Leucine-rich glioma inactivated 3 regulates adipogenesis through ADAM23

Burden of Mendelian disorders in a large Middle Eastern biobank

BACKGROUND

Genome sequencing of large biobanks from under-represented ancestries provides a valuable resource for the interrogation of Mendelian disease burden at world population level, complementing small-scale familial studies.

METHODS

Here, we interrogate 6045 whole genomes from Qatar-a Middle Eastern population with high consanguinity and understudied mutational burden-enrolled at the national Biobank and phenotyped for 58 clinically-relevant quantitative traits. We examine a curated set of 2648 Mendelian genes from 20 panels, annotating known and novel pathogenic variants and assessing their penetrance and impact on the measured traits.

RESULTS

We find that 62.5% of participants are carriers of at least 1 known pathogenic variant relating to recessive conditions, with homozygosity observed in 1 in 150 subjects (0.6%) for which Peninsular Arabs are particularly enriched versus other ancestries (5.8-fold). On average, 52.3 loss-of-function variants were found per genome, 6.5 of which affect a known Mendelian gene. Several variants annotated in ClinVar/HGMD as pathogenic appeared at intermediate frequencies in this cohort (1-3%), highlighting Arab founder effect, while others have exceedingly high frequencies (> 5%) prompting reconsideration as benign. Furthermore, cumulative gene burden analysis revealed 56 genes having gene carrier frequency > 1/50, including 5 ACMG Tier 3 panel genes which would be candidates for adding to newborn screening in the country. Additionally, leveraging 58 biobank traits, we systematically assess the impact of novel/rare variants on phenotypes and discover 39 candidate large-effect variants associating with extreme quantitative traits. Furthermore, through rare variant burden testing, we discover 13 genes with high mutational load, including 5 with impact on traits relevant to disease conditions, including metabolic disorder and type 2 diabetes, consistent with the high prevalence of these conditions in the region.

CONCLUSIONS

This study on the first phase of the growing Qatar Genome Program cohort provides a comprehensive resource from a Middle Eastern population to understand the global mutational burden in Mendelian genes and their impact on traits in seemingly healthy individuals in high consanguinity settings.

Leucine rich repeat LGI family member 3: Integrative analyses support its prognostic association with pancreatic adenocarcinoma

Leucine rich repeat LGI family member 3 (LGI3) is a member of the LGI protein family. Previous studies of our group have reported that LGI3 is expressed in adipose tissue, skin and brain, and serves as a multifunctional cytokine. LGI3 may also be involved in cytokine networks in various cancers. This study aimed to analyze differentially expressed genes in pancreatic adenocarcinoma (PAC) tissues and PAC cohort data in order to evaluate the prognostic role of LGI3. The expression microarray and the PAC cohort data were analyzed by bioinformatic methods for differential expression, protein-protein interactions, functional enrichment and pathway analyses, gene co-expression network analysis, and prognostic association analysis. Results showed that LGI3 expression was significantly reduced in PAC tissues. Nineteen upregulated genes and 31 downregulated genes in PAC tissues were identified as LGI3-regulated genes. Protein-protein interaction network analysis demonstrated that 92% (46/50) of the LGI3-regulated genes that were altered in PACs belonged to a protein-protein interaction network cluster. Functional enrichment and gene co-expression network analyses demonstrated that these genes in the network cluster were associated with various processes including inflammatory and immune responses, metabolic processes, cell differentiation, and angiogenesis. PAC cohort analyses revealed that low expression levels of LGI3 were significantly associated with poor PAC prognosis. Analysis of favorable or unfavorable prognostic gene products in PAC showed that 93 LGI3-regulated genes were differentially associated with PAC prognosis. LGI3 expression was correlated with the tumor-infiltration levels of various immune cells. Taken together, these results suggested that LGI3 may be a potential prognostic marker of PAC.

Identification of ADAM23 as a Potential Signature for Psoriasis Using Integrative Machine-Learning and Experimental Verification

Background

Psoriasis is a common chronic, recurrent, and inflammatory skin disease. Identifying novel and potential biomarkers is valuable in the treatment and diagnosis of psoriasis. The goal of this study was to identify novel key biomarkers of psoriasis and analyze the potential underlying mechanisms.

Methods

Psoriasis-related datasets were downloaded from the Gene Expression Omnibus database to screen differential genes in the datasets. Functional and pathway enrichment analyses were performed on the differentially expressed genes (DEGs). Candidate biomarkers for psoriasis were identified from the GSE30999 and GSE6710 datasets using four machine learning algorithms, namely, random forest (RF), least absolute shrinkage and selection operator (LASSO) logistic regression, weighted gene co-expression network analysis (WGCNA), and support vector machine recursive feature elimination (SVM-RFE), and were validated using the GSE41662 dataset. Next, we used CIBERSORT and single-cell RNA analysis to explore the relationship between ADAM23 and immune cells. Finally, we validated the expression of the identified biomarkers expressions in human and mouse experiments.

Results

A total of 709 overlapping DEGs were identified, including 426 upregulated and 283 downregulated genes. Enhanced by enrichment analysis, the differentially expressed genes (DEGs) were spatially arranged in relation to immune cell involvement, immune-activating processes, and inflammatory signals. Based on the enrichment analysis, the DEGs were mapped to immune cell involvement, immune-activating processes, and inflammatory signals. Four machine learning strategies and single-cell RNA sequencing analysis showed that ADAM23, a disintegrin and metalloprotease, may be a unique, critical biomarker with high diagnostic accuracy for psoriasis. Based on CIBERSORT analysis, ADAM23 was found to be associated with a variety of immune cells, such as macrophages and mast cells, and it was upregulated in the macrophages of psoriatic lesions in patients and mice.

Conclusion

ADAM23 may be a potential biomarker in the diagnosis of psoriasis and may contribute to the pathogenesis by regulating immunological activity in psoriatic lesions.

Polygenic overlap with body-mass index improves prediction of treatment-resistant schizophrenia

Treatment resistant schizophrenia (TRS) is characterized by repeated treatment failure with antipsychotics. A recent genome-wide association study (GWAS) of TRS showed a polygenic architecture, but no significant loci were identified. Clozapine is shown to be the superior drug in terms of clinical effect in TRS; at the same time it has a serious side effect profile, including weight gain. Here, we sought to increase power for genetic discovery and improve polygenic prediction of TRS, by leveraging genetic overlap with Body Mass Index (BMI). We analysed GWAS summary statistics for TRS and BMI applying the conditional false discovery rate (cFDR) framework. We observed cross-trait polygenic enrichment for TRS conditioned on associations with BMI. Leveraging this cross-trait enrichment, we identified 2 novel loci for TRS at cFDR <0.01, suggesting a role of MAP2K1 and ZDBF2. Further, polygenic prediction based on the cFDR analysis explained more variance in TRS when compared to the standard TRS GWAS. These findings highlight putative molecular pathways which may distinguish TRS patients from treatment responsive patients. Moreover, these findings confirm that shared genetic mechanisms influence both TRS and BMI and provide new insights into the biological underpinnings of metabolic dysfunction and antipsychotic treatment.

Alterations of DNA methylation during adipogenesis differentiation of mesenchymal stem cells isolated from adipose tissue of patients with obesity is associated with type 2 diabetes

Adipogenesis regulation is crucial for mature adipocyte function. In obesity, a major driver of type 2 diabetes (T2D), this process is disrupted and remains poorly characterized. Here we identified altered DNA methylation profiles in diabetic obese patients, during three adipocytes differentiation stages. We isolated mesenchymal cells from visceral adipose tissue of obese patients with and without T2D to analyse DNA methylation profiles at 0, 3, and 18 days of ex vivo differentiation and documented their impact on gene expression. Methylation and gene expression were analysed with EPIC and Clarion S arrays, respectively. Patients with T2D had epigenetic alterations in all the analysed stages, and these were mainly observed in genes important in adipogenesis, insulin resistance, cell death programming, and immune effector processes. Importantly, at 3 days, we found six-fold more methylated CpG alterations than in the other stages. This is the first study to document epigenetic markers that persist through all three adipogenesis stages and their impact on gene expression, which could be a cellular metabolic memory involved in T2D. Our data provided evidence that, throughout the adipogenesis process, alterations occur in methylation that might impact mature adipocyte function, cause tissue malfunction, and potentially, lead to the development of T2D.

Temporal Lobe Epilepsy: What do we understand about protein alterations?

During neuronal diseases, neuronal proteins get disturbed due to changes in the connections of neurons. As a result, neuronal proteins get disturbed and cause epilepsy. At the genetic level, many mutations may take place in proteins like axon guidance proteins, leucine-rich glioma inactivated 1 protein, microtubular protein, pore-forming, chromatin remodeling, and chemokine proteins which may lead toward temporal lobe epilepsy. These proteins can be targeted in the future for the treatment purpose of epilepsy. Novel avenues can be developed for therapeutic interventions by these new insights.

Integrative proteomic network analyses support depot-specific roles for leucine rich repeat LGI family member 3 in adipose tissues

LGI family member 3 (LGI3) is a member of the LGI protein family. In our previous studies, LGI3 was determined to be expressed in adipose tissues, skin and the brain, where it served as a pleiotropic cytokine. The results indicated that LGI3 levels are increased in adipose tissues of obese individuals in comparison with control individuals and that LGI3 suppressed adipogenesis via its receptor, disintegrin and metalloproteinase domain-containing protein 23. Additionally, it was reported that LGI3 upregulates tumor necrosis factor-α and downregulated adiponectin and hypothesized that LGI3 may act as a proinflammatory adipokine involved in adipose tissue inflammation. In the present study, cytokine arrays were used to analyze cytokine levels in adipose tissues and plasma of LGI3-knockout mice and signaling protein arrays used to analyze the expression and phosphorylation of these proteins in LGI3-treated preadipocytes. The results suggested that expression levels of 129 gene products (24 cytokines and 105 signaling proteins) were altered in response to LGI3 deficiency or LGI3 treatment, respectively. Protein-protein interaction network analysis of LGI3-regulated gene products revealed that 94% of the gene products (21 cytokines and 100 signaling proteins) formed an interaction network cluster. Functional enrichment analysis for the LGI3-regulated gene products, including those from our previous studies, revealed an association with numerous biological processes, including inflammatory responses, cellular differentiation and development and metabolic regulation. Gene co-expression network analysis revealed that these LGI3-regulated gene products were involved in various biological processes in an overlapping and differential manner between subcutaneous and visceral adipose tissues. Notably, inflammatory responses were more strongly associated with the LGI3-regulated gene co-expression network in visceral adipose tissues than in subcutaneous adipose tissues. Analysis of expression quantitative trait loci identified four single nucleotide variants that affect expression of LGI3 in an adipose depot-specific manner. Taken together, the results suggested that LGI3 may serve depot-specific roles as an adipokine in adipose tissues.

Endocytosis of the non-catalytic ADAM23: Recycling and long half-life properties

A Disintegrin And Metalloprotease 23 (ADAM23) is a member of the ADAMs family of transmembrane proteins, mostly expressed in nervous system, and involved in traffic and stabilization of Kv1-potassium channels, synaptic transmission, neurite outgrowth, neuronal morphology and cell adhesion. Also, ADAM23 has been linked to human pathological conditions, such as epilepsy, cancer metastasis and cardiomyopathy. ADAM23 functionality depends on the molecule presence at the cell surface and along the secretory pathway, as expected for a cell surface receptor. Because endocytosis is an important functional regulatory mechanism of plasma membrane receptors and no information is available about the traffic or turnover of non-catalytic ADAMs, we investigated ADAM23 internalization, recycling and half-life properties. Here, we show that ADAM23 undergoes constitutive internalization from the plasma membrane, a process that depends on lipid raft integrity, and is redistributed to intracellular vesicles, especially early and recycling endosomes. Furthermore, we observed that ADAM23 is recycled from intracellular compartments back to the plasma membrane and thus has longer half-life and higher cell surface stability compared with other ADAMs. Our findings suggest that regulation of ADAM23 endocytosis/stability could be exploited therapeutically in diseases in which ADAM23 is directly involved, such as epilepsy, cancer progression and cardiac hypertrophy.

Leucine-rich glioma inactivated 3: a novel keratinocyte-derived melanogenic cytokine in vitiligo patients

BACKGROUND

In-vitro studies showed that Leucine-rich glioma inactivated 3 (LGI3) is a keratinocyte-derived cytokine that stimulates melanin synthesis and is increased after ultra violet B (UVB) irradiation. So, we postulated that LGI3 may be involved in vitiligo aetiopathogenesis and may participate in narrow band ultra violet B (NB-UVB) induced pigmentation in vitiligo.

OBJECTIVES

To assess this hypothesis, lesional LGI3 immunohistochemical expression of vitiligo patients before and after NB-UVB phototherapy was studied, and its correlation with repigmentation was evaluated.

METHODS

Forty vitiligo patients and 20 age, sex, and skin phenotype-matched controls were enrolled. Patients were treated with NB-UVB thrice weekly for 12 weeks. VASI score was evaluated before and after NB-UVB sessions. For vitiligo patients, baseline LGI3 immunohistochemical staining was estimated, and compared to that of controls and to its post-treatment data in those patients. Results: Baseline LGI3 immunohistochemical studied parameters (expression, intensity, percentage and H score) were significantly lower in vitiligo cases than controls (p=0.003, 0.013, 0.001 and 0.001 respectively). After 12 weeks of NB-UVB phototherapy, these LGI3 immunohistochemical parameters were up-regulated and became comparable to that of controls (p >0.05 for all). There was a significant positive correlation between the improvement of both VASI score and LGI3 H score mean values (r=-0.349 , p=0.027).

STUDY LIMITATIONS

Small number of investigated subjects.

CONCLUSIONS

Decreased LGI3 protein may play an active role in vitiligo pathogenesis and its up-regulation after NB-UVB phototherapy, may actively participate in NB-UVB photo-induced melanogenesis.

Leucine rich repeat LGI family member 3: Integrative analyses reveal its prognostic association with non-small cell lung cancer

Leucine rich repeat LGI family member 3 (LGI3) is a member of the LGI protein family. Our previous studies reported that LGI3 was expressed in adipose tissues, brain and skin, where it served roles as a multifunctional cytokine and pro-inflammatory adipokine. It was hypothesized that LGI3 may be involved in cytokine networks in cancer. The present study aimed to analyze differentially expressed genes in non-small cell lung cancer (NSCLC) tissues and NSCLC cohort data, to evaluate the prognostic role of LGI3. Expression microarray and NSCLC cohort data were statistically analyzed by bioinformatic methods, and protein-protein interactions, functional enrichment and pathway, gene coexpression network (GCN) and prognostic association analyses were performed. The results demonstrated that the expression levels of LGI3 and its receptor a disintegrin and metalloproteinase domain-containing protein 22 were significantly decreased in NSCLC tissues. A total of two upregulated genes and 11 downregulated genes in NSCLC tissues were identified as LGI3-regulated genes. Protein-protein interaction network analysis demonstrated that all LGI3-regulated genes that were altered in NSCLC were involved in a protein-protein interaction network cluster. Functional enrichment, Kyoto Encyclopedia of Genes and Genomes pathway and GCN analyses demonstrated the association of these genes with the immune and inflammatory responses, angiogenesis, the tumor necrosis factor pathway, and chemokine and peroxisome proliferator-activated receptor signaling pathways. Analysis of NSCLC cohorts revealed that low expression levels of LGI3 was significantly associated with poor prognosis of NSCLC. Analysis of the somatic mutations of the LGI3 gene in NSCLC revealed that the amino acid residues altered in NSCLC included two single nucleotide polymorphism sites and three phylogenetically coevolved amino acid residues. Taken together, these results suggest that LGI3 may be a potential prognostic marker of NSCLC.

ADAM23 promotes neuronal differentiation of human neural progenitor cells

Background

ADAM23 is widely expressed in the embryonic central nervous system and plays an important role in tissue formation.

Results

In this study, we showed that ADAM23 contributes to cell survival and is involved in neuronal differentiation during the differentiation of human neural progenitor cells (hNPCs). Upregulation of ADAM23 in hNPCs was found to increase the number of neurons and the length of neurite, while its downregulation decreases them and triggers cell apoptosis. RNA microarray analysis revealed mechanistic insights into genes and pathways that may become involved in multiple cellular processes upon up- or downregulation of ADAM23.

Conclusions

Our results suggest that ADAM23 regulates neuronal differentiation by triggering specific signaling pathways during hNPC differentiation.

Electronic supplementary material

The online version of this article (doi:10.1186/s11658-017-0045-1) contains supplementary material, which is available to authorized users.

Leucine-rich glioma inactivated 3: integrative analyses support its prognostic role in glioma

Background

Leucine-rich glioma inactivated 3 (LGI3) is a secreted protein member of LGI family. We previously reported that LGI3 was expressed in brain, adipose tissues and skin, where it played roles as a multifunctional cytokine. We postulated that LGI3 may be involved in cytokine network in cancers.

Aim

This study aimed to analyze differentially expressed genes in glioma tissues and glioma cohort data to investigate the prognostic role of LGI3 and its receptors.

Materials and methods

Expression microarray data from Gene Expression Omnibus and glioma cohort data were analyzed using bioinformatic tools for statistical analysis, protein–protein interactions, functional enrichment and pathway analyses and prognostic association analysis.

Results

We found that LGI3 and its receptors, ADAM22 and ADAM23, were significantly downregulated in glioma tissues. Eleven upregulated genes and two downregulated genes in glioma tissues were found to be the previously reported LGI3-regulated genes. Protein–protein interaction network analysis showed that 85% of the LGI3-regulated and glioma-altered genes formed a cluster of interaction network. Functional enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses revealed the association of these genes with hypoxia responses, p53 and Akt signaling and various cancer-related pathways including glioma. Analysis of expression microarray data of glioma cohorts demonstrated that low expression levels of LGI3, ADAM22 and ADAM23 were significantly associated with poor prognosis of glioma.

Conclusion

These results propose that LGI3 and its receptors may play a prognostic role in glioma.

Leucine-rich glioma inactivated 3: Integrative analyses support its role in the cytokine network

Leucine-rich glioma inactivated (LGI)3 is a secreted protein member of LGI family. We previously repo-rted that LGI3 was upregulated in adipose tissues from obese mice and suppressed adipogenesis through its receptor, a disintegrin and metalloproteinase domain-containing protein 23 (ADAM23). We demonstrated that LGI3 regulated tumor necrosis factor-α and adiponectin, and proposed that LGI3 may be a pro-inflammatory adipokine involved in adipose tissue inflammation. In this study, we analyzed adipokine and cytokine profiles in LGI3 knockout mice and demonstrated that multiple factors were increased or decreased in the adipose tissues and plasma of the LGI3 knockout mice. Phosphoprotein array analysis revealed increases in the phosphorylation levels of Akt, AMP-activated protein kinase (AMPK), Bad, extracellular signal-regulated kinase (Erk)1/2, glycogen synthase kinase 3α (GSK3α), phosphatase and tensin homolog (PTEN) and eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) in the LGI3-treated 3T3-L1 pre-adipocytes. Treatment with LGI3 increased the expression of various inflammatory genes in pre-adipocytes, adipocytes and macrophages. Integrative functional enrichment analysis for all LGI3-regulated gene products suggested their involvement in a number of biological processes, including cancer, inflammatory response, response to wounding, as well as cell proliferation and differentiation. Protein interaction network analysis of LGI3‑regulated gene products revealed that 94% of the gene products formed a cluster of interaction networks. Taken together, these results support the critical involvement of LGI3 in the cytokine network by interplaying with multiple adipokines, cytokines and signaling proteins.

A glucocorticoid- and diet-responsive pathway toggles adipocyte precursor cell activity in vivo

Obesity is driven by excess caloric intake, which leads to the expansion of adipose tissue by hypertrophy and hyperplasia. Adipose tissue hyperplasia results from the differentiation of adipocyte precursor cells (APCs) that reside in adipose depots. Investigation into this process has elucidated a network of mostly transcription factors that drive APCs through the differentiation process. Using in vitro and in vivo approaches, our study revealed a signaling pathway that inhibited the initiation of the adipocyte differentiation program. Mouse adipocytes secreted the extracellular protease ADAMTS1, which triggered the production of the cytokine pleiotrophin (PTN) through the Wnt/β-catenin pathway, and promoted proliferation rather than differentiation of APCs. Glucocorticoid exposure in vitro or in vivo reduced ADAMTS1 abundance in adipocytes. In addition, mice fed a high-fat diet showed decreased Adamts1 expression in the visceral perigonadal adipose depot, which expanded by adipogenesis in response to the diet, and increased Adamts1 expression in the subcutaneous inguinal adipose depot, which did not induce adipogenesis. Similar to what occurred in mouse subcutaneous adipose tissue, diet-induced weight gain increased the expression of ADAMTS1, PTN, and certain Wnt target genes in the subcutaneous adipose depot of human volunteers, suggesting the relevance of this pathway to physiological adipose tissue homeostasis and the pathogenesis of obesity. Thus, this pathway functions as a toggle on APCs, regulating a decision between differentiation and proliferation and coordinating the response of adipose tissue to systemic cues.

Dendritic cell expression of ADAM23 governs T cell proliferation and cytokine production through the α(v)β(3) integrin receptor

ADAM23 is a member of the brain macrophage-derived chemokine family. Structural homology of ADAM proteins suggests their function as integrin receptors. Previous studies have linked ADAM23 as a dominant contributor to brain development and cancer metastasis. The present studies now show that ADAM23 expression on DCs partially governs antigen-presentation capacities to responder CD4⁺ T cells. With the use of RNAi approaches, knockdown of ADAM23 in murine BMDCs resulted in impaired T cell activation, proliferation, and cytokine production. Knockdown did not alter the maturation profile of DCs (i.e., costimulatory molecule expression or production of proinflammatory cytokines) but markedly impaired cognate T cell responses. There was a significant decrease in antigen-specific clonal expansion coupled with a global decrease in Th cytokine production. Impaired early activation and proliferation did not alter/skew the balance of Th polarization but significantly depressed total levels of IL-2, IFN-γ, IL-4, and IL-17 cytokine production in CD4⁺ T cells primed by ADAM23 knockdown versus control DCs. Finally, neutralizing antibodies targeting the α(v)β(3) integrin receptors resulted in similar phenotypes of impaired CD4⁺ T cell responses. Taken together, these studies show a novel role of ADAM23 in governing DC antigen presentation to cognate CD4⁺ T cells.

Genomic structure and marker-derived gene networks for growth and meat quality traits of Brazilian Nelore beef cattle

BACKGROUND

Nelore is the major beef cattle breed in Brazil with more than 130 million heads. Genome-wide association studies (GWAS) are often used to associate markers and genomic regions to growth and meat quality traits that can be used to assist selection programs. An alternative methodology to traditional GWAS that involves the construction of gene network interactions, derived from results of several GWAS is the AWM (Association Weight Matrices)/PCIT (Partial Correlation and Information Theory). With the aim of evaluating the genetic architecture of Brazilian Nelore cattle, we used high-density SNP genotyping data (~770,000 SNP) from 780 Nelore animals comprising 34 half-sibling families derived from highly disseminated and unrelated sires from across Brazil. The AWM/PCIT methodology was employed to evaluate the genes that participate in a series of eight phenotypes related to growth and meat quality obtained from this Nelore sample.

RESULTS

Our results indicate a lack of structuring between the individuals studied since principal component analyses were not able to differentiate families by its sires or by its ancestral lineages. The application of the AWM/PCIT methodology revealed a trio of transcription factors (comprising VDR, LHX9 and ZEB1) which in combination connected 66 genes through 359 edges and whose biological functions were inspected, some revealing to participate in biological growth processes in literature searches.

CONCLUSIONS

The diversity of the Nelore sample studied is not high enough to differentiate among families neither by sires nor by using the available ancestral lineage information. The gene networks constructed from the AWM/PCIT methodology were a useful alternative in characterizing genes and gene networks that were allegedly influential in growth and meat quality traits in Nelore cattle.

Genome-wide association analysis identifies three new susceptibility loci for childhood body mass index

A large number of genetic loci are associated with adult body mass index. However, the genetics of childhood body mass index are largely unknown. We performed a meta-analysis of genome-wide association studies of childhood body mass index, using sex- and age-adjusted standard deviation scores. We included 35 668 children from 20 studies in the discovery phase and 11 873 children from 13 studies in the replication phase. In total, 15 loci reached genome-wide significance (P-value < 5 × 10(-8)) in the joint discovery and replication analysis, of which 12 are previously identified loci in or close to ADCY3, GNPDA2, TMEM18, SEC16B, FAIM2, FTO, TFAP2B, TNNI3K, MC4R, GPR61, LMX1B and OLFM4 associated with adult body mass index or childhood obesity. We identified three novel loci: rs13253111 near ELP3, rs8092503 near RAB27B and rs13387838 near ADAM23. Per additional risk allele, body mass index increased 0.04 Standard Deviation Score (SDS) [Standard Error (SE) 0.007], 0.05 SDS (SE 0.008) and 0.14 SDS (SE 0.025), for rs13253111, rs8092503 and rs13387838, respectively. A genetic risk score combining all 15 SNPs showed that each additional average risk allele was associated with a 0.073 SDS (SE 0.011, P-value = 3.12 × 10(-10)) increase in childhood body mass index in a population of 1955 children. This risk score explained 2% of the variance in childhood body mass index. This study highlights the shared genetic background between childhood and adult body mass index and adds three novel loci. These loci likely represent age-related differences in strength of the associations with body mass index.

LGI Proteins and Epilepsy in Human and Animals

Leucine‐rich glioma‐inactivated (LGI) protein was first thought to have a suppressor effect in the formation of some cancers. Developments in physiology and medicine made it possible to characterize the function of the LGI protein family and its crucial role in different conditions more precisely. These proteins play an important role in synaptic transmission, and dysfunction may cause hyperexcitability. Genetic mutation of LGI1was confirmed to be the cause of autosomal dominant lateral temporal lobe epilepsy in humans. The LGI2 mutation was identified in benign familial juvenile epilepsy in Lagotto Romagnolo (LR) dogs. Cats with familial spontaneous temporal lobe epilepsy have been reported, and the etiology might be associated with LGI protein family dysfunction. In addition, an autoimmune reaction against LGI1 was detected in humans and cats with limbic encephalitis. These advances prompted a review of LGI protein function and its role in different seizure disorders.

Leucine-rich glioma inactivated 3 and tumor necrosis factor-α regulate mutually through NF-κB

Leucine-rich glioma inactivated 3 (LGI3) is a secreted protein member of LGI family. We previously reported that LGI3 increased in obese adipose tissues and suppressed adipogenesis through its receptor, ADAM23. We proposed that LGI3 may be a pro-inflammatory adipokine secreted predominantly by preadipocytes and macrophages. In this study, we showed that LGI3 and tumor necrosis factor-α (TNF-α) upregulated each other in 3T3-L1 cells. Treatment of 3T3-L1 preadipocytes with LGI3 protein increased TNF-α mRNA and protein. LGI3 treatment led to NF-κB activation and binding to an NF-κB binding site (-523 to -514) in TNF-α promoter. TNF-α treatment increased mRNA and protein expression of LGI3 and ADAM23. TNF-α increased NF-κB binding to a predicted binding site (-40 to -31) in LGI3 promoter. High fat diet-fed mice showed that LGI3 and TNF-α were increased and colocalized in adipose tissue inflammation. Taken together, these results suggested that mutual upregulation of LGI3 and TNF-α may play a role in adipose tissue inflammation in obesity.

Intratumoral heterogeneity of ADAM23 promotes tumor growth and metastasis through LGI4 and nitric oxide signals

Intratumoral heterogeneity (ITH) represents an obstacle for cancer diagnosis and treatment, but little is known about its functional role in cancer progression. The A Desintegrin And Metalloproteinase 23 (ADAM23) gene is epigenetically silenced in different types of tumors, and silencing is often associated with advanced disease and metastasis. Here, we show that invasive breast tumors exhibit significant ADAM23-ITH and that this heterogeneity is critical for tumor growth and metastasis. We demonstrate that while loss of ADAM23 expression enhances invasion, it causes a severe proliferative deficiency and is not itself sufficient to trigger metastasis. Rather, we observed that, in ADAM23-heterotypic environments, ADAM23-negative cells promote tumor growth and metastasis by enhancing the proliferation and invasion of adjacent A23-positive cells through the production of LGI4 (Leucine-rich Glioma Inactivated 4) and nitric oxide (NO). Ablation of LGI4 and NO in A23-negative cells significantly attenuates A23-positive cell proliferation and invasion. Our work denotes a driving role of ADAM23-ITH during disease progression, shifting the malignant phenotype from the cellular to the tissue level. Our findings also provide insights for therapeutic intervention, enforcing the need to ascertain ITH to improve cancer diagnosis and therapy.

LGI proteins in the nervous system

The development and function of the vertebrate nervous system depend on specific interactions between different cell types. Two examples of such interactions are synaptic transmission and myelination. LGI1-4 (leucine-rich glioma inactivated proteins) play important roles in these processes. They are secreted proteins consisting of an LRR (leucine-rich repeat) domain and a so-called epilepsy-associated or EPTP (epitempin) domain. Both domains are thought to function in protein–protein interactions. The first LGI gene to be identified, LGI1, was found at a chromosomal translocation breakpoint in a glioma cell line. It was subsequently found mutated in ADLTE (autosomal dominant lateral temporal (lobe) epilepsy) also referred to as ADPEAF (autosomal dominant partial epilepsy with auditory features). LGI1 protein appears to act at synapses and antibodies against LGI1 may cause the autoimmune disorder limbic encephalitis. A similar function in synaptic remodelling has been suggested for LGI2, which is mutated in canine Benign Familial Juvenile Epilepsy. LGI4 is required for proliferation of glia in the peripheral nervous system and binds to a neuronal receptor, ADAM22, to foster ensheathment and myelination of axons by Schwann cells. Thus, LGI proteins play crucial roles in nervous system development and function and their study is highly important, both to understand their biological functions and for their therapeutic potential. Here, we review our current knowledge about this important family of proteins, and the progress made towards understanding their functions.

Leucine-rich glioma inactivated 3 associates negatively with adiponectin

Leucine-rich glioma inactivated 3 (LGI3) is a secreted protein member of LGI/epitempin family. We previously reported that LGI3 was expressed in adipose tissues and suppressed adipogenesis through its receptor, ADAM23. We proposed that LGI3 may be a candidate adipokine with pro-inflammatory activity. To investigate the role of LGI3 in adipose tissues, we analyzed cytokine profile in LGI3 knockout mice. Protein array analysis showed that adiponectin was significantly increased in adipose tissues and plasma of LGI3 knockout mice. SiRNA-mediated knockdown of LGI3 increased adiponectin in 3T3-L1 preadipocytes. Treatment of differentiating 3T3-L1 cells with LGI3 protein decreased adiponectin in a dose-dependent manner. High fat diet (HFD)-fed mice showed expression of LGI3 in adipose tissue macrophages in addition to adipocytes that expressed LGI3 in both normal chow-fed and HFD-fed mice. The 60-kDa LGI3 was selectively increased in adipose tissues of HFD mice in which adiponectin was downregulated. Taken together, these results suggested that LGI3 may participate in adipose tissue homeostasis by negatively regulating adiponectin.