Nucleoporin genes in human diseases

The Role of Non-Canonical Hsp70s (Hsp110/Grp170) in Cancer

Although cancers account for over 16% of all global deaths annually, at present, no reliable therapies exist for most types of the disease. As protein folding facilitators, heat shock proteins (Hsps) play an important role in cancer development. Not surprisingly, Hsps are among leading anticancer drug targets. Generally, Hsp70s are divided into two main subtypes: canonical Hsp70 (Escherichia coli Hsp70/DnaK homologues) and the non-canonical (Hsp110 and Grp170) members. These two main Hsp70 groups are delineated from each other by distinct structural and functional specifications. Non-canonical Hsp70s are considered as holdase chaperones, while canonical Hsp70s are refoldases. This unique characteristic feature is mirrored by the distinct structural features of these two groups of chaperones. Hsp110/Grp170 members are larger as they possess an extended acidic insertion in their substrate binding domains. While the role of canonical Hsp70s in cancer has received a fair share of attention, the roles of non-canonical Hsp70s in cancer development has received less attention in comparison. In the current review, we discuss the structure-function features of non-canonical Hsp70s members and how these features impact their role in cancer development. We further mapped out their interactome and discussed the prospects of targeting these proteins in cancer therapy.

ESCRT recruitment by the S. cerevisiae inner nuclear membrane protein Heh1 is regulated by Hub1-mediated alternative splicing

Misassembled nuclear pore complexes (NPCs) are removed by sealing off the surrounding nuclear envelope (NE), which is conducted by the endosomal sorting complexes required for transport (ESCRT) machinery. Recruitment of ESCRT proteins to the NE is mediated by the interaction between the ESCRT member Chm7 and the inner nuclear membrane protein Heh1, which belongs to the conserved LEM family. Increased ESCRT recruitment results in excessive membrane scission at damage sites but its regulation remains poorly understood. Here, we show that Hub1-mediated alternative splicing of HEH1 pre-mRNA, resulting in production of its shorter form Heh1-S, is critical for the integrity of the NE in Saccharomyces cerevisiae ESCRT-III mutants lacking Hub1 or Heh1-S display severe growth defects and accumulate improperly assembled NPCs. This depends on the interaction of Chm7 with the conserved MSC domain, which is only present in the longer variant Heh1-L. Heh1 variants assemble into heterodimers, and we demonstrate that a unique splice segment in Heh1-S suppresses growth defects associated with the uncontrolled interaction between Heh1-L and Chm7. Together, our findings reveal that Hub1-mediated splicing generates Heh1-S to regulate ESCRT recruitment to the NE.This article has an associated First Person interview with the first author of the paper.

MRNA Transcription, Translation, and Defects in Developmental Cognitive and Behavioral Disorders

The growth of expertise in molecular techniques, their application to clinical evaluations, and the establishment of databases with molecular genetic information has led to greater insights into the roles of molecular processes related to gene expression in neurodevelopment and functioning. The goal of this review is to examine new insights into messenger RNA transcription, translation, and cellular protein synthesis and the relevance of genetically determined alterations in these processes in neurodevelopmental, cognitive, and behavioral disorders.

CIC de novo loss of function variants contribute to cerebral folate deficiency by downregulating FOLR1 expression

Background Cerebral folate deficiency (CFD) syndrome is characterised by a low concentration of 5-methyltetrahydrofolate in cerebrospinal fluid, while folate levels in plasma and red blood cells are in the low normal range. Mutations in several folate pathway genes, including FOLR1 (folate receptor alpha, FRα), DHFR (dihydrofolate reductase) and PCFT (proton coupled folate transporter) have been previously identified in patients with CFD.

Methods In an effort to identify causal mutations for CFD, we performed whole exome sequencing analysis on eight CFD trios and identified eight de novo mutations in seven trios.

Results Notably, we found a de novo stop gain mutation in the capicua (CIC) gene. Using 48 sporadic CFD samples as a validation cohort, we identified three additional rare variants in CIC that are putatively deleterious mutations. Functional analysis indicates that CIC binds to an octameric sequence in the promoter regions of folate transport genes: FOLR1, PCFT and reduced folate carrier (Slc19A1; RFC1). The CIC nonsense variant (p.R353X) downregulated FOLR1 expression in HeLa cells as well as in the induced pluripotent stem cell (iPSCs) derived from the original CFD proband. Folate binding assay demonstrated that the p.R353X variant decreased cellular binding of folic acid in cells.

Conclusion This study indicates that CIC loss of function variants can contribute to the genetic aetiology of CFD through regulating FOLR1 expression. Our study described the first mutations in a non-folate pathway gene that can contribute to the aetiology of CFD.

Loss of the nucleoporin Aladin in central nervous system and fibroblasts of Allgrove Syndrome

Allgrove syndrome (AS) is a rare disease with broad neurological involvement. Neurodegeneration can affect spinal motor neurons, Purkinje cells, striatal neurons and the autonomic system. The mechanisms that lead to neuronal loss are still unclear. Recessive mutations in the AAAS gene affect the encoded protein Aladin, which would normally localize to the cytoplasmic face of the nuclear membrane as part of the nuclear pore complex (NPC). While the NPC is known to be a key factor for nucleocytoplasmic transport, the precise role of Aladin has not been elucidated yet. Here, we explored the consequences of the homozygous AAAS mutation c.464G>A (p.R155H) in central nervous system tissues and fibroblasts of a novel AS patient presenting motor neuron disease, cerebellar ataxia and autonomic dysfunction. Neuropathological analyses showed severe loss of motor neurons and Purkinje cells, with significant reduction in the perinuclear expression of Aladin. A reduced amount of protein was detected in the nuclear membrane fraction of the patient's brain. RNA analysis revealed a significant reduction of the transcript AAAS-1, while the AAAS-2 transcript was upregulated in fibroblasts. To our knowledge, this is the first study to demonstrate the effects of AAAS mutations in the human central nervous system.

The Hitchhiker's Guide to Nucleocytoplasmic Trafficking in Neurodegeneration

The widespread nature of nucleocytoplasmic trafficking defects and protein accumulation suggests distinct yet overlapping mechanisms in a variety of neurodegenerative diseases. Detailed understanding of the cellular pathways involved in nucleocytoplasmic transport and its dysregulation are essential for elucidating neurodegenerative pathogenesis and pinpointing potential areas for therapeutic intervention. The transport of cargos from the nucleus to the cytoplasm is generally regulated by the structure and function of the nuclear pore as well as the karyopherin α/β, importin, exportin, and mRNA export mechanisms. The disruption of these crucial transport mechanisms has been extensively described in the context of neurodegenerative diseases. One common theme in neurodegeneration is the cytoplasmic aggregation of proteins, including nuclear RNA binding proteins, repeat expansion associated gene products, and tau. These cytoplasmic aggregations are partly a consequence of failed nucleocytoplasmic transport machinery, but can also further disrupt transport, creating cyclical feed-forward mechanisms that exacerbate neurodegeneration. Here we describe the canonical mechanisms that regulate nucleocytoplasmic trafficking as well as how these mechanisms falter in neurodegenerative diseases.

Biallelic Variants in the Nuclear Pore Complex Protein NUP93 Are Associated with Non-progressive Congenital Ataxia

Nuclear pore complexes (NPCs) are the gateways of the nuclear envelope mediating transport between cytoplasm and nucleus. They form huge complexes of 125 MDa in vertebrates and consist of about 30 different nucleoporins present in multiple copies in each complex. Here, we describe pathogenic variants in the nucleoporin 93 (NUP93) associated with an autosomal recessive form of congenital ataxia. Two rare compound heterozygous variants of NUP93 were identified by whole exome sequencing in two brothers with isolated cerebellar atrophy: one missense variant (p.R537W) results in a protein which does not localize to NPCs and cannot functionally replace the wild type protein, whereas the variant (p.F699L) apparently supports NPC assembly. In addition to its recently described pathological role in steroid-resistant nephrotic syndrome, our work identifies NUP93 as a candidate gene for non-progressive congenital ataxia.

Coagulation FXIII-A Protein Expression Defines Three Novel Sub-populations in Pediatric B-Cell Progenitor Acute Lymphoblastic Leukemia Characterized by Distinct Gene Expression Signatures

Background: Leukemic B-cell precursor (BCP) lymphoblasts were identified as a novel expression site for coagulation factor XIII subunit A (FXIII-A). Flow cytometry (FC) revealed three distinct expression patterns, i.e., FXIII-A negative, FXIII-A dim, and FXIII-A bright subgroups. The FXIII-A negative subgroup was significantly associated with the “B-other” genetic category and had an unfavorable disease outcome.

Methods: RNA was extracted from bone marrow lymphoblasts of 42 pediatric patients with BCP-acute lymphoblastic leukemia (ALL). FXIII-A expression was determined by multiparameter FC. Genetic diagnosis was based on conventional cytogenetic method and fluorescence in situ hybridization. Affymetrix GeneChip Human Primeview array was used to analyze global expression pattern of 28,869 well-annotated genes. Microarray data were analyzed by Genespring GX14.9.1 software. Gene Ontology analysis was performed using Cytoscape 3.4.0 software with ClueGO application. Selected differentially expressed genes were validated by RT-Q-PCR.

Results: We demonstrated, for the first time, the general expression of F13A1 gene in pediatric BCP-ALL samples. The intensity of F13A1 expression corresponded to the FXIII-A protein expression subgroups which defined three characteristic and distinct gene expression signatures detected by Affymetrix oligonucleotide microarrays. Relative gene expression intensity of ANGPTL2, EHMT1 FOXO1, HAP1, NUCKS1, NUP43, PIK3CG, RAPGEF5, SEMA6A, SPIN1, TRH, and WASF2 followed the pattern of change in the intensity of the expression of the F13A1 gene. Common enhancer elements of these genes revealed by in silico analysis suggest that common transcription factors may regulate the expression of these genes in a similar fashion. PLAC8 was downregulated in the FXIII-A bright subgroup. Gene expression signature of the FXIII-A negative subgroup showed an overlap with the signature of “B-other” samples. DFFA, GIGYF1, GIGYF2, and INTS3 were upregulated and CD3G was downregulated in the “B-other” subgroup. Validated genes proved biologically and clinically relevant. We described differential expression of genes not shown previously to be associated with pediatric BCP-ALL.

Conclusions: Gene expression signature according to FXIII-A protein expression status defined three novel subgroups of pediatric BCP-ALL. Multiparameter FC appears to be an easy-to-use and affordable method to help in selecting FXIII-A negative patients who require a more elaborate and expensive molecular genetic investigation to design precision treatment.

In Vivo Expression of NUP93 and Its Alteration by NUP93 Mutations Causing Focal Segmental Glomerulosclerosis

Introduction

Mutations in genes encoding nucleoporins (NUPs; components of nuclear pore complexes [NPCs]), such as NUP93, have been reported to cause steroid-resistant nephrotic syndrome (SRNS) or focal segmental glomerulosclerosis (FSGS), which often progresses to end-stage renal disease (ESRD) in childhood. The expression of NUP93 in renal or extrarenal tissues, and the mechanism by which NUP93 mutations cause this renal phenotype, remain unclear.

Methods

The expression of NUP93 in normal control kidney and in a patient with FSGS carrying NUP93 mutations was examined by immunofluorescence analysis. The expression of NUP93 in blood cells was analyzed by Western blot analysis.

Results

Immunofluorescence analysis detected NUP93 expression in nuclei of all glomerular and tubulointerstitial cells in human kidneys. Whole-exome sequencing identified a compound heterozygous NUP93 mutation comprising a novel missense mutation p.Arg525Trp, and a previously reported mutation, p.Tyr629Cys, in a patient with FSGS that developed ESRD at the age of 6 years. In the patient’s kidney, the intensity of NUP93 immunofluorescence was significantly decreased in the nuclei of both glomerular and extraglomerular cells. The expression of CD2-associated protein (CD2AP) and nephrin in the patient’s podocytes was relatively intact. The amount of NUP93 protein was not significantly altered in the peripheral blood mononuclear cells of the patient.

Conclusion

NUP93 is expressed in the nuclei of all the cell types of the human kidney. Altered NUP93 expression in glomerular cells as well as extraglomerular cells by NUP93 mutations may underlie the pathogenic mechanism of SRNS or FSGS.

Linking Nucleoporins, Mitosis, and Colon Cancer

Suppression of a nuclear pore protein Nup358/RanBP2 is linked to mitotic cell death, but the clinical relevance of this link is unknown. In a recent issue of Cell, Vecchione et al. (2016) show that in approximately 10% of BRAF-like colorectal cancer (CC) patients, Nup358/RanBP2 is critical for survival. Treatment with vinorelbine, a microtubule-depolymerizing drug that inhibits mitosis, might be a potential treatment for these CCs.

Molecular assay for an intronic variant in NUP93 that causes steroid resistant nephrotic syndrome

Advances in molecular genetics have revealed that approximately 30% of cases with steroid-resistant nephrotic syndrome (SRNS) are caused by single-gene mutations. More than 50 genes are responsible for SRNS. One such gene is the nucleoporin, 93-KD (NUP93). Thus far, few studies have reported mutations of NUP93 in SRNS. Here, we describe an NUP93 biallelic mutation in a 9-year-old boy with focal segmental glomerular sclerosis (FSGS). Notably, one mutation comprised an intronic variant; we conducted in vivo and in vitro analysis to characterize this variant. We found two heterozygous mutations in NUP93: c.2137-18G>A in intron 19 and a novel nonsense mutation c.727A>T (p.Lys243*) in exon 8. We conducted RNA sequencing and in vitro splicing assays by using minigene construction, combined with protein expression analysis to determine the pathogenicity of the intronic variant. Both RNA sequencing and in vitro splicing assay showed exon 20-skipping by the intronic variant. In protein expression analysis, aberrant subcellular localization with small punctate vesicles in the cytoplasm was observed for the intronic variant. Taken together, we concluded that c.2137-18G>A was linked to pathogenicity due to aberrant splicing. NUP93 variants are quite rare; however, we have shown that even intronic variants in NUP93 can cause SRNS. This study provides a fundamental approach to validate the intronic variant, as well as new insights regarding the clinical spectrum of SRNS caused by rare gene variants.

Moderate Nucleoporin 133 deficiency leads to glomerular damage in zebrafish

Although structural nuclear pore proteins (nucleoporins) are seemingly required in every cell type to assemble a functional nuclear transport machinery, mutations or deregulation of a subset of them have been associated with specific human hereditary diseases. In particular, previous genetic studies of patients with nephrotic syndrome identified mutations in Nup107 that impaired the expression or the localization of its direct partner at nuclear pores, Nup133. In the present study, we characterized the zebrafish nup133 orthologous gene and its expression pattern during larval development. Using a morpholino-mediated gene knockdown, we show that partial depletion of Nup133 in zebrafish larvae leads to the formation of kidney cysts, a phenotype that can be rescued by co-injection of wild type mRNA. Analysis of different markers for tubular and glomerular development shows that the overall kidney development is not affected by nup133 knockdown. Likewise, no gross defect in nuclear pore complex assembly was observed in these nup133 morphants. On the other hand, nup133 downregulation results in proteinuria and moderate foot process effacement, mimicking some of the abnormalities typically featured by patients with nephrotic syndrome. These data indicate that nup133 is a new gene required for proper glomerular structure and function in zebrafish.

Genome analysis of the rice coral Montipora capitata

Corals comprise a biomineralizing cnidarian, dinoflagellate algal symbionts, and associated microbiome of prokaryotes and viruses. Ongoing efforts to conserve coral reefs by identifying the major stress response pathways and thereby laying the foundation to select resistant genotypes rely on a robust genomic foundation. Here we generated and analyzed a high quality long-read based ~886 Mbp nuclear genome assembly and transcriptome data from the dominant rice coral, Montipora capitata from Hawai’i. Our work provides insights into the architecture of coral genomes and shows how they differ in size and gene inventory, putatively due to population size variation. We describe a recent example of foreign gene acquisition via a bacterial gene transfer agent and illustrate the major pathways of stress response that can be used to predict regulatory components of the transcriptional networks in M. capitata. These genomic resources provide insights into the adaptive potential of these sessile, long-lived species in both natural and human influenced environments and facilitate functional and population genomic studies aimed at Hawaiian reef restoration and conservation.

Triple A patient cells suffering from mitotic defects fail to localize PGRMC1 to mitotic kinetochore fibers

Background

Membrane-associated progesterone receptors are restricted to the endoplasmic reticulum and are shown to regulate the activity of cytochrome P450 enzymes which are involved in steroidogenesis or drug detoxification. PGRMC1 and PGRMC2 belong to the membrane-associated progesterone receptor family and are of interest due to their suspected role during cell cycle. PGRMC1 and PGRMC2 are thought to bind to each other; thereby suppressing entry into mitosis. We could previously report that PGRMC2 interacts with the nucleoporin ALADIN which when mutated results in the autosomal recessive disorder triple A syndrome. ALADIN is a novel regulator of mitotic controller Aurora kinase A and depletion of this nucleoporin leads to microtubule instability.

Results

In the current study, we present that proliferation is decreased when ALADIN, PGRMC1 or PGRMC2 are over-expressed. Furthermore, we find that depletion of ALADIN results in mislocalization of Aurora kinase A and PGRMC1 in metaphase cells. Additionally, PGRMC2 is over-expressed in triple A patient fibroblasts.

Conclusion

Our results emphasize the possibility that loss of the regulatory association between ALADIN and PGRMC2 gives rise to a depletion of PGRMC1 at kinetochore fibers. This observation may explain part of the symptoms seen in triple A syndrome patients.

Integrative structure and functional anatomy of a nuclear pore complex

Despite the central role of Nuclear Pore Complexes (NPCs) as gatekeepers of RNA and protein transport between the cytoplasm and nucleoplasm, their large size and dynamic nature have impeded a full structural and functional elucidation. Here, we have determined a subnanometer precision structure for the entire 552-protein yeast NPC by satisfying diverse data including stoichiometry, a cryo-electron tomography map, and chemical cross-links. The structure reveals the NPC’s functional elements in unprecedented detail. The NPC is built of sturdy diagonal columns to which are attached connector cables, imbuing both strength and flexibility, while tying together all other elements of the NPC, including membrane-interacting regions and RNA processing platforms. Inwardly-directed anchors create a high density of transport factor-docking Phe-Gly repeats in the central channel, organized in distinct functional units. Taken together, this integrative structure allows us to rationalize the architecture, transport mechanism, and evolutionary origins of the NPC.

TDP-43 pathology disrupts nuclear pore complexes and nucleocytoplasmic transport in ALS/FTD

The cytoplasmic mislocalization and aggregation of TAR DNA-binding protein-43 (TDP-43) is a common histopathological hallmark of the amyotrophic lateral sclerosis and frontotemporal dementia disease spectrum (ALS/FTD). However, the composition of aggregates and their contribution to the disease process remain unknown. Here we used proximity-dependent biotin identification (BioID) to interrogate the interactome of detergent-insoluble TDP-43 aggregates and found them enriched for components of the nuclear pore complex and nucleocytoplasmic transport machinery. Aggregated and disease-linked mutant TDP-43 triggered the sequestration and/or mislocalization of nucleoporins and transport factors, and interfered with nuclear protein import and RNA export in mouse primary cortical neurons, human fibroblasts and induced pluripotent stem cell-derived neurons. Nuclear pore pathology is present in brain tissue in cases of sporadic ALS and those involving genetic mutations in TARDBP and C9orf72. Our data strongly implicate TDP-43-mediated nucleocytoplasmic transport defects as a common disease mechanism in ALS/FTD.

Alterations of the nuclear transport system in hepatocellular carcinoma - New basis for therapeutic strategies

Hepatocellular carcinoma (HCC) is among the most prevalent human malignancies worldwide with rising incidence in industrialised countries, few therapeutic options and poor prognosis. To expand and improve therapeutic strategies, identification of drug targets involved in several liver cancer-related pathways is crucial. Virtually all signal transduction cascades cross the nuclear envelope and therefore require components of the nuclear transport system (NTS), including nuclear transport receptors (e.g. importins and exportins) and the nuclear pore complex. Accordingly, members of the NTS represent promising targets for therapeutic intervention. Selective inhibitors of nuclear export have already entered clinical trials for various malignancies. Herein, we review the current knowledge regarding alterations of the NTS and their potential for targeted therapy in HCC.

Computer Analysis of Glioma Transcriptome Profiling: Alternative Splicing Events

Here we present the analysis of alternative splicing events on an example of glioblastoma cell culture samples using a set of computer tools in combination with database integration. The gene expression profiles of glioblastoma were obtained from cell culture samples of primary glioblastoma which were isolated and processed for RNA extraction. Transcriptome profiling of normal brain samples and glioblastoma were done by Illumina sequencing. The significant differentially expressed exon-level probes and their corresponding genes were identified using a combination of the splicing index method. Previous studies indicated that tumor-specific alternative splicing is important in the regulation of gene expression and corresponding protein functions during cancer development. Multiple alternative splicing transcripts have been identified as progression markers, including generalized splicing abnormalities and tumor- and stage-specific events. We used a set of computer tools which were recently applied to analysis of gene expression in laboratory animals to study differential splicing events. We found 69 transcripts that are differentially alternatively spliced. Three cancer-associated genes were considered in detail, in particular: APP (amyloid beta precursor protein), CASC4 (cancer susceptibility candidate 4) and TP53. Such alternative splicing opens new perspectives for cancer research.

Obesity-associated gene TMEM18 has a role in the central control of appetite and body weight regulation

An intergenic region of human chromosome 2 (2p25.3) harbors genetic variants which are among those most strongly and reproducibly associated with obesity. The gene closest to these variants is TMEM18, although the molecular mechanisms mediating these effects remain entirely unknown. Tmem18 expression in the murine hypothalamic paraventricular nucleus (PVN) was altered by changes in nutritional state. Germline loss of Tmem18 in mice resulted in increased body weight, which was exacerbated by high fat diet and driven by increased food intake. Selective overexpression of Tmem18 in the PVN of wild-type mice reduced food intake and also increased energy expenditure. We provide evidence that TMEM18 has four, not three, transmembrane domains and that it physically interacts with key components of the nuclear pore complex. Our data support the hypothesis that TMEM18 itself, acting within the central nervous system, is a plausible mediator of the impact of adjacent genetic variation on human adiposity.

Relocalization of DNA lesions to the nuclear pore complex

Early screens in yeast for mutations exhibiting sensitivity to DNA damage identified nuclear pore components, but their role in DNA repair was not well understood. Over the last decade, studies have revealed that several types of persistent DNA lesions relocate to either the nuclear pore complex (NPC) or nuclear envelope (NE). Of these two sites, the nuclear pore appears to be crucial for DNA repair of persistent double-strand breaks, eroded telomeres and sites of fork collapse at expanded CAG repeats. Using a combination of cell biological imaging techniques and yeast genetic assays for DNA repair, researchers have begun to understand both the how and why of lesion relocation to the NPC. Here we review the types of lesions that relocate to the NPC, mediators of relocation and the functional consequences of relocation understood to date. The emerging theme is that relocation to the NPC regulates recombination to influence repair pathway choice and provide a rescue mechanism for lesions or DNA structures that are resistant to repair.

The roles of the nuclear pore complex in cellular dysfunction, aging and disease

The study of the Nuclear Pore Complex (NPC), the proteins that compose it (nucleoporins), and the nucleocytoplasmic transport that it controls have revealed an unexpected layer to pathogenic disease onset and progression. Recent advances in the study of the regulation of NPC composition and function suggest that the precise control of this structure is necessary to prevent diseases from arising or progressing. Here we discuss the role of nucleoporins in a diverse set of diseases, many of which directly or indirectly increase in occurrence and severity as we age, and often shorten the human lifespan. NPC biology has been shown to play a direct role in these diseases and therefore in the process of healthy aging.

Causes and consequences of nuclear gene positioning

The eukaryotic genome is organized in a manner that allows folding of the genetic material in the confined space of the cell nucleus, while at the same time enabling its physiological function. A major principle of spatial genome organization is the non-random position of genomic loci relative to other loci and to nuclear bodies. The mechanisms that determine the spatial position of a locus, and how position affects function, are just beginning to be characterized. Initial results suggest that there are multiple, gene-specific mechanisms and the involvement of a wide range of cellular machineries. In this Commentary, we review recent findings from candidate approaches and unbiased screening methods that provide initial insight into the cellular mechanisms of positioning and their functional consequences. We highlight several specific mechanisms, including tethering of genome regions to the nuclear periphery, passage through S-phase and histone modifications, that contribute to gene positioning in yeast, plants and mammals.

Identification of a novel putative interaction partner of the nucleoporin ALADIN

It has been shown that the nucleoporin ALADIN plays a significant role in the redox homeostasis of the cell, but its function in steroidogenesis contributing to adrenal atrophy in triple A syndrome remains largely unknown. In an attempt to identify new interaction partners of ALADIN, co-immunoprecipitation followed by proteome analysis was conducted in different expression models using the human adrenocortical tumour cell line NCI-H295R. Our results suggest an interaction of ALADIN with the microsomal protein PGRMC2. PGRMC2 is shown to be activity regulator of CYP P450 enzymes and, therefore, to be a possible target for adrenal dysregulation in triple A syndrome. We show that there is a sexual dimorphism regarding the expression of Pgrmc2 in adrenals and gonads of wild-type (WT) and Aaas knock-out (KO) mice. Female Aaas KO mice are sterile due to delayed oocyte maturation and meiotic spindle assembly. A participation in meiotic spindle assembly confirms the recently investigated involvement of ALADIN in mitosis and emphasises an interaction with PGRMC2 which is a regulator of the cell cycle. By identification of a novel interaction partner of ALADIN, we provide novel aspects for future research of the function of ALADIN during cell cycle and for new insights into the pathogenesis of triple A syndrome.

Nucleoporin-mediated regulation of cell identity genes

Here, Ibarra et al. investigate the contribution of nuclear envelope components to the regulation of cell type-specific gene expression and show a role for NPC components in the regulation of cell type-specific gene expression The authors found that nucleoporin-associated superenhancers localize preferentially to the nuclear periphery, and, in the absence of nucleoporins, transcriptional changes of SE-associated genes were observed.

The organization of the genome in the three-dimensional space of the nucleus is coupled with cell type-specific gene expression. However, how nuclear architecture influences transcription that governs cell identity remains unknown. Here, we show that nuclear pore complex (NPC) components Nup93 and Nup153 bind superenhancers (SE), regulatory structures that drive the expression of key genes that specify cell identity. We found that nucleoporin-associated SEs localize preferentially to the nuclear periphery, and absence of Nup153 and Nup93 results in dramatic transcriptional changes of SE-associated genes. Our results reveal a crucial role of NPC components in the regulation of cell type-specifying genes and highlight nuclear architecture as a regulatory layer of genome functions in cell fate.