser extent PMAIP1, were also observed. The changes in gene expression were found irrespective of the presence of BCL2 mutations. Conclusions: Preclinical investigation into potential resistance mechanisms indicated that reduction in several genes confer resistance to VEN. Some of these alterations were observed in clinical samples, including several distinct mutations in BCL2 and other BCL-2 family members.Our data suggest that BCL2 mutations are subclonal and further data are needed to evaluate their role in resistance to VEN monotherapy. Additional ongoing analyses of genomic data may identify genomic alterations in other biological pathways that potentially convey VEN resistance. Emergence of resistance is likely multifactorial with modulation of the apoptotic family members via both acquired mutations and changes in gene expression pattern. Disclosures Chyla: Abbvie, Inc: Employment, Other: Stock or options. Popovic:AbbVie: Employment, Other: Stock or options. Lu:AbbVie: Employment, Other: Stock or options. Dunbar:AbbVie: Employment, Other: Stock or options. Quarless:AbbVie: Employment, Other: Stock or options. Robinson:AbbVie: Employment, Other: Stock or options. Warder:AbbVie: Employment, Other: Stock or options. Jacobson:AbbVie: Employment, Other: Stock or options. Zhou:AbbVie: Employment, Other: Stock or options. Souers:AbbVie: Employment, Other: Stock or options. Waring:AbbVie: Employment, Other: Stock or options. Bhathena:AbbVie: Employment, Other: Stock or options. Leverson:AbbVie Inc: Employment, Other: Stock or options. Kim:AbbVie: Employment, Other: Stock or options. </jats:sec