Human Molecular Genetics

Spinocerebellar ataxia type 3 (SCA3) is an inherited, fatal neurodegenerative disease caused by a pathological CAG repeat expansion in the ATXN3 gene, resulting in the selective degeneration of vulnerable neuronal populations. Recent work has identified impairments in oligodendrocyte maturation as a novel and robust feature of SCA3 pathogenesis. Oligodendrocytes synthesize myelin structural components through the endoplasmic reticulum (ER), rendering this organelle essential for white matter integrity. Despite this, the role of ER function in SCA3 remains unclear. In this study, we show that loss of FICD-mediated AMPylation, a post-translational modification regulating the ER-resident HSP70 chaperone, BiP, rescues motor impairments in a transgenic SCA3 mouse model. Ficd-/- SCA3 mice exhibit significantly reduced levels of nuclear ATXN3 in vulnerable brain regions, while Ficd+/+ littermates show an increased burden of AMPylated BiP in the spinal cord, identifying aberrant AMPylation as a novel contributor of SCA3 pathology. Using unbiased proteomics, we demonstrate that Ficd deletion mitigates the pathological decrease in myelin structural proteins and oligodendrocyte maturation factors, restoring levels of mature, myelinating oligodendrocytes. In parallel, we show that Ficd activates SREBP2-dependent cholesterol biosynthesis to support myelination. Taken as a whole, these findings posit ER homeostasis as a critical driver of oligodendrocyte pathology and identify FICD as a novel target for alleviating non-neuronal toxicity in SCA3.

A pair of paralogs, Chchd3 and Chchd6, two components of mitochondrial contact site and cristae organizing system (MICOS), have been identified to be candidate pathogenetic genes in congenital heart disease (CHD). Previous research found that knockdown (KD) of the single Chchd3/6 (Chchd3) gene and other MICOS components in Drosophila impaired heart function, likely due to a deficit in mitochondrial organization, ATP production, actomyosin levels, and thus severely diminished contractility. However, the underlying mechanisms of how MICOS deficiency leads to these defects are not clear. Here, we performed genetic manipulations in the Drosophila heart to probe for possible interactions between MICOS-compromised mitochondria and other organelles and processes. We found that moderate reduction in Pink1/parkin-mediated mitophagy synergistically aggravated cardiac Chchd3 KD phenotypes, indicating a major interaction. Further, Chchd3 KD increased the level of reactive oxygen species (ROS) and endoplasmic reticulum (ER) stress. Interestingly, KD of catalase (CAT) also elevated cardiac ROS levels, but surprisingly did not compromise contractility either by itself or in combination with Chchd3 KD to aggravate the cardiac phenotype. However, CAT overexpression (OE) in Chchd3 KD hearts restored contractility, but only partially, even though elevated ROS due to Chchd3 KD was fully normalized. Similarly, counteracting ER stress by overexpressing Xbp1 (or spliced mouse Xbp1) also partially rescued the heart function defects induced by Chchd3 KD. Overall, these data indicate a critical role of mitophagy and ER/oxidative stress in cardiac homeostasis involving Chchd3, which suggests that deficiency of MICOS function contributes to heart dysfunction via multiple stress responsive pathways.

BackgroundOverweight and obese individuals often exhibit lower mortality rates or better prognoses than lean or normal-weight individuals with stroke and other diseases, a phenomenon called the "obesity paradox". Carotid atherosclerosis is the primary cause of ischemic stroke, and body weight serves as a reliable surrogate for adiposity in mice. MethodsPhenotypic and genetic connections of carotid atherosclerosis with body weight were evaluated in 299 F2 mice derived from BALB/cJ and LP/J Apoe knockout (Apoe-/-) mice. F2 mice were fed a Western diet for 12 weeks. Atherosclerotic lesion sizes in left carotid arteries, body weight, coat color, plasma lipids, glucose, small dense LDL ApoB, and malondialdehyde were measured, and 11,000 single nucleotide polymorphism (SNP) markers were genotyped. ResultsCarotid lesion sizes inversely correlated with body weight in both sexes. Genome-wide scans identified two significant quantitative trait loci (QTLs) for carotid atherosclerosis on chromosomes (Chr) 6 and 15 in an additive sex model, and five QTLs on Chr 6, 7, 12, 13, and 15 in an interactive sex model. Adjusting for body weight variation downgraded Chr 15 QTL (Cath5) in both models, whereas other QTLs upgraded in the additive sex model and downgraded in the interactive sex model. Human syntenic region of Cath5 associated with carotid intima-medial thickness (cIMT) and waist-to-hip ratio (WHR). ConclusionsThese findings indicate that the obesity paradox in carotid atherosclerosis is partially driven by shared genetic components that exert opposing effects on adiposity and plaque development and act through sex-dependent mechanisms.

BackgroundTuberous Sclerosis Complex (TSC) is a genetic disorder caused by variants in TSC1 or TSC2, leading to mTORC1 hyperactivation and autophagy suppression. Although TSC tumorigenesis typically follows a "two-hit" model, the role of TSC2 haploinsufficiency in autophagy regulation remains unclear. We evaluated autophagy markers in haploinsufficient and gene-edited TSC2 primary cells and investigated the role of metformin in modulating autophagy levels. MethodsPrimary fibroblast cultures were obtained from one healthy individual and three from patients carrying heterozygous germline TSC2 variants: the pathogenic variants c.1008T>G and c.4375C>T.A variant of uncertain significance (VUS) c.724A>T. CRISPR/Cas9-RNP editing was used to model loss of heterozygosity (LOH) in cell pools carrying each variant. Cultures were treated with rapamycin, HBSS, metformin, bafilomycin A1, or vehicle controls, and autophagy was assessed by autolysosomes formation by flow cytometry (acridine orange) and autophagosomes immunofluorescence (LC3 and p-S6K). ResultsIn wild-type cells, only HBSS increased autophagy-positive (acridine orange-positive) cells versus control (15.6% vs. 7.5%; p=0.003). In heterozygous pathogenic cells, rapamycin and metformin increased autophagic cells: c.1008T>G (16.2%, p=0.006; 17.6%, p=0.002) and c.4375C>T (12.5%, p=0.003; 13.3%, p=0.001), versus DMSO controls (9.2% and 7.1%, respectively). VUS c.724A>T cells, with rapamycin increasing autophagic cells (9.74% vs. 6.5%; p=0.0152). In CRISPR-edited cells, all treatments increased the number of autophagic cells compared to the heterozygous cells: c.1008T>G (rapamycin 27.1% vs. 16.7%, p<0.001; metformin 27.2% vs. 17.6%, p<0.001) and c.4375C>T (rapamycin 21.3% vs. 13.1%, p=0.0021; metformin 21.5% vs. 13.6%, p=0.0029). Editing also restored metformin responsiveness in VUS cells (12.5% vs. 8.4%; p=0.0055). Immunochemistry confirmed increased total LC3II and decreased p-S6K across treated cells compared to the control (DMSO). ConclusionThese findings demonstrate that TSC2 haploinsufficiency functionally impairs autophagy prior to second-hit loss. Metformin effectively restores autophagy with phenotypical changes of mTORC1 blockade, highlighting an accessible translational strategy to restore and induce autophagy in TSC cells.

Heterozygous pathogenic variants in CSNK2A1 or CSNK2B encoding the Casein Kinase 2 (CK2) protein complex, lead to pediatric neurodevelopmental disorders, Okur-Chung Neurodevelopmental Syndrome (OCNDS) and Poirier-Bienvenu Neurodevelopmental Syndrome (POBINDS). OCNDS and POBINDS are characterized by a range of symptoms, including developmental delay, intellectual disability, facial dysmorphism, and seizures. Despite over 250 reported cases of OCNDS and POBINDS, we do not fully understand how specific alterations in CK2 relate to the heterogeneity observed in patients. To investigate this, we used the fruit fly, Drosophila melanogaster, as a model system. To assess variant impact, we co-expressed human CSNK2A1 and CSNK2B reference or disease-causing variants in flies. In parallel, we determined the role of Drosophila CkII in the developing and mature nervous system, specifically in neurons and glia. We found that 12/13 variants tested act as full or partial loss-of-function with one CSNK2A1 variant showing gain-of-function. Phospho-proteomic studies in neurons revealed separate signatures for loss- and gain-of-function variants. We found that neuronal and glial CkII is critical for organismal development. Reduction of neuronal CkII in the adult nervous system causes motor and seizure-like phenotypes. Finally, given the known role of CK2 in potentiating Wnt/{beta}-catenin signalling, we show that Wnt agonists partially rescue phenotypes associated with adult-specific neuronal reduction of CkII. This work generates Drosophila models of CSNK2A1 and CSNK2B expression to functionally assess variant impact, as well as an adult-specific neuronal loss-of-function model for drug screening and mechanistic studies.

Purpose: Age-related Macular Degeneration (AMD), a degenerative disease of aging, leads to central vision loss and has a strong genetic risk. Genetic heritability, used to quantify genetic influence on a trait, has mainly focused on twin study designs but these are vulnerable to bias. Studying relatives beyond twins is necessary to bring clarity to the genetic burden of AMD and help focus the search for additional genetic risk loci. Methods: Through both single nucleotide polymorphism (SNP) and pedigree-based heritability methods, the heritability of AMD was analyzed using relationship informed analyses of families from an Amish population (n = 525). AMD status was determined using the Beckman grading scale (285 controls and 240 cases). An estimate of genetic relatedness preceded SNP heritability estimation, whereas the pedigree heritability model utilized genealogical reports. Primary models were adjusted for age, sex, and population structure. A comparison of SNP- and pedigree-based models followed heritability estimation. Sensitivity models adjusting for all possible combinations of three known strong AMD genetic risk variants were constructed. Results: SNP heritability is 55% +/- 13% (p= 9.87e-06) and the pedigree heritability is 49% +/- 18% (p= 3.06e-04). The sensitivity analyses revealed that the estimates were robust to changes in the inclusion of AMD variants as covariates. Conclusions: These heritability estimates support existing twin and SNP-based AMD heritability estimates and corroborate the substantial involvement of genetics in AMD. Adjusting for known AMD variants revealed that additional genetic contribution exists, supporting a large polygenic effect in AMD.

Congenital NAD deficiency disorder (CNDD) is a gene x environment disorder caused by disruptions of the kynurenine pathway. To date, CNDD has been associated with biallelic variants in three kynurenine pathway genes: KYNU, HAAO, and NADSYN1. We identified two sisters with congenital anomalies overlapping with CNDD who have biallelic variants in a gene encoding a different kynurenine pathway enzyme, KMO. The surviving child also has elevated levels of metabolites upstream of KMO with low NAD+ levels in plasma, suggesting that KMO deficiency is a novel CNDD. To explore the pathogenicity of KMO deficiency, we generated a global Kmo knockout mouse model (Kmo-/-) and utilized dietary interventions to better model human gene x environment interactions. Although Kmo-/- mice are viable and fertile on typical breeder chow, they exhibit elevated serum kynurenine and are functionally vitamin B3-dependent. Under conditions of limited maternal vitamin B3 intake, a greater proportion of Kmo-/- embryos develop congenital anomalies and have significantly lower NAD+ levels than Kmo+/- littermates. Exploratory untargeted metabolomics performed in Kmo-/- embryos suggested that NAD+ deficiency may perturb the pyrimidine, purine, and pentose phosphate pathways. These findings establish KMO deficiency as a new cause of CNDD and highlight a critical gene x environment interaction influencing NAD metabolism and congenital anomalies.

Left ventricular hypertrophy, common in cardiometabolic and renal disease, is a major risk factor for cardiovascular morbidity and mortality. Left ventricular mass is a highly heritable, polygenic trait. Linkage studies in WKY and SHRSP rats have identified a quantitative trait locus for left ventricular mass index on chromosome 14. Congenic strains, where trait-associated genetic loci are introduced into a control strain, can identify causal genetic mediators relevant to human disease. Chromosome 14 congenic (WKY.SPGla14a), WKY, and SHRSP strains underwent cardiac phenotyping and transcriptome profiling at; 1-3 days (neonate), 5 weeks, and 16-weeks. Compared to WKY, LVMI was significantly increased in SHRSP and WKY.SPGla14a at 5 weeks (LVMISHRSP-WKY=0.26g/kg, LVMIWKY.SPGla14a-WKY=0.30g/kg), prior to measured hypertension in this model. SHRSP blood pressure was significantly greater than WKY.SPGla14a, and WKY from 12-20 weeks (AUCdiff=497 vs WKY, AUCdiff=412 vs WKY.SPGla14a). Cardiac transcriptome analysis of neonate, 5-week, and 16-week hearts identified significantly increased expression of secreted phosphoprotein 1 (Spp1/osteopontin) in SHRSP and WKY.SPGla14a compared to WKY, which is positioned within the transferred congenic region. Overexpression of Spp1 mRNA significantly increased H9c2 cell size and was shown to be transferred in small extracellular vesicles (sEV). Overexpression of Spp1 in neonatal chromosome 14 congenic and SHRSP strains preceded development of increased cardiac mass and onset of hypertension. The congenic strategy identified Spp1 as a positional and functional candidate gene determining increased LVMI in the SHRSP model of human cardiovascular disease.

Parkinsons disease (PD) arises through disruption of multiple interconnected cellular processes, but the genetic contributions to these processes may differ across ancestries. We investigated functional convergence among genes harboring pathogenic or likely pathogenic (P/LP) variants and variants of uncertain significance (VUS) in a multicenter Indian cohort recruited through the Genetics of Parkinsons Disease in India Young Onset Parkinsons Disease project (GOPI YOPD). The cohort included 668 participants (463 males 69.3%) with a mean age at motor onset of 39.4+/-8.8 years. P/LP variants and VUS identified through previously reported whole-exome or whole genome sequencing were retained as separate evidential categories. The P/LP-associated gene set comprised 11 unique genes and the VUS associated set comprised 40 unique genes. Separate STRING functional-enrichment analyses evaluated Gene Ontology Biological Process, Molecular Function and Cellular Component terms, KEGG pathways, WikiPathways and STRING local network clusters. Terms meeting a Benjamini Hochberg false discovery rate threshold of <0.05 were organized into eight non-mutually-exclusive ontology/pathway categories. Gene to pathway mappings were subsequently projected to individual participants to estimate pathway representation and examine clinical associations. At least one reportable P/LP variant or VUS was identified in 336/668 participants (50.3%): 35 had a P/LP variant alone, 282 had VUS alone and 19 had a P/LP variant together with VUS in one or more additional genes. The most frequently represented categories were mitochondrial organization (247/336, 73.5%), autophagy related processes (228/336, 67.9%) and regulation of synaptic vesicle transport (201/336, 59.8%). PRKN was the most frequent P/LP-associated gene, occurring in 29/54 P/LP carriers, followed by PLA2G6 and PINK1. Lysosomal transport was represented exclusively by VUS-associated genes, particularly GBA1, VPS13C and LRRK2. Among P/LP carriers, additional VUS in distinct genes were not associated with age at onset (P = 0.81) or family history (52.6% versus 31.4%; P = 0.15). No pathway phenotype association remained significant after correction for multiple testing. Genetic findings in this Indian cohort converged across an interconnected mitochondrial autophagic lysosomal vesicular network, with different contributions from P/LP-associated and VUS associated gene sets. This study provides the first pathway resolved South Asian genetic profile and a framework for comparative studies across populations.

Despite substantial advances in diagnostic testing, 10-15% of Usher syndrome patients remain without a genetic diagnosis, having significant implications for genetic counseling and potential future therapeutic interventions. In this study, genome sequencing data from probands clinically presenting with Usher syndrome were analyzed. Two novel deep-intronic variants were identified in PCDH15, c.3983+3635A>G and c.3123-1728A>G, in two independent patients. Both deep-intronic variants were classified as likely pathogenic and predicted to alter PCDH15 pre-mRNA splicing. Using a minigene splice assay and iPSC-derived photoreceptor precursor cells from patients, we confirmed that both variants lead to the inclusion of a pseudoexon in the PCDH15 transcript introducing a stop codon and subsequent premature termination of protein translation. We designed and evaluated antisense oligonucleotides (ASOs) with the purpose of redirecting aberrant pre-mRNA splicing caused by both deep-intronic variants. For both variants, designed ASOs were successful in restoring normal splicing patterns, highlighting their potential as a future therapeutic intervention strategy to halt the progression of retinitis pigmentosa caused by these novel variants. Overall, these findings contribute to the understanding of Usher syndrome caused by deep-intronic pathogenic variants in PCDH15 and describe for the first time the use of an ASO-mediated splice correction strategy for individuals diagnosed with these variants.

Tandem repeat expansions (TREs) cause over 50 neurological conditions, yet their contribution to neurodegenerative disease risk at a population scale remains incompletely characterized. We performed a TRE association study across 6,539 short tandem repeat loci in 276,411 individuals from the UK Biobank and 44,370 individuals from the All of Us Research Program, using two composite neurodegenerative phenotypes to increase statistical power and capture pleiotropic effects. Meta-analysis across the two cohorts identified associations at eight established pathogenic TRE loci, including C9orf72, DMPK, HTT, ATXN2, ATXN3, CACNA1A, CNBP, and PPP2R2B, recovering known disease-associated expansions from short-read sequencing data at biobank scale. We also identified candidate associations at three additional loci. An intronic AATAA expansion in DAPK1 reached significance (q = 0.0045), with fine-mapping and conditional analysis supporting the repeat as the likely variant underlying the association. An intronic ATTTT expansion in ANK3 (q = 0.034) was observed exclusively in individuals of African and Latino/admixed American ancestry, underscoring the importance of ancestrally diverse cohorts for genetic discovery. An exonic polyalanine expansion in RPL14 was also significant (q = 0.039), where longer alleles were consistently associated with reduced RPL14 expression across independent datasets. Together, these findings identify candidate risk loci for neurodegenerative disease that may expand the contribution of TREs to neurodegenerative disease beyond known repeat expansion disorders.

Primary cilia coordinate signaling pathways that regulate tissue homeostasis and development, and defects in cilia contribute to numerous ciliopathies. However, the transcriptional consequences of disrupting ciliary protein localization remain poorly defined. ARL13B is a cilia-enriched regulatory GTPase required for ciliary trafficking and signaling. The ARL13BV358A variant is undetectable in cilia yet retains known biochemical functions, providing a unique model to investigate the functions of ciliary ARL13B independently of ciliogenesis. To define transcriptional programs associated with loss of ciliary ARL13B, we generated two independent Arl13bV358A/V358A kidney epithelial cell lines and matched rescue lines. The ARL13BV358A mutation did not affect ciliation frequency or cilia length but altered ciliary protein composition, including loss of ARL3 and INPP5E localization and increased accumulation of GPR161 and TULP3. RNA sequencing revealed expression changes in genes associated with ciliary biology, mechanotransduction, epithelial organization, and kidney-related phenotypes. Despite similar ciliary phenotypes, the independently-derived, mutant clones displayed substantial transcriptomic heterogeneity, highlighting a potential source of variation in CRISPR-based transcriptional studies. By integrating data from the independent mutant and rescue clones, we identified a high-confidence set of 131 genes whose expression reproducibly tracked with loss and restoration of ciliary ARL13B. Together, these findings demonstrate that ciliary ARL13B is required to maintain normal ciliary composition and gene expression programs and underscores the value of multi-clone, rescue-based experimental designs for robust transcriptomic analyses. Summary for ReviewersThis study examined how excluding the protein ARL13B from primary cilia affects kidney epithelial cells. The researchers created two independent cell lines carrying a modified form of ARL13B,along with matched rescue cell lines. The findings show that ciliary ARL13B helps maintain normal ciliary composition. By comparing the cell lines, the researchers identified a high-confidence set of genes associated with loss of ciliary ARL13B. By highlighting the importance of using independent gene-edited clones and rescue-based controls, these results advance understanding of how cilia regulate kidney cell function and provide guidance for designing robust transcriptomic analyses.

IntroductionFetal development represents a critical window during which genetic and environmental influences shape lifelong health. DNA methylation (DNAm) is a candidate underlying mechanism. While individual prenatal exposures have been related to DNAm, no studies have investigated the broader prenatal exposome, nor incorporated genetics with the exposome. Here, we integrated the prenatal exposome and genetics as predictors of DNAm at birth. MethodsWe used data from the Dutch Generation R (n=2282) and English Avon Longitudinal Study of Parents and Children (ALSPAC; n=809) cohorts. We performed epigenome-wide elastic net regression, using Generation R for model development/internal validation and ALSPAC for external validation, to predict DNAm at each CpG site. We used three models: Model 1 included 42 prenatal exposures, Model 2 additionally included child sex, gestational age and birth weight, and Model 3 further included meQTLs. ResultsIn Model 1, the prenatal exposome explained on average 0.7% of DNAm variation across 347 validated CpGs (0.1% of tested CpGs). This increased to 40,044 CpGs (10.2%) with 1.3% of variation explained in Model 2, and 91,305 CpGs (23.2%) with 3.0% of variation explained in Model 3. In Model 1, prenatal smoking was the largest predictor, followed by delivery characteristics, among which meconium-stained amniotic fluid was a novel finding. In Model 3, typically both SNPs and multiple prenatal exposures were selected. DiscussionWe find that genomic associations with cord blood DNAm are stronger and more widespread than prenatal exposures, although typically, the prenatal exposome explains additional variation in DNAm beyond genetic influences.

Our labs have been studying neurofibromin function and phenotype for over a decade with the intent of generating targeted therapeutics for Neurofibromatosis type 1 (NF1). In the process, we have generated numerous human cell lines containing variants within the NF1 gene. Herein, we present data characterizing these cell lines and make them publicly available for use by researchers both within and outside the NF1 community. We describe lines that contain both well-characterized patient-specific variants either at their endogenous locus or as exogenous cDNAs, as well as variants of uncertain significance (VUS), engineered as heterozygous, homozygous, and compound heterozygous variants. Methods to generate each line and subsequent validation steps are detailed including targeted sequencing, Western blot analysis for neurofibromin expression and ERK activation. The utility of each line is dependent on the variant of interest, the parental cell line, and the mechanism of action relevant to possible therapeutic targeting.

The canonical Wnt/beta-catenin signaling pathway plays a key role in cardiovascular development, preservation, and pathology. Variations in critical Wnt pathway genes may influence an individual's susceptibility to cardiovascular disease (CVD), although data from specific populations are scarce. In this case-control study, we analyzed 15 single-nucleotide polymorphisms (SNPs) within eight Wnt pathway genes (APC, AXIN2, LRP6, CTNNB1, TCF7L2, DKK3, DKK4, and SFRP3) among 151 CVD patients and 129 healthy controls. We examined the genotypic and allelic distributions for correlations with CVD risk utilizing odds ratios, confidence intervals, and chi-square tests, while controlling for age and gender. We discovered that the APC variants rs459552 and rs454886 conferred protective effects, with age- and gender-dependent variation. AXIN2 SNP rs11079571 made men more likely to get CVD, and rs3923086 made people over 58 more susceptible. The DKK4 variant rs3763511 was associated with an elevated risk of cardiovascular disease, particularly among males and older individuals (age M/F). In SFRP3, rs7775 was associated with an elevated risk in older individuals (age M/F), whereas rs288326 showed a protective effect. For LRP6, rs2284396 increased the risk of CVD in females, while rs2075241 conferred protection in males. We did not identify significant associations for the CTNNB1, TCF7L2, or DKK3 variants. The present data indicate that specific Wnt pathway variants are associated with cardiovascular disease risk, contingent on age and gender. To verify these outcomes and determine whether these variants can serve as genetic markers of cardiovascular disease risk, larger, more diverse studies with a whole genome sequencing approach are necessary.

Non-invasive prenatal testing (NIPT) was initially developed to detect chromosomal abnormalities in fetuses through the analysis of cell-free fetal DNA in maternal blood. Recent advancements have expanded NIPT's applications to include the detection of viral infections during pregnancy. However, interpreting pathogen-derived cell-free DNA (cf-DNA) remains clinically complex. This study explores the clinical relevance of hepatitis B virus (HBV) cf-DNA using a dataset of approximately 500,000 NIPT visits and an independent validation cohort of 582 pregnant women (40 HBV-infected), aligned with HBV epidemiology from both population and individual perspectives. Our analysis reveals that HBV cf-DNA is a strong biomarker of high viral infectivity rather than a general marker of infection, suggesting its potential to identify pregnant women at heightened risk of vertical transmission by the end of the first trimester. Additionally, HBV-positive women showed a small but consistent reduction in fetal fraction relative to HBV-negative women across gestational weeks 9 - 17, an association compatible with an early effect of HBV on the placental contribution to cell-free DNA, although the observational design and unmeasured maternal covariates preclude causal inference.

Bi-allelic variants of RNU4ATAC, transcribed into the minor spliceosome component U4atac snRNA, are associated to variable severity of microcephaly, growth retardation, skeletal dysplasia and immunodeficiency as main features. Previous studies highlighted the dramatic effect of U4atac deficiency on splicing of U12-type introns, which represent less than 1% of all introns in the human genome. More recently, our team evidenced a link between U4atac and the primary cilium/centrosome complex through the identification of patients carrying RNU4ATAC bi-allelic variants and exhibiting an atypical Joubert syndrome, a well-known ciliopathy. Yet, the underlying mechanisms remain elusive. Here, we further explored the link of RNU4ATAC to primary cilium and aimed at identifying ciliary U12-type intron containing genes that contribute to the brain abnormalities seen in patients. For that, we performed a transcriptomic analysis of heads of our morpholino oligonucleotide (MO)-mediated u4atac zebrafish model. Through the combined analysis of the generated dataset with those obtained from RNU4ATAC patient cells, we identified two candidate genes: TMEM107, coding for a structural protein of the cilium transition zone, and RFX7, encoding a transcription factor involved in primary cilium formation. By conducting complementary genetic approaches in zebrafish model, we showed that both gene orthologues, tmem107l and rfx7b, functionally interact with u4atac and are required for correct brain development. Altogether, our findings establish TMEM107 and RFX7 as key components of the molecular pathway linking U4atac dysfunction to ciliary defects and impaired brain development, providing new physiopathological insights and therapeutic perspectives for RNU4ATAC-related disorders.

Background. Type 2 diabetes (T2D) and coronary artery disease (CAD) frequently co-occur, yet the biological pathways that jointly determine risk remain incompletely understood. Most genetic studies have examined shared risk from a single-disease perspective, limiting insight into the mechanisms that generate discordant risk between conditions. Methods. We applied PLACO to multi-ancestry GWAS data of T2D and CAD to identify shared loci, prioritising shared causal signals using colocalisation. Shared variants were clustered by their associations with 77 cardiometabolic traits, and cluster-specific genetic risk scores (GRS) were tested for association with 17 clinical biomarkers and 1,254 binary outcomes in 378,772 UK Biobank (UKB) participants. Two-sample Mendelian randomisation (MR) was used to test the causal role of liver fat. Results. We identified 149 loci shared between T2D and CAD; most novel loci had discordant effects (35 of 42), in contrast to the predominantly concordant signals reported previously. Clustering 187 independent shared variants revealed seven mechanistic clusters, three of them centred on liver fat and defined by discordant T2D?CAD effects. Enrichment analyses and cluster-GRS associations in UKB highlight associations between higher liver fat and T2D risk with a cardioprotective lipid profile and reduced CAD risk. Genetically higher liver fat increased T2D risk but lowered CAD risk in MR analyses; partitioning liver fat instruments by their effect on ApoB-containing lipoproteins indicates that the CAD effects are determined more by effects of circulating ApoB rather than liver fat itself. Conclusions. Liver fat largely sets the direction of T2D risk, whereas the fate of that lipid, retained in the liver with low circulating ApoB or exported as ApoB-containing lipoproteins, sets the direction of CAD risk. This liver-centric partitioning provides a mechanistic framework for the discordant cardiometabolic effects of hepatic lipid and lipid-lowering pathways, with implications for precision prevention.

Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disease characterised by progressive motor neuron loss and corticospinal tract degeneration. The genetic landscape of ALS is complex, with increasing recognition of shared genetic and phenotypic features with other neurodegenerative conditions, particularly those involving repeat expansions. Given that repeat expansions in disorders like spinocerebellar ataxia type 27B (SCA27B), caused by an intronic GAA repeat expansion in Fibroblast Growth Factor 14 (FGF14), are recognised to extend beyond cerebellar ataxia with frequent pyramidal signs, we hypothesised that FGF14 repeat expansions might also contribute to ALS and degeneration of corticospinal pathways, and sought to investigate whether repeat length is associated with clinical phenotype. We screened 62 individuals with ALS using PacBio HiFi long-read whole-genome sequencing and compared repeat-size distributions with 256 healthy controls from the Human Pangenome Reference Consortium. Repeat expansions were confirmed using flanking PCR and repeat-primed PCR. We identified pathogenic-range FGF14 GAA [&ge;]250 expansions, the established threshold for SCA27B, in 3/62 ALS cases (4.8%) and none in controls. Further analysis revealed that GAA expansions [&ge;]200 repeats were enriched in ALS compared to controls (8.1% vs 0.4%; p = 0.0013), suggesting a broader pathogenic spectrum for FGF14 GAA repeats in ALS. In contrast, GAAGGA expansions were not significantly associated. Expanded pure GAA alleles were predicted to form triplex (H-DNA) structures, with the repeat-containing isoform (1B) being the predominant FGF14 transcript in motor neurons. These findings demonstrate that FGF14 GAA repeat expansions extend into the motor neuron disease spectrum.

Preeclampsia (PE) is a hypertensive pregnancy-specific disorder and a leading cause of maternal and fetal mortality. A common feature of PE placentas and maternal plasma is dyslipidemia, or abnormal lipid levels, which can increase oxidative stress and endothelial dysfunction. However, the precise transcriptional, post-transcriptional, and epigenetic mechanisms underlying these abnormalities remain poorly characterized. Identifying such changes may clarify disease mechanisms and identify lipid-related PE biomarkers. We conducted a large-scale meta-analysis integrating public placental datasets from NCBI GEO, comprising four DNA methylation (DNAm) datasets (n = 172), three RNA-sequencing datasets (n = 92), and an independent RNA microarray validation cohort (n =146). We evaluated differential DNAm (limma), gene expression (DESeq2), transcript-level shifts (Swish), and alternative splicing (rMATS) in PE versus control placentas, with all analyses stratified by fetal sex via an interaction term model. We also performed placental cell-type deconvolution to quantify PE-associated cell-type proportion changes. Our results demonstrated that lipid-related regulation changes in PE placentas occur primarily at the gene and transcript level, with DNAm showing no changes. We also identified significant isoform switching in PE that were undetected by differential gene expression analysis, and primarily driven by alternative transcription initiation and termination sites rather than alternative splicing. A subset of these isoform switches mapped to pathways dysregulated in PE and were predicted to cause functional protein changes. An interaction term model identified several sex-specific differentially expressed genes (DEGs) in PE, including a subset of male-specific downregulated genes involved in oxidative metabolism. However, many of the remaining sex-specific DEGs across both sexes were previously uncharacterized in the literature. These findings suggest that transcriptional and isoform-level regulation play a role in PE-associated dyslipidemia, with certain regulatory pathways displaying fetal sex-specific patterns. Highlights- Preeclampsia-associated dyslipidemia manifests at the gene and transcript level - Reciprocal isoform switches were missed by standard gene-level analyses - Alternative transcript initiation and termination drove isoform switching - Sex-interaction modeling identified sex-specific transcriptional shifts in PE