Biology subjects

Gibson, W. T.

Publications and source records attributed to Gibson, W. T..

4 recordsLinked to original sources

bioRxiv2024

Mimicking Human EED Variants in Drosophila: A Promising Strategy to Analyze Human EED Variant Function

The Polycomb Repressive Complex 2 is an epigenetic reader/writer that methylates histone H3K27. Rare germline partial loss of function (pLoF) variants in core members of the complex (EZH2, EED, SUZ12) cause overgrowth and intellectual disability syndromes, whereas somatic variants are implicated in cancer. However, up to 1% of the general population will have a rare variant in one of these genes, most of which would be classified as variants of uncertain significance (VoUS). Towards screening these VoUS for partial LoF alleles that may contribute to disease, here we report functional assays in Drosophila to interrogate EED missense variants. We mimicked the amino acid change(s) of EED variants into its Drosophila ortholog, esc, and tested their function. Known likely benign variants functioned wildtype and known pathogenic variants were LoF. We further demonstrate the utility of this calibrated assay as a scalable approach to assist clinical interpretation of human EED VoUS.

genetics↗

bioRxiv2024

NPAS4 is an allostatic regulator of POMC neuronal activity during diet-induced obesity

RationaleObesity is characterized by a chronic positive energy balance and altered function of cell types that regulate food intake. These cell types include proopiomelanocortin (POMC) neurons in the arcuate nucleus (ARC) of the hypothalamus that detect peripheral signals and promote a reduction in food intake upon activation. Downstream of neuronal activation, activity- regulated genes such as Neuronal PAS domain protein 4 (Npas4) are induced as part of the response to environmental stimuli. Npas4 is known to have cytoprotective roles in both neurons and pancreatic beta cells. A previous Npas4 knockout study in both mouse pancreatic beta cells and ARC neurons implied a potential role of Npas4 in regulating food intake. However, the specific sites of Npas4 action in the ARC are unknown. We hypothesized that Npas4 in POMC neurons of the ARC has a role in regulating food intake during obesity. MethodsWe quantified Npas4 expression in POMC neurons of the arcuate nucleus in mice exposed to various positive energy states known to activate POMC neurons using RNAscope fluorescent in situ hybridization. Next, we generated adult male mice with a conditional Npas4 knockout specifically in their ARC POMC neurons (POMC-NPAS4 KO) and metabolically characterized them for 30 weeks on regular chow or 60% high-fat diet (HFD) at room temperature. In addition, we performed single cell RNA sequencing (scRNA-seq) on microdissected ARC tissue and neighbouring regions from fasted or 1hr refed POMC-NPAS4 KO mice and controls at 6 weeks of HFD, in order to identify Npas4-regulated and feeding- regulated transcriptional changes in POMC neurons. ResultsNpas4 was expressed in POMC neurons, and its expression was induced in response to positive energy states such as refeeding, oral glucose, and acute HFD feeding. HFD-fed POMC- NPAS4 KO males showed significantly reduced body weight starting at 10 weeks of HFD, and weighed 8-10 grams less than controls by 30 weeks. With metabolic cages and manual food intake measurements, we determined this difference was not the result of increased energy expenditure or physical activity, but was due to decreased food intake prior to the observed lack of gain in body weight. Using the ARC single-cell dataset, we found that POMC neurons of KO mice showed an enhanced refeeding-induced transcriptional response, dysregulated immediate early gene expression in response to refeeding, and reduced expression of genes encoding GABA-A receptor subunits. Furthermore, cell-to-cell communication analysis revealed that POMC neurons of KO mice specifically lost inhibitory GABAergic signaling inputs, some of which came from agouti-related protein (AgRP) neurons, and gained excitatory glutamatergic signaling inputs compared to POMC neurons of control littermates. ConclusionsTaken together, the results suggest that activity-dependent expression of Npas4 in POMC neurons tempers the activity of these cells upon overnutrition. Loss of Npas4 causes cell- autonomous loss of the capacity to sense nutrient intake. Molecularly, this is driven by reduced expression of inhibitory GABA-A receptors and an overall increase in POMC neuronal activity, leading to decreased food intake and decreased weight gain. In conclusion, for the first time we report a role for the transcription factor Npas4 in POMC neurons of the ARC, and demonstrate it plays an indispensable role in controlling feeding behavior in states of overnutrition.

physiology↗

bioRxiv2022

GTF2I dosage regulates neuronal differentiation and social behavior in 7q11.23 neurodevelopmental disorders

Copy number variations at 7q11.23 cause neurodevelopmental disorders with shared and opposite manifestations. Deletion causes Williams-Beuren syndrome (WBS), while duplication causes 7q11.23 microduplication syndrome (7Dup). Converging evidence indicates GTF2I, from the 7q11.23 locus, is a key mediator of the cognitive-behavioral phenotypes associated with WBS and 7Dup. Here we integrate molecular profiling of patient-derived cortical organoids (COs) and transgenic mouse models to dissect 7q11.23 disease mechanisms. Proteomic and transcriptomic profiling of COs revealed opposite dynamics of neural progenitor proliferation and transcriptional imbalances, leading to precocious excitatory neuron production in 7Dup. The accelerated excitatory neuron production in 7Dup COs could be rescued by GTF2I knockdown. Transgenic mice with Gtf2i duplication recapitulated early neuronal differentiation defects and ASD-like behaviors. Remarkably, inhibition of LSD1, a downstream effector of GTF2I, was sufficient to rescue ASD-like phenotypes. We propose that the GTF2I-LSD1 axis constitutes a molecular pathway amenable to therapeutic intervention.

neuroscience↗

bioRxiv2020

ACE 2 Coding Variants: A Potential X-linked Risk Factor for COVID-19 Disease

Viral genetic variants are widely known to influence disease progression among infected humans. Given the recent and rapid emergence of pandemic SARS-CoV-2 infection, the cause of COVID-19 disease, viral protein variants have attracted research interest. However, little has yet been written about genetic risk factors among human hosts. Human genetic variation has proven to affect disease progression and outcome for important diseases such as HIV infection and malaria infestation. The fact that the human ACE2 protein is encoded on the X chromosome means that males who carry rare ACE2 coding variants will express those variants in all ACE2-expressing cells, whereas females will typically express those variants in a mosaic distribution determined by early X-inactivation events. This sex-based difference in ACE2 expression has unique implications for epidemiological studies designed to assess host genetic factors influencing progression from asymptomatic SARS-coV-2 infection to COVID-19. Here we present theoretical modelling of rare ACE2 coding variants documented to occur naturally in several human superpopulations and subpopulations, and show that rare variants predicted to affect the binding of ACE2 to the SARS-CoV-2 spike protein exist in people. Though the rs4646116 (p.Lys26Arg) allele is found in 1 in 70 Ashkenazi Jewish males, and in 1 in 172 non-Finnish European males, this allele is found at higher frequencies in females. Furthermore, the class of missense ACE2 alleles predicted to affect SARS-CoV-2 binding are found in aggregate among 1.43% and 2.16% of Ashkenazi males and females, respectively, as well as in 0.58% and 1.24% of European males and females outside of Finland. These alleles are rarer in other population groups, and almost absent from East Asians genotyped to date. Though we are aware that full genome-wide and exome-wide sequencing studies may ultimately be required to assess human genetic susceptibility to SARS-CoV-2 fully, we argue on the basis of strong prior probabilities that genotyping of this class of alleles is justified in cases of atypical SARS-CoV-2 diseases, such as asymptomatic super-spreaders (if any are identified), and in neonatal/paediatric-onset COVID-19 disease. Even relatively rare susceptibility factors (1% or fewer carriers) may become quantitatively important in the context of hundreds of thousands of infections. A small number of asymptomatic carriers, or a small number of super-spreaders, or a small segment of the population that is disproportionately likely to require intensive care, can magnify the medical, social and economic impacts of a pandemic of this size. The speed of the pandemic and the large number of affected cases worldwide justify efforts to identify all possible risk factors for adverse outcomes, including efforts to identify genetic susceptibility factors in human hosts.

bioinformatics↗