Biology subjects

Christian, S.

Publications and source records attributed to Christian, S..

5 recordsLinked to original sources

bioRxiv2025

Cell-type-specific dysregulated gene expression in the frontal cortex of an Angelman syndrome pig model

Angelman syndrome is a neurodevelopmental disorder caused by the loss of the maternal allele of the ubiquitin-protein ligase E3A (UBE3A) gene. UBE3A is imprinted with maternal-allelic expression in neurons of the central nervous system (CNS) and biallelic expression in other cell types. Consequently, in Angelman syndrome, UBE3A is substantially reduced in CNS neurons and reduced by half in other cells. It is unclear how cell-type-specific gene expression in the brain is dysregulated in Angelman syndrome, as previous studies have lacked cell type resolution. Using single nuclei RNA-sequencing, we show that gene expression is dysregulated in neuronal subtypes in the frontal cortex of neonatal pigs with a UBE3A maternal deletion. A total of 3,812 unique genes were dysregulated across ten cell type clusters, with most of the dysregulated genes (3,154 genes) in excitatory neurons. Pathway analysis revealed alterations in oxidative phosphorylation, proteasome function, and synaptic function. Additionally, somatostatin (SST) -- a secreted neuropeptide involved in GABAergic inhibition and synaptic plasticity-- was reduced in inhibitory neurons in the cortex and hypothalamus, which correlated with lower circulating SST protein in neonates but not adolescent pigs. Overall, these findings provide greater clarity on the cell-type-specific dysregulation of gene expression and cellular pathways caused by the loss of UBE3A in CNS neurons, expanding our understanding of the molecular pathology in Angelman syndrome.

genetics↗

bioRxiv2025

Antisense Oligonucleotide Quantification via Splint-Ligation PCR Assay in Non-Human Primate Central Nervous System Tissues and Biofluids

Antisense oligonucleotides (ASOs) are chemically modified single-stranded oligonucleotides used to modulate the expression or processing of a target RNA transcript. The development of ASOs to treat human disease requires extensive preclinical studies in animal models. A critical component of these studies is determining the concentration of the ASO in tissues and biofluids, which are used to estimate the distribution, half-life, and dose-response relationship. The methods used to quantify ASOs are often constrained by low sensitivities, poor dynamic ranges, and the use of highly specialized equipment. Here, we describe the development of a Splint-Ligation-based quantitative PCR assay to measure the concentration of ASOs in nonhuman primate tissues and biofluids. Our results show that the Splint-Ligation Assay is highly sensitive and has a broad dynamic range in nonhuman primate central nervous system tissues and biofluids, ranging from picomolar to micromolar concentrations. Overall, our results show that the Splint-Ligation PCR Assay is a reliable, sensitive, and feasible method of ASO quantification.

pharmacology and toxicology↗

bioRxiv2022

Unique features of the gut microbiome characterized in animal models of Angelman Syndrome

A large subset of patients with Angelman syndrome (AS) suffer from concurrent gastrointestinal (GI) issues, including constipation, poor feeding, and reflux. AS is caused by the loss of ubiquitin ligase E3A (UBE3A) gene expression in the brain. Clinical features of AS, which include developmental delays, intellectual disability, microcephaly, and seizures, are primarily due to the deficient expression or function of the maternally inherited UBE3A allele. The association between neurodevelopmental delay and GI disorders is part of the increasing evidence suggesting a link between the brain and the gut microbiome via the microbiota-gut-brain (MGB) axis. To investigate the associations between colonization of the gut microbiota in AS, we characterized the fecal microbiome in three animal models of AS containing maternal deletions of Ube3A, including mouse, rat, and pig, using 16S ribosomal RNA amplicon sequencing. Overall changes in the microbial composition of all three animal models of AS in both the phylum and genus levels of bacterial abundance were identified. Specific bacterial groups were significantly increased across all animal models, including: Lachnospiraceae Incertae sedis, Desulfovibrios sp., and Odoribacter, which have been correlated with neuropsychiatric disorders. Taken together, these findings suggest that specific changes to the local environment in the gut are driven by a Ube3a maternal deletion, unaffected by varying housing conditions and are prominent and detectable across multiple small and large model species. These findings may begin to uncover the underlying mechanistic causes of GI disorders in AS patients and provide future therapeutic options for AS patients. IMPORTANCEAngelman syndrome (AS) associated gastrointestinal (GI) symptoms significantly impact quality of life in patients. Using AS models in mouse, rat, and pig, AS animals showed impaired colonization of the gut microbiota compared to wild type (healthy) control animals. Unique changes in AS microbiomes across all three animal models may be important in causing GI symptoms and may help to identify ways to treat these comorbidities in patients in the future.

microbiology↗

bioRxiv2021

Development of an ASO therapy for Angelman syndrome by targeting an evolutionarily conserved region at the start of the UBE3A-AS transcript

Angelman syndrome is a devastating neurogenetic disorder for which there is currently no effective treatment. It is caused by mutations or epimutations affecting the expression or function of the maternally inherited allele of the ubiquitin-protein ligase E3A (UBE3A) gene. The paternal UBE3A allele is imprinted in neurons of the central nervous system (CNS) by the UBE3A antisense (UBE3A-AS) transcript, which represents the distal end of the SNHG14 transcription unit. Reactivating the expression of the paternal UBE3A allele in the CNS has long been pursued as a therapeutic option for Angelman syndrome. Here, we designed and optimized antisense oligonucleotides (ASO) targeting an evolutionarily conserved region demarcating the start of the human UBE3A-AS transcript and show that ASOs targeting this region can reverse imprinting of UBE3A in cultured Angelman syndrome neurons and throughout the CNS of a non-human primate model. Findings from this study advanced the first investigational molecular therapy for Angelman syndrome into clinical development (ClinicalTrials.gov, NCT04259281). SUMMARYHere, we describe the preclinical studies supporting the first investigational molecular therapy for Angelman syndrome to advance into clinical development (ClinicalTrials.gov, NCT04259281).

genetics↗

bioRxiv2018

Targeting a Therapy-Resistant Cancer Cell State Using Masked Electrophiles as GPX4 Inhibitors

We recently discovered that inhibition of the lipid peroxidase GPX4 can selectively kill cancer cells in a therapy-resistant state through induction of ferroptosis. Although GPX4 lacks a conventional druggable pocket, covalent small-molecule inhibitors are able to overcome this challenge by reacting with the GPX4 catalytic selenocysteine residue to eliminate enzymatic activity. Unfortunately, all currently-reported GPX4 inhibitors achieve their activity through reactive chloroacetamide groups. We demonstrate that such chloroacetamide-containing compounds are poor starting points for further advancement given their promiscuity, instability, and low bioavailability. Development of improved GPX4 inhibitors, including those with therapeutic potential, requires the identification of new electrophilic chemotypes and mechanisms of action that do not suffer these shortcomings. Here, we report our discovery that nitrile oxide electrophiles, and a set of remarkable chemical transformations that generates them in cells from masked precursors, provide an effective strategy for selective targeting of GPX4. Our results, which include structural insights, target engagement assays, and diverse GPX4-inhibitor tool compounds, provide critical insights that may galvanize development of improved compounds that illuminate the basic biology of GPX4 and therapeutic potential of ferroptosis induction. In addition, our discovery that nitrile oxide electrophiles engage in highly selective cellular interactions and are bioavailable in their masked forms may be relevant for targeting other currently undruggable proteins, such as those revealed by recent proteome-wide ligandability studies.

biochemistry↗