Jean-François Deleuze

Understanding the fine-scale genetic structure of human populations is essential for both demographical history and genomic medicine. The POPGEN project was initiated as part of the France Genomic Medicine Initiative to construct a whole-genome reference panel representative of the ancestral genetic diversity that existed across metropolitan France at the beginning of the 20th century. Building on previous studies that reported significant fine-scale population structure within France, POPGEN aimed to improve geographic coverage and generate regional allele frequency data to support medical and population genetics applications. We recruited 15,000 participants from the largest French population-based cohort, CONSTANCES, based on the birthplace proximity of their four grandparents and sent saliva kits at their homes. The high return rate (68.3%) demonstrates feasibility of large-scale self-sampling in the general population. Genotyping data from the 9,772 samples that could be processed confirm the presence of widespread fine-scale structure across France, and extend this finding to previously underrepresented regions. These results highlight the value of recruitment strategies based on grandparents’ origin for capturing subtle genetic structure. The development of sampling strategies that best capture genetic diversity at the finest scales will indeed be essential to characterize population structure across Europe and to enable more accurate analyses in medical genetics, especially when addressing rare variant interpretation and fine-scale ancestry adjustment for association tests and polygenic scores calibration. The thorough description of our recruitment strategy would provide useful insights for other initiatives like the Genome of Europe (GoE) project, which aims to generate whole-genome references encompassing European diversity.

Public databases such as gnomAD inform on genetic variants observed in people originating from Europe. However, regional ancestries are not equally represented. In particular, individuals of French origin remain under-represented in international sequencing datasets. To address this gap in the European geo-genetic map and contribute to European initiatives in Genomic Medicine, we sequenced the whole genomes of 856 individuals selected based on the birthplaces of their four grandparents to build a first French-ancestry reference panel. We report here a comprehensive catalog of genetic variants, their geographical distribution across metropolitan France, and their overlap with variants referenced in gnomAD. These data start to fill the French gap in the available European data. They will support international efforts to catalog genomic variation among regional populations and to develop reference genome panels for case-control studies and genotype imputation, a prerequisite for improving our understanding of how genomic variability influences health and disease.

Vector-borne, protist parasites have evolved complex developmental programs to adapt to very distinct host environments. How these important pathogens transition between insect and mammalian stages is only poorly understood. Here, we investigated stage differentiation in Leishmania donovani , a trypanosomatid parasite with constitutive gene transcription, offering a model to study post-transcriptional regulation. Using a five-layer integrative systems analysis (genome to metabolome), we compared hamster-derived amastigotes and culture-derived promastigotes. Genomic adaptation was excluded as a major driver of differentiation, while differential mRNA turnover emerged as a key mechanism of stage-specific gene expression. Transcriptomic and proteomic comparisons revealed a broad dynamic range of protein abundance changes that correlated poorly with mRNA levels. This discrepancy was linked to (i) altered snoRNA expression and rRNA modifications, indicating stage-specific tuning of translation, and (ii) differential protein degradation, supported by proteomics following proteasome inhibition with lactacystin. Lactacystin impaired amastigote-to-promastigote differentiation, highlighting the importance of proteasomal activity. Overall, our analysis links Leishmania development to coordinated post-transcriptional regulatory networks. Our findings provide a powerful new resource for research programs that aim to dissect the emergent properties of regulatory networks and feedback loops underlying Leishmania stage differentiation, serving as a blueprint for other vector-borne pathogens that rely on disease-associated developmental transitions.

The Developmental Origins of Health and Disease (DOHaD) hypothesis proposes that the perinatal environment shapes susceptibility to complex traits across life [1]. The placenta, a transient organ mediating maternal-fetal exchange, plays a central role in this process and has emerged as a key molecular archive in utero [2–4]. Placental DNA methylation (DNAm) is a unique mediator between prenatal exposures, fetal genetics and later-life outcomes [5–9]. DNAm quantitative trait loci (mQTL) have helped disentangling causal mechanisms underlying GWAS loci for complex diseases [10–15]. Despite growing evidence that placental genomic regulation has broad and profound effects on the developmental programming of early– and later-life health outcomes [17], existing placental studies remain limited in scale and largely focused on growth-and neuro-related traits [12–16]. Here, we construct a high-resolution placental mQTL resource and systematically investigate how placental DNAm relates to early– and later-life traits, and to shared vulnerability and complex interactions among them. Teaser: Placental DNA methylation reveals molecular clues to how life before birth shapes health across the lifespan.

Gestational diabetes mellitus (GDM) affects ~14% of pregnancies and increases maternal type 2 diabetes mellitus (T2DM) risk. The GenDiP Consortium presents trans-generational, multi-ancestry genome-wide association study meta-analyses of GDM and pregnancy glycemic traits in up to 38,305 GDM cases and 776,145 controls. We identify 37 GDM-associated loci (7 novel) and five novel loci for pregnancy glycemic traits, all operating through the maternal genome. We classify 12 GDM variants with stronger effects in GDM than T2DM into five biologically informed categories, revealing pleiotropy patterns, pregnancy-dependent effect modification, and diagnostic heterogeneity. While all these loci overlap with T2DM and/or non-pregnant glycaemic traits, four (G6PC2, CAST-PCSK1, HKDC1, FOXA2) lack genome-wide-significant T2DM associations; GCK shows distinct causal variants for GDM, and MTNR1B exhibits pregnancy-amplified effects. Our findings provide new genetic insights into GDM and highlight the need for larger, ancestrally diverse studies of GDM and glycaemic traits during pregnancy to understand potential pregnancy-specific effects.

The genetic architecture of sporadic Early-Onset Alzheimer Disease (sEOAD, onset ≤65 years) remains largely unknown. To assess the de novo mutation (DNM) hypothesis, we performed a nationwide recruitment of 37 novel sEOAD patients-unaffected parents trios. After assessing known monogenic genes, we performed trio-based exome sequencing and jointly analyzed novel trios with 12 previously reported ones. Of these, we selected 16 trios for genome sequencing. We identified three patients with a pathogenic DNM in APP or PSEN1. Then, from the 46 remaining trios, we identified 38 non-synonymous coding DNM and 4 de novo copy number variants (CNVs) in exome data. Four DNM (2 novel, in SPHK2 and DDR1) and bi-allelic inherited variants in two genes affected Alzheimer disease-related genes. No significant burden of rare coding variants in exome/genome data from 5643 EOAD cases and 16097 controls was identified using nested windows centered on each DNM position, at the transcript level. From genome data, one non-coding DNM was predicted to affect splicing in an AD-associated gene, PINX1. Overall, 48% probands carried ≥1 inherited risk factor with odds ratio (OR) > 1.5 and GWAS-defined Genetic Risk Scores (GRS) distribution was more consistent with random distribution than enrichment in higher scores in probands. We confirm that DNMs in known monogenic genes explain sEOAD in a minority of cases, while candidate DNMs in other genes might account for a small proportion of additional cases. The majority of sEOAD patients may have a complex etiology including multiple inherited variants, however, GRS might not explain most of its genetic component.

Vector-borne, protist parasites have evolved complex developmental programs to adapt to very distinct host environments. How these important pathogens transition between insect and mammalian stages is only poorly understood. Here we investigate stage differentiation in the trypanosomatid parasite Leishmania that shows constitutive gene transcription, thus providing a unique model system to assess how development is governed by post-transcriptional mechanisms. Using a five-layer integrative systems analysis (from genome to metabolome), we examined hamster-isolated Leishmania donovani amastigotes and culture-derived, insect-stage promastigotes. This approach enabled us to rule out genomic adaptation as a key driver of parasite stage differentiation, while confirming the pivotal role of differential mRNA turnover in stage-specific gene expression. Assessing transcriptomic against proteomic expression changes uncovered an unexpectedly broad dynamic range of stage-regulated changes in protein abundance that only poorly correlated with mRNA levels. This discrepancy correlated with (i) alterations in snoRNA expression and changes in rRNA modification they guide suggesting stage-specific adaptation of the protein translation apparatus that can uncouple mRNA from protein abundancies, and (ii) differential protein degradation as revealed by quantitative proteomics of parasites treated with the proteasomal inhibitor lactacystin. Lactacystin treatment stalled the transition of spleen-derived amastigotes into promastigotes in culture, further underscoring the role of proteasomal activity in stage differentiation. Integration of our five-layer systems analysis established the first link between Leishmania development and the expression of co-regulated genetic networks encompassing mRNA turnover, protein translation, phosphorylation, and degradation. Our findings provide a powerful new resource for research programs that aim to dissect the emergent properties of regulatory networks and feedback loops underlying Leishmania stage differentiation, serving as a blueprint for other vector-borne pathogens that rely on disease-associated developmental transitions.

Background: Short read sequencing technologies have dominated the field of human whole genome sequencing in the past years in terms of cost, throughput, and accuracy. However, thanks to recent technological evolution, long read approaches have become increasingly competitive and complementary to short reads. With the gap in the cost per genome closing slowly between both approaches, long reads might replace short read sequencing in future research and clinical applications. Still, comprehensive evaluation is necessary to conclude on the performance and general advantages of each technology. Results: In this study, we compared the latest chemistries of major suppliers of short and long read technologies: Illumina short reads, Illumina Complete Long Reads (ICLR), Pacific Biosciences HiFi reads (PacBio), and Oxford Nanopore Technologies long reads (ONT). Using the HG002 human reference sample and established bioinformatics guidelines, we assessed their variant calling performance against the latest available truth sets at different levels of coverage. For single nucleotide variant detection, all technologies were equivalent. Despite the latest improvements in chemistry, indel calling with ONT continues to lag in accuracy behind other technologies. In contrast, long reads delivered a clear advantage in structural variant detection, surpassing short reads in both accuracy and sensitivity. The hybrid ICLR approach achieved intermediate performance, narrowing the gap between short and long read sequencing. Furthermore, long reads enhanced haplotype-phasing resolution, enabling the phasing of over 80% of the genome. Conclusions: These findings highlight the specific strengths and limitations of recent sequencing technologies, aiding the decision-making in future research projects, technological platforms development, and clinical applications.