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Histone modifications by histone deacetylases (HDACs) are essential for controlling chromatin structure and regulating gene expression. Functionally, HDACs act as enzymatic subunits within diverse multisubunit corepressor complexes, thereby targeting distinct sets of genes. Here, we identify C16orf87 as a previously uncharacterized functional subunit of the MIER corepressor complex that mediates HDAC1 and MIER1 protein interactions. Homozygous knockout of C16orf87 alters chromatin accessibility and reduces cell migration in human cells, and impairs embryonic development of zebrafish. Based on these findings, we propose renaming C16orf87 as HDAC Interacting Protein (HDIP) to reflect its newly revealed function.

Background and Aims: Metabolic dysfunction-associated fatty liver disease (MASLD) is the most prevalent chronic liver pathology in western countries, with serious public health consequences. Efforts to identify causal genes for MASLD have been hampered by the relative paucity of human data from gold standard magnetic resonance quantification of hepatic fat. To overcome insufficient sample size, genome-wide association studies using MASLD surrogate phenotypes have been used, but only a small number of loci have been identified to date. In this study, we combined genome-wide association studies of MASLD composite surrogate phenotypes with genetic colocalization studies followed by functional in vitro screens to identify bona fide causal genes for MASLD. Approach and

Results: We used the UK Biobank to explore the associations of our novel MASLD score, and genetic colocalization to prioritize putative causal genes for in vitro validation. We created a functional genomic framework to study MASLD genes in vitro using CRISPRi. Our data identify VKORC1, TNKS, LYPLAL1, and GPAM as regulators of lipid accumulation in hepatocytes and suggest the involvement of VKORC1 in the lipid storage related to the development of MASLD.

Conclusions: Complementary genetic and genomic approaches are useful for the identification of MASLD genes. Our data supports VKORC1 as a bona fide MASLD gene. We have established a functional genomic framework to study at scale putative novel MASLD genes from human genetic association studies.

Hundreds of loci have been robustly associated with obesity-related traits, but functional characterization of candidate genes remains a bottleneck. Aiming to systematically characterize candidate genes for a role in accumulation of lipids in adipocytes and other cardiometabolic traits, we developed a pipeline using CRISPR/Cas9, non-invasive, semi-automated fluorescence imaging and deep learning-based image analysis in live zebrafish larvae. Results from a dietary intervention show that 5 days of overfeeding is sufficient to increase the odds of lipid accumulation in adipocytes by 10 days post-fertilization (dpf, n = 275). However, subsequent experiments show that across 12 to 16 established obesity genes, 10 dpf is too early to detect an effect of CRISPR/Cas9-induced mutations on lipid accumulation in adipocytes (n = 1014), and effects on food intake at 8 dpf (n = 1127) are inconsistent with earlier results from mammals. Despite this, we observe effects of CRISPR/Cas9-induced mutations on ectopic accumulation of lipids in the vasculature (sh2b1 and sim1b) and liver (bdnf); as well as on body size (pcsk1, pomca, irs1); whole-body LDLc and/or total cholesterol content (irs2b and sh2b1); and pancreatic beta cell traits and/or glucose content (pcsk1, pomca, and sim1a). Taken together, our results illustrate that CRISPR/Cas9- and image-based experiments in zebrafish larvae can highlight direct effects of obesity genes on cardiometabolic traits, unconfounded by their - not yet apparent - effect on excess adiposity.

Background/Aims: Metabolic dysfunction-associated steatotic liver disease (MASLD) may progress to liver inflammation, fibrosis, cirrhosis and hepatocellular carcinoma. So far, genome-wide association studies explain a small fraction of MASLD heritability.

Methods: We sought to identify novel genetic determinants of MASLD by exploring interactions between genetic variants and body mass index (BMI). First, we examined genome-wide interactions with BMI for circulating alanine aminotransferase (ALT) levels using UK Biobank data. For identified loci, we next examined associations with hepatic proton density fat fraction (PDFF) in 35,146 independent UK Biobank participants. Associations with PDFF were replicated in four independent European cohorts, followed by a phenome-wide association study. Finally, we used human liver epigenomic maps and CRISPR/Cas9 experiments in vitro and in vivo to functionally characterize the CYP7A1 locus.

Results: Thirteen loci interact with BMI for ALT (P<5E-8), including eight well-known genetic modulators of MASLD. Two loci-UBXN2B/CYP7A1 and GIPR-are additionally associated with PDFF. For the intronic rs34783010 in GIPR, the minor T allele is associated with lower BMI and higher HbA1c and liver triglyceride content in humans. The UBXN2B/CYP7A1 locus is associated with PDFF in four additional European cohorts. Epigenomic data and in vitro experiments in human liver cells prioritise rs10504255 and CYP7A1 as the functional effectors in this locus. Perturbation of CYP7A1 orthologues using CRISPR/Cas 9 results in less liver fat in 10-day-old, metabolically challenged zebrafish larvae.

Conclusions: A genome-wide single nucleotide polymorphismxBMI design fuelled identification of two MASLD genes: CYP7A1 and GIPR.

Drug combination and repurposing are potential therapeutic strategies for the treatment of metabolic dysfunction-associated steatotic liver disease (MASLD). Here, we have demonstrated that, in rats, both pemafibrate and telmisartan reverse hepatic steatosis induced by a high-fat, high-fructose diet. Pemafibrate attenuated liver steatosis via a PPAR alpha-mediated increase in fatty acid catabolism, while the antisteatotic response to telmisartan did not rely on PPAR modulation. Our results in rats and in a zebrafish larva model of liver lipid accumulation suggest that part of telmisartan's antisteatotic effects are driven through the blockade of the angiotensin II type 1 receptor, along with a reduction in the expression of several lipogenic genes, which also contributes to some extent. Telmisartan's response is mediated by the upregulation of hepatic phosphoenolpyruvate carboxykinase 1 (PCK1) expression. Liver metabolomic analysis revealed that by increasing PCK1, telmisartan diverted the metabolic flux of fructose from lipid towards glucose synthesis, which was subsequently fueled to the polyol pathway, thereby preserving glucose homeostasis. Moreover, telmisartan increased the hepatic levels of spermine and spermidine, which may counteract the putative detrimental effects caused by the accumulation of metabolites of the polyol route. Targeting different intrahepatic pathways, both PPARdependent and independent, the combination of pemafibrate and telmisartan, each at half the individual dose, was equally effective as the full dose of either drug alone to reduce liver lipid accumulation in the rat model. Our findings support the repurposing potential of these drugs, with the additional advantage of addressing both hepatic and cardiometabolic MASLD-associated complications.

Cardiometabolic diseases encompass a series of metabolic insults that are connected through an intricate network of shared and unique etiological pathways. Obesity and insulin resistance -leading to type-2 diabetes (T2D)- are major risk factors for developing metabolic dysfunction-associated steatotic liver disease (MASLD), which in turn, increases the risk of cardiovascular events. Genome-wide association studies (GWAS) have identified thousands of variants associated with risk of cardiometabolic diseases. However, the translation of those associations into causal mechanisms remains a challenge. In this thesis, we developed and validated model systems that use zebrafish larvae to functionally characterize the role of cardiometabolic candidate genes on disease development.

In Study I, I contributed to the validation of CRISPR/Cas9 and image-based approaches to study the role of genetic factors in adiposity. We concluded that 10-days post-fertilization is too early to detect meaningful genetic effects on adiposity in zebrafish larvae. However, we did observe genetic effects on cardiometabolic traits that are independent of body fat accumulation.

In Study II, we targeted 61 T2D candidate genes. I identified 21 genes that affect at least one of five examined T2D traits in zebrafish larvae upon gene perturbation, including 12 -out of 13- well established T2D genes. I performed follow-up experiments to identify genes that also affect basal glucose content in 7-day-old larvae and/or early developmental traits in 3-day-old larvae. With the three efforts combined, I highlighted sirt1 and poldip2 as T2D genes.

In Study III, I successfully validated an image-based model system in zebrafish larvae to characterize the role of candidate genes and drugs in MASLD. We then examined 100 cardiometabolic candidate and identified 13 genes that affect liver fat content upon perturbation. Amongst the 13 genes, I emphasised the role of glucose transporter 2 (GLUT2) as putatively causal genes for MASLD. Additionally, I provided evidence for 8 other genes not previously implicated in MASLD. Finally, in Study IV we went from a genome-wide interaction study (GEWIS) of Body Mass Index (BMI) for alanine aminotransferase (ALT), to pinpointing and functionally characterizing in zebrafish larvae the putative causal gene (cyp7a1) for a role in MASLD.

We hope these contributions help to improve our understanding of disease aetiology and fuel further efforts that could potentially result in new therapeutic targets for patients.

SARS-CoV-2, responsible for the current pandemic, is a Β-coronavirus that binds to ECA-2 receptors to infect the target cell. Fever, cough, and shortness of breath are the most common symptoms. Neurologic symptoms are gaining interest because of its association with pulmonary disease, direct Central Nervous System invasion by the virus, or post-infection onset. In this report, we describe a 52 years old male patient, with hypertension and diabetes mellitus type 2, presenting classic clinic of Guillain Barre Syndrome at the admission and respiratory symptoms 15 days before the appearance of neurologic symptoms. Antibody tests for SARS-CoV-2 were positives on two occasions and he reported the epidemiological continuous and direct nexus with people confirmed to be infected by SARS-CoV-2. Dysarthric language, dysphonia, facial diplegia, quadriparesis, and areflexia were finding at physical examination. The patient was transferred to ICU because of dyspnea but mechanical ventilation was not required and human immunoglobulin was administrated with significant im provement. A nasopharyngeal swab was taken at day 23 of the disease onset for RT-PCR, which resulted negative. We discuss the type and quality of specimen collection, phase of the disease when it is taken and the operator’s expertise as determinants of the sensibility of this test. Despite this negative result, the clinical and epidemiological diagnosis of SARS-CoV-2 is clear. According to the literature review, this is the first Guillain Barre Syndrome post-infection by SARS-CoV-2 reported in Venezuela to the date.