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Redistribution of lamina-associated domains reshapes Foxa2 binding in development of NAFLD

ABSTRACT: Non-alcoholic fatty liver disease (NAFLD) is highly prevalent in type 2 diabetes mellitus and the elderly, impacting 40% of individuals over 70. Regulation of heterochromatin at the nuclear lamina has been associated with aging and age-dependent metabolic changes. We have shown that changes at the lamina in aged hepatocytes and laminopathy models lead to redistribution of lamina-associated domains (LADs), opening of repressed chromatin, and upregulation of genes regulating lipid synthesis and storage, culminating in fatty liver. Here we test the hypothesis that change in expression of lamina-associated proteins and nuclear shape leads to redistribution of LADs, followed by altered binding of pioneer factor FOXA2, uprregulation of lipid synthesis and storage, and culminating in steatosis in younger NAFLD patients (aged 21-51). Changes in nuclear morphology alter LAD partitioning and reduced lamin B1 signal correlates with increased FOXA2 binding prior to severe steatosis in young mice placed on Western det. Nuclear shape is also changed in younger NAFLD patients. LADs are redistrubted and Lamin B1 signal decreases similarly in mild and severe steatosis. In contrast, FOXA2 binding is similar in normal and NAFLD patients with moderate steatosis and is repositioned only in NAFLD patients with more severe lipid accumulation. Hence, changes at the nuclear lamina reshape FOXA2 binding with progression of the disease. Our results suggest a role for nuclear lamina in etiology of NAFLD, irrespective of aging, with potential for improved stratification of patients and novel treatments aimed at restoring nuclear lamina function.

ORGANISM(S): Mus musculus Homo sapiens

PROVIDER: GSE197399 | GEO | 2022/11/10

REPOSITORIES: GEO

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Project description:Purpose: Many mammalian genes exhibit circadian expression patterns concordant with periodic binding of transcription factors, chromatin modifications and chromosomal interactions. We determined whether lamina-associated domains (LADs) display oscillatory circadian patterns of interaction with nuclear lamin B1 during hte circadian cycle, and identified any relationship to changes in gene expression patterns in oscillatory LADs or in their vinicity. Methods: To this end, we mapped LADs by chromatin immunoprecipitation-sequencing (ChIP-seq) of lamin B1 (LMNB1) (antibody ab16048, Abcam) from mouse livers colected every 6 h, for 30 h, after entrainment of the circadian clock by 24-h fasting and refeeding. Gene expression profiles were also analyzed by RNA-sequencing (RNA-seq) at the same time points. Results and Conclusions: We report periodic interactions of chromatin domains with nuclear lamin B1, suggesting rhythmic associations of fractions of the genome with the nuclear lamina. Entrainment of the circadian clock by fasting and refeeding is accompanied in mouse liver by a gain of lamin-chromatin interactions followed by oscillations in these interactions at hundreds of lamina-associated domains (LADs). A subset of these oscillations exhibit periodicity and affect one or both LAD borders or entire stand-alone LADs. Periodic LADs are however not a dominant feature of these variable LADs, as most LADs are conserved during the circadian cycle. LAD oscillations are for the most part asynchronous between the 5’ and 3’ ends of LADs. Periodic LADs also uncoupled from gene expression patterns, periodic or not, within or in vicinity of these LADs. Accordingly, periodic genes, including central clock-control genes, are located megabases away from LADs, suggesting their residence in a transcriptionally permissive environment throughout the circadian cycle. Our data suggest autonomous oscillatory associations of fractions of the genome with the nuclear lamina, providing new evidence for rhythmic spatial configurations of chromatin. However, our data also argue that periodic LADs constitute a minor fraction of variable LADs, and reflect stochasticity in variable lamin-chromatin interactions during the circadian cycle.

Project description:Purpose: to qualify and quantify the rearrangement of interactions of nuclear lamins A/C and B with the genome, in relation to nuclearradial repositioning of loci and changes in gene expression, in HepG2 cells exposed to cyclosporin A. .To compare HepG2 cell line transcriptome profiling (RNA-seq) with radially positioning of the chromatin anchored at the nuclear periphery before and after CsA treatment. Methods: To this end, we mapped lamin A and lamin B lamina-associated domains (LADs) by chromatin immunoprecipitation-sequencing (ChIP-seq) of lamin A/C (antibody sc7292x, Santa Cruz Biotechnology) and lamin B1 (antibody ab16048, Abcam), respectively. HepG2 cells were either cultured under proliferative conditions (controls) or exposed for 3 days to 10 uM cyclosporin A. We also assesed the transcriptome by RNA-seq under each condition in duplicate cultures. Results: CsA elicits accumulation of pre-lamin A in HepG2 cells, raising the hypothesis of a global rearrangement of lamin-chromatin interactions. We show here the existence of overlapping and distinct lamin A and B lamina-associated domains (which we refer to as A- and B-LADs, respectively). Whereas B-LADs largely remain constitutive, CsA elicits the formation of facultative A-LADs. Re-localization of A-LADs occur mainly on preexisting B-LADs. However, LAD rearrangement does not correlate with systematic changes in gene expression within LADs. We find a reorganization of A- and B-LADs after CsA treatment, entailing distinct contributions of A- and B- type lamins. to genome organization. Indeed, classification of lamin A LADs and lamin B LADs into properties of ‘A-only’, ‘B-only’ and ‘A-B’ LADs show an overall loss of A-only LADs after CsA treatment. A- only and B-only LADs are highly dynamic with A-B LADs being more stable.The rearrangement of lamin association after CsA treatment correlates with repositioning of loci in the nuclear space with, notably, a loss of lamin B associated with a re-localization of loci towards the nuclear center and conversely, a gain of lamin B linked to a repositioning of loci towards the nuclear periphery. Predictions on radial repositioning of LADs, and of loci within, from 3D structural models of the genome were supported by fluorescence in situ hybridization (FISH) analyses. Conclusions: We show that, while they amply co-localize on well-conserved LADs, lamins A and B also interact with distinct genomic regions that can interchange (switch) between lamin A and B upon CsA treatment. We unveil distinct lamin A and B interactions with chromatin, suggesting complementary contributions to genome conformation. Our data suggest that and lamins A and B may differentially modulate genome organization.

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Redistribution of lamina-associated domains reshapes Foxa2 binding in development of NAFLD

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