Biology subjects

Lefebvre, L.

Publications and source records attributed to Lefebvre, L..

5 recordsLinked to original sources

bioRxiv2026

Genomic imprinting of the metabolic regulator gene Klf14 is regulated by a paternal sub-TAD anchored at Mest and a shared enhancer in mice.

KLF14 acts as a master regulator of gene expression in adipose tissue and variants at the human KLF14 gene show strong and reproducible association with type 2 diabetes and metabolic syndrome. Risk alleles are only pathologic when maternally inherited, consistent with the observation that KLF14/Klf14 is a maternally-expressed imprinted gene in human and mouse. However, how genomic imprinting is regulated at this important locus is currently unknown. In both species, KLF14/Klf14 is located [~]200 kb away from the paternally imprinted gene MEST/Mest, which is regulated by a maternal gametic differentially methylated region (gDMR) at its CpG island (CGI) promoter. Although the Klf14 CGI is kept unmethylated in most tissues, maternally-inherited DNA methylation (DNAme) marks are paradoxically required for Klf14 expression in mouse. Here, we show that Mest and Klf14 reside within the same topologically associating domain (TAD) in both mouse embryonic stem cells (ESCs) and differentiated cells, defined by sites of biallelic CTCF binding at the boundaries. Using allele-specific 4C-seq in F1 hybrid ESCs, we show that CTCF binding specifically to the unmethylated Mest gDMR generates a paternal allele-specific sub-TAD encompassing Klf14. We further show through CRISPR-Cas9-mediated mutagenesis, that deletions of the paternal Mest promoter region in ESCs as well as in vivo in mutant mice, results in both loss of Mest expression and acquisition of biallelic expression at Klf14. By analyzing epigenetic marks and chromatin looping in the Klf14-expressing pituitary cell line AtT-20, we identify a putative enhancer element shared by Mest and Klf14, providing a mechanistic model for the regulation of Klf14 imprinting. This work defines a new role for the Mest maternally methylated gDMR, revealing that it exerts long-range effects via allele-specific modulation of TAD structures and consequently act as an imprinting control region (ICR) in the regulation of Klf14 imprinting. Conservation of this TAD organisation at the human locus suggests that a similar regulatory mechanism operates at KLF14.

developmental biology↗

bioRxiv2026

The elongation of Mest transcript into MestXL sustains, but does not initiate, the maternal allele bias of its convergent gene Copg2 during neurogenesis

Precise gene dosage control is critical for establishing cellular identity and development, especially for imprinted genes, where dosage imbalances are linked to severe pathologies such as neurodevelopmental disorders. The Mest/Copg2 imprinted locus is a paradigm for this fine-tuned regulation. While Mest is constitutively expressed from the paternal allele, Copg2 expression shifts from biallelic to a maternal allele bias specifically during neural differentiation, a transition proposed to involve transcriptional interference mediated by the long Mest isoform, MestXL, which extends into the Copg2 locus. However, the mechanisms underlying this allelic switch, and whether factors beyond MestXL contribute, are elusive. To address this, we employed a stem cell-based brain organoid model, integrating multi-omic analyses, 3D chromatin structure mapping, and functional approaches to dissect the regulatory events governing the induction and maintenance of Copg2 maternal allele bias throughout neural lineage specification. Our findings challenge the prevailing model by demonstrating that the maternal allele bias of Copg2 during neural differentiation is not solely driven by MestXL-mediated transcriptional interference. Instead, our data support a temporal and neural stage-specific two-step mechanism: putative enhancer-driven activation of the maternal allele in neural progenitor cells is followed by MestXL-dependent repression of the paternal allele in neuron-enriched stages. This uncovers an unexpected layer of complexity in the regulation of imprinted gene dosage during brain development, with profound implications for understanding the molecular underpinnings of neurodevelopmental disorders.

molecular biology↗

bioRxiv2025

Visual input drives diverse ER calcium signals in neurons in vivo

The endoplasmic reticulum (ER) has long been thought to shape calcium signals in neurons, but stimulus-driven ER calcium fluctuations have not been directly measured in vivo. To measure neuronal ER calcium signals in vivo, we paired visual stimulus presentation with two photon imaging of ER and cytosolic calcium reporters in four different cell types in the Drosophila visual system. We found that visual input elicits diverse ER calcium signals, with the ER acting as a calcium sink or source depending on the cell type, subcellular compartment (dendrite versus axon), and type of visual stimulus. ER calcium signals were not simply a reflection of cytosolic signals, indicating that the ER, rather than acting as a passive calcium buffer, actively processes calcium signals in neurons in a context-specific fashion. Thus, ER-based signal processing may contribute to functional diversity across neuronal cell types, thereby enhancing the computational capacity of neural circuits.

neuroscience↗

bioRxiv2022

Parent-of-origin detection and chromosome-scale haplotyping using long-read DNA methylation sequencing and Strand-seq

Hundreds of loci in human genomes have alleles that are methylated differentially according to their parent of origin. These imprinted loci generally show little variation across tissues, individuals, and populations. We show that such loci can be used to distinguish the maternal and paternal homologs for all autosomes, without the need for the parental DNA. We integrate methylation-detecting nanopore sequencing with the long-range phase information in Strand-seq data to determine the parent of origin of chromosome-length haplotypes for both DNA sequence and DNA methylation in five trios with diverse genetic backgrounds. The parent of origin was correctly inferred for all autosomes with an average mismatch error rate of 0.31% for SNVs and 1.89% for indels. Because our method can determine whether an inherited disease allele originated from the mother or the father, we predict that it will improve the diagnosis and management of many genetic diseases.

genomics↗

bioRxiv2019

Evolution of imprinting via lineage-specific insertion of retroviral promoters

Imprinted genes are expressed from a single parental allele. In mammals, this unusual mode of transcription generally depends on the epigenetic silencing of one allele by DNA methylation (DNAme) established in the germline. While many species-specific imprinted orthologues have been documented in eutherians, the molecular mechanisms underlying the evolutionary switch from biallelic to imprinted expression are currently unknown. During mouse oogenesis, gametic differentially methylated regions (gDMRs) acquire DNAme in a process guided by transcription. Here we show that transcription initiating in proximal lineage-specific endogenous retroviruses (ERVs) is likely responsible for DNAme established in oocytes at 4/6 mouse-specific and 17/110 human-specific maternal imprinted gDMRs (igDMRs). The latter can be further divided into Catarrhini (Old World monkeys and apes)- or Hominoidea (ape)-specific igDMRs, which are embedded within transcription units initiating in ERVs specific to these primate lineages. Using CRISPR-Cas9 mutagenesis, we deleted the relevant murine-specific ERVs upstream of the maternally methylated genes Impact and Slc38a4. Strikingly, imprinting at these genes was lost in the offspring of females harboring these deletions and biallelic expression was observed. Our work reveals a novel evolutionary mechanism whereby maternally silenced genes arise from biallelically expressed progenitors.

genetics↗