It is known that undifferentiated embryonic gonads (UEG) in embryos of mammals have a dual nature. They consist of an outer layer of cortex, from which in the process of differentiation develop female sex cells, and from the inner layer – medulla – develop male gametes. During the determination of sex, one of the layers of the gonad develops and the other is suppressed. Therefore, the sex of the future fetus depends on which of the tissue cells - medulla or cortex - survives in the UEG. However, almost nothing is known about the causes for the survival of the medulla or cortex.We believe that, perhaps, the main cause for the development of one of the layers of the gonad and the suppression of the other is cell thermoregulation. The survival of the tissue cells of medulla depends on whether they can avoid heat death, which is determined by their ability to effectively remove excess metabolic heat from the cell nucleus. Since excess thermal energy is released into the cytoplasm through a dense layer of condensed chromatin around the nucleus, consisting predominantly of chromosomal constitutive heterochromatin regions (cHR), the fate of the medulla directly depends on the cHR in its cells.Seemingly, the sex in mammals and human is determined by the cHR on Y chromosomes. It is important not so much the amount of cHR on Y chromosome as its localization in the interphase cell around the nucleoli. Thanks to this localization, excess heat is more effectively removed from the "hottest" point of the nucleus, where ribosomes are formed, which is also necessary for the production of proteins that inhibit the development of cortex cells. Otherwise medulla doomed to degeneration and a cortex tissue will remain in the UEG.

Abstract Study question How does the sex chromosome complement affect the transcriptome and development of oocytes during follicular growth in the mouse ovary? Summary answer Highly expressed X-linked genes adjust their transcript levels according to the X dosage. Y-linked genes affect the transcript levels of some X-linked and autosomal genes. What is known already Female mice carrying XO and XY chromosomes on the C57BL/6J (B6) genetic background are healthy but encounter subfertility and infertility, respectively. Our previous results have shown that the XY oocyte is defective in its cytoplasm; its replacement with that of an XX oocyte at the GV stage allows for production of healthy offspring after fertilization. Since transcription is shut down in the oocyte by the end of growth phase, the mRNAs and proteins necessary for meiotic progression and early embryonic development are accumulated during follicular growth. Study design, size, duration 30 oocytes of 50–59 μm diameter were pooled for each genotype in biological triplicate and subjected to RNA-Sequencing. Total RNA extracted from 10–30 pooled oocytes of each size range and genotype in biological triplicate were subjected to qRT-PCR. All experiments were performed between 2019–2021. Participants/materials, setting, methods XY and XO females were generated by cross between B6 females with B6.YTIR and B6.XPafY males, respectively. Oocytes in the growth phase were collected at 8–18 days postpartum (dpp), whereas fully-gr

Abstract The Four Core Genotypes (FCG) mouse model has become a valuable model to study the mechanistic basis for biological sex differences. This model allows discrimination between influences of gonadal sex (ovaries or testes) from those associated with genetic sex (presence of XX or XY chromosome complement). FCG mice have illuminated distinct effects of gonadal and chromosomal sex on traits ranging from brain structure and behavior to vulnerability to obesity, atherosclerosis, multiple sclerosis, Alzheimer’s and other diseases. A recent study determined that the Y Sry− chromosome used in a specific line of C57BL/6J FCG mice harbors nine genes that have been duplicated from the X chromosome. This report raised concern that scores of publications that previously used the FCG model may therefore be flawed, but did not provide details regarding how studies can be evaluated for potential impact (or lack of impact) of the translocation. Here we (1) provide a practical description of the genetic translocation for researchers using the FCG model, (2) document that a majority of the studies cited in the recent report are unlikely to be affected by the translocation, (3) provide a scheme for interpreting data from studies with FCG mice harboring the Y Sry− translocation, and (4) delineate expression levels of the nine translocated genes across tissue/cell types as a filter for evaluating their potential involvement in specific phenotypes.

<h4>Background/objectives</h4>Sex differences in lung cancer incidence and outcomes are well recognized, yet the relative contributions of sex chromosomes and gonadal sex remain incompletely defined. We aimed to disentangle chromosomal complement and hormonal sex in urethane-induced lung tumorigenesis using the Four Core Genotypes mouse model.<h4>Methods</h4>Mice (6-8 weeks old) with independently varied chromosomal complement (XX vs. XY) and gonadal sex received urethane (1 g/kg body weight) weekly for 10 weeks and were evaluated after a 20-week latency period. Tumor multiplicity, tumor area, normalized tumor burden, and Ki-67 proliferation indices were quantified histologically. Hepatic <i>Cyp2e1</i> expression was measured to assess carcinogen bioactivation. Tumor mutations were analyzed by Sanger sequencing. RAS Q61R immunoreactivity and ERK phosphorylation were evaluated to assess oncogenic signaling. Bronchoalveolar lavage fluid cellularity was analyzed. Survival was monitored. Statistical analyses tested the main effects of chromosomal complement, gonadal sex, and their interaction.<h4>Results</h4>Tumor multiplicity (<i>p</i> = 0.0729), tumor area (<i>p</i> = 0.5302), normalized tumor burden (<i>p</i> = 0.5316), and <i>Ki-67</i> indices (<i>p</i> = 0.6551) did not differ among genotypes. Hepatic <i>Cyp2e1</i> expression was comparable across groups (genotype <i>p</i> = 0.076; treatment <i>p</i> = 0.445). Sanger sequencing confirmed canonical Kras Q61R mutations. Anti-RAS (Q61R) immunohistochemistry revealed a significant genotype effect on mutant RAS expression (<i>F</i>(3,23) = 3.48, <i>p</i> = 0.032), with the highest H-scores observed in XYF mice compared with male gonadal genotypes; ERK phosphorylation did not differ. Bronchoalveolar lavage fluid analysis revealed increased lymphocytes after urethane exposure without genotype-dependent effects. Survival differed significantly, with XX females demonstrating prolonged survival relative to XY males.<h4>Conclusions</h4>Sex influenced survival independently of tumor burden, indicating that sex-associated differences in lung cancer outcomes are likely driven by systemic or microenvironmental factors rather than tumor-intrinsic growth mechanisms.

Avian genomes are typically stable, yet instances of chromosome fissions, fusions and translocations are known across various lineages. For example, multiple sex chromosome translocations have been described in the superfamily Sylvioidea. In this study, we examine the sex chromosomes in two Sylvioidea families, Nicatoridae and Cisticolidae, using whole-genome data. We found sex-linkage of chromosomes Z and 4A, consistent with findings in other Sylvioidea species. We also identify sex-linkage of parts of chromosome 4, marking a novel discovery for Nicatoridae and a previously documented feature in Cisticolidae. These families are non-sister taxa, and the size of the translocated region of chromosome 4 differs between them, supporting independent translocation events. We uncover variation in recombination suppression and evolutionary strata on chromosome 4 between families, as well as between two genera within Cisticolidae. This study reveals both recurrent and independent trajectories in sex chromosome evolution, deepening our understanding of complex genomes.

people. Sex generally refers to an organism's biological sex, while gender usually refers to either social roles typically associated with the sex of a person While in ordinary speech, the terms sex and gender are often used interchangeably, in contemporary academic literature, the terms often have distinct meanings, especially when referring to people. Sex generally refers to an organism's biological sex, while gender usually refers to either social roles typically associated with the sex of a person (gender role) or personal identification of one's ow While in ordinary speech, the terms sex and gender are often used interchangeably, in contemporary academic literature, the terms often have distinct meanings, especially when referring to people. Sex generally refers to an organism's biological sex, while gender usually refers to either social roles typically associated with the sex of a person (gender role) or personal identification of one's own gender based on their own personal sense of it (gender identity). Most contemporary social scientists, behavioral scientists and biologists, many legal systems and government bodies and intergovernmental agencies such as the WHO make a distinction between gender and sex. In most individuals, the various biological determinants of sex are congruent, and sex is consistent with the individual's gender identity, but in rare circumstances, an individual's assigned sex and gender do not align, and the person may be transgender. Though sex and gender have been used interchangeably at least as early as the fourteenth century, this usage was not common by the late 1900s. Issac Madison Bentley defined gender as the "socialized obverse of sex" in 1945. Sexologist John Money popularized this distinction…