Trim37-deficient mice recapitulate several features of the multi-organ disorder Mulibrey nanism

TRIM56 protects against nonalcoholic fatty liver disease by promoting the degradation of fatty acid synthase

Nonalcoholic fatty liver disease (NAFLD) encompasses a disease continuum from simple steatosis to nonalcoholic steatohepatitis (NASH). However, there are currently no approved pharmacotherapies for NAFLD, although several drugs are in advanced stages of clinical development. Because of the complex pathophysiology and heterogeneity of NAFLD, the identification of potential therapeutic targets is clinically important. Here, we demonstrated that tripartite motif 56 (TRIM56) protein abundance was markedly downregulated in the livers of individuals with NAFLD and of mice fed a high-fat diet. Hepatocyte-specific ablation of TRIM56 exacerbated the progression of NAFLD, while hepatic TRIM56 overexpression suppressed it. Integrative analyses of interactome and transcriptome profiling revealed a pivotal role of TRIM56 in lipid metabolism and identified the lipogenesis factor fatty acid synthase (FASN) as a direct binding partner of TRIM56. TRIM56 directly interacted with FASN and triggered its K48-linked ubiquitination-dependent degradation. Finally, using artificial intelligence-based virtual screening, we discovered an orally bioavailable small-molecule inhibitor of FASN (named FASstatin) that potentiates TRIM56-mediated FASN ubiquitination. Therapeutic administration of FASstatin improved NAFLD and NASH pathologies in mice with an optimal safety, tolerability, and pharmacokinetics profile. Our findings provide proof of concept that targeting the TRIM56/FASN axis in hepatocytes may offer potential therapeutic avenues to treat NAFLD.

Role of the tripartite motif-containing (TRIM) family of proteins in insulin resistance and related disorders

Emerging evidence suggests that the ubiquitin-mediated degradation of insulin-signalling-related proteins may be involved in the development of insulin resistance and its related disorders. Tripartite motif-containing (TRIM) proteins, a superfamily belonging to the E3 ubiquitin ligases, are capable of controlling protein levels and function by ubiquitination, which is essential for the modulation of insulin sensitivity. Recent research has indicated that some of these TRIMs act as key regulatory factors of metabolic disorders such as type 2 diabetes mellitus, obesity, nonalcoholic fatty liver disease, and atherosclerosis. This review provides a comprehensive overview of the latest evidence linking TRIMs to the regulation of insulin resistance and its related disorders, their roles in regulating multiple signalling pathways or cellular processes, such as insulin signalling pathways, peroxisome proliferator-activated receptor signalling pathways, glucose and lipid metabolism, the inflammatory response, and cell cycle control, as well as recent advances in the development of TRIM-targeted drugs.

The TRIM37 variants in Mulibrey nanism patients paralyze follicular helper T cell differentiation

The Mulibrey (Muscle-liver-brain-eye) nanism caused by loss-of-function variants in TRIM37 gene is an autosomal recessive disorder characterized by severe growth failure and constrictive pericarditis. These patients also suffer from severe respiratory infections, co-incident with an increased mortality rate. Here, we revealed that TRIM37 variants were associated with recurrent infection. Trim37 FIN_major (a representative variant of Mulibrey nanism patients) and Trim37 knockout mice were susceptible to influenza virus infection. These mice showed defects in follicular helper T (T_FH) cell development and antibody production. The effects of Trim37 on T_FH cell differentiation relied on its E3 ligase activity catalyzing the K27/29-linked polyubiquitination of Bcl6 and its MATH domain-mediated interactions with Bcl6, thereby protecting Bcl6 from proteasome-mediated degradation. Collectively, these findings highlight the importance of the Trim37-Bcl6 axis in controlling the development of T_FH cells and the production of high-affinity antibodies, and further unveil the immunologic mechanism underlying recurrent respiratory infection in Mulibrey nanism.

Proteolysis in Reproduction: Lessons From Gene-Modified Organism Studies

The physiological roles of proteolysis are not limited to degrading unnecessary proteins. Proteolysis plays pivotal roles in various biological processes through cleaving peptide bonds to activate and inactivate proteins including enzymes, transcription factors, and receptors. As a wide range of cellular processes is regulated by proteolysis, abnormalities or dysregulation of such proteolytic processes therefore often cause diseases. Recent genetic studies have clarified the inclusion of proteases and protease inhibitors in various reproductive processes such as development of gonads, generation and activation of gametes, and physical interaction between gametes in various species including yeast, animals, and plants. Such studies not only clarify proteolysis-related factors but the biological processes regulated by proteolysis for successful reproduction. Here the physiological roles of proteases and proteolysis in reproduction will be reviewed based on findings using gene-modified organisms.

TRIM37: a critical orchestrator of centrosome function

Loss of function mutations in the E3 ubiquitin ligase TRIM37 result in MULIBREY nanism, a disease characterized by impaired organ growth and a high propensity to develop different tumor types. Additionally, increased copy number of TRIM37 is a feature of some breast cancers and neuroblastomas. The molecular role played by TRIM37 in such loss and gain of function conditions has been a focus of research in the last decade, which led notably to the identification of critical roles of TRIM37 in centrosome biology. Specifically, deletion of TRIM37 results in the formation of aberrant centrosomal proteins assemblies, including Centrobin-PLK4 assemblies, which can act as extra MTOCs, thus resulting in defective chromosome segregation. Additionally, TRIM37 overexpression targets the centrosomal protein CEP192 for degradation, thereby preventing centrosome maturation and increasing the frequency of mitotic errors. Interestingly, increased TRIM37 protein levels sensitize cells to the PLK4 inhibitor centrinone. In this review, we cover the emerging roles of TRIM37 in centrosome biology and discuss how this knowledge may lead to new therapeutic strategies to target specific cancer cells.

Modeling Rare Human Disorders in Mice: The Finnish Disease Heritage

The modification of genes in animal models has evidently and comprehensively improved our knowledge on proteins and signaling pathways in human physiology and pathology. In this review, we discuss almost 40 monogenic rare diseases that are enriched in the Finnish population and defined as the Finnish disease heritage (FDH). We will highlight how gene-modified mouse models have greatly facilitated the understanding of the pathological manifestations of these diseases and how some of the diseases still lack proper models. We urge the establishment of subsequent international consortiums to cooperatively plan and carry out future human disease modeling strategies. Detailed information on disease mechanisms brings along broader understanding of the molecular pathways they act along both parallel and transverse to the proteins affected in rare diseases, therefore also aiding understanding of common disease pathologies.

TRIM37 prevents formation of condensate-organized ectopic spindle poles to ensure mitotic fidelity

Centrosomes are composed of a centriolar core surrounded by pericentriolar material that nucleates microtubules. The ubiquitin ligase TRIM37 localizes to centrosomes, but its centrosomal roles are not yet defined. We show that TRIM37 does not control centriole duplication, structure, or the ability of centrioles to form cilia but instead prevents assembly of an ectopic centrobin-scaffolded structured condensate that forms by budding off of centrosomes. In ∼25% of TRIM37-deficient cells, the condensate organizes an ectopic spindle pole, recruiting other centrosomal proteins and acquiring microtubule nucleation capacity during mitotic entry. Ectopic spindle pole-associated transient multipolarity and multipolar segregation in TRIM37-deficient cells are suppressed by removing centrobin, which interacts with and is ubiquitinated by TRIM37. Thus, TRIM37 ensures accurate chromosome segregation by preventing the formation of centrobin-scaffolded condensates that organize ectopic spindle poles. Mutations in TRIM37 cause the disorder mulibrey nanism, and patient-derived cells harbor centrobin condensate-organized ectopic poles, leading us to propose that chromosome missegregation is a pathological mechanism in this disorder.

The role of TRIM family proteins in autophagy, pyroptosis, and diabetes mellitus

The ubiquitin-proteasome system, which is one of the systems for cell protein homeostasis and degradation, happens through the ordered and coordinated action of three types of enzymes, E1 ubiquitin-activating enzyme, E2 ubiquitin-carrier enzyme, E3 ubiquitin-protein ligase. Tripartite motif-containing (TRIM) family proteins are the richest subfamily of really interesting new gene E3 ubiquitin ligases, which play a critical role not only in many biological processes, including proliferation, apoptosis, pyroptosis, innate immunity, and autophagy, but also many diseases like cancer, diabetes mellitus, and neurodegenerative disease. Increasing evidence suggests that TRIM family proteins play a vital role in modulating autophagy, pyroptosis, and diabetes mellitus. The aim of this review is to discuss the role of TRIM proteins in the regulation of autophagy, pyroptosis, diabetes mellitus, and diabetic complications.

TRIM37 prevents formation of centriolar protein assemblies by regulating Centrobin

TRIM37 is an E3 ubiquitin ligase mutated in Mulibrey nanism, a disease with impaired organ growth and increased tumor formation. TRIM37 depletion from tissue culture cells results in supernumerary foci bearing the centriolar protein Centrin. Here, we characterize these centriolar protein assemblies (Cenpas) to uncover the mechanism of action of TRIM37. We find that an atypical de novo assembly pathway can generate Cenpas that act as microtubule-organizing centers (MTOCs), including in Mulibrey patient cells. Correlative light electron microscopy reveals that Cenpas are centriole-related or electron-dense structures with stripes. TRIM37 regulates the stability and solubility of Centrobin, which accumulates in elongated entities resembling the striped electron dense structures upon TRIM37 depletion. Furthermore, Cenpas formation upon TRIM37 depletion requires PLK4, as well as two parallel pathways relying respectively on Centrobin and PLK1. Overall, our work uncovers how TRIM37 prevents Cenpas formation, which would otherwise threaten genome integrity.

Dynamic Profiles and Transcriptional Preferences of Histone Modifications During Spermiogenesis

During spermiogenesis, extensive histone modifications take place in developing haploid spermatids besides morphological alterations of the genetic material to form compact nuclei. Better understanding on the overall transcriptional dynamics and preferences of histones and enzymes involved in histone modifications may provide valuable information to dissect the epigenetic characteristics and unique chromatin status during spermiogenesis. Using single-cell RNA-Sequencing, the expression dynamics of histone variants, writers, erasers, and readers of histone acetylation and methylation, as well as histone phosphorylation, ubiquitination, and chaperones were assessed through transcriptome profiling during spermiogenesis. This approach provided an unprecedented panoramic perspective of the involving genes in epigenetic modifier/histone variant expression during spermiogenesis. Results reported here revealed the transcriptional ranks of histones, histone modifications, and their readers during spermiogenesis, emphasizing the unique preferences of epigenetic regulation in spermatids. These findings also highlighted the impact of spermatid metabolic preferences on epigenetic modifications. Despite the observed rising trend on transcription levels of all encoding genes and histone variants, the transcriptome profile of genes in histone modifications and their readers displayed a downward expression trend, suggesting that spermatid nuclei condensation is a progressive process that occurred in tandem with a gradual decrease in overall epigenetic activity during spermiogenesis.

CD4+ T Cell Defects in a Mulibrey Patient With Specific TRIM37 Mutations

Mulibrey (muscle-liver-brain-eye) syndrome (MUL) is an autosomal recessive disorder caused by mutations in the TRIpartite motif (TRIM)37 gene, encoding for TRIM37 a member of the TRIM E3 ubiquitin ligase protein family. MUL patients are characterized by growth retardation, dysmorphic features, and a wide range of abnormalities affecting different organs. However, T-cell abnormalities have not been observed in MUL subjects, to date. Here we described the immunological features of a MUL child carrying recently identified TRIM37 mutations, a 17q22 deletion of maternal origin combined with a TRIM37 variant of paternal origin. Here we found quantitative and functional defects in CD4⁺ T cells from this MUL case. Low levels of TRIM37 protein were specifically detected in CD4⁺ T cells of MUL patient and associated with their altered proliferation and cytokine production. Of note, both CD4⁺ and CD8⁺ T lymphocytes of MUL child displayed an effector memory phenotype compared with healthy children. This clinical case research highlighted the possible role of TRIM37 in the control of immune cell number and function, especially in CD4⁺ T cells. Finally, this study may contribute to the novel mechanistic studies aim of identifying, in depth, the role of the TRIM37 protein in the immune system.

TRIM E3 Ubiquitin Ligases in Rare Genetic Disorders

The TRIM family comprises proteins characterized by the presence of the tripartite motif composed of a RING domain, one or two B-box domains and a coiled-coil region. The TRIM shared domain structure underscores a common biochemical function as E3 ligase within the ubiquitination cascade. The TRIM proteins represent one of the largest E3 ligase families counting in human more than 70 members. These proteins are implicated in a plethora of cellular processes such as apoptosis, cell cycle regulation, muscular physiology, and innate immune response. Consistently, their alteration results in several pathological conditions emphasizing their medical relevance. Here, the genetic and pathogenetic mechanisms of rare disorders directly caused by mutations in TRIM genes will be reviewed. These diseases fall into different pathological areas, from malformation birth defects due to developmental abnormalities, to neurological disorders and progressive teenage neuromuscular disorders. In many instances, TRIM E3 ligases act on several substrates thus exerting pleiotropic activities: the need of unraveling disease-specific TRIM pathways for a precise targeting therapy avoiding dramatic side effects will be discussed.

Premature ovarian insufficiency and early depletion of the ovarian reserve in the monogenic Mulibrey nanism disorder

STUDY QUESTION

What is the timing of onset and clinical course of premature ovarian insufficiency (POI) in patients with Mulibrey nanism (MUL), a monogenic disorder caused by mutations of the peroxisomal TRIM37 gene?

SUMMARY ANSWER

The number of ovarian follicles is highly reduced already in infant and young MUL girls and the majority of them will have early depletion of follicles resulting in clinical and biochemical signs of POI.

WHAT IS KNOWN ALREADY

Both female and male patients with MUL show failure of sexual maturation, signs of hypogonadism and infertility.

STUDY DESIGN, SIZE, DURATION

We studied the gonadal function, pubertal development and ovarian reserve in 33 MUL patients aged 5.1-47.3 years (median age 22.3) at the end of observation. The patients were followed between 2004 and 2014 and 19 pubertal or postpubertal patients were enrolled in a cross-sectional study.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The period of postnatal activation of the hypothalamic-pituitary-gonadal axis (minipuberty), pubertal development and menstrual history were assessed longitudinally. The cross-sectional study included gynecological examination, analysis of reproductive hormones and ultrasonography with evaluation of ovarian volume and antral follicle count.

MAIN RESULTS AND THE ROLE OF CHANCE

Infant girls experienced a transient minipuberty with a high FSH surge. In childhood, gonadotropins were normal or slightly elevated but began to rise to hypergonadotropic levels in prepuberty. Anti-Müllerian hormone (AMH) levels remained undetectable or low throughout childhood. The onset of puberty occurred spontaneously and the median age at menarche was 12.5 years. Of the patients, 54% never attained regular menses and 10 years from menarche, only 8% of the women menstruated regularly. In the cross-sectional study, none of the patients had normal ovarian morphology under ultrasonography. Ovaries were hypoplastic and 82% had no or fewer than two visible antral follicles. AMH levels were undetectable in the vast majority (89%).

LIMITATIONS, REASONS FOR CAUTION

The Finnish MUL patients genotypically form a homogenous group and therefore it is possible, that different TRIM37 mutations lead to different hypogonadal phenotypes. However, to date there is no known genotype-phenotype correlation in MUL.

WIDER IMPLICATIONS OF THE FINDINGS

In MUL, AMH is a useful marker of ovarian function. MUL should be added to the list of syndromes associated with POI and correspondingly, TRIM37 should be added to the list of genes associated with POI. To our knowledge, TRIM37 is the first known gene coding for a peroxisomal membrane protein associated with female gonadal failure and infertility. Elucidating the role of syndromic genes in reproduction may aid in a greater understanding of ovarian biology.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the Finnish Foundation for Pediatric Research, Finska Läkaresällskapet, the Sigrid Jusélius Foundation and Helsinki University Hospital Research Funds. The authors declare no conflicts of interest.

TRIAL REGISTRATION NUMBER

Not applicable.

TRIMming down to TRIM37: Relevance to Inflammation, Cardiovascular Disorders, and Cancer in MULIBREY Nanism

TRIpartite motif (TRIM) proteins are part of the largest subfamilies of E3 ligases that mediate the transfer of ubiquitin to substrate target proteins. In this review, we focus on TRIM37 in the normal cell and in pathological conditions, with an emphasis on the MULIBREY (MUscle-LIver-BRain-EYe) genetic disorder caused by TRIM37 mutations. TRIM37 is characterized by the presence of a RING domain, B-box motifs, and a coiled-coil region, and its C-terminal part includes the MATH domain specific to TRIM37. MULIBREY nanism is a rare autosomal recessive caused by TRIM37 mutations and characterized by severe pre- and postnatal growth failure. Constrictive pericarditis is the most serious anomaly of the disease and is present in about 20% of patients. The patients have a deregulation of glucose and lipid metabolism, including type 2 diabetes, fatty liver, and hypertension. Puzzlingly, MULIBREY patients, deficient for TRIM37, are plagued with numerous tumors. Among non-MULIBREY patients affected by cancer, a wide variety of cancers are associated with an overexpression of TRIM37. This suggests that normal cells need an optimal equilibrium in TRIM37 expression. Finding a way to keep that balance could lead to potential innovative drugs for MULIBREY nanism, including heart condition and carcinogenesis treatment.

Histone H2A Monoubiquitination in Neurodevelopmental Disorders

Covalent histone modifications play an essential role in gene regulation and cellular specification required for multicellular organism development. Monoubiquitination of histone H2A (H2AUb1) is a reversible transcriptionally repressive mark. Exchange of histone H2A monoubiquitination and deubiquitination reflects the succession of transcriptional profiles during development required to produce cellular diversity from pluripotent cells. Germ-line pathogenic variants in components of the H2AUb1 regulatory axis are being identified as the genetic basis of congenital neurodevelopmental disorders. Here, we review the human genetics findings coalescing on molecular mechanisms that alter the genome-wide distribution of this histone modification required for development.

TRIM37, a novel E3 ligase for PEX5-mediated peroxisomal matrix protein import

Most proteins destined for the peroxisomal matrix depend on the peroxisomal targeting signals (PTSs), which require the PTS receptor PEX5, whose deficiency causes fatal human peroxisomal biogenesis disorders (PBDs). TRIM37 gene mutations cause muscle-liver-brain-eye (mulibrey) nanism. We found that TRIM37 localizes in peroxisomal membranes and ubiquitylates PEX5 at K464 by interacting with its C-terminal 51 amino acids (CT51), which is required for PTS protein import. PEX5 mutations (K464A or ΔCT51), or TRIM37 depletion or mutation, reduce PEX5 abundance by promoting its proteasomal degradation, thereby impairing its functions in cargo binding and PTS protein import in human cells. TRIM37 or PEX5 depletion induces apoptosis and enhances sensitivity to oxidative stress, underscoring the cellular requirement for functional peroxisomes. Therefore, TRIM37-mediated ubiquitylation stabilizes PEX5 and promotes peroxisomal matrix protein import, suggesting that mulibrey nanism is a new PBD.