Genetic Characteristics of Non B Cell-Derived Immunoglobulin Genes.

It is widely acknowledged that immunoglobulins (Igs) are produced solely by B-lineage cells. The Ig gene is created by the rearrangement of a group of gene segments [variable (V), diversity (D), and joining (J) segments rearrangement, or V(D)J recombination], which results in the vast diversity of B cell-derived Ig responsible for recognising various antigens. Ig subsequently undergoes somatic hypermutation (SHM) and class switch recombination (CSR) after exposure to antigens, thus converting the low-affinity IgM to IgG, IgA, or IgE antibodies. IgM and IgD are primarily expressed in naïve B cells that have not been exposed to antigens, they do not undergo somatic hypermutation; hence, their variable region sequences remain the same as those in the germline. In contrast, IgG, IgA, and IgE are expressed in antigen-stimulated memory B cells or plasma cells, and thus, they often possess high-frequency mutations in their variable region sequences. Since the discovery that Ig can be produced by non-B cells, Qiu's group has investigated and compared the genetic characteristics of B cell-derived Ig and non-B cell-derived Ig. These findings demonstrated that non-B cell-derived Ig shares certain similarities with B cell-derived Ig in that the sequence of its constant region is identical to that of B cell-derived Ig, and its variable region is also strictly dependent on the rearrangement of V, D, and J gene segments. Moreover, akin to B cell-derived Ig, the V regions of IgM and IgD are rarely mutated, while IgG, IgA, and IgE produced by cancer cells are frequently mutated. However, the non-B cell-derived Ig V region sequence displays unique characteristics. (1) Unlike the vast diversity of B cell-derived Igs, non-B cell-derived Igs exhibit restricted diversity; cells from the same lineage always select the same V(D)J recombination patterns; (2) Both mRNA and proteins of RAG1/RAG2 recombinase have been detected in Ig positive cancer cell lines and normal tissues. But Ig recombination could also be found in RAG1-/- and RAG2-/- mice, suggesting that they are not necessary for the rearrangement of non-B cell-derived Igs. These features of non-B cell-derived Igs suggest a potentially undiscovered mechanism of V(D)J recombination, ligation, and SHM in non-B cells, which necessitates further investigation with advanced technology in molecular biology.

Systematic characterization of immunoglobulin loci and deep sequencing of the expressed repertoire in the Atlantic cod (Gadus morhua).

BACKGROUND: The Atlantic cod is a prolific species in the Atlantic, despite its inconsistent specific antibody response. It presents a peculiar case within vertebrate immunology due to its distinct immune system, characterized by the absence of MHCII antigen presentation pathway, required for T cell-dependent antibody responses. Thorough characterisation of immunoglobulin loci and analysis of the antibody repertoire is necessary to further our understanding of the Atlantic cod's immune response on a molecular level. RESULTS: A comprehensive search of the cod genome (gadmor3.0) identified the complete set of IgH genes organized into three sequential translocons on chromosome 2, while IgL genes were located on chromosomes 2 and 5. The Atlantic cod displayed a moderate germline V gene diversity, comprising four V gene families for both IgH and IgL, each with distinct chromosomal locations and organizational structures. 5'RACE sequencing revealed a diverse range of heavy chain CDR3 sequences and relatively limited CDR3 diversity in light chains. The analysis highlighted a differential impact of V-gene germline CDR3 length on receptor CDR3 length between heavy and light chains, underlining different recombination processes. CONCLUSIONS: This study reveals that the Atlantic cod, despite its inconsistent antibody response, maintains a level of immunoglobulin diversity comparable to other fish species. The findings suggest that the extensive recent duplications of kappa light chain genes do not result in increased repertoire diversity. This research provides a comprehensive view of the Atlantic cod's immunoglobulin gene organization and repertoire, necessary for future studies of antibody responses at the molecular level.

The Gene Rearrangement and Transcriptional Regulation of Non B Cell-Derived Immunoglobulin.

Traditionally, immunoglobulin (Ig) expression has been attributed solely to B cells/plasma cells with well-documented and accepted regulatory mechanisms governing Ig expression in B cells. Ig transcription is tightly controlled by a series of transcription factors. However, increasing evidence has recently demonstrated that Ig is not only produced by B cell lineages but also by various types of non-B cells (non-B-Ig). Under physiological conditions, non-B-Ig not only exhibits antibody activity but also regulates cellular biological activities (such as promoting cell proliferation, adhesion, and cytoskeleton protein activity). In pathological conditions, non-B-Ig is implicated in the development of various diseases including tumour, kidney disease, and other immune-related disorders. The mechanisms underline Ig gene rearrangement and transcriptional regulation of Ig genes in non-B cells are not fully understood. However, existing evidence suggests that these mechanisms in non-B cells differ from those in B cells. For instance, non-B-Ig gene rearrangement occurs in an RAG-independent manner; and Oct-1 and Oct-4, rather than Oct-2, are required for the transcriptional regulation of non-B derived Igs. In this chapter, we will describe and compare the mechanisms of gene rearrangement and expression regulation between B-Ig and non-B-Ig.

Non B Cell-Derived Immunoglobulin, A Brighter Horizon for the Future.

The canonical theory of immunology stating that "Immunoglobulin (Ig) is produced by B lymphocytes and exerts antibody activity" has been established since the 1970s. However, the discovery of non B cell-derived Igs (non B-Igs), which can exert multiple biological activities in addition to their antibody activities, necessitates a reevaluation of the classic concept of Ig. This has been documented with a number of characteristics related to their structure, modification, genetic regulation as well as the functions associated with clinical conditions, particularly multiple cancers. The discovery of non B-Ig provides us with a new perspective to better understand not only basic immunology, but also various Ig-related clinical manifestations including autoimmune diseases, chronic inflammation, and anaphylaxis. Notably, non B-Ig can directly promote the occurrence of malignant tumours.

Functions and Clinical Relevance of Liver-Derived Immunoglobulins.

Liver is the largest internal organ of the body with vital functions. In addition to its endocrine and exocrine activities, liver also plays a pivotal role in the immune system, including haematopoietic functions. Liver parenchymal cells, which are epithelial cells, have been found to possess innate immune functions by expressing pattern-recognition receptors (PRRs), producing complement components, and secreting cytokines. Intriguingly, in recent years, it has been discovered that liver epithelial cells also produce immunoglobulins (Igs), which have long been thought to be produced exclusively by B cells. Notably, even liver epithelial cells from B lymphocyte-deficient mice, including SCID mice and µMT mice, could also produce Igs. Compelling evidence has revealed both the physiological and pathological functions of liver-derived Igs. For instance, liver epithelial cells-derived IgM can serve as a source of natural and specific antibodies that contribute to innate immune responses, while liver-produced IgG can act as a growth factor to promote cell proliferation and survival in normal hepatocytes and hepatocarcinoma. Similar to that in B cells, the toll-like receptor 9 (TLR9)-MyD88 signaling pathway is also actively involved in promoting liver epithelial cells to secrete IgM. Liver-derived Igs could potentially serve as biomarkers, prognostic indicators, and therapeutic targets in the clinical setting, particularly for liver cancers and liver injury. Nevertheless, despite significant advances, much remains unknown about the mechanisms governing Ig transcription in liver cells, as well as the detailed functions of liver-derived Igs and their involvement in diseases and adaptive immunity. Further studies are still needed to reveal these underlying, undefined issues related to the role of liver-derived Igs in both immunity and diseases.

The Expression of Non B Cell-Derived Immunoglobulins.

Although V(D)J recombination and immunoglobulin (Ig) production are traditionally recognised to occur only in B lymphocytes and plasma cells, the expression of Igs in non-lymphoid cells, which we call non B cell-derived Igs (non B Igs), has been documented by growing studies. It has been demonstrated that non B-Igs can be widely expressed in most cell types, including, but not limited to, epithelial cells, cardiomyocytes, hematopoietic stem/progenitor cells, myeloid cells, and cells from immune-privileged sites, such as neurons and spermatogenic cells. In particular, malignant tumour cells express high level of IgG. Moreover, different from B-Igs that mainly localised on the B cell membrane and in the serum and perform immune defence function mainly, non B-Igs have been found to distribute more widely and play critical roles in immune defence, maintaining cell proliferation and survival, and promoting progression. The findings of non B-Igs may provide a wealthier breakthrough point for more therapeutic strategies for a wide range of immune-related diseases.

Expression and Clinical Significance of Non B Cell-Derived Immunoglobulins in the Urinary System and Male Reproductive System.

The urinary system comprises kidneys, ureters, bladder, and urethra with its primary function being excretion, referring to the physiological process of transporting substances that are harmful or surplus out of the body. The male reproductive system consists of gonads (testis), vas deferens, and accessory glands such as the prostate. According to classical immunology theory, the tissues and organs mentioned above are not thought to produce immunoglobulins (Igs), and any Ig present in the relevant tissues under physiological and pathological conditions is believed to be derived from B cells. For instance, most renal diseases are associated with uncontrolled inflammation caused by pathogenic Ig deposited in the kidney. Generally, these pathological Igs are presumed to be produced by B cells. Recent studies have demonstrated that renal parenchymal cells can produce and secrete Igs, including IgA and IgG. Glomerular mesangial cells can express and secrete IgA, which is associated with cell survival and adhesion. Likewise, human podocytes demonstrate the ability to produce and secrete IgG, which is related to cell survival and adhesion. Furthermore, renal tubular epithelial cells also express IgG, potentially involved in the epithelial-mesenchymal transition (EMT). More significantly, renal cell carcinoma, bladder cancer, and prostate cancer have been revealed to express high levels of IgG, which promotes tumour progression. Given the widespread Ig expression in the urinary and male reproductive systems, continued efforts to elucidate the roles of Igs in renal physiological and pathological processes are necessary.

Comparison of Non B-Ig and B-Ig.

Immunoglobulin (Ig) has been widely acknowledged to be produced solely by B-lineage cells. However, growing evidence has demonstrated the expression of Ig in an array of cancer cells, as well as normal cells including epithelial cells, epidermal cells, mesangial cells, monocytes, and neutrophils. Ig has even been found to be expressed in non-B cells at immune-privileged sites such as neurons and spermatogenic cells. Despite these non-B cell-derived Igs (non-B-Igs) sharing the same symmetric structures with conventional Igs (B-Igs), further studies have revealed unique characteristics of non-B-Ig, such as restricted variable region and aberrant glycosylation. Moreover, non-B-Ig exhibits properties of promoting malignant behaviours of cancer cells, therefore it could be utilised in the clinic as a potential therapeutic biomarker or target. The elucidation of the generation and regulation of non-B-Ig will certainly broaden our understanding of immunology.

Functions and Clinical Significance of Myocardial Cell-Derived Immunoglobulins.

Immunoglobulins (Igs) have been widely accepted to be exclusively expressed by B cells. Nonetheless, this theory is challenged by mounting evidence which suggests that Igs can also be generated by non B cells (non B-Ig), including cardiomyocytes (CM). Non B-Ig exhibits unique physical and chemical characteristics, unique variable region sequences and functions, which diverge from those of B-Ig. For instance, non B-Ig demonstrates hydrophobicity, limited diversity in the variable region, and extracellular matrix protein activity. Likewise, cardiomyocytes can express different classes of Igs, including IgM, IgG, and free Igκ light chains (cardiomyocyte derived-Igs, CM-Igs). In particular, CM-Igs can be secreted into the extracellular space in various cardiovascular diseases, such as myocardial ischaemia and myocardial fibrosis where they might be involved in complement activation and direct damage to cardiomyocytes. Nevertheless, the precise pathological activity of CM-Igs remains unclear. Recently, Zhu et al. focused on studying the sequence characteristics and functions of CM-Igκ; they discovered that the CM-Igκ exhibits a unique VJ recombination pattern, high hydrophobicity, and is principally located on the intercalated discs and cross striations of the cardiomyocytes. Interestingly, loss of Igκ in cardiomyocytes results in structural disorders in intercalated discs and dysfunction in myocardial contraction and conduction. Mechanically, Igκ promotes the stabilisation of plectin, a cytoskeleton cross-linker protein that connects desmin to desomsome, to maintain the normal structure of the intercalated disc. This finding indicates that CM-Igκ plays an integral role in maintaining cytoskeleton structure. Consequently, it is imperative to reveal the physiological functions and mechanisms of pathological injury associated with CM-Igs.

Expression, Function, and Significance of Non B Cell-Derived Immunoglobulin in Haematological System.

Acute myeloid leukaemia (AML) is a collection of genetically diverse diseases characterised by abnormal proliferation of immature haematopoietic cells and disruption of normal haematopoiesis. Myeloid cells and lymphocytes originate from different haematopoietic precursors within the bone marrow. It has been traditionally assumed that myeloid cells cannot produce immunoglobulin (Ig), a marker of B cells and plasma cells. However, in recent years, all five Ig classes have been detected in CD34+ haematopoietic stem cells, mature monocytes and neutrophils, differentiated macrophages and tumour-associated macrophages, acute myeloid leukaemia cell lines, as well as myeloblasts of AML. The rearranged V(D)J sequences exhibit unique restricted or biased V gene usage and evidence of somatic mutation. Furthermore, AML-derived Igs could promote cell proliferation, induce apoptosis, and enhance migration. Elevated levels of Ig expression predict inferior clinical outcomes. These findings indicate that AML-derived Ig plays a role in AML pathogenesis and progression, and could serve as a novel biomarker for risk stratification, disease monitoring, and targeted therapy. In this chapter, we provide a comprehensive review of recent literature on the expression, function, and significance of non B cell-derived Ig in the haematological system, with a focus on AML.

The role of CD83 in the pathogenesis of immune thrombocytopenia.

BACKGROUND: CD83 are closely related to the pathogenesis of immune thrombocytopenia (ITP), but the exact mechanism remains unclear. AIM: To explore the relationship between CD83 and CD4+ T cell subsets and clarify the role of CD83 in the pathogenesis of ITP. METHODS: RT-qPCR and Flow cytometry were used to illustrate CD83 expression. The downregulation and overexpression of DC-CD83 were co-cultured with CD4+ T cells to detect cell proliferation, co-cultured supernatant cytokines and Tregs expression. RESULTS: The results indicate that the ITP patients showed higher expression of CD83 than the healthy controls. The proliferation of CD4+ T cells was inhibited by downregulation of DCs-CD83 but promoted by overexpression of DCs-CD83. siRNA-CD83 inhibited proinflammatory IFN-γ and IL-17 secretion while raising TGF-ß, IL-10 concentrations. Overexpression of DCs-CD83 promoted Tregs expression. CONCLUSION: The Th1/Th2 and Th17/Tregs polarization were reversed via interfering DCs with siRNA-CD83. CD83 plays an important role in ITP pathogenesis, suggesting novel treatment for ITP patients.

Two-dimensional high-throughput on-cell screening of immunoglobulins against broad antigen repertoires.

Identifying high-affinity antibodies in human serum is challenging due to extremely low number of circulating B cells specific to the desired antigens. Delays caused by a lack of information on the immunogenic proteins of viral origin hamper the development of therapeutic antibodies. We propose an efficient approach allowing for enrichment of high-affinity antibodies against pathogen proteins with simultaneous epitope mapping, even in the absence of structural information about the pathogenic immunogens. To screen therapeutic antibodies from blood of recovered donors, only pathogen transcriptome is required to design an antigen polypeptide library, representing pathogen proteins, exposed on the bacteriophage surface. We developed a two-dimensional screening approach enriching lentiviral immunoglobulin libraries from the convalescent or vaccinated donors against bacteriophage library expressing the overlapping set of polypeptides covering the spike protein of SARS-CoV-2. This platform is suitable for pathogen-specific immunoglobulin enrichment and allows high-throughput selection of therapeutic human antibodies.

Functional surface expression of immunoglobulin cleavage systems in a candidate Mycoplasma vaccine chassis.

The Mycoplasma Immunoglobulin Binding/Protease (MIB-MIP) system is a candidate 'virulence factor present in multiple pathogenic species of the Mollicutes, including the fast-growing species Mycoplasma feriruminatoris. The MIB-MIP system cleaves the heavy chain of host immunoglobulins, hence affecting antigen-antibody interactions and potentially facilitating immune evasion. In this work, using -omics technologies and 5'RACE, we show that the four copies of the M. feriruminatoris MIB-MIP system have different expression levels and are transcribed as operons controlled by four different promoters. Individual MIB-MIP gene pairs of M. feriruminatoris and other Mollicutes were introduced in an engineered M. feriruminatoris strain devoid of MIB-MIP genes and were tested for their functionality using newly developed oriC-based plasmids. The two proteins are functionally expressed at the surface of M. feriruminatoris, which confirms the possibility to display large membrane-associated proteins in this bacterium. However, functional expression of heterologous MIB-MIP systems introduced in this engineered strain from phylogenetically distant porcine Mollicutes like Mesomycoplasma hyorhinis or Mesomycoplasma hyopneumoniae could not be achieved. Finally, since M. feriruminatoris is a candidate for biomedical applications such as drug delivery, we confirmed its safety in vivo in domestic goats, which are the closest livestock relatives to its native host the Alpine ibex.

Organisation of the Atlantic salmon (Salmo salar) thymus and its content of Ig-expressing cells.

The thymus of fishes is located as a dual organ in a rostrodorsal projection within the gill chamber and is covered by the operculum. The histological organization of the teleost fish thymus displays considerable diversity, particularly in salmonids where a clear distinction between the thymus cortex and medulla is yet to be defined. Recent interest has focused on the role of B cells in thymic function, but the presence of these cells within the salmon thymus remains poorly understood. In this morphological study, we applied in situ hybridization to investigate developing Atlantic salmon thymi for the expression of recombination activating (Rag) genes 1 and 2. We identified the location of the cortex, aligning with the previously described inner zone. Expression of IgM and IgD transcripts was predominantly observed in cells within the outer and subcapsular zones, with lesser expression in the cortex and inner zone. IgT expression was confined to a limited number of cells in the inner zone and capsule. The location of the thymus medulla could not be established. Our results are discussed in the context of the recently identified lymphoid organs, namely the intrabranchial lymphoid tissue (ILT) and the salmon bursa.

The expression characteristic and prognostic role of Siglec-15 in lung adenocarcinoma.

Sialic acid-binding immunoglobulin-like lectin-15 (Siglec-15) has been identified as an immune suppressor and a promising candidate for immunotherapy of cancer management. However, the association between Siglec-15 expression and clinicopathological features of lung adenocarcinoma (LUAD), especially the prognostic role, is not fully elucidated. In this present study, a serial of bioinformatics analyses in both tissue and cell levels were conducted to provide an overview of Siglec-15 expression. Real-time quantitative PCR (qPCR) test, western blotting assay, and immunohistochemistry (IHC) analyses were conducted to evaluate the expression of Siglec-15 in LUAD. Survival analysis and Kaplan-Meier curve were employed to describe the prognostic parameters of LUAD. The results of bioinformatics analyses demonstrated the up-regulation of Siglec-15 expression in LUAD. The data of qPCR, western blotting, and IHC analyses further proved that the expression of Siglec-15 in LUAD tissues was significantly increased than that in noncancerous tissues. Moreover, the expression level of Siglec-15 protein in LUAD was substantially associated with TNM stage. LUAD cases with up-regulated Siglec-15 expression, positive N status, and advance TNM stage suffered a critical unfavorable prognosis. In conclusion, Siglec-15 could be identified as a novel prognostic biomarker in LUAD and targeting Siglec-15 may provide a promising strategy for LUAD immunotherapy.

High Level Immunoglobulin Gene Expression and Reduced Intra-tumoral Bacteria Associated With the Transition from Initial to Progressive Diffuse Intrinsic Pontine Glioma.

BACKGROUND/AIM: In the past decade, diffuse intrinsic pontine glioma (DIPG), the most common childhood brainstem glioma, has benefitted from an increase in tissue-based research because of improved biopsy collection techniques. However, the adaptive immune receptor (IR) features represented by tumor material and tumor infiltrating lymphocytes have remained poorly understood. MATERIALS AND METHODS: Herein, we characterized the adaptive immune parameters of DIPG through the recovery of IR recombination reads from RNAseq files representing initial and progressive DIPG samples. RESULTS: An elevated level of immunoglobulin gene expression in the progressive DIPG sample files and a reduced number of bacterial sequencing read recoveries in comparison to RNAseq files representing the initial form of DIPG, was found. Furthermore, the RNAseq files representing both initial and progressive DIPG samples had significant numbers of reads representing Cutibacterium acnes, a bacterium previously linked to prostate cancer development. Results also indicated an opportunity to distinguish overall survival probabilities based on IGL complementarity determining region-3 amino acid sequence physicochemical parameters. CONCLUSION: Genomics analyses allow for a better understanding of adaptive IR features and bacterial infections in the DIPG setting.

IGSF3 is a homophilic cell adhesion molecule that drives lung metastasis of melanoma by promoting adhesion to vascular endothelium.

The immunoglobulin superfamily (IgSF) is one of the largest families of cell-surface molecules involved in various cell-cell interactions, including cancer-stromal interactions. In this study, we undertook a comprehensive RT-PCR-based screening for IgSF molecules that promote experimental lung metastasis in mice. By comparing the expression of 325 genes encoding cell-surface IgSF molecules between mouse melanoma B16 cells and its highly metastatic subline, B16F10 cells, we found that expression of the immunoglobulin superfamily member 3 gene (Igsf3) was significantly enhanced in B16F10 cells than in B16 cells. Knockdown of Igsf3 in B16F10 cells significantly reduced lung metastasis following intravenous injection into C57BL/6 mice. IGSF3 promoted adhesion of B16F10 cells to vascular endothelial cells and functioned as a homophilic cell adhesion molecule between B16F10 cells and vascular endothelial cells. Notably, the knockdown of IGSF3 in either B16F10 cells or vascular endothelial cells suppressed the transendothelial migration of B16F10 cells. Moreover, IGSF3 knockdown suppressed the extravasation of B16F10 cells into the lungs after intravenous injection. These results suggest that IGSF3 promotes the metastatic potential of B16F10 cells in the lungs by facilitating their adhesion to vascular endothelial cells.

Differential analysis of immunoglobulin gene expression pattern in chickens of distinct breeds and developmental periods.

Immunoglobulin is an essential component of the body's defense against pathogens, aiding in the recognition and clearance of foreign antigens. Research concerning immunoglobulin gene and its diversity of expression across different breeds within the same species is relatively scarce. In this study, we employed RACE (Rapid Amplification of cDNA Ends) technology, prepared DNA libraries, performed high-throughput sequencing, and conducted related bioinformatics analysis to analyze the differences in immunoglobulin gene diversity and expression at different periods in Hy-line brown hens, Lueyang black-bone chickens, and Beijing-You chickens. The study found that the composition of chicken immunoglobulin genes is relatively simple, with both the light chain and heavy chain having a functional V gene. Additionally, the mechanisms of immunoglobulin diversity generation tended to be consistent among different breeds and periods of chickens, primarily relying on abundant junctional diversity, somatic hypermutation (SHM), and gene conversion (GCV) to compensate for the limitations of low-level V(D)J recombination. As the age increased, the junctional diversity of IgH and IgL tended to diversify and showed similar expression patterns among different breeds. In the three chicken breeds, the predominant types of mutations observed in IGHV and IGLV SHM were A to G and G to A transitions. Specifically, IGLV exhibited a preference for A to G mutations, whereas IGHV displayed a bias toward G to A mutations. The regions at the junctions between framework regions (FR) and complementarity-determining regions (CDR) and within the CDR regions themselves are typically prone to mutations. The locations of GCV events in IGLV and IGHV do not show significant differences, and replacement segments are concentrated in the central regions of FR1, CDR, and FR2. Importantly, gene conversion events are not random occurrences. Additionally, our investigation revealed that CDRH3 in chickens of diverse breeds and periods the potential for diversification through the incorporation of cysteine. This study demonstrates that the diversity of immunoglobulin expression tends to converge among Hy-line brown hens, Lueyang black-bone chickens, and Beijing-You chickens, indicating that the immunoglobulin gene expression mechanisms in different breeds of chickens do not exhibit significant differences due to selective breeding.

Immunoglobulins play a key role in the organism's defense against pathogens, and their diverse expression allows the body to generate a wide array of antibodies. This diversity serves as a critical safeguard for the immune system against various pathogens. Natural geographical variances and artificial breeding and selection can potentially lead to different immune responses in distinct populations of the same species when confronted with the same pathogen. In this study, we investigated the diversity of immunoglobulin gene expression in the natural state of different chicken breeds (Hy-line brown hens, Lueyang black-bone chickens, and Beijing-You chickens) and at different periods from the perspective of immunoglobulin gene expression mechanism. We analyzed the diversity of immunoglobulin based on the results of high-throughput sequencing by extracting Fabricius bursa RNA, RACE (Rapid Amplification of cDNA Ends) technique, and constructing DNA libraries. Our study reveals that the junctional diversity, somatic hypermutation, CDR3 diversity, and gene conversion expression of immunoglobulins in Hy-line brown hens, Lueyang black-bone chickens, and Beijing-You chickens converge during the same time period. This indicates that the immunoglobulin gene expression mechanisms in different chicken breeds do not exhibit significant variations as a result of selective breeding.

Deep learning insights into the architecture of the mammalian egg-sperm fusion synapse.

A crucial event in sexual reproduction is when haploid sperm and egg fuse to form a new diploid organism at fertilization. In mammals, direct interaction between egg JUNO and sperm IZUMO1 mediates gamete membrane adhesion, yet their role in fusion remains enigmatic. We used AlphaFold to predict the structure of other extracellular proteins essential for fertilization to determine if they could form a complex that may mediate fusion. We first identified TMEM81, whose gene is expressed by mouse and human spermatids, as a protein having structural homologies with both IZUMO1 and another sperm molecule essential for gamete fusion, SPACA6. Using a set of proteins known to be important for fertilization and TMEM81, we then systematically searched for predicted binary interactions using an unguided approach and identified a pentameric complex involving sperm IZUMO1, SPACA6, TMEM81 and egg JUNO, CD9. This complex is structurally consistent with both the expected topology on opposing gamete membranes and the location of predicted N-glycans not modeled by AlphaFold-Multimer, suggesting that its components could organize into a synapse-like assembly at the point of fusion. Finally, the structural modeling approach described here could be more generally useful to gain insights into transient protein complexes difficult to detect experimentally.

The Risk Genes for Neuropsychiatric Disorders negr1 and opcml Are Expressed throughout Zebrafish Brain Development.

The immunoglobulin LAMP/OBCAM/NTM (IgLON) family of cell adhesion molecules comprises five members known for their involvement in establishing neural circuit connectivity, fine-tuning, and maintenance. Mutations in IgLON genes result in alterations in these processes and can lead to neuropsychiatric disorders. The two IgLON family members NEGR1 and OPCML share common links with several of them, such as schizophrenia, autism, and major depressive disorder. However, the onset and the underlying molecular mechanisms have remained largely unresolved, hampering progress in developing therapies. NEGR1 and OPCML are evolutionarily conserved in teleosts like the zebrafish (Danio rerio), which is excellently suited for disease modelling and large-scale screening for disease-ameliorating compounds. To explore the potential applicability of zebrafish for extending our knowledge on NEGR1- and OPCML-linked disorders and to develop new therapeutic strategies, we investigated the spatio-temporal expression of the two genes during early stages of development. negr1 and opcml are expressed maternally and subsequently in partially distinct domains of conserved brain regions. Other areas of expression in zebrafish have not been reported in mammals to date. Our results indicate that NEGR1 and OPCML may play roles in neural circuit development and function at stages earlier than previously anticipated. A detailed functional analysis of the two genes based on our findings could contribute to understanding the mechanistic basis of related psychiatric disorders.