👤 Derek B Archer

G protein-coupled receptors (GPCRs) recognize ligands on the cell surface, initiating intracellular signaling pathways that control a variety of biological processes, from neurotransmission and hormone regulation to light detection and smell. As entryways into these pathways, GPCRs are key pharmacological targets, with 30% of FDA-approved drugs targeting them. High-throughput GPCR-based sensors in yeast are proven platforms for the identification of novel GPCR ligands. Most human GPCRs (hGPCRs), however, led to small increases in the signal after activation, hindering the development of high-throughput (HT) assays. To streamline the generation of HT assays for biomedically important hGPCRs, here we analyze five fluorescent reporters in the context of hGPCR-based sensors. Using the serotonin receptor 4 (HTR4)-based sensor as a testbed, we identify YPet, a yellow fluorescent protein previously evolved for improved intracellular fluorescence, as the optimal fluorescent reporter when using flow cytometry, fluorescence-activated cell sorting, or a fluorescent plate reader. YPet increases the dynamic range of hGPCR-based sensors in general, enabling the engineering of HTR4-, MC4R- S1PR2-, HTR1A-, and Mel1A-based sensors with vastly higher increases in signal than previously engineered sensors. YPet even allowed the construction of a functional HTR1D-based sensor, a sensor that had been difficult for the field to construct. Finally, the fast maturation of YPet reduces the time to readout from 4 h to 30 min, unlocking point-of-care diagnostic applications previously inaccessible to hGPCR-based sensors in yeast. Looking ahead, the identification of YPet as the optimal fluorescent reporter for yeast hGPCR-based sensors opens the door to the standardized generation of hGPCR high-throughput assays in this host, and sets the stage for ultrahigh-throughput single-cell experiments toward the identification of new ligands for known GPCRs, GPCR deorphanization, and GPCR engineering to bind designer ligands. Show less

The APOE-ε4 allele is the strongest genetic risk factor for late-onset Alzheimer's disease. However, APOE-ε4 is not deterministic, highlighting the need to identify additional genetic and environmental factors. APOE-ε4 has been linked to accelerated cognitive decline, so we sought to investigate genetic factors that modify APOE-ε4-associated cognitive decline. We conduct cross-ancestry APOE-ε4-stratified and interaction GWAS using harmonized cognitive data from 32,778 participants, including 29,354 non-Hispanic White and 3,424 non-Hispanic Black individuals. Our primary outcome is late-life cognition, measured using harmonized composite scores for memory, executive function, and language, modeled as continuous traits reflecting both normative cognitive aging and disease-related decline. We identify two genome-wide significant loci in APOE-ε4 carriers, reaching genome-wide significance for executive function. These loci also demonstrate nominal associations across the other domains, suggesting broad effects on cognition. In non-carriers, we identify a genome-wide significant association at ITGB8 restricted to executive function, and another locus associated with language. We further link these loci to SEMA6D, GRIN3A, and ITGB8 through expression and methylation databases. Post-GWAS analyses implicate additional genes including SLCO1A2, and DNAH11. Genetic correlation analyses reveal differences by APOE-ε4 status for immune-related traits, suggesting immune-related predispositions may exacerbate cognitive risk in APOE-ε4 carriers. Show less

"SuperAgers" are oldest-old adults (ages 80+) whose memory performance more closely resembles middle-aged adults. The present study examined apolipoprotein E (APOE) allele frequency in non-Hispanic Black (NHB) and non-Hispanic White (NHW) SuperAgers compared to controls and Alzheimer's disease dementia cases. In 18,080 participants from eight cohorts, harmonized clinical diagnostics and memory, executive function, and language domain scores were used to identify SuperAgers, cases, and controls across age-defined bins. NHW SuperAgers had significantly lower frequency of APOE-ε4 alleles and higher frequency of APOE-ε2 alleles compared to all cases and controls, including oldest-old controls. Similar patterns were found in a small yet substantial sample of NHB SuperAgers; however, not all comparisons with controls reached significance. We demonstrated strong evidence that APOE allele frequency relates to SuperAger status. Further research is needed with a larger sample of NHB SuperAgers to determine if mechanisms conferring cognitive resilience differ across race groups. Apolipoprotein E (APOE) allele frequency differs between SuperAgers and cases APOE allele frequency differs between non-Hispanic White SuperAgers and controls The relationship of APOE and non-Hispanic Black SuperAger status is unclear. Show less

New methods estimate amyloid positivity onset age (EAOA) from amyloid positron emission tomography (PET). We explore the genetics of EAOA to identify molecular factors underlying the earliest Alzheimer's disease (AD) changes. Harmonized amyloid PET data from 4216 participants were used in genome-wide survival, tissue-specific gene expression, and genetic covariance analyses of EAOA. Variants in apolipoprotein E (APOE), ABCA7, and RASGEF1C associated with earlier EAOA. APOE ε4/ε4 and ε3/ε4 converted 6.3 and 5 years earlier than ε3/ε3, respectively. ε2 was protective against earlier EAOA. rs4147929, an expression quantitative trait locus for ABCA7, associated with a 4 year earlier EAOA. This variant was associated with lower brain expression of ABCA7, which was associated with increased amyloid pathology at autopsy. Multiple immune-related diseases shared genetic covariance with EAOA. APOE, ABCA7, and RASGEF1C associated with earlier EAOA, with supporting evidence from tissue-specific expression analyses, offering insights into intervenable targets at early stages of AD. Novel methods estimate how long ago a patient converted to amyloid positivity. Estimating this amyloid clock allows us to determine the onset of the earliest Alzheimer's disease changes. We evaluated what genes influence when someone converts to amyloid positivity. Apolipoprotein E (APOE), ABCA7, and RASGEF1C associated with earlier age of amyloid positivity. Genetic results were supported by tissue-specific expression analyses. Show less

We report a case of slipped capital femoral epiphysis (SCFE), an on target skeletal toxicity of a pan-FGFR TKI inhibitor, erdafitinib. A 13-year-old boy was diagnosed to have an optic pathway/hypothalamic glioma with signs of increased intracranial pressure and obstructive hydrocephalus requiring placement of ventriculo-peritoneal (VP) shunt. Sequencing of the tumor showed FGFR1-tyrosine kinase domain internal tandem duplication (FGFR1-KD-ITD). He developed hypothalamic obesity with rapid weight gain and BMI >30. At 12 weeks of treatment with erdafitinib, he developed persistent knee pain. X-ray of the right hip showed SCFE. Erdafitinib was discontinued, and he underwent surgical pinning of the right hip. MRI at discontinuation of erdafitinib showed a 30% decrease in the size of the tumor, which has remained stable at 6 months follow-up. Our experience and literature review suggest that pediatric patients who are treated with pan-FGFR TKIs should be regularly monitored for skeletal side effects. Show less

The liver X receptors (LXR)α and LXRβ are transcription factors belonging to the nuclear receptor family, which play a central role in metabolic homeostasis, being master regulators of key target genes in the glucose and lipid pathways. Wild-type (WT), LXRα(-/-), and LXRβ(-/-) mice were fed a chow diet with (treated) or without (control) the synthetic dual LXR agonist GW3965 for 5 wk. GW3965 raised intrahepatic triglyceride (TG) level but, surprisingly, reduced serum TG level through the activation of serum lipase activity. The serum TG reduction was associated with a repression of both catecholamine-stimulated lipolysis and relative glucose incorporation into lipid in isolated adipocytes through activation of LXRβ. We also demonstrated that LXRα is required for basal (nonstimulated) adipocyte metabolism, whereas LXRβ acts as a repressor of lipolysis. On the contrary, in skeletal muscle (SM), the lipogenic and cholesterol transporter LXR target genes were markedly induced in WT and LXRα(-/-) mice and to a lesser extent in LXRβ(-/-) mice following treatment with GW3965. Moreover, TG content was reduced in SM of LXRβ(-/-) mice, associated with increased expression of the main TG-lipase genes Hsl and Atgl. Energy expenditure was increased, and a switch from glucose to lipid oxidation was observed. In conclusion, we provide evidence that LXR might be an essential regulator of the lipid balance between tissues to ensure appropriate control of the flux of fuel. Importantly, we show that, after chronic treatment with GW3965, SM becomes the target tissue for LXR activation, as opposed to liver, in acute treatment. Show less

Chromosomal rearrangements of the human MLL (mixed lineage leukemia) gene are associated with high-risk infant, pediatric, adult and therapy-induced acute leukemias. We used long-distance inverse-polymerase chain reaction to characterize the chromosomal rearrangement of individual acute leukemia patients. We present data of the molecular characterization of 1590 MLL-rearranged biopsy samples obtained from acute leukemia patients. The precise localization of genomic breakpoints within the MLL gene and the involved translocation partner genes (TPGs) were determined and novel TPGs identified. All patients were classified according to their gender (852 females and 745 males), age at diagnosis (558 infant, 416 pediatric and 616 adult leukemia patients) and other clinical criteria. Combined data of our study and recently published data revealed a total of 121 different MLL rearrangements, of which 79 TPGs are now characterized at the molecular level. However, only seven rearrangements seem to be predominantly associated with illegitimate recombinations of the MLL gene (≈ 90%): AFF1/AF4, MLLT3/AF9, MLLT1/ENL, MLLT10/AF10, ELL, partial tandem duplications (MLL PTDs) and MLLT4/AF6, respectively. The MLL breakpoint distributions for all clinical relevant subtypes (gender, disease type, age at diagnosis, reciprocal, complex and therapy-induced translocations) are presented. Finally, we present the extending network of reciprocal MLL fusions deriving from complex rearrangements. Show less

The liver plays a pivotal role in the physiological adaptation to fasting and a better understanding of the metabolic adaptive responses may give hints on new therapeutic strategies to control the metabolic diseases. The liver X receptors (LXRs) are well-established regulators of lipid and glucose metabolism. More recently fibroblast growth factor 21 (FGF21) has emerged as an important regulator of energy homeostasis. We hypothesized that the LXR transcription factors could influence Fgf21 expression, which is induced in response to fasting. Wild-type, LXRα(-/-), and LXRβ(-/-) mice were treated for 3 d with vehicle or the LXR agonist GW3965 and fasted for 12 h prior to the killing of the animals. Interestingly, serum FGF21 levels were induced after fasting, but this increase was blunted when the mice were treated with GW3965 independently of genotypes. Compared with wild-type mice, GW3965-treated LXRα(-/-) and LXRβ(-/-) mice showed improved insulin sensitivity and enhanced ketogenic response at fasting. Of note is that during fasting, GW3965 treatment tended to reduce liver triglycerides as opposed to the effect of the agonist in the fed state. The LXR-dependent repression of Fgf21 seems to be mainly mediated by the recruitment of LXRβ onto the Fgf21 promoter upon GW3965 treatment. This repression by LXRβ occurs through the recruitment and stabilization of the repressor complex composed of retinoid-related orphan receptor-α/Rev-Erbα/histone deacetylase 3 onto the Fgf21 promoter. Our data clearly demonstrate that there is a cross talk between the LXR and FGF21 signaling pathways in the adaptive response to fasting. Show less

Brown adipocytes are multilocular lipid storage cells that play a crucial role in nonshivering thermogenesis. Uncoupling protein 1 (UCP1) is a unique feature of brown fat cells that allows heat generation on sympathetic nervous system stimulation. As conventional transcriptional factors that are activated in various signaling pathways, liver-X receptors (LXRs) play important roles in many physiological processes. The role of LXRs in the regulation of energy homeostasis remains unclear, however. Female WT, LXRαβ(-/-), LXRα(-/-), and LXRβ(-/-) mice were fed with either a normal diet (ND) or a high-carbohydrate diet (HCD) supplemented with or without GW3965-LXR agonist. LXRαβ(-/-) mice exhibited higher energy expenditure (EE) as well as higher UCP1 expression in brown adipose tissue (BAT) compared with WT mice on the HCD. In addition, long-term treatment of WT mice with GW3965 showed lower EE at thermoneutrality (30 °C) and lower Ucp1 expression level in BAT. Furthermore, H&E staining of the BAT of LXRαβ(-/-) mice exhibited decreased lipid droplet size compared with WT mice on the HCD associated with a more intense UCP1-positive reaction. Quantification of triglyceride (TG) content in BAT showed lower TG accumulation in LXRβ(-/-) mice compared with WT mice. Surprisingly, GW3965 treatment increased TG content (twofold) in the BAT of WT and LXRα(-/-) mice but not in LXRβ(-/-) mice. Furthermore, glucose transporter (GLUT4) in the BAT of LXRα(-/-) and LXRβ(-/-) mice was sixfold and fourfold increased, respectively, compared with WT mice on the ND. These findings suggest that LXRα as well as LXRβ could play a crucial role in the regulation of energy homeostasis in female mice and may be a potential target for the treatment of obesity and energy regulation. Show less

Mammalian liver-X-receptors (LXRs) are transcription factors activated by oxysterols. They play an essential role in lipid and glucose metabolism. We have cloned the open reading frame of zebrafish lxr and describe its genomic organization. Zebrafish lxr encodes a 50-kDa protein with high sequence similarity to mammalian LXRalpha. In transfection assays, the encoded protein showed transcriptional activity in response to LXR-ligands. Treatment of adult zebrafish with the synthetic LXR ligand, GW3965, induced expression of genes involved in hepatic cholesterol and lipid pathways. Using qPCR and in situ hybridization, we found ubiquitous expression of lxr mRNA during the first 24 hr of development, followed by more restricted expression, particularly to the liver at 3dpf and the liver and intestine at 4dpf. In adult fish, all examined organs expressed lxr. In addition to a metabolic role of lxr, the temporal expression pattern suggests a developmental role in, e.g., the liver and CNS. Show less

In the small intestine, the expression of the apolipoprotein (apo) C-III and A-IV genes is restricted to the enterocytes of the villi. We have previously shown that, in transgenic mice, specific expression of the human apo C-III requires a hormone-responsive element (HRE) located in the distal region of the human apoA-IV promoter. This HRE binds the hepatic nuclear factors (HNF)-4alpha and gamma. Here, intraduodenal injections in mice and infections of human enterocytic Caco-2/TC7 cells with an adenovirus expressing a dominant-negative form of HNF-4alpha repress the expression of the apoA-IV gene, demonstrating that HNF-4 controls the apoA-IV gene expression in enterocytes. We show that HNF-4alpha and gamma functionally interact with a second HRE present in the proximal region of the human apoA-IV promoter. New sets of transgenic mice expressing mutated forms of the promoter, combined with the human apo C-III enhancer, demonstrate that, whereas a single HRE is sufficient to reproduce the physiological cephalo-caudal gradient of apoA-IV gene expression, both HREs are required for expression that is restricted to villi. The combination of multiple HREs may specifically recruit regulatory complexes associating HNF-4 and either coactivators in villi or corepressors in crypts. Show less