Structure and Functions of Sidekicks

Functional insights into immunoglobulin superfamily proteins in invertebrate neurobiology and immunity

The Immunoglobulin Superfamily (IgSF) represents a vital protein family widely distributed in animal genomes, encompassing multifunctional proteins with immunoglobulin-like domains, including immunoglobulins. These proteins play pivotal roles in various biological processes, such as development, differentiation, adhesion, activation, regulation, and signal transduction. While the functions of IgSF in vertebrates are relatively well understood, their roles in invertebrates remain underexplored. This review aims to comprehensively summarize the functions and mechanisms of IgSF in invertebrates, focusing on arthropods, mollusks, and other primitive phyla. In arthropods, research on IgSF has primarily emphasized its roles in the nervous system, especially in axonal and synaptic regulation, and its critical functions in the immune system. Studies in mollusks have predominantly highlighted the immunological functions of IgSF in pathogen recognition, clearance responses, and signal transduction. In contrast, research on protozoa and platyhelminths has mainly focused on identifying IgSF molecules, with relatively limited insights into their functional roles. In sponges, IgSF is primarily associated with cell adhesion and intercellular recognition. By exploring the genetic and protein structural diversity of IgSF in invertebrates, this review reveals their multifunctionality and complexity in biological systems. It not only enhances our understanding of the roles of IgSF in invertebrates but also lays the groundwork for future studies on their potential applications in evolutionary biology and disease models.

Adaptive genomic signatures of globally invasive populations of the yellow fever mosquito Aedes aegypti

In the arboviral vector Aedes aegypti, adaptation to anthropogenic environments has led to a major evolutionary shift separating the domestic Aedes aegypti aegypti (Aaa) ecotype from the wild Aedes aegypti formosus (Aaf) ecotype. Aaa mosquitoes are distributed globally and have higher vectorial capacity than Aaf, which remained in Africa. Despite the evolutionary and epidemiological relevance of this separation, inconsistent morphological data and a complex population structure have hindered the identification of genomic signals distinguishing the two ecotypes. Here we assessed the correspondence between the geographic distribution, population structure and genome-wide selection of 511 Aaf and 123 Aaa specimens and report adaptive signals in 186 genes that we call Aaa molecular signatures. Our results indicate that Aaa molecular signatures arose from standing variation associated with extensive ancestral polymorphisms in Aaf populations and have been co-opted for self-domestication through genomic and functional redundancy and local adaptation. Overall, we show that the behavioural shift of Ae. aegypti mosquitoes to live in association with humans relied on the fine regulation of chemosensory, neuronal and metabolic functions, as seen in the domestication processes of rabbits and silkworms. Our results also provide a foundation for the investigation of new genic targets for the control of Ae. aegypti populations.

A genome-wide association study of methamphetamine use among people with HIV

BACKGROUND

Amphetamine-like stimulants are the most used psychostimulants in the world; methamphetamine use is the most prevalent in people with HIV. Prolonged methamphetamine use can cause lasting damage to the heart, gut, and brain, as well as auditory hallucinations and paranoid thinking. However, relatively little is known about methamphetamine use and its genetic contributors.

METHODS

Using genetic information from the Centers for AIDS Research Network of Integrated Clinical Systems (CNICS) cohort, we conducted a multi-ancestry genome-wide association study (GWAS) of methamphetamine use among people with HIV (n = 1,196 reported ever use, n = 4,750 reported never use).

RESULTS

No single nucleotide polymorphism was statistically associated with methamphetamine use at the genome-wide level (p < 5 * 10-8) in our study. Further, we did not replicate previously suggested genetic variants from other studies (all p > 0.05 in our analysis).

DISCUSSION

Our study suggests that there is no single strong genetic contributor to lifetime use of methamphetamine in people with HIV enrolled in CNICS. Larger studies with more refined outcome assessment are warranted to further understand the contribution of genetics to methamphetamine use and use disorder. Investigation into social and environmental contributors to methamphetamine use are similarly necessary.

Integrated gene expression and alternative splicing analysis in human and mouse models of Rett syndrome

Mutations of the MECP2 gene lead to Rett syndrome (RTT), a rare developmental disease causing severe intellectual and physical disability. How the loss or defective function of MeCP2 mediates RTT is still poorly understood. MeCP2 is a global gene expression regulator, acting at transcriptional and post-transcriptional levels. Little attention has been given so far to the contribution of alternative splicing (AS) dysregulation to RTT pathophysiology. To perform a comparative analysis of publicly available RNA sequencing (RNA-seq) studies and generate novel data resources for AS, we explored 100 human datasets and 130 mouse datasets from Mecp2-mutant models, processing data for gene expression and alternative splicing. Our comparative analysis across studies indicates common species-specific differentially expressed genes (DEGs) and differentially alternatively spliced (DAS) genes. Human and mouse dysregulated genes are involved in two main functional categories: cell-extracellular matrix adhesion regulation and synaptic functions, the first category more significantly enriched in human datasets. Our extensive bioinformatics study indicates, for the first time, a significant dysregulation of AS in human RTT datasets, suggesting the crucial contribution of altered RNA processing to the pathophysiology of RTT.

IDclust: Iterative clustering for unsupervised identification of cell types with single cell transcriptomics and epigenomics

The increasing diversity of single-cell datasets require systematic cell type characterization. Clustering is a critical step in single-cell analysis, heavily influencing downstream analyses. However, current unsupervised clustering algorithms rely on biologically irrelevant parameters that require manual optimization and fail to capture hierarchical relationships between clusters. We developed IDclust, a framework that identifies clusters with significant biological features at multiple resolutions using biologically meaningful thresholds like fold change, adjusted P-value and fraction of expressing cells. By iteratively processing and clustering subsets of the dataset, IDclust guarantees that all clusters found have significantly different features and stops only when no more interpretable cluster is found. It also creates a hierarchy of clusters, enabling visualization of the hierarchical relationships between different clusters. Analyzing multiple single-cell transcriptomic reference datasets, IDclust achieves superior clustering accuracy compared to state of the art algorithms. We showcase its utility by identifying previously unannotated clusters and identifying branching patterns in scATAC datasets. Using it's unsupervised nature and ability to analyze different -omics, we compare the resolution of different histone marks in multi-omic paired-tag dataset. Overall, IDclust automates single-cell exploration, facilitates cell type annotation and provides a biologically interpretable basis for clustering.

Brain single-cell transcriptomics highlights comorbidity-related cell type-specific changes of Parkinson's disease with major depressive disorder after paraquat exposure

Paraquat (PQ), a commonly used herbicide, is a potent environmental neurotoxin associated with Parkinson's disease (PD) and major depressive disorder (MDD). While the involvement of various brain cell types in the etiology of each disorder is well recognized, the specific cell subtypes implicated in the comorbidity of PD and MDD, especially under PQ neurotoxicity, remain poorly understood. In this study, we used single-cell RNA sequencing (scRNA-seq) to analyze brain tissues from mice with PQ-induced PD with MDD. By integrating genomic data with scRNA-seq profiles, we identified differences in cellular heterogeneity related to the pathogenesis of PD and MDD under PQ exposure. Our analysis of risk enrichment in genes with cell type-specific expression patterns revealed that astrocytes are predominantly linked to the comorbidity of PQ-induced PD and MDD. Furthermore, we identified a specific astrocyte subtype that plays a major role in the comorbidity-related changes observed in PQ-induced PD and MDD. This subtype appears to interact with and potentially transform into MDD-specific and PD-specific subtypes. Additionally, pathways related to chemical synaptic function and neuro-projection development were involved in all key stages of PD and MDD co-occurrence. We also identified RNF7 and MTCH2 as shared diagnostic hub genes for PD and MDD, which changed significantly in astrocytes following PQ exposure. These genes may serve as potential markers for astrocyte-specific prognostic diagnosis of PQ-induced PD with MDD. In summary, this study provides the first scRNA-seq profile of comorbidity in a PQ-exposed model. It highlights the heterogeneity of astrocytes in comorbidity and elucidates potential mechanisms underlying the co-occurrence of PD and MDD. These findings emphasize the need for further research into the pathogenesis of PD comorbid with MDD and offer novel insights into PQ neurotoxicity.

Meta-GWAS on PCSK9 concentrations reveals associations of novel loci outside the PCSK9 locus in White populations

BACKGROUND AND AIMS

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a key regulator of lipid homeostasis. A few earlier genome-wide association studies (GWAS) investigated genetic variants associated with circulating PCSK9 concentrations. However, uncertainty remains about some of the genetic loci discovered beyond the PCSK9 locus. By conducting the largest PCSK9 meta-analysis of GWAS (meta-GWAS) so far, we aimed to identify novel loci and validate the previously reported loci that regulate PCSK9 concentrations.

METHODS

We performed GWAS for PCSK9 concentrations in two large cohorts (GCKD (n = 4,963) and KORA F3 (n = 2,895)). These were meta-analyzed with previously published data encompassing together 20,579 individuals. We further conducted a second meta-analysis in statin-naïve individuals (n = 15,390). A genetic risk score (GRS) was constructed on PCSK9-increasing SNPs and assessed its impact on the risk for coronary artery disease (CAD) in 394,943 statin-naïve participants (17,077 with events) of the UK Biobank by performing CAD-free survival analysis.

RESULTS

Nine loci were genome-wide significantly associated with PCSK9 concentrations. These included the previously described PCSK9, APOB, KCNA1/KCNA5, and TM6SF2/SUGP1 loci. All imputed SNPs in the PCSK9 locus account for ∼15% of variance of PCSK9 concentrations. We further identified FADS2 as a novel locus that was also found in statin-naïve participants. All imputed SNPs within the FADS2 locus explain ∼1.2% of variance of PCSK9 concentrations. Additionally, four further loci (a region on chromosome 5, SDK1, SPATA16 and HPR) were genome-wide significant in either the main model or the statin-naïve subset. The linear increase in a PCSK9 genetic risk score was associated with 1.41-fold (95%CI 1.16-1.72, p < 0.001) higher risk for incident CAD.

CONCLUSIONS

We identified five novel loci (FADS2, SPATA16, SDK1, HPR and a region on chromosome 5) for PCSK9 concentrations that would require further research. Additionally, we confirm the genome-wide significant loci that were previously detected.

7p22.2 Microduplication: A Pathogenic CNV?

Partial duplication of the short arm of chromosome 7 is a rare chromosome rearrangement. The phenotype spectrum associated with this rearrangement is extremely variable even if in the last decade the use of high-resolution microarray technology for the investigation of patients carrying this rearrangement allowed for the identification of the 7p22.1 sub-band causative of this phenotype and to recognize the corresponding 7p22.1 microduplication syndrome. We report two unrelated patients that carry a microduplication involving the 7.22.2 sub-band. Unlike 7p22.1 microduplication carriers, both patients only show a neurodevelopmental disorder without malformations. We better characterized the clinical pictures of these two patients providing insight into the clinical phenotype associated with the microduplication of the 7p22.2 sub-band and support for a possible role of this sub-band in the 7p22 microduplication syndrome.

Exposure to war and conflict: The individual and inherited epigenetic effects on health, with a focus on post-traumatic stress disorder

War and conflict are global phenomena, identified as stress-inducing triggers for epigenetic modifications. In this state-of-the-science narrative review based on systematic principles, we summarise existing data to explore the outcomes of these exposures especially in veterans and show that they may result in an increased likelihood of developing gastrointestinal, auditory, metabolic and circadian issues, as well as post-traumatic stress disorder (PTSD). We also note that, despite a potential "healthy soldier effect", both veterans and civilians with PTSD exhibit the altered DNA methylation status in hypothalamic-pituitary-adrenal (HPA) axis regulatory genes such as NR3C1. Genes associated with sleep (PAX8; LHX1) are seen to be differentially methylated in veterans. A limited number of studies also revealed hereditary effects of war exposure across groups: decreased cortisol levels and a heightened (sex-linked) mortality risk in offspring. Future large-scale studies further identifying the heritable risks of war, as well as any potential differences between military and civilian populations, would be valuable to inform future healthcare directives.

Structure and evolution of neuronal wiring receptors and ligands

One of the fundamental properties of a neuronal circuit is the map of its connections. The cellular and developmental processes that allow for the growth of axons and dendrites, selection of synaptic targets, and formation of functional synapses use neuronal surface receptors and their interactions with other surface receptors, secreted ligands, and matrix molecules. Spatiotemporal regulation of the expression of these receptors and cues allows for specificity in the developmental pathways that wire stereotyped circuits. The families of molecules controlling axon guidance and synapse formation are generally conserved across animals, with some important exceptions, which have consequences for neuronal connectivity. Here, we summarize the distribution of such molecules across multiple taxa, with a focus on model organisms, evolutionary processes that led to the multitude of such molecules, and functional consequences for the diversification or loss of these receptors.

SDK1-ALK Fusion in a Lung Adenocarcinoma Patient With Excellent Response to ALK Inhibitor Treatment: A Case Report

Background

Rearrangements of Anaplastic lymphoma kinase (ALK) have been discovered as a novel driver mutation in patients with non–small-cell lung cancer (NSCLC). Patients’ responses to ALK tyrosine kinase inhibitors (TKIs) may vary depending on the variations of ALK rearrangements they have. It is imperative for clinicians to identify druggable ALK fusions in routine practice.

Case Presentation

In this study, we discovered a rare ALK rearrangement type (SDK1–ALK) in a Chinese lung adenocarcinoma patient who responded well to ALK inhibitor SAF-189s. The positive expression of ALK in lung biopsy tissue was verified by IHC analysis. A new SDK1-ALK fusion was discovered using NGS. The patient was treated with SAF-189s (160 mg per day) as a first-line therapy and went into continuous remission, with a 12 months progression-free survival at the last follow-up.

Conclusion

This is the first case of SDK1-ALK fusion with an excellent response to an ALK inhibitor, which will provide better understanding of ALK-TKI applications for NSCLC patients with ALK fusion in the future.

Loss of a Newly Discovered microRNA in Chinese Hamster Ovary Cells Leads to Upregulation of NGNA Sialylation on Monoclonal Antibodies

Chinese hamster ovary (CHO) cells are known not to express appreciable levels of the sialic acid residue N‐glycolylneuraminic acid (NGNA) on monoclonal antibodies. However, we actually have identified a recombinant CHO cell line expressing an IgG with unusually high levels of NGNA sialylation (>30%). Comprehensive multi‐OMICs based experimental analyses unraveled the root cause of this atypical sialylation: (1) expression of the cytidine monophosphate‐N‐acetylneuraminic acid hydroxylase (CMAH) gene was spontaneously switched on, (2) CMAH mRNA showed an anti‐correlated expression to the newly discovered Cricetulus griseus (cgr) specific microRNA cgr‐miR‐111 and exhibits two putative miR‐111 binding sites, (3) miR‐111 expression depends on the transcription of its host gene SDK1, and (4) a single point mutation within the promoter region of the sidekick cell adhesion molecule 1 (SDK1) gene generated a binding site for the transcriptional repressor histone H4 transcription factor HINF‐P. The resulting transcriptional repression of SDK1 led to a downregulation of its co‐expressed miR‐111 and hence to a spontaneous upregulation of CMAH expression finally increasing NGNA protein sialylation.

The distribution of a missense mutation in SDK1 gene across native Chinese breeds

Sidekick cell adhesion molecule 1 (SDK1) gene belonging to the immunoglobulin superfamily (IgSF) is reported to be associated with disease resistance. A novel missense mutation (XM_015469413.1: c.2678 A > G: p. Asp893Gly) in bovine SDK1 gene was observed in the Bovine Genome Variation Database (BGVD). The purpose of the current study was to determine the allelic frequency distribution of XM_015469413.1: c.2678 A > G: p. Asp893Gly and analyze its association with disease resistance in native Chinese cattle. Here, we explored the allele frequency of the missense mutation (M_015469413.1: c.2678 A > G: p. Asp893Gly) in 542 individuals from 27 Chinese indigenous cattle breeds using PCR and DNA sequencing methods. The frequency of the mutant allele (G) gradually decreased from the southern cattle groups to the northern cattle groups, whereas the frequency of the wild-type allele A showed an opposite pattern, consistent with the distribution of indicine and taurine cattle in China. Thus, our results proved that the bovine SDK1 gene might be candidate genes associated with disease resistance in Chinese cattle.