👤 Stephen Lam

Hypothalamic neurons expressing either POMC or AGRP sense nutritional state directly and indirectly and transmit these neuropeptide signals to other brain centres through the melanocortin 3 and 4 receptors. MC4R is primarily concerned with the control of appetite and energy expenditure while MC3R is more closely related to the control of linear growth and the timing of puberty. The role of MC3R in the long-term control of energy balance and body composition is less clear, particularly in humans. We have undertaken studies in humans, domestic dogs and mice with the goal of clarifying the relative impact of MC3R deficiency on energy balance, growth and sexual development. By studying three large consanguineously enriched cohorts, totalling approximately 300K people, we identified nine individuals who are homozygous for functionally null MC3R variants. The body mass index (BMI) of the homozygous MC3R variant carriers was not significantly different from that of age, sex and demographically matched controls, with six of the nine homozygotes having a BMI <30 kg/m Show less

The effects of lipid traits on colorectal cancer (CRC) risk and the extent to which obesity may modify these effects remain unclear. To examine the associations between lipid traits and CRC risk using an observational study and Mendelian randomization (MR) analyses, and the role of weight status in the potential associations. In the Guangzhou Biobank Cohort Study (GBCS), lipid profiles were measured during 2003-2008, and CRC events were identified through record linkage with the cancer registry. MR analyses assessed the causal effects of lipid traits on CRC using a genome-wide association study meta-analysis of 185,616 Europeans. Among 28,576 GBCS participants followed until 2020, 599 CRC events occurred. Participants in the highest quartile of apolipoprotein B (apoB) had a higher CRC risk (hazard ratio [HR] 1.43, 95% CI 1.02-2.01). This association remained in those with overweight/obesity (HR 2.21, 95% CI 1.28-3.83). MR analyses supported a detrimental effect of apoB on CRC (odds ratio 1.12 per 1 SD, 95% CI 1.02-1.22). MR analyses also showed positive associations for total cholesterol and the apoB/apolipoprotein A-I ratio, which were not significant in the observational study. Higher apoB levels were associated with an increased CRC risk in both observational and MR analyses, suggesting a potential role of apoB in CRC prevention, especially among participants with overweight/obesity. However, the limitations of single-time lipid measurements and the use of different ancestries across study designs indicate the need for further research to confirm the robustness and generalizability of the findings. Show less

Cerebrospinal fluid (CSF) proteomics offers insights into molecular changes in aging and Alzheimer's disease (AD). Key AD biomarkers, in particular amyloid-β (Aβ) and tau, in CSF are strongly associated with Show less

Nucleoporins are increasingly recognized as tissue-specific regulators beyond their structural roles in the nuclear pore complex. Here, we identify nucleoporin Nup358 as a critical repressor of Wnt signaling required for intestinal epithelium integrity. Ablation of Nup358 in adult mice causes a catastrophic loss of crypt-villus architecture and disrupts the intestinal epithelial layer. Notably, while the intestinal stem cell (ISC) pool remains stable, the transit-amplifying (TA) progenitor compartment is depleted. Mechanistically, we show that the interaction of Nup358 with Dvl1 through its N-terminal domain inhibits Dvl1 spontaneous phase separation. In the absence of Nup358, Dvl1 biomolecular condensates promote Tankyrase-mediated degradation of Axin1, leading to the constitutive stabilization of β-catenin and ligand-independent Wnt activation, negatively impacting cell differentiation and TA progenitor survival. Our results demonstrate that Nup358 acts as a molecular safeguard that dampens Wnt signaling levels in intestinal crypts. By preventing Dvl1-mediated Wnt signal amplification, Nup358 allows ISCs to transition into the TA compartment and initiate the differentiation programs essential for intestinal homeostasis. Show less

An acute increase of lipids in the upper small intestine (USI) of rodents and humans triggers lipid-sensing pathways to reduce food intake. However, USI lipid sensing does not reduce feeding in high-fat (HF) fed conditions, and the underlying mechanism remains elusive. Here, we report that HF feeding in male rats impaired USI lipid infusion to stimulate glucose-dependent insulinotropic polypeptide (GIP) secretion and decrease refeeding, and the defects of USI lipid sensing were restored by metformin. Next, we found that infusion of GIP receptor (GIPR) agonist in the nucleus of the solitary tract (NTS), but not mediobasal hypothalamus or area postrema, resulted in decreased refeeding in chow-fed rats. The anorectic effect of NTS GIPR agonist remained intact in HF rats and was inhibited by a genetic knockdown of GIPR. Finally, an inhibition of NTS GIPR also negated the ability of USI lipid sensing with metformin to decrease refeeding despite an increase in plasma GIP levels in HF rats. Thus, USI lipid sensing in HF rats is enhanced by metformin to trigger an endocrine GIP to NTS GIPR axis to reduce food intake, thereby unveiling small intestinal lipid-sensing pathways as potential targets to enhance GIP action and reduce weight in obesity. High-fat (HF) feeding in rats impairs upper small intestine (USI) lipid sensing to increase plasma glucose-dependent insulinotropic polypeptide (GIP) levels and reduce feeding. Metformin enhances USI lipids to increase GIP and reduce feeding in HF-fed rats. GIP activates the GIP receptor (GIPR) in the nucleus of the solitary tract (NTS), which reduces food intake in HF-fed rats. GIPR in the NTS is required for small intestinal lipids with metformin to reduce feeding. Show less

Glucagon-like peptide-1 receptor (GLP-1R) and glucose-dependent insulinotropic polypeptide receptor (GIPR) agonists have recently been shown to play a significant role in the treatment of diabetes and obesity. Better understanding of their signaling and mechanism of action could further improve their therapeutic effects. In the current study, we investigate the impact of biased cyclic AMP (cAMP) signaling of GLP-1R and GIPR, individually, as well as the combined effects of a unimolecular dually biased GLP-1R/GIPR agonist, CT-859, on glucose, food consumption, and body weight regulation. Our data demonstrate that biased agonism of either GLP-1R or GIPR leads to better glycemic regulation, greater food intake suppression, and weight loss. In addition, concerted biased activation of both GLP-1R and GIPR results in substantially higher efficacy. Activation of GLP-1R and GIPR with a combination of individually biased agonists or via a dually biased unimolecular approach with CT-859 may provide significant therapeutic advantages for the treatment of diabetes and obesity. Show less

Obesity is a heritable disease, but its genetic basis is incompletely understood. Canine population history facilitates trait mapping. We performed a canine genome-wide association study for body condition score-a measure of obesity-in 241 Labrador retrievers. Using a cross-species approach, we showed that canine obesity genes are also associated with rare and common forms of obesity in humans. The lead canine association was within the gene DENN domain containing 1B ( Show less

Clinical case-based studies have identified rare pathogenic variants in several genes as causes of severe early-onset obesity, but their penetrance and interaction with polygenic susceptibility in the general population remain unclear. We analyzed the United Kingdom Biobank (UKBB) whole-exome sequence data to assess the effects of heterozygous variants in 9 previously reported genes on adult body mass index (BMI) and recalled childhood adiposity. Among 419 581 UKBB participants, we identified heterozygous carriers of coding variants that were (1) experimentally characterized as loss of function (LoF), or (2) bioinformatically predicted as rare (minor allele frequency <0.1%) LoF. We assessed variant-level and gene-level population penetrance of obesity and associations with adult BMI and recalled childhood adiposity, and tested the statistical interaction between rare variant carriage and a BMI polygenic score. Considering experimentally characterized LoF variants (excluding MC4R), we identified 22 heterozygous and 2 homozygous variants in 3 autosomal recessive genes (POMC, PCSK1, LEPR), and 3 autosomal dominant genes (SH2B1, SIM1, KSR2) with at least 10 carriers in the UKBB. Obesity penetrance among carriers ranged from 8% to 29% (median 23%), and none was significantly different from noncarriers (24%, all P > .05). For bioinformatically predicted rare LoF variants, gene-based burden tests showed that carriage of heterozygous variants in MC4R, PCSK1, and POMC was associated with higher adult BMI (effect sizes ranged from 0.5 to 2.5 kg/m2, all P < .003), with no significant interaction effects with common variant polygenic risk of BMI. This study provides the population-specific report of variant penetrance of known obesity genes and confirmed the heterozygous rare variant effects in MC4R, POMC, and PCSK1. We also underscore the utility of population-based studies in supporting variant classifications. Show less

Amphetamine (AMPH) exerts metabolic and cardiovascular effects. The central melanocortin system is a key regulator of both metabolic and cardiovascular functions. Here, we show that the melanocortin system partially mediates AMPH-induced anorexia, energy expenditure, tachycardia, and hypertension. AMPH increased α-melanocyte stimulating hormone (αMSH) secretion from the hypothalamus, elevated blood pressure and heart rate (HR), increased brown adipose tissue (BAT) thermogenesis, and reduced both food intake (FI) and body weight (BW). In melanocortin 4 receptor-deficient (MC4R knockout [KO]) mice, metabolic and cardiovascular effects of AMPH were significantly attenuated. Antagonism of serotonergic and noradrenergic neurotransmitter systems attenuated AMPH-induced αMSH secretion as well as AMPH-induced metabolic and cardiovascular effects. We propose that AMPH increases serotonergic activation of proopiomelanocortin (POMC) neurons and reduces the noradrenergic inhibition of POMC neurons, thereby disinhibiting them. Together, these presynaptic mechanisms result in increased POMC activity, increased αMSH secretion, and increased activation of MC4R pathways that regulate both the metabolic and cardiovascular systems. Show less

Brain metastasis occurs in up to 40% of patients with non-small cell lung cancer (NSCLC). Considerable genomic heterogeneity exists between the primary lung tumor and respective brain metastasis; however, the identity of the genes capable of driving brain metastasis is incompletely understood. Here, we carried out an in vivo genome-wide CRISPR activation screen to identify molecular drivers of brain metastasis from an orthotopic xenograft model derived from a patient with NSCLC. We found that activating expression of the Alzheimer's disease-associated beta-secretase 1 (BACE1) led to a substantial increase in brain metastases. Furthermore, genetic and pharmacological inhibition of BACE1 blocked NSCLC brain metastasis. Mechanistically, we identified that BACE1 acts through epidermal growth factor receptor to drive this metastatic phenotype. Together, our data highlight the power of in vivo CRISPR activation screening to unveil molecular drivers and potential therapeutic targets of NSCLC brain metastasis. Show less

Overt immune activation by viral infections can lead to cytokine storm syndromes, such as hemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS). We aimed to compare the immune response to different viral pathogens to understand the connection between infections and cytokine storm syndromes. We recruited children who sought care at the emergency department with fever for ≥3 days. We performed immune profiling using Olink proximity extension assay and flow cytometry. We compared the findings with cases of HLH, MAS, Kawasaki disease (KD), and multisystem inflammatory syndrome in children (MIS-C). We enrolled 352 febrile patients and studied 110 cases of confirmed common viral infections. We found that Epstein-Barr virus (EBV) uniquely triggered high levels of multiple cytokines (IL-18, IL-27, TNF, FLT3 ligand, and lymphotoxin alpha) and IFN-γ-induced chemokines (CXCL9/10/11 and CCL19). These patterns are similar to the hyperinflammatory response associated with HLH/MAS but are less consistent with the findings in KD and MIS-C. Flow cytometry analysis revealed that CD38 This work broadens our understanding of common viral infections in children and provides an immunologic basis for the link between EBV infection and HLH/MAS. Show less

This study was aimed at assessing the diagnostic utility of whole genome sequence analysis in a well-characterised research cohort of individuals referred with a clinical suspicion of Cornelia de Lange syndrome (CdLS) in whom prior genetic testing had not identified a causative variant. Short-read whole genome sequencing was performed on 195 individuals from 105 families, 108 of whom were affected. 100/108 of the affected individuals had prior relevant genetic testing, with no pathogenic variant being identified. The study group comprised 42 trios in which both parental samples were available for testing (42 affected individuals and 126 unaffected parents), 61 singletons (unrelated affected individuals), and two families with more than one affected individual. The results showed that 32 unrelated probands from 105 families (30.5%) had likely causative coding region-disrupting variants. Four loci were identified in > 1 proband: Show less

Obesity is a major risk factor for many common diseases and has a substantial heritable component. To identify new genetic determinants, we performed exome-sequence analyses for adult body mass index (BMI) in up to 587,027 individuals. We identified rare loss-of-function variants in two genes (BSN and APBA1) with effects substantially larger than those of well-established obesity genes such as MC4R. In contrast to most other obesity-related genes, rare variants in BSN and APBA1 were not associated with normal variation in childhood adiposity. Furthermore, BSN protein-truncating variants (PTVs) magnified the influence of common genetic variants associated with BMI, with a common variant polygenic score exhibiting an effect twice as large in BSN PTV carriers than in noncarriers. Finally, we explored the plasma proteomic signatures of BSN PTV carriers as well as the functional consequences of BSN deletion in human induced pluripotent stem cell-derived hypothalamic neurons. Collectively, our findings implicate degenerative processes in synaptic function in the etiology of adult-onset obesity. Show less

Smoothened inhibitors, such as vismodegib, exhibit remarkable success in treating patients with locally advanced basal cell carcinoma (LaBCC). Yet, vismodegib efficacy is hindered by notable side effects, which often lead to treatment discontinuation and subsequent relapse in patients with LaBCC. Prolonged remission was previously reported in patients with LaBCCs who underwent surgical debulking before starting vismodegib. In this study, we enrolled 4 patients with LaBCC who underwent debulking followed by vismodegib therapy to assess their clinical outcomes and analyze the cutaneous molecular changes occurring as a result of surgical intervention. After LaBCC debulking, patients underwent a punch biopsy of residual basal cell carcinoma tissue 1 week later. RT-qPCR analysis of 24 Notch and Wnt signaling-associated genes revealed elevated Show less

Overweight and obesity are endemic in developed countries, with a substantial negative impact on human health. Medications developed to treat obesity include agonists for the G-protein coupled receptors glucagon-like peptide-1 (GLP-1R; e.g. liraglutide), serotonin 2C (5-HT We profiled PPG neurons in the nucleus of the solitary tract (PPG We found that 5-HT These findings identify a necessary mechanism through which obesity medication lorcaserin produces its therapeutic benefit, namely brainstem PPG Show less

Multiple factors can contribute to sub-fecundity, including genetics, lifestyle, and environmental contaminants. PFASs are characterized as "forever chemicals" due to their ubiquitous contamination and their persistence in the environment, wildlife, and humans. Numerous studies have demonstrated that PFAS exposure adversely affects multiple bodily functions, including liver metabolism and gonadal function. It is unclear, however, how the disruption of hepatic fatty acid metabolism affects testicular function. In this study, male mice were administered 0.3 and 3 μg/g body weight of PFOS for 21 days. Our data showed that PFOS exposure caused hepatic steatosis, as evidenced by significant increases in triglyceride levels, expression of ATP-citrate lyase, and fatty acid synthase, as well as fasting insulin levels. PFOS perturbed the expression levels of hepatokines, of which fibroblast growth factor-21 ( This study revealed potential links between PFOS-elicited changes in hepatic metabolism and their impacts on testicular biology. This study provides insights into alternative targets elicited by PFOS that can be used to develop diagnostic and therapeutic strategies for improving testicular dysfunction. Show less

Prenatal exposure to perfluorooctanesulfonate (PFOS) increases fetus' metabolic risk; however, the investigation of the underlying mechanism is limited. In this study, pregnant mice in the gestational days (GD, 4.5-17.5) were exposed to PFOS (0.3 and 3 μg/g of body weight). At GD 17.5, PFOS perturbed maternal lipid metabolism and upregulated metabolism-regulating hepatokines ( Show less

White matter (WM) injury is frequently observed along with dementia. Positron emission tomography with amyloid-ligands (Aβ-PET) recently gained interest for detecting WM injury. Yet, little is understood about the origin of the altered Aβ-PET signal in WM regions. Here, we investigated the relative contributions of diffusion MRI-based microstructural alterations, including free water and tissue-specific properties, to Aβ-PET in WM and to cognition. We included a unique cohort of 115 participants covering the spectrum of low-to-severe white matter hyperintensity (WMH) burden and cognitively normal to dementia. We applied a bi-tensor diffusion-MRI model that differentiates between (i) the extracellular WM compartment (represented via free water), and (ii) the fiber-specific compartment (via free water-adjusted fractional anisotropy [FA]). We observed that, in regions of WMH, a decrease in Aβ-PET related most closely to higher free water and higher WMH volume. In contrast, in normal-appearing WM, an increase in Aβ-PET related more closely to higher cortical Aβ (together with lower free water-adjusted FA). In relation to cognitive impairment, we observed a closer relationship with higher free water than with either free water-adjusted FA or WM PET. Our findings support free water and Aβ-PET as markers of WM abnormalities in patients with mixed dementia, and contribute to a better understanding of processes giving rise to the WM PET signal. Show less

The glucocorticoid receptor (GR) is an important anti-cancer target in lymphoid cancers but has been understudied in solid tumors like lung cancer, although glucocorticoids are often given with chemotherapy regimens to mitigate side effects. Here, we identify a dexamethasone-GR mediated anti-cancer response in a subset of aggressive non-small cell lung cancers (NSCLCs) that harbor Serine/Threonine Kinase 11 (STK11/LKB1) mutations. High tumor expression of carbamoyl phosphate synthase 1 (CPS1) was strongly linked to the presence of LKB1 mutations, was the best predictor of NSCLC dexamethasone (DEX) sensitivity ( Show less

Lung adenocarcinoma is the most common type of lung cancer. Known risk variants explain only a small fraction of lung adenocarcinoma heritability. Here, we conducted a two-stage genome-wide association study of lung adenocarcinoma of East Asian ancestry (21,658 cases and 150,676 controls; 54.5% never-smokers) and identified 12 novel susceptibility variants, bringing the total number to 28 at 25 independent loci. Transcriptome-wide association analyses together with colocalization studies using a Taiwanese lung expression quantitative trait loci dataset (n = 115) identified novel candidate genes, including FADS1 at 11q12 and ELF5 at 11p13. In a multi-ancestry meta-analysis of East Asian and European studies, four loci were identified at 2p11, 4q32, 16q23, and 18q12. At the same time, most of our findings in East Asian populations showed no evidence of association in European populations. In our studies drawn from East Asian populations, a polygenic risk score based on the 25 loci had a stronger association in never-smokers vs. individuals with a history of smoking (P Show less

Chromatin regulation involves the selective recruitment of chromatin factors to facilitate DNA repair, replication and transcription. Here we demonstrate the utility of coupling unbiased functional genomics with chromatin immunoprecipitation (CRISPR-ChIP) to identify the factors associated with active chromatin modifications in mammalian cells. Specifically, an integrated reporter containing a cis-regulatory element of interest and a single guide RNA provide a chromatinized template for a direct readout for regulators of histone modifications associated with actively transcribed genes such as H3K4me3 and H3K79me2. With CRISPR-ChIP, we identify all the nonredundant COMPASS complex members required for H3K4me3 and demonstrate that RNA polymerase II is dispensable for the maintenance of H3K4me3. As H3K79me2 has a putative oncogenic function in leukemia cells driven by MLL translocations, using CRISPR-ChIP we reveal a functional partitioning of H3K79 methylation into two distinct regulatory units: an oncogenic DOT1L complex directed by the MLL fusion protein in a Menin-dependent manner and a separate endogenous DOT1L complex, where catalytic activity is directed by MLLT10. Overall, CRISPR-ChIP provides a powerful tool for the unbiased interrogation of the mechanisms underpinning chromatin regulation. Show less

Biomarker identification is imperative for invasive breast carcinoma, which is more aggressive and associated with higher mortality and worse prognosis in younger patients (<45 years) than in older patients (>50 years). The current study aimed to investigate angiopoietin-like protein 4 (ANGPTL4) and insulin-like growth factor-1 (IGF-1) protein expression in breast tissue from young patients with breast carcinoma. Immunohistochemical staining was applied in formalin-fixed, paraffin-embedded samples of breast carcinoma tissue from young patients aged <45 years at the time of diagnosis. Both proteins were expressed in the majority of cases. The highest frequency of positive ANGPTL4 and IGF-1 expression was observed in the luminal A subtype, whereas the HER2-overexpression subtype exhibited the lowest expression frequency for both proteins. There was no significant association between ANGPTL4 (p = 0.897) and IGF-1 (p = 0.091) expression and molecular subtypes of breast carcinoma. The histological grade was a significant predictor of ANGPTL4 expression (grade 1 vs. grade 3, adjusted odds ratio = 12.39, p = 0.040). Therefore, ANGPTL-4 and IGF-1 expressions are common in young breast carcinoma tissue. There is a potential use of them as biomarkers in breast carcinoma. Show less

The area postrema (AP) and nucleus tractus solitarius (NTS) located in the hindbrain are key nuclei that sense and integrate peripheral nutritional signals and consequently regulate feeding behaviour. While single-cell transcriptomics have been used in mice to reveal the gene expression profile and heterogeneity of key hypothalamic populations, similar in-depth studies have not yet been performed in the hindbrain. Using single-nucleus RNA sequencing, we provide a detailed survey of 16,034 cells within the AP and NTS of mice in the fed and fasted states. Of these, 8,910 were neurons that group into 30 clusters, with 4,289 from mice fed ad libitum and 4,621 from overnight fasted mice. A total of 7,124 nuclei were from non-neuronal cells, including oligodendrocytes, astrocytes, and microglia. Interestingly, we identified that the oligodendrocyte population was particularly transcriptionally sensitive to an overnight fast. The receptors GLP1R, GIPR, GFRAL, and CALCR, which bind GLP1, GIP, GDF15, and amylin, respectively, are all expressed in the hindbrain and are major targets for anti-obesity therapeutics. We characterise the transcriptomes of these four populations and show that their gene expression profiles are not dramatically altered by an overnight fast. Notably, we find that roughly half of cells that express GIPR are oligodendrocytes. Additionally, we profile POMC-expressing neurons within the hindbrain and demonstrate that 84% of POMC neurons express either PCSK1, PSCK2, or both, implying that melanocortin peptides are likely produced by these neurons. We provide a detailed single-cell level characterisation of AP and NTS cells expressing receptors for key anti-obesity drugs that are either already approved for human use or in clinical trials. This resource will help delineate the mechanisms underlying the effectiveness of these compounds and also prove useful in the continued search for other novel therapeutic targets. Show less

Mutations in the melanocortin 4 receptor gene (MC4R) are associated with obesity but little is known about the prevalence and impact of such mutations throughout human growth and development. We examined the MC4R coding sequence in 5,724 participants from the Avon Longitudinal Study of Parents and Children, functionally characterized all nonsynonymous MC4R variants and examined their association with anthropometric phenotypes from childhood to early adulthood. The frequency of heterozygous loss-of-function (LoF) mutations in MC4R was ~1 in 337 (0.30%), considerably higher than previous estimates. At age 18 years, mean differences in body weight, body mass index and fat mass between carriers and noncarriers of LoF mutations were 17.76 kg (95% CI 9.41, 26.10), 4.84 kg m Show less

A forward genetic Sleeping Beauty (SB) insertional mutagenesis screen, followed by high-throughput transcriptome sequencing, was used to identify driver genes responsible for hepatocellular carcinoma (HCC)-associated metastasis. Using RNA-sequencing (RNA-seq) to identify transposon-endogenous transcriptome fusion genes, the phylogenetic lineage between the parental liver tumor and secondary metastasis can be determined to provide mechanistic insight to genetic changes involved in the metastatic evolution process. In the current study, two novel candidate genes were identified to be potentially involved in HCC-associated metastatic progression, canopy FGF signaling regulator 2 (Cnpy2) and actinin alpha 2 (Actn2). Transposon-Cnpy2 fusion transcripts were identified in both primary liver tumors and lung metastases. Its significant association with clinicopathological characteristics and correlated gene enrichment in metastasis-related mechanisms suggest its potential role in modulating local invasion and angiogenesis. Other known driver genes for human HCC that can also promote metastatic progression include epidermal growth factor receptor (Egfr) and RNA imprinted and accumulated in nucleus (Rian). Metabolic pathway related gene carbamoyl phosphate synthetase (Cps1) was identified to play an important role in early HCC development, while cell junction-related pathway gene Rac family small GTPase 1 (Rac1) was identified to take part in both HCC and pro-metastatic progression. Importantly, actinin alpha 2 (Actn2) was identified exclusively in the secondary metastasis site and its role in HCC-related metastatic process was elucidated using in vitro approaches. ACTN2-overexpression in human liver cancer cells displayed enhanced cellular motility and invasion abilities, indicating its possible function in later stage of metastasis, such as extravasation and lung colonization. Show less