Y chromosome-linked B and NK cell deficiency in mice

X, but not Y, Chromosomal Complement Contributes to Stroke Sensitivity in Aged Animals

Post-menopausal women become vulnerable to stroke and have poorer outcomes and higher mortality than age-matched men, and previous studies suggested that sex chromosomes play a vital role in mediating stroke sensitivity in the aged. It is unknown if this is due to effects of the X or Y chromosome. The present study used the XY* mouse model (with four genotypes: XX and XO gonadal females and XY and XXY gonadal males) to compare the effect of the X vs. Y chromosome compliment in stroke. Aged (18-20 months) and gonadectomized young (8-12 weeks) mice were subjected to a 60-min middle cerebral artery occlusion. Infarct volume and behavioral deficits were quantified 3 days after stroke. Microglial activation and infiltration of peripheral leukocytes in the aged ischemic brain were assessed by flow cytometry. Plasma inflammatory cytokine levels by ELISA, and brain expression of two X chromosome-linked genes, KDM6A and KDM5C by immunochemistry, were also examined. Both aged and young XX and XXY mice had worse stroke outcomes compared to XO and XY mice, respectively; however, the difference between XX vs. XXY and XO vs. XY aged mice was minimal. Mice with two copies of the X chromosome showed more robust microglial activation, higher brain-infiltrating leukocytes, elevated plasma cytokine levels, and enhanced co-localization of KDM6A and KDM5C with Iba1+ cells after stroke than mice with one X chromosome. The number of X chromosomes mediates stroke sensitivity in aged mice, which might be processed through the X chromosome-linked genes and the inflammatory responses.

Sex and Gender Differences in Bacterial Infections

There is a growing awareness of the importance of sex and gender in medicine and research. Women typically have stronger immune responses to self and foreign antigens than men, resulting in sex-based differences in autoimmunity and infectious diseases. In both animals and humans, males are generally more susceptible than females to bacterial infections. At the same time, gender differences in health-seeking behavior, quality of health care, and adherence to treatment recommendations have been reported. This review explores our current understanding of differences between males and females in bacterial diseases. We describe how genetic, immunological, hormonal, and anatomical factors interact to influence sex-based differences in pathophysiology, epidemiology, clinical presentation, disease severity, and prognosis, and how gender roles affect the behavior of patients and providers in the health care system.

Sex-limited chromosomes and non-reproductive traits

Sex chromosomes are typically viewed as having originated from a pair of autosomes, and differentiated as the sex-limited chromosome (e.g. Y) has degenerated by losing most genes through cessation of recombination. While often thought that degenerated sex-limited chromosomes primarily affect traits involved in sex determination and sex cell production, accumulating evidence suggests they also influence traits not sex-limited or directly involved in reproduction. Here, we provide an overview of the effects of sex-limited chromosomes on non-reproductive traits in XY, ZW or UV sex determination systems, and discuss evolutionary processes maintaining variation at sex-limited chromosomes and molecular mechanisms affecting non-reproductive traits.

A polygenic risk score predicts mosaic loss of chromosome Y in circulating blood cells

Background

Mosaic loss of Y chromosome (LOY) is the most common somatic change that occurs in circulating white blood cells of older men. LOY in leukocytes is associated with increased risk for all-cause mortality and a range of common disease such as hematological and non-hematological cancer, Alzheimer’s disease, and cardiovascular events. Recent genome-wide association studies identified up to 156 germline variants associated with risk of LOY. The objective of this study was to use these variants to calculate a novel polygenic risk score (PRS) for LOY, and to assess the predictive performance of this score in a large independent population of older men.

Results

We calculated a PRS for LOY in 5131 men aged 70 years and older. Levels of LOY were estimated using microarrays and validated by whole genome sequencing. After adjusting for covariates, the PRS was a significant predictor of LOY (odds ratio [OR] = 1.74 per standard deviation of the PRS, 95% confidence intervals [CI] 1.62–1.86, p < 0.001). Men in the highest quintile of the PRS distribution had > fivefold higher risk of LOY than the lowest (OR = 5.05, 95% CI 4.05–6.32, p < 0.001). Adding the PRS to a LOY prediction model comprised of age, smoking and alcohol consumption significantly improved prediction (AUC = 0.628 [CI 0.61–0.64] to 0.695 [CI 0.67–0.71], p < 0.001).

Conclusions

Our results suggest that a PRS for LOY could become a useful tool for risk prediction and targeted intervention for common disease in men.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-021-00716-z.

Leukocytes with chromosome Y loss have reduced abundance of the cell surface immunoprotein CD99

Mosaic loss of chromosome Y (LOY) in immune cells is a male-specific mutation associated with increased risk for morbidity and mortality. The CD99 gene, positioned in the pseudoautosomal regions of chromosomes X and Y, encodes a cell surface protein essential for several key properties of leukocytes and immune system functions. Here we used CITE-seq for simultaneous quantification of CD99 derived mRNA and cell surface CD99 protein abundance in relation to LOY in single cells. The abundance of CD99 molecules was lower on the surfaces of LOY cells compared with cells without this aneuploidy in all six types of leukocytes studied, while the abundance of CD proteins encoded by genes located on autosomal chromosomes were independent from LOY. These results connect LOY in single cells with immune related cellular properties at the protein level, providing mechanistic insight regarding disease vulnerability in men affected with mosaic chromosome Y loss in blood leukocytes.

Nuclear Aurora kinase A triggers programmed death-ligand 1-mediated immune suppression by activating MYC transcription in triple-negative breast cancer

Background

Increasing studies have reported that oncogenes regulate components of the immune system, suggesting that this is a mechanism for tumorigenesis. Aurora kinase A (AURKA), a serine/threonine kinase, is involved in cell mitosis and is essential for tumor cell proliferation, metastasis, and drug resistance. However, the mechanism by which AURKA is involved in immune response regulation is unclear. Therefore, this study aimed to investigate the role of AURKA in immune regulation in triple‐negative breast cancer (TNBC).

Methods

Peripheral blood mononuclear cells (PBMCs) were co‐cultured with TNBC cells. The xCELLigence Real‐Time Cell Analyzer‐MP system was used to detect the killing efficiency of immune cells on TNBC cells. The expression of immune effector molecules was tested by quantitative real‐time polymerase chain reaction (qRT‐PCR) to evaluate immune function. Furthermore, to validate AURKA‐regulated immune response in vivo, 4T1 murine breast cancer cell line with AURKA overexpression or downregulation was engrafted into BALB/c mice. The distribution and proportion of immune cells in tumors were further evaluated by immunohistochemistry and flow cytometry.

Results

Downregulation of AURKA in TNBC cells increased immune response by activating CD8⁺ T cell proliferation and activity. Nuclear rather than cytoplasmic AURKA‐derived programmed death‐ligand 1 (PD‐L1) expression was independent of its kinase activity. Mechanistic investigations showed that nuclear AURKA increased PD‐L1 expression via an MYC‐dependent pathway. PD‐L1 overexpression mostly reversed AURKA silencing‐induced expression of immune effector molecules, including interleukin‐ (IL‐2), interferon‐γ (IFN‐γ), and perforin. Moreover, AURKA expression was negatively correlated with the enrichment and activity of tumor‐infiltrating CD8⁺ T cells in 4T1 engrafted BALB/c mouse model.

Conclusions

Nuclear AURKA elevated PD‐L1 expression via an MYC‐dependent pathway and contributed to immune evasion in TNBC. Therapies targeting nuclear AURKA may restore immune responses against tumors.

Immune cells lacking Y chromosome show dysregulation of autosomal gene expression

Epidemiological investigations show that mosaic loss of chromosome Y (LOY) in leukocytes is associated with earlier mortality and morbidity from many diseases in men. LOY is the most common acquired mutation and is associated with aberrant clonal expansion of cells, yet it remains unclear whether this mosaicism exerts a direct physiological effect. We studied DNA and RNA from leukocytes in sorted- and single-cells in vivo and in vitro. DNA analyses of sorted cells showed that men diagnosed with Alzheimer's disease was primarily affected with LOY in NK cells whereas prostate cancer patients more frequently displayed LOY in CD4 + T cells and granulocytes. Moreover, bulk and single-cell RNA sequencing in leukocytes allowed scoring of LOY from mRNA data and confirmed considerable variation in the rate of LOY across individuals and cell types. LOY-associated transcriptional effect (LATE) was observed in ~ 500 autosomal genes showing dysregulation in leukocytes with LOY. The fraction of LATE genes within specific cell types was substantially larger than the fraction of LATE genes shared between different subsets of leukocytes, suggesting that LOY might have pleiotropic effects. LATE genes are involved in immune functions but also encode proteins with roles in other diverse biological processes. Our findings highlight a surprisingly broad role for chromosome Y, challenging the view of it as a "genetic wasteland", and support the hypothesis that altered immune function in leukocytes could be a mechanism linking LOY to increased risk for disease.

Mild reproductive impact of a Y chromosome deletion on a C57BL/6J substrain

A recently reported deletion of about 40 Mb in length between 6.12/6.57 and 46.73/47.31 Mb on the Y chromosome long arm of the C57BL/6JBomTac inbred strain made us closely examine the strain’s breeding history and reproductive characteristics. We verified that the two copies of Rbm31y that are present inside the putative deletion were indeed deleted. This inbred strain presents an expected litter size for a C57BL/6 substrain. In vitro fertilization (IVF) efficiency and breeding efficiencies are comparable to those of the C57BL/6NTac substrain; however, the male/female sex ratio in the C57BL/6JBomTac is mildly skewed towards females. There is an increase in the percentage of sperm shape abnormalities found in C57BL/6JBomTac (35%) versus C57BL/6NTac (11%). The most frequent type of sperm abnormality observed is bent heads (19%). Additionally, there is deregulation of several transcripts expressed in the testes. We determined that this mutation arose in the C57BL/6JBomTac Foundation Colony in 2008, and it was completely fixed in the colony by 2009.

Genetic variation in chromosome Y regulates susceptibility to influenza A virus infection

Males of many species, ranging from humans to insects, are more susceptible than females to parasitic, fungal, bacterial, and viral infections. One mechanism that has been proposed to account for this difference is the immunocompetence handicap model, which posits that the greater infectious disease burden in males is due to testosterone, which drives the development of secondary male sex characteristics at the expense of suppressing immunity. However, emerging data suggest that cell-intrinsic (chromosome X and Y) sex-specific factors also may contribute to the sex differences in infectious disease burden. Using a murine model of influenza A virus (IAV) infection and a panel of chromosome Y (ChrY) consomic strains on the C57BL/6J background, we present data showing that genetic variation in ChrY influences IAV pathogenesis in males. Specific ChrY variants increase susceptibility to IAV in males and augment pathogenic immune responses in the lung, including activation of proinflammatory IL-17-producing γδ T cells, without affecting viral replication. In addition, susceptibility to IAV segregates independent of copy number variation in multicopy ChrY gene families that influence susceptibility to other immunopathological phenotypes, including survival after infection with coxsackievirus B3. These results demonstrate a critical role for genetic variation in ChrY in regulating susceptibility to infectious disease.

Clinical and laboratory features of cats with feline infectious peritonitis--a retrospective study of 231 confirmed cases (2000-2010)

OBJECTIVES

The objectives of this study were to review signalment, clinical signs and laboratory features in a large number of naturally occurring cases of feline infectious peritonitis (FIP), and to evaluate potential changes in diagnostic criteria for FIP and compare findings in cats with and without effusion.

METHODS

The medical records of 231 cats with confirmed FIP that presented to the Clinic of Small Animal Medicine of the Ludwig-Maximilian University of Munich, Germany, were reviewed for signalment, history, and clinical and laboratory parameters. Age, sex and breed distribution of the cats were compared with the clinic population.

RESULTS

Male sex and young age were significantly correlated with FIP. Neutering status was not associated with FIP. No breed predisposition was observed and the majority of cats presented were domestic shorthair and mixed breed. Microcytosis of peripheral erythrocytes was found in 35.1% of cats, of which 42.4% did not have concurrent anaemia. Band neutrophilia was documented in 44.3% (81/183), of which 35.8% did not have mature neutrophilia. Lymphopenia, observed significantly more often with effusion, was documented in only 26.8% of cats without effusion. Hyperbilirubinaemia also occurred significantly more often in cats with vs without effusion. While serum total protein was increased in only 17.5% of cats, hyperglobulinaemia was documented in 89.1%. Nearly 85.0% of cats had an albumin-to-globulin (A:G) ratio <0.8, while 67.8% had an A:G ratio <0.6.

CONCLUSIONS AND RELEVANCE

Microcytosis was common and can increase suspicion of FIP in the presence of other typical clinical and laboratory abnormalities. The low prevalence of lymphopenia in cats without effusion suggests that this is not a useful parameter in non-effusive FIP. The frequent occurrence of a left shift in the absence of a mature neutrophilia complicates the differentiation of effusive FIP and septic peritonitis. Globulins and A:G ratio were of higher diagnostic value than hyperproteinaemia.

OX40 ligand newly expressed on bronchiolar progenitors mediates influenza infection and further exacerbates pneumonia

Influenza virus epidemics potentially cause pneumonia, which is responsible for much of the mortality due to the excessive immune responses. The role of costimulatory OX40-OX40 ligand (OX40L) interactions has been explored in the non-infectious pathology of influenza pneumonia. Here, we describe a critical contribution of OX40L to infectious pathology, with OX40L deficiency, but not OX40 deficiency, resulting in decreased susceptibility to influenza viral infection. Upon infection, bronchiolar progenitors increase in number for repairing the influenza-damaged epithelia. The OX40L expression is induced on the progenitors for the antiviral immunity during the infectious process. However, these defense-like host responses lead to more extensive infection owing to the induced OX40L with α-2,6 sialic acid modification, which augments the interaction with the viral hemagglutinin. In fact, the specific antibody against the sialylated site of OX40L exhibited therapeutic potency in mitigating the OX40L-mediated susceptibility to influenza. Our data illustrate that the influenza-induced expression of OX40L on bronchiolar progenitors has pathogenic value to develop a novel therapeutic approach against influenza.

Y genetic variation and phenotypic diversity in health and disease

Sexually dimorphic traits arise through the combined effects of sex hormones and sex chromosomes on sex-biased gene expression, and experimental mouse models have been instrumental in determining their relative contribution in modulating sex differences. A role for the Y chromosome (ChrY) in mediating sex differences outside of development and reproduction has historically been overlooked due to its unusual genetic composition and the predominant testes-specific expression of ChrY-encoded genes. However, ample evidence now exists supporting ChrY as a mediator of other physiological traits in males, and genetic variation in ChrY has been linked to several diseases, including heart disease, cancer, and autoimmune diseases in experimental animal models, as well as humans. The genetic and molecular mechanisms by which ChrY modulates phenotypic variation in males remain unknown but may be a function of copy number variation between homologous X-Y multicopy genes driving differential gene expression. Here, we review the literature identifying an association between ChrY polymorphism and phenotypic variation and present the current evidence depicting the mammalian ChrY as a member of the regulatory genome in males and as a factor influencing paternal parent-of-origin effects in female offspring.

Sex-biased chromatin and regulatory cross-talk between sex chromosomes, autosomes, and mitochondria

Several autoimmune and neurological diseases exhibit a sex bias, but discerning the causes and mechanisms of these biases has been challenging. Sex differences begin to manifest themselves in early embryonic development, and gonadal differentiation further bifurcates the male and female phenotypes. Even at this early stage, however, there is evidence that males and females respond to environmental stimuli differently, and the divergent phenotypic responses may have consequences later in life. The effect of prenatal nutrient restriction illustrates this point, as adult women exposed to prenatal restrictions exhibited increased risk factors of cardiovascular disease, while men exposed to the same condition did not. Recent research has examined the roles of sex-specific genes, hormones, chromosomes, and the interactions among them in mediating sex-biased phenotypes. Such research has identified testosterone, for example, as a possible protective agent against autoimmune disorders and an XX chromosome complement as a susceptibility factor in murine models of lupus and multiple sclerosis. Sex-biased chromatin is an additional and likely important component. Research suggesting a role for X and Y chromosome heterochromatin in regulating epigenetic states of autosomes has highlighted unorthodox mechanisms of gene regulation. The crosstalk between the Y chromosomes and autosomes may be further mediated by the mitochondria. The organelles have solely maternal transmission and exert differential effects on males and females. Altogether, research supports the notion that the interaction between sex-biased elements might exert novel regulatory functions in the genome and contribute to sex-specific susceptibilities to autoimmune and neurological diseases.

The Y chromosome as a regulatory element shaping immune cell transcriptomes and susceptibility to autoimmune disease

Understanding the DNA elements that constitute and control the regulatory genome is critical for the appropriate therapeutic management of complex diseases. Here, using chromosome Y (ChrY) consomic mouse strains on the C57BL/6J (B6) background, we show that susceptibility to two diverse animal models of autoimmune disease, experimental allergic encephalomyelitis (EAE) and experimental myocarditis, correlates with the natural variation in copy number of Sly and Rbmy multicopy ChrY genes. On the B6 background, ChrY possesses gene regulatory properties that impact genome-wide gene expression in pathogenic CD4(+) T cells. Using a ChrY consomic strain on the SJL background, we discovered a preference for ChrY-mediated gene regulation in macrophages, the immune cell subset underlying the EAE sexual dimorphism in SJL mice, rather than CD4(+) T cells. Importantly, in both genetic backgrounds, an inverse correlation exists between the number of Sly and Rbmy ChrY gene copies and the number of significantly up-regulated genes in immune cells, thereby supporting a link between copy number variation of Sly and Rbmy with the ChrY genetic element exerting regulatory properties. Additionally, we show that ChrY polymorphism can determine the sexual dimorphism in EAE and myocarditis. In humans, an analysis of the CD4(+) T cell transcriptome from male multiple sclerosis patients versus healthy controls provides further evidence for an evolutionarily conserved mechanism of gene regulation by ChrY. Thus, as in Drosophila, these data establish the mammalian ChrY as a member of the regulatory genome due to its ability to epigenetically regulate genome-wide gene expression in immune cells.