Biology subjects

Ferguson-Smith, A. C.

Publications and source records attributed to Ferguson-Smith, A. C..

14 recordsLinked to original sources

bioRxiv2026

IAP retrotransposons contribute to the transcriptional diversity of the murine placenta

Transposable elements (TEs) have made important contributions to the evolution of the placenta, and are argued to have played a role in the wide inter-species diversification of this critical developmental organ. Co-option of TEs by host genomes has led to the genesis of important placental genes, as well as trophoblast-specific gene regulatory elements. But whilst multiple TE subfamilies have been shown to act as transcriptional enhancers in early mouse trophoblast development, it remains unclear to what extent TEs regulate placental gene expression after the establishment of a functional fetal-maternal interface. Here, we characterised the TE regulatory and transcriptional landscape in mouse placenta and gauged their evolutionary dynamics through a comparative approach. We found that overall, the gene regulatory potential of TEs is greatly diminished in differentiated mouse trophoblast when compared to their stem cell counterpart. However, evolutionarily young intracisternal A particle (IAP) elements are highly expressed in the placenta and create several alternative, placenta-specific transcriptional start sites for protein-coding genes. IAP elements that are active in the placenta drive species-specific expression of associated genes and display wide genetic diversity between mouse strains. These putative co-option events are therefore evolutionarily recent and may represent a prime example of how TE activity can drive fast placental evolution.

genetics↗

bioRxiv2026

Regulatory Mechanisms of Maternal Imprinting at the Dlk1-Dio3 Domain

Genomic imprinting is an epigenetic process causing parent-of-origin specific gene expression. The Dlk1-Dio3 domain is one of the largest imprinted clusters. While DNA methylation at an intergenic CpG-island (IG-CGI) within the imprinting control region (ICR) controls expression from the paternal chromosome, mechanisms regulating the unmethylated maternal chromosome remain unknown. Within the transcriptional regulatory element (IG-TRE) of the ICR, deletions identified a minimal region in vitro exhibiting both silencing and enhancing activity, with SOX2 and ZFP281 contributing to enhancer function on the maternal chromosome. In vivo, however, this deletion did not affect maternal expression in embryos; instead it activated Dlk1 on both parental chromosomes. Combining deletion of this IG-TRE with the lethal IG-CGI deletion rescued lethality by balancing Dlk1 expression, despite persistent maternal gene upregulation. These results demonstrate that loss of expression at this domain is more detrimental than gain highlighting the importance of in vivo analysis. Identification of active regulatory factors on the unmethylated maternal chromosome challenges the prevailing view that imprinting is primarily a methylation-driven phenomenon, further revealing the sophisticated hierarchical mechanisms governing imprinting control.

genetics↗

bioRxiv2025

Young KRAB-zinc finger gene clusters are highly dynamic incubators of ERV-driven genetic heterogeneity in mice

KRAB-zinc finger proteins (KZFPs) comprise the largest family of mammalian transcription factors, rapidly evolving within and between species. Most KZFPs repress endogenous retroviruses (ERVs) and other retrotransposons, with KZFP gene numbers correlating with the ERV load across species, suggesting coevolution. How new KZFPs emerge in response to ERV invasions is currently unknown. Using a combination of long-read sequencing technologies and genome assembly, we present a first detailed comparative analysis of young KZFP gene clusters in the mouse lineage, which has undergone recent KZFP gene expansion and ERV infiltration. Detailed annotation of KZFP genes in a cluster on Mus musculus Chromosome 4 revealed parallel expansion and diversification of this locus in different mouse strains (C57BL/6J, 129S1/SvImJ and CAST/EiJ) and species (Mus spretus and Mus pahari). Our data supports a model by which new ERV integrations within young KZFP gene clusters likely promoted recombination events leading to the emergence of new KZFPs that repress them. At the same time, ERVs also increased their numbers by duplication instead of retrotransposition alone, unraveling a new mechanism for ERV enrichment at these loci.

genetics↗

bioRxiv2024

Dynamic allelic expression in mouse mammary gland across the adult developmental cycle

The mammary gland, which primarily develops postnatally, undergoes significant changes during pregnancy and lactation to facilitate milk production. Through the generation and analysis of 480 transcriptomes, we provide the most detailed allelic expression map of the mammary gland, cataloguing cell-type-specific expression from ex-vivo purified cell populations over 10 developmental stages, enabling comparative analysis. The work identifies genes involved in the mammary gland cycle, parental-origin-specific and genetic background-specific expression at cellular and temporal resolution, genes associated with human lactation disorders and breast cancer. Genomic imprinting, a mechanism regulating gene expression based on parental origin, is crucial for controlling gene dosage and stem cell potential throughout development. The analysis identified 25 imprinted genes monoallelically expressed in the mammary gland, with several showing allele-specific expression in distinct cell types. No novel imprinted genes were identified and the absence of biallelically expressed imprinted genes suggests that, unlike in brain, selective absence of imprinting does not regulate gene dosage in the mammary gland. This research highlights transcriptional dynamics within mammary gland cells and identifies novel candidate genes potentially significant in the tissue during gestation and lactation. Overall, this comprehensive atlas represents a valuable resource for future studies on expression and transcriptional dynamics in mammary cells.

developmental biology↗

bioRxiv2023

ZFP57 is a regulator of postnatal growth and life-long health

Early-life factors, including nutrition, shape long-term health outcomes. Despite the essential role of lactation in maternal nutritional support, the influence of epigenetic factors on lactation and postnatal growth remains poorly understood. Zinc-finger protein 57 (ZFP57), is an epigenetic regulator of genomic imprinting, a process that directs gene expression based on parental origin, playing a vital role in mammalian prenatal growth. Here, we identify a novel function of ZFP57 in regulating the mammary gland, where it serves as a key modulator of postnatal resource control, independently of imprinted genes. ZFP57 influences multiple aspects of mammary gland function, including ductal branching and cellular homeostasis. Its absence leads to significant differential gene expression, related to alveologenesis, lactogenesis and milk synthesis, associated with delayed lactation and altered milk composition. This results in life-long impacts on offspring including the development of metabolic syndrome. Cross-fostering reveals intricate dynamics between mother and offspring during lactation. Pups raised by a dam of a different genotype than their birth mother exhibit exacerbated metabolic features in adulthood, providing additional insight into the programming of offspring long-term health by maternal context. This study deepens our understanding of the interplay between epigenetic factors, lactation, and postnatal resource control and identifies ZFP57 as a major regulator of both pre and postnatal resource control in mammals.

developmental biology↗

bioRxiv2023

Post-translational regulation of the Numb/Notch pathway in neurogenesis and cancer by Dlk2

Perturbations in fundamental developmental pathways have a profound influence on tumorigenesis. Numb plays a pivotal role in vertebrate development, including neurogenesis and is a key negative regulator of Notch signaling1, 2. Perturbation of Numb expression affects brain morphology and cell fate3. While extensive research has been conducted on canonical Notch ligands, regulation by vertebrate-specific non-canonical ligands is not understood. Here we identify Delta like non-canonical Notch ligand 2/EGFL9 (Dlk2) as a regulator of zebrafish neurogenesis with mutants exhibiting early increase and subsequent depletion of neural stem cells, decreased radial glial cells density, impaired neuronal cell distribution, and hypersensitivity to stimuli mimicking the embryonic murine Numb/Numblike null phenotype3. Numb function is inactivated by aberrant phosphorylation4, and we show that Dlk2 protein exhibits a high affinity direct interaction with Numb, with loss of Dlk2 in zebrafish telencephalon increasing Numb Ser276 phosphorylation with a concomitant increase in Notch signaling. Patients with tumors exhibiting reduced levels of Dlk2 have a poorer prognosis, while overexpression of Dlk2 in human cancer cell lines reduces cell proliferation. Our findings identify Dlk2 as a key partner of Numb, a gatekeeper of its activity, and an important player in a network of protein interactions regulating both neurogenesis and cancer with potential therapeutic implications.

cell biology↗

bioRxiv2023

A co-ordinated transcriptional programme in the maternal liver supplies LC-PUFAs to the conceptus using phospholipids

Essential fatty acids (EFAs) and their derivatives, the long and very long chain polyunsaturated fatty acids (LC-PUFAs), are preferentially transported by the mother to the fetus. Failure to supply EFAs is strongly linked with stillbirth, fetal growth restriction, and impaired neurodevelopmental outcomes. However, dietary supplementation during pregnancy is unable to simply reverse these outcomes, suggesting imperfectly understood interactions between dietary EFA intake and the molecular mechanisms of maternal supply. Here we combine untargeted lipidomics with transcriptional profiling of healthy and genetically-manipulated murine models to understand the maternal adaptations required to provide LC-PUFAs to the developing fetus. We discovered a late pregnancy-specific, selective activation of the Liver X Receptor signalling pathway which dramatically increases maternal supply of LC-PUFAs within circulating phospholipids. Crucially, genetic ablation of this pathway in the mother reduced LC-PUFA accumulation by the fetus. Overall our work suggests new molecular strategies for improving maternal-fetal transfer of these important lipids.

physiology↗

bioRxiv2023

Mitotic heritability of DNA methylation at intermediately methylated sites is imprecise

DNA methylation is considered a stable epigenetic mark due to its presumed long-term inheritance through cell divisions. Here, we perform high-throughput bisulfite sequencing on clonally derived cell lines to quantitatively measure mitotic methylation inheritance at the nucleotide level. We find that although DNA methylation is generally faithfully maintained at hypo- and hypermethylated sites, this is not the case at intermediately methylated CpGs. Low fidelity intermediate methylation is interspersed throughout the genome and within genes with no or low transcriptional activity. Moreover, we determine that the probabilistic changes that occur at intermediately methylated sites are due to DNMT1 rather than DNMT3A/3B activity. The observed lack of clonal inheritance at intermediately methylated sites challenges the concept of DNA methylation as a consistently stable epigenetic mark.

genetics↗

bioRxiv2022

Weak parent-of-origin expression bias: is this imprinting?

In mouse and human, genes subjected to genomic imprinting have been shown to function in development, behaviour, and post-natal adaptations. Failure to correctly imprint genes in human is associated with developmental syndromes, adaptive and metabolic disorders during life as well as numerous forms of cancer. In recent years researchers have turned to RNA-seq technologies applied to reciprocal hybrid strains of mice to identify novel imprinted genes, causing a 3-fold increase in genes reported as having a parental origin specific expression bias. The functional relevance of parental origin-specific expression bias is not fully appreciated especially since many are reported with only minimal parental bias (e.g. 51:49). Here we present an in-depth meta-analysis of previously generated RNA-seq data and show that the methods used to generate and analyse libraries greatly influence the calling of allele-specific expression. Validation experiments show that most novel genes called with parental-origin specific allelic bias are artefactual, with the mouse strain contributing a larger effect on expression biases than parental origin. Of the weak novel genes that do validate, most are located at the periphery of known imprinted domains, suggesting they may be affected by local allele- and tissue-specific conformation. Together these findings highlight the need for robust tools, definitions, and validation of putative imprinted genes to provide meaningful information within imprinting databases and to understand the functional and mechanistic implications of the process.

genomics↗

bioRxiv2021

Subnuclear localisation is associated with gene activation not repression or parental origin at the imprinted Dlk1-Dio3 locus

At interphase, de-condensed chromosomes have a non-random three-dimensional architecture within the nucleus, however, little is known about the extent to which nuclear organisation might influence expression or vice versa. Here, using imprinting as a model, we use 3D RNA- and DNA-fluorescence-in-situ-hybridisation in normal and mutant mouse embryonic stem cells to assess the relationship between imprinting control, gene expression and allelic distance from the nuclear periphery. We compared the two parentally inherited imprinted domains at the Dlk1-Dio3 domain and find a small but reproducible trend for the maternally inherited domain to be further away from the periphery if the maternally expressed gene Gtl2/Meg3 is active compared to when it is silenced. Using Zfp57KO ES cells, which harbour a paternal to maternal epigenotype switch, we observe active alleles significantly further away from the nuclear periphery with the distance from the periphery being proportional to the number of alleles active within the cell. This distribution of alleles suggests an activating effect of the nuclear interior rather than a repressive association with the nuclear periphery. Although we see a trend for the paternally inherited copy of the locus to be closer to the nuclear periphery, this appears to be linked to stochastic gene expression differences rather than parental origin. Our results suggest that transcriptional activity, rather than transcriptional repression or parental origin, defines sub-nuclear localisation at an endogenous imprinted domain. Author summaryGenomic imprinting is an epigenetically regulated process that results in the preferential expression of a subset of developmentally regulated genes from maternally or paternally inherited chromosomes. We have used imprinted genes as a model system to investigate the relationship between the localisation of genes within the cell nucleus and their active expression while at the same time distinguishing gene repression by genomic imprinting, and gene repression by other mechanisms that act on the active allele. We find that there is a significant correlation between transcription and distance to the edge of the nucleus for the Gtl2/Meg3 gene in the imprinted Dlk1-Dio3 region. However, this correlation has a very small effect size and the nuclear envelope, which is commonly thought to act as a repressive environment for gene expression, does not appear to play a major role. We show that position effects, which have been shown for artificially lamina-targeted genes, also exist for endogenous loci and consider the possible biological relevance of the observed small effect.

molecular biology↗

bioRxiv2020

A spontaneous genetically-induced epiallele at a retrotransposon shapes host genome function

Intracisternal A-particles (IAPs) are endogenous retroviruses (ERVs) responsible for most insertional mutations in the mouse. Full-length IAPs harbour genes flanked by long terminal repeats (LTRs). Here, we identify a solo LTR IAP variant (C57iap1solo) recently formed in the inbred C57BL/6J mouse strain. In contrast to the C57BL/6J full-length IAP at this locus (C57iap1full), C57iap1solo lacks DNA methylation and H3K9 trimethylation. The distinct DNA methylation levels between the two alleles are established during preimplantation development, likely due to loss of KRAB zinc finger protein binding at the C57iap1solo variant. C57iap1solo methylation increases and becomes more variable in a hybrid genetic background yet is unresponsive to maternal dietary methyl supplementation. Differential epigenetic modification of the two variants is associated with metabolic differences and tissue-specific changes in adjacent gene expression. Our characterisation of C57iap1 as a genetically-induced epiallele with functional consequences establishes a new model to study transposable element repression and host-element co-evolution.

genetics↗

bioRxiv2020

Genomic properties of variably methylated retrotransposons in mouse

Transposable elements (TEs) are enriched in cytosine methylation, preventing their mobility within the genome. We previously identified a genome-wide repertoire of candidate intracisternal A particle (IAP) TEs in mice that exhibit inter-individual variability in this methylation (VM-IAPs) with implications for genome function. Here we validate these metastable epialleles and discover a novel class that exhibit tissue specificity (tsVM-IAPs) in addition to those with uniform methylation in all tissues (constitutive- or cVM-IAPs); both types have the potential to regulate genes in cis. Screening for variable methylation at other TEs shows that this phenomenon is largely limited to IAPs, which are amongst the youngest and most active endogenous retroviruses. We identify sequences enriched within cVM-IAPs, but determine that these are not sufficient to confer epigenetic variability. CTCF is enriched at VM-IAPs with binding inversely correlated with DNA methylation. We uncover dynamic physical interactions between cVM-IAPs with low methylation ranges and other genomic loci, suggesting that VM-IAPs have the potential for long-range regulation. Our findings indicate that a recently evolved interplay between genetic sequence, CTCF binding, and DNA methylation at young TEs can result in inter-individual variability in transcriptional outcomes with implications for phenotypic variation.

genetics↗

bioRxiv2020

Disruption of folate metabolism causes germline epigenetic instability and distinguishes HIRA as a biomarker of maternal transgenerational epigenetic inheritance

The mechanism behind transgenerational epigenetic inheritance (TEI) is unclear, particularly through the maternal grandparental line. We previously showed that disruption of folate metabolism in mice by the Mtrrgt hypomorphic mutation results in TEI of congenital malformations. Either maternal grandparent can initiate this phenomenon, which persists for at least four wildtype generations. In this work, we use a genome-wide approach to reveal genetic stability in the Mtrrgt model and epigenome-wide differential DNA methylation in the germline of Mtrr+/gt maternal grandfathers. While epigenetic reprogramming occurs, wildtype grandprogeny and great grandprogeny exhibit transcriptional memory of germline methylation defects. One region encompasses the Hira gene, which is misexpressed in embryos at least until the F3 generation in a manner that distinguishes Hira transcript expression as a biomarker of maternal phenotypic inheritance.

genomics↗

bioRxiv2019

Obstacles to Studying Alternative Splicing Using scRNA-seq

BackgroundEarly single-cell RNA-seq (scRNA-seq) studies suggested that it was unusual to see more than one isoform being produced from a gene in a single cell, even when multiple isoforms were detected in matched bulk RNA-seq samples. However, these studies generally did not consider the impact of dropouts or isoform quantification errors, potentially confounding the results of these analyses.\n\nResultsIn this study, we take a simulation based approach in which we explicitly account for dropouts and isoform quantification errors. We use our simulations to ask to what extent it is possible to study alternative splicing using scRNA-seq. Additionally, we ask what limitations must be overcome to make splicing analysis feasible. We find that the high rate of dropouts associated with scRNA-seq is a major obstacle to studying alternative splicing. In mice and other well established model organisms, the relatively low rate of isoform quantification errors poses a lesser obstacle to splicing analysis. We find that different models of isoform choice meaningfully change our simulation results.\n\nConclusionsTo accurately study alternative splicing with single-cell RNA-seq, a better understanding of isoform choice and the errors associated with scRNA-seq is required. An increase in the capture efficiency of scRNA-seq would also be beneficial. Until some or all of the above are achieved, we do not recommend attempting to resolve isoforms in individual cells using scRNA-seq.

bioinformatics↗