👤 Mark Curtis

The induction of nausea and emesis represents a significant barriers to optimizing weight loss medications for the treatment of obesity. Identifying mechanisms that improve tolerability and/or enhance efficacy without induction of emetic neurocircuitry could provide substantial therapeutic benefits. Candidate peptide YY (PYY)-based approaches for obesity treatment are no exception, as PYY-based therapeutics are uniformly associated with nausea and emesis. Recently, interest in glucose-dependent insulinotropic polypeptide receptor (GIPR)-based therapeutics has resurfaced, with some paradoxical findings from several preclinical studies showing that both GIPR agonism and antagonism, when combined with glucagon-like peptide-1 receptor (GLP-1R) agonists, result in greater body weight loss and superior glycemic control compared to GLP-1R agonism alone. Here, we investigated the effects of pharmacological modulation of the GIPR system on the actions of PYY. We found that systemic GIPR agonism attenuated PYY-induced malaise while preserving its anorectic and body weight-lowering effects in rats. Interestingly, GIPR antagonism enhanced PYY-induced hypophagia and body weight loss without compromising its malaise tolerability profile. Furthermore, inhibition of GIPR signaling significantly reduced PYY-induced c-Fos expression in the area postrema (AP) of the hindbrain. Since both NPY2R and GIPR are expressed in the same AP neurons, this suggests a potential neuronal pathway by which GIPR modulates the effects of PYY. Overall, our findings underscore the multifaceted actions of the GIPR system and highlight the therapeutic potential of both GIPR agonism and antagonism in enhancing and improving the effects of PYY-based obesity treatments. Show less

Serotonergic psychedelics are re-emerging as therapeutic candidates across psychiatry, particularly for treatment-resistant depression. Their rapid and sustained antidepressant effects, alongside evidence for neuroplastic, dopaminergic, and glutamatergic modulation, have prompted interest in whether they could address depressive and negative symptoms in schizophrenia spectrum disorders (SSDs). This narrative review summarizes mechanistic, preclinical, and early clinical findings relevant to psychedelic use in SSDs. Schizophrenia and major depressive disorder share disturbances in dopamine, glutamate, and neuroplasticity, and both involve large-scale network abnormalities. Schizophrenia is associated with widespread dysconnectivity, mesocortical hypodopaminergia, and striatal hyperdopaminergia linked to NMDA receptor hypofunction. Depression is characterized by fronto-limbic and default mode network hyperconnectivity, mesolimbic hypodopaminergia, and reduced cortical glutamatergic tone. Depressive symptoms within SSDs may reflect an intermediate phenotype combining depressive-like hyperconnectivity with schizophrenia-related global dysconnectivity, suggesting that psychedelics' capacity to transiently increase network flexibility and recalibrate maladaptive connectivity may be clinically relevant. Preclinical studies show increased dendritic spine density, enhanced BDNF expression, restored reward sensitivity, and modulation of network dynamics after psychedelic administration. Clinically, uncontrolled exposure appears associated with increased psychosis-related presentations, whereas limited case reports suggest controlled administration may be tolerated in carefully selected, clinically stable individuals with SSDs. To date, only one early-phase trial (MDMA in schizophrenia) is ongoing, and no randomized trials have evaluated psilocybin or LSD in SSDs. Overall, psychedelics are biologically and mechanistically plausible but remain unproven for depressive and negative symptoms in SSDs, which partially overlap. Carefully designed, safety-focused early-phase studies in clinically stable patients are therefore a prerequisite for broader clinical application. Show less

Oncogenic KRAS mutations are present in >90% of pancreatic ductal adenocarcinoma (PDAC) with KRASG12D being the most common. Mutant-selective KRASG12D inhibitors (KRASiG12D) have demonstrated promising initial clinical activity in KRASG12D-mutant PDAC. However, adaptive resistance to KRASi constrains efficacy in some tumor types, such as colorectal cancer, where EGFR-mediated RAS-MAPK pathway reactivation can be targeted toimprove response. Some studies have suggested a similar role for EGFR in PDAC, but the mechanisms of adaptive resistance to KRAS inhibition are unclear. Mechanisms of adaptive resistance to KRASiG12D were investigated in a panel of KRASG12D-mutant PDAC models. We observed RTK-driven adaptive reactivation of RAS pathway signaling following KRASiG12D in PDAC models. EGFR was a primary driver of adaptive RAS-MAPK reactivation in some models, but limited to those with epithelial differentiation. Conversely, adaptive RAS MAPK reactivation in models with mesenchymal differentiation was primarily driven by FGFR signaling. In clinical PDAC specimens from TCGA, EGFR and ERBB3 expression was highly correlated with expression of epithelial markers, while expression of FGFR1 and mesenchymal markers were correlated. Notably, a RAS(ON) multi-selective inhibitor, which inhibits both wild-type and mutant RAS, abrogated RAS-MAPK reactivation in combination with KRASi in both epithelial and mesenchymal models and led to more consistent antitumor activity compared to combinations of KRASi and EGFR blockade. In PDAC, adaptive RAS-MAPK reactivation following KRASG12D inhibition can be mediated by different RTKs and influenced by cell state. Combinations of mutant-selective KRASi and RAS(ON) multi-selective inhibitors may represent a promising universal strategy to surmount adaptive resistance in PDAC patients. Show less

Transitions of cancer cells between distinct cell states, which are typically driven by transcription reprogramming, fuel tumor plasticity, metastasis, and therapeutic resistance. Whether the transitions between cell states can be therapeutically targeted remains unknown. Here, using the epithelial-to-mesenchymal transition (EMT) as a model, we show that the transcription reprogramming during a cell-state transition induces genomic instability through R-loops and transcription-replication conflicts, and the cell-state transition cannot occur without the ATR kinase, a key regulator of the replication stress response. ATR inhibition during EMT not only increases transcription- and replication-dependent genomic instability but also disrupts transcription reprogramming. Unexpectedly, ATR inhibition elevates R-loop-associated DNA damage at the SNAI1 gene, a key driver of the transcription reprogramming during EMT, triggering ATM- and Polycomb-mediated transcription repression of SNAI1. Beyond SNAI1, ATR also suppresses R-loops and antagonizes repressive chromatin at a subset of EMT genes. Importantly, inhibition of ATR in tumors undergoing EMT reduces tumor growth and metastasis, suggesting that ATR inhibition eliminates cancer cells in transition. Thus, during EMT, ATR not only protects genome integrity but also enables transcription reprogramming, revealing that ATR is a safeguard of cell-state transitions and a target to suppress tumor plasticity. Show less

A previous study of 200,000 exome-sequenced UK Biobank participants investigating the association between rare coding variants and BMI had implicated two genes, MC4R and PCSK1, at exome-wide significance. In addition, further 66 genes were significant with an uncorrected p value of <0.001. Exome sequence data have become available for further 270,000 participants, and weighted burden analyses to test for association with BMI were carried out in this sample for all the 68 genes highlighted by the previous study. Three novel genes, in addition to MC4R and PCSK1, were significant after correction for multiple testing: PTOV1, GALNT9, and ATP8B2. All five genes were exome-wide significant in the whole sample of 470,000 participants. Rare coding variants impairing gene function were associated with reduced BMI for ATP8B2 but increased BMI for the other genes, and for all genes, loss of function variants had larger effect sizes than nonsynonymous variants. The biological mechanisms whereby the novel genes might affect BMI are not clear, although impairment of ATP8B2 might possibly have an effect on insulin secretion. Functional studies might throw further light on how these genes are involved in regulation of body weight. Collectively, the identified variants are very rare and do not make a major contribution to variation in BMI in the population. This research has been conducted using the UK Biobank Resource. Show less

Relational aggression (RA) is characterised by social manipulation and covert harm, often involving fluid and overlapping experiences of both perpetration and victimisation. We used latent profile analysis (LPA) to identify subgroups of young Australian adults based on their self-reported experiences of RA and explore whether these RA typologies are associated with broader aggressive traits and behaviours. We used a community sample of Australian adults aged 18-25 ( Show less

A previous study of 200,000 exome-sequenced UK Biobank participants investigating the association between rare coding variants and hyperlipidaemia had implicated four genes, LDLR, PCSK9, APOC3 and IFITM5, at exome-wide significance. In addition, a further 43 protein-coding genes were significant with an uncorrected p value of <0.001. Exome sequence data has become available for a further 270,000 participants and weighted burden analysis to test for association with hyperlipidaemia was carried out in this sample for the 47 genes highlighted by the previous study. There was no evidence to implicate IFITM5 but LDLR, PCSK9, APOC3, ANGPTL3, ABCG5 and NPC1L1 were all statistically significant after correction for multiple testing. These six genes were also all exome-wide significant in the combined sample of 470,000 participants. Variants impairing function of LDLR and ABCG5 were associated with increased risk whereas variants in the other genes were protective. Variant categories associated with large effect sizes are cumulatively very rare and the main benefit of this kind of study seems to be to throw light on the molecular mechanisms impacting hyperlipidaemia risk, hopefully supporting attempts to develop improved therapies. Show less

A number of genes have been identified in which rare variants can cause obesity. Here we analyse a sample of exome sequenced subjects from UK Biobank using BMI as a phenotype with the aims of identifying genes in which rare, functional variants influence BMI and characterising the effects of different categories of variant. There were 199,807 exome sequenced subjects for whom BMI was recorded. Weighted burden analysis of rare, functional variants was carried out, incorporating population principal components and sex as covariates. For selected genes, additional analyses were carried out to clarify the contribution of different categories of variant. Statistical significance was summarised as the signed log 10 of the p value (SLP), given a positive sign if the weighted burden score was positively correlated with BMI. Two genes were exome-wide significant, MC4R (SLP = 15.79) and PCSK1 (SLP = 6.61). In MC4R, disruptive variants were associated with an increase in BMI of 2.72 units and probably damaging nonsynonymous variants with an increase of 2.02 units. In PCSK1, disruptive variants were associated with a BMI increase of 2.29 and protein-altering variants with an increase of 0.34. Results for other genes were not formally significant after correction for multiple testing, although SIRT1, ZBED6 and NPC2 were noted to be of potential interest. Because the UK Biobank consists of a self-selected sample of relatively healthy volunteers, the effect sizes noted may be underestimates. The results demonstrate the effects of very rare variants on BMI and suggest that other genes and variants will be definitively implicated when the sequence data for additional subjects becomes available. Show less

Weighted burden analysis can incorporate variants with different frequencies and annotations into a combined test for association between a gene and a phenotype. However there has not been a systematic exploration of which weighting schemes provide maximum power to detect association. Here we assess different weighting schemes using a number of genes for which exome-wide evidence of association with common phenotypes was obtained in 200,000 exome-sequenced UK Biobank participants. We find that there are marked differences in optimal weighting schemes between genes, both with respect to allele frequency and to annotation, implying that there is no "one-size-fits-all" scheme which is generally optimal. It seems helpful to weight rare variants more highly than common ones, to give loss of function variants higher weights than protein-altering variants and to assign higher weights to protein-altering variants predicted to have more severe effects. However with the data currently available it does not seem possible to make more specific recommendations. This research has been conducted using the UK Biobank Resource. Show less

Modulators of epithelial-to-mesenchymal transition (EMT) have recently emerged as novel players in the field of leukemia biology. The mechanisms by which EMT modulators contribute to leukemia pathogenesis, however, remain to be elucidated. Here we show that overexpression of SNAI1, a key modulator of EMT, is a pathologically relevant event in human acute myeloid leukemia (AML) that contributes to impaired differentiation, enhanced self-renewal, and proliferation of immature myeloid cells. We demonstrate that ectopic expression of Snai1 in hematopoietic cells predisposes mice to AML development. This effect is mediated by interaction with the histone demethylase KDM1A/LSD1. Our data shed new light on the role of SNAI1 in leukemia development and identify a novel mechanism of LSD1 corruption in cancer. This is particularly pertinent given the current interest surrounding the use of LSD1 inhibitors in the treatment of multiple different malignancies, including AML. Show less

Genome-wide association studies have generally failed to identify polymorphisms associated with antidepressant response. Possible reasons include limited coverage of genetic variants that this study tried to address by exome genotyping and dense imputation. A meta-analysis of Genome-Based Therapeutic Drugs for Depression (GENDEP) and Sequenced Treatment Alternatives to Relieve Depression (STAR*D) studies was performed at the single-nucleotide polymorphism (SNP), gene and pathway levels. Coverage of genetic variants was increased compared with previous studies by adding exome genotypes to previously available genome-wide data and using the Haplotype Reference Consortium panel for imputation. Standard quality control was applied. Phenotypes were symptom improvement and remission after 12 weeks of antidepressant treatment. Significant findings were investigated in NEWMEDS consortium samples and Pharmacogenomic Research Network Antidepressant Medication Pharmacogenomic Study (PGRN-AMPS) for replication. A total of 7062 950 SNPs were analyzed in GENDEP (n=738) and STAR*D (n=1409). rs116692768 (P=1.80e-08, ITGA9 (integrin α9)) and rs76191705 (P=2.59e-08, NRXN3 (neurexin 3)) were significantly associated with symptom improvement during citalopram/escitalopram treatment. At the gene level, no consistent effect was found. At the pathway level, the Gene Ontology (GO) terms GO: 0005694 (chromosome) and GO: 0044427 (chromosomal part) were associated with improvement (corrected P=0.007 and 0.045, respectively). The association between rs116692768 and symptom improvement was replicated in PGRN-AMPS (P=0.047), whereas rs76191705 was not. The two SNPs did not replicate in NEWMEDS. ITGA9 codes for a membrane receptor for neurotrophins and NRXN3 is a transmembrane neuronal adhesion receptor involved in synaptic differentiation. Despite their meaningful biological rationale for being involved in antidepressant effect, replication was partial. Further studies may help in clarifying their role. Show less

The chronic stage multiple sclerosis (MS), an inflammatory demyelinating disease of the central nervous system (CNS), remains refractory to current treatments. This refractory nature may be due to the fact that current treatments are primarily immunomodulatory, which prevent further demyelination but lack the capacity to promote remyelination. Several approaches, including transplantation of neural stem cells (NSCs) or antagonists to LINGO-1, a key part of the receptor complex for neuroregeneration inhibitors, have been effective in suppressing the acute stage of experimental autoimmune encephalomyelitis (EAE), an animal model of MS. However, their effect on the chronic stage EAE is not known. Here, we show that transplantation of NSCs had only a slight therapeutic effect when treatment started at the chronic stage of EAE (e.g., injected at day 40 postimmunization). However, NSCs engineered to produce LINGO-1-Fc, a soluble LINGO-1 antagonist, significantly promoted neurological recovery as demonstrated by amelioration of clinical signs, improvement in axonal integrity, and enhancement of oligodendrocyte maturation and neuron repopulation. Significantly enhanced NAD production and Sirt2 expression were also found in the CNS of mice treated with LINGO-1-Fc-producing NSC. Moreover, differentiation of LINGO-1-Fc-producing NSCs into oligodendrocytes in vitro was largely diminished by an NAMPT inhibitor, indicating that LINGO-1-Fc enhances the NAMPT/NAD/Sirt2 pathway. Together, our study establishes a CNS-targeted, novel LINGO-1-Fc delivery system using NSCs, which represents a novel and effective NSC-based gene therapy approach for the chronic stage of MS. Show less

We used RNA sequencing to analyze transcript profiles of ten autopsy brain regions from ten subjects. RNA sequencing techniques were designed to detect both coding and non-coding RNA, splice isoform composition, and allelic expression. Brain regions were selected from five subjects with a documented history of smoking and five non-smokers. Paired-end RNA sequencing was performed on SOLiD instruments to a depth of >40 million reads, using linearly amplified, ribosomally depleted RNA. Sequencing libraries were prepared with both poly-dT and random hexamer primers to detect all RNA classes, including long non-coding (lncRNA), intronic and intergenic transcripts, and transcripts lacking poly-A tails, providing additional data not previously available. The study was designed to generate a database of the complete transcriptomes in brain region for gene network analyses and discovery of regulatory variants. Of 20,318 protein coding and 18,080 lncRNA genes annotated from GENCODE and lncipedia, 12 thousand protein coding and 2 thousand lncRNA transcripts were detectable at a conservative threshold. Of the aligned reads, 52 % were exonic, 34 % intronic and 14 % intergenic. A majority of protein coding genes (65 %) was expressed in all regions, whereas ncRNAs displayed a more restricted distribution. Profiles of RNA isoforms varied across brain regions and subjects at multiple gene loci, with neurexin 3 (NRXN3) a prominent example. Allelic RNA ratios deviating from unity were identified in > 400 genes, detectable in both protein-coding and non-coding genes, indicating the presence of cis-acting regulatory variants. Mathematical modeling was used to identify RNAs stably expressed in all brain regions (serving as potential markers for normalizing expression levels), linked to basic cellular functions. An initial analysis of differential expression analysis between smokers and nonsmokers implicated a number of genes, several previously associated with nicotine exposure. RNA sequencing identifies distinct and consistent differences in gene expression between brain regions, with non-coding RNA displaying greater diversity between brain regions than mRNAs. Numerous RNAs exhibit robust allele selective expression, proving a means for discovery of cis-acting regulatory factors with potential clinical relevance. Show less

Markers at the pericentriolar material 1 gene (PCM1) have shown genetic association with schizophrenia in both a University College London (UCL) and a USA-based case-control sample. In this paper we report a statistically significant replication of the PCM1 association in a large Scottish case-control sample from Aberdeen. Resequencing of the genomic DNA from research volunteers who had inherited haplotypes associated with schizophrenia showed a threonine to isoleucine missense mutation in exon 24 which was likely to change the structure and function of PCM1 (rs370429). This mutation was found only as a heterozygote in 98 schizophrenic research subjects and controls out of 2246 case and control research subjects. Among the 98 carriers of rs370429, 67 were affected with schizophrenia. The same alleles and haplotypes were associated with schizophrenia in both the London and Aberdeen samples. Another potential aetiological base pair change in PCM1 was rs445422, which altered a splice site signal. A further mutation, rs208747, was shown by electrophoretic mobility shift assays to create or destroy a promoter transcription factor site. Five further non-synonymous changes in exons were also found. Genotyping of the new variants discovered in the UCL case-control sample strengthened the evidence for allelic and haplotypic association (P=0.02-0.0002). Given the number and identity of the haplotypes associated with schizophrenia, further aetiological base pair changes must exist within and around the PCM1 gene. PCM1 protein has been shown to interact directly with the disrupted-in-schizophrenia 1 (DISC1) protein, Bardet-Biedl syndrome 4, and Huntingtin-associated protein 1, and is important in neuronal cell growth. In a separate study we found that clozapine but not haloperidol downregulated PCM1 expression in the mouse brain. We hypothesize that mutant PCM1 may be responsible for causing a subtype of schizophrenia through abnormal cell division and abnormal regeneration in dividing cells in the central nervous system. This is supported by our previous finding of orbitofrontal volumetric deficits in PCM1-associated schizophrenia patients as opposed to temporal pole deficits in non-PCM1-associated schizophrenia patients. Caution needs to be exercised in interpreting the actual biological effects of the mutations we have found without further cell biology. However, the DNA changes we have found deserve widespread genotyping in multiple case-control populations. Show less

Recent studies have reported large common regions of homozygosity (ROHs) that are the result of autozygosity, that is, the cooccurrence within individuals of long haplotypes that have a high frequency in the population. A recent study reports that such regions are found more commonly in individuals with schizophrenia compared with controls, and identified nine 'risk ROHs' that were individually more common in cases. Of these, four contained or neighboured genes associated with schizophrenia (NOS1AP/UHMK1, ATF2, NSF and PIK3C3). We have applied the same methodology to a UK sample of 506 cases with bipolar disorder and 510 controls. There was no overall excess of common ROHs among bipolar individuals. With one exception, the haplotypes accounting for the ROHs appeared to be distributed according to the Hardy-Weinberg equilibrium. One ROH was individually more common among cases (uncorrected P = 0.0003). This ROH spanned the chromosome 2p23.3 gene ITSN2 (the gene for intersectin 2 isoform 2). However, inspection of the homozygous haplotypes and haplotype-based tests for association failed to provide a clearer understanding of why this ROH was occurring more commonly. Overall, we conclude that, in contrast with schizophrenia, common ROHs are rarely associated with susceptibility to bipolar disorder. This supports the idea that predominantly different genes are increasing susceptibility to schizophrenia and bipolar affective disorders. Show less