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Fairness-aware supervised hierarchical contrastive semantic learning for sexual dimorphism analysis.

MOTIVATION: Sexual dimorphism is a fundamental biological determinant driving systematic differences in disease susceptibility, progression, and clinical outcomes. However, current sex-combined AI-based genomic models often exhibit algorithmic bias and fail to capture these sex-specific mechanisms, creating a critical barrier to unbiased precision medicine. Ensuring fairness in the context of sexual dimorphism requires understanding and addressing the distinct biological mechanisms functioning in each sex, rather than focusing solely on equalizing predictive performance. RESULTS: We propose a fairness-aware supervised hierarchical contrastive learning approach, called FairHICON, to discover unbiased sex-common and sex-specific predictive features. Evaluations on cancer and asthma transcriptomic datasets demonstrate that FairHICON significantly outperforms state-of-the-art benchmarks, improving predictive performance by up to 9% while effectively reducing the performance gap between male and female sexes. Furthermore, prognostic validation confirms that the identified sex-specific pathways stratify patient survival significantly better within their corresponding sex groups. This validates FairHICON to elucidate the molecular heterogeneity of sexual dimorphism, advancing inclusive precision medicine. AVAILABILITY AND IMPLEMENTATION: The source code and data is available at https://github.com/datax-lab/FairHICON.

Sex Characteristics

Integrated methylome and transcriptome analysis provides insight into DNA methylation-mediated networks in sexual dimorphism of Vernicia montana.

BACKGROUND: Sexual dimorphism is fundamental to reproduction in dioecious plants and is regulated by both genetic and epigenetic mechanisms. DNA methylation is a central epigenetic mark known to influence phenotypic variation in plants. However, its specific role in shaping sexual dimorphism in dioecious trees remains poorly understood. To address this question, we performed integrated genome-wide DNA methylome and transcriptome analyses of four tissue types in the dioecious tung tree (Vernicia montana), including male and female flower buds and their corresponding leaves. RESULTS: Our analysis revealed distinct DNA methylation patterns between male and female tissues. Notably, the coordination between DNA methylation reprogramming and transcriptional regulation appeared to be more strongly associated with reproductive development than with vegetative growth in V. montana. We identified a set of sex-biased genes that may reflect different reproductive strategies between the sexes. Further analysis identified several key transcription factors (TFs) potentially associated with promoter differentially methylated regions (DMRs), including flowering-time regulators (e.g., FRS5, REM16, and VRN1) and TFs involved in hormone signaling pathways such as jasmonic acid, auxin, and salicylic acid signaling. Cis-regulatory element analysis showed that some promoter DMRs overlapped with hormone response elements related to abscisic acid, auxin, and gibberellin. Co-expression network analysis further revealed potential regulatory correlations among promoter DMR-mediated TFs, hormone-responsive pathways, and key floral development regulators. CONCLUSIONS: Collectively, our results suggest that interactions among DNA methylation, transcriptional regulation, and hormone-responsive pathways may contribute to the establishment of sexual dimorphism in V. montana. This study provides the first integrated view of these regulatory layers in V. montana and supports a species-specific regulatory framework for understanding the epigenetic basis of sexual dimorphism in this economically important dioecious tree. The proposed framework is based on multi-omics analyses and warrants further validation through targeted functional studies.

DNA Methylation

Effects of sex steroids on the development of sexual dimorphism in mouse innominate bone.

The sexual dimorphism of the innominate bone was examined in 14 strains of mice. In female mice of all strains, the pubis was significantly longer and thinner than that in the strain-matched males. In 13 of 14 strains, the ischium in the male was longer and thicker than in the female. In the testicular-feminized male (Tfm) mouse, the ischium was longer and thinner than that in the wild-type male, resembling that of the wild-type female. The pubis of the Tfm mouse was longer than in the wild-type males. The pubis width in the Tfm mouse was between those of the wild-type male and female. Gonadectomy at ages of 5, 10, 20, 30, and 60 days in both sexes showed that the ischium develops as the female type when sex hormones are absent. In contrast, postnatal testicular androgen induces the male-type ischium. Gonadectomy at 60 days had a slight effect on the pubis, indicating that sexual dimorphism of the pubis was determined before 60 days of age. Estrogen receptors (ER) were immunohistochemically demonstrated in bone cells of 0- to 60-day-old mice. ER was found exclusively in the periosteum of the pubis at the day of birth; however, it appeared in bone cells of all parts of pelvis at 10-60 days. These results indicate that sexual dimorphism of the pubis is consistent for the 14 mouse strains examined, and that the shape of the pubis is determined by sex steroids before 60 days of age. Since ER exist in the bone cells, morphogenesis of the pelvis may be regulated by these sex steroids.

Animals

Sexual dimorphism in newborns and adults.

A total of 1034 newborns were used to analyze sexual dimorphism with respect to 37 somatic traits and ratios between them, describing body shape. Arithmetic means and standard deviations were calculated for both sexes. Similarly, sexual dimorphism of adults was analyzed. Sexual differences in newborns were statistically significant for most measurements but only for some body proportions (relative chest size, foot shape, relative lower extremity length, and the ratio of head to chest circumference). The highest degree of sexual dimorphism in newborns was shown by the index standardized on the mean (dsex/mean) of such traits as the thickness of subcutaneous fat tissue on the thigh, subscapular fat tissue and fat tissue on the 10th rib, body weight, hand breadth, and relative chest size (Marty index). A moderate dimorphism was found for the length of upper extremities, forearm with the hand, head with the neck, hand and trunk, the size of the nose and foot, the breadth of hips and mandible, and the upper-face height. A low dimorphism was found for body length, circumference and breadth of head, face diameter, chest circumference, foot shape, relative length of lower extremities, and proportion between head and chest circumferences. Sexual differences (dsex/mean) for all the somatic traits examined in adults were statistically significant. The dimorphism of all the traits (except hip breadth) was higher in adults than in newborns. The highest increase in sexual dimorphism was noted for chest breadth (ca 55 times), then for chest depth (ca 17 times), thickness of subcutaneous fat tissue on arm (ca. 17 times), and the length of lower extremities (ca 15 times). Sexual differences in proportions (shape) of the body were also better pronounced in adults than in newborns. Sexual dimorphism standardized for dispersion (dsex/SD) in newborns differed from that in adults with respect to the degree of its expression and the sequence of the traits showing the highest and the lowest levels of dimorphism. This results from intra-group variation of different traits.

Adipose Tissue

Variable resource allocation pattern, biased sex-ratio, and extent of sexual dimorphism in subdioecious Hippophae rhamnoides.

Evolutionary maintenance of dioecy is a complex phenomenon and varies by species and underlying pathways. Also, different sexes may exhibit variable resource allocation (RA) patterns among the vegetative and reproductive functions. Such differences are reflected in the extent of sexual dimorphism. Though rarely pursued, investigation on plant species harbouring intermediate sexual phenotypes may reveal useful information on the strategy pertaining to sex-ratios and evolutionary pathways. We studied H. rhamnoides ssp. turkestanica, a subdioecious species with polygamomonoecious (PGM) plants, in western Himalaya. The species naturally inhabits a wide range of habitats ranging from river deltas to hill slopes. These attributes of the species are conducive to test the influence of abiotic factors on sexual dimorphism, and RA strategy among different sexes. The study demonstrates sexual dimorphism in vegetative and reproductive traits. The sexual dimorphism index, aligned the traits like height, number of branches, flower production, and dry-weight of flowers with males while others including fresh-weight of leaves, number of thorns, fruit production were significantly associated with females. The difference in RA pattern is more pronounced in reproductive traits of the male and female plants, while in the PGM plants the traits overlap. In general, habitat conditions did not influence either the extent of sexual dimorphism or RA pattern. However, it seems to influence secondary sex-ratio as females show their significant association with soil moisture. Our findings on sexual dimorphism and RA pattern supports attributes of wind-pollination in the species. The observed extent of sexual dimorphism in the species reiterates limited genomic differences among the sexes and the ongoing evolution of dioecy via monoecy in the species. The dynamics of RA in the species appears to be independent of resource availability in the habitats as the species grows in a resource-limited and extreme environment.

Hippophae

The nature and development of sex attractant specificity in cockroaches of the genus Periplaneta. I. Sexual dimorphism in the distribution of antennal sense organs in five species.

Sexual dimorphism in the distribution of antennal sense organs is common among adults of the genus Periplaneta. In three out of the four strains of Periplaneta americana examined, adult males had more contact chemoreceptros than females. In the fourth strain of P. americana and in P. australasiae, P. brunnea, P. fuliginosa, and P. japonica, no statistically supportable sexual dimorphism of contact chemoreceptors was found. However, in all strains and species of Periplaneta examined, sexual dimorphism was found in the total number and/or density of olfactory sensilla. Male adults had nearly twice as many olfactory sensilla as female adults. These observations are consistent with the behavioral observation that males within the genus Periplaneta rely on the reception of an airborne pheromone for the initiation of courtship behavior. In P. americana, where sexual dimorphism was found in the contact chemoreceptors, contact stimuli release the full wing raising display and presentation in males during courtship.

Animals

Estrogen receptive neurons in the preoptic area of the rat are postsynaptic targets of a sexually dimorphic enkephalinergic fiber plexus.

The periventricular preoptic area (pePOA) is a sexually dimorphic component of the rat forebrain that contains a sexually dimorphic Met-enkephalin immunoreactive (ENK-ir) fiber plexus. This plexus is especially dense in the female while only scattered ENK-ir fibers are present in the pePOA of the male. Abundant estrogen receptive neurons are located in the pePOA of both the female and male. This experiment was conducted to determine if estrogen receptive neurons in the pePOA are postsynaptic targets of ENK-ir terminals. Double label ultrastructural localization of estrogen receptor (ER)-ir neurons and ENK-ir fibers was performed using the chromogens 3,3',5,5'-tetramethylbenzidine (TMB) and diaminobenzidine tetrahydrochloride (DAB), respectively. TMB-stained ER-ir neurons contained electron dense crystalline spicules located predominantly in their nuclei. Flocculent DAB reaction product was distributed over membraneous structures in ENK-ir fibers and terminals. Numerous ER-ir neurons were present in the pePOA of the male and female. In females, many ENK-ir terminals, both synaptic and non-synaptic, contacted the perikarya of ER-ir neurons. In contrast, many fewer ENK-ir terminals made contact on ER-ir neurons in the male. Thus, these results provide morphological evidence that ENK-ir neurons can regulate ER-ir neurons in the pePOA. Moreover, because expression of the ENK-ir pePOA fiber plexus is estrogen-sensitive in the female, these results suggest strongly that estrogen may regulate these neurons both pre- and postsynaptically. Finally, these results provide additional evidence for the involvement of the sexually dimorphic pePOA ENK-ir fibers plexus in the control of estrogen-mediated function in the female.

Animals

Effects of sex and androgen treatment on dendritic dimensions of neurons in the sexually dimorphic preoptic/anterior hypothalamic area of male and female ferrets.

A sexually dimorphic group of cells at the dorsal border of the preoptic/anterior hypothalamic area (POA/AH) of ferrets has been previously identified in Nissl-stained tissue. In this study, Golgi-stained tissue was examined in order 1) to determine whether sex differences exist in dendritic dimensions of neurons from this region, and 2) to assess the effects of adult androgen treatment on dendritic morphology in ferrets of both sexes. Brains from adult ferrets given daily injections of testosterone propionate (5 mg/kg body weight) or oil vehicle for 5 weeks after gonadectomy were impregnated by Golgi-Cox procedures. After sectioning at 120 microns, 78 multipolar neurons were selected from the sexually dimorphic POA/AH of 12 ferrets and reconstructed in three dimensions with the aid of a computer-assisted neuron tracing system. Large sex differences were observed in somal area and most aspects of dendritic morphology, including total length, number of branches, and total dendritic surface area. Androgen also appeared to accentuate dendritic arborization in both sexes, but this effect was weaker than the sex effect, more apparent in males than females, and restricted to fewer variables. The most statistically significant effects of adult androgen treatment in males were found for total dendritic surface area and percentage of fourth order dendrites, and in females, average dendritic thickness. These data show that strong sex differences exist in dendritic structure of neurons in the POA/AH, and suggest that alterations in levels of gonadal steroids in adulthood may promote synaptic remodeling in a region of the brain involved in the control of sexually dimorphic behaviors.

Animals

Sexual dimorphism in metacarpal dimensions and body size of Mexican school children.

The hypothesis that patterns of sexual dimorphism in transverse dimensions of the metacarpal only reflect sex differences in body size was investigated in a sample of 324 Mexican school children 6.00-10.99 years of age. Several patterns of sexual dimorphism in second metacarpal dimensions are seen with regard to stature and weight. Sex differences in medullary diameter and percent cortical area are not related to sexual dimorphism in body size, while sex differences in cortical thickness are related to, but not fully explained by, differences in body size. Dimorphism in metacarpal diaphyseal diameter is related to differences in body size, but, at a constant body size and age, boys still have significantly larger diaphyseal diameters than girls. Finally, sexual dimorphism in cortical area is closely associated with sex differences in body size.

Age Factors

Human marriage systems and sexual dimorphism in stature.

Contemporary populations of Homo sapiens are sexually dimorphic on a variety of traits. In terms of stature, men are reliably between 4% and 10% taller than women in well-sampled human populations. Are cross-cultural differences in the magnitude of sexual dimorphism consistent with expectations from sexual selection theory? Prior studies have provided conflicting answers to this question in part because they failed to agree on how the force of sexual selection should or could be operationalized. Here we offer a simple and unbiased method for operationalizing sexual selection and retest two separate predictions from earlier work (Alexander et al., 1979) about its expected impact on stature dimorphism in a sample of 155 societies. Neither prediction matches the observed cross-cultural distribution of dimorphism. However, this is not the consequence of a random distribution of dimorphism across societies. Instead, the data exhibit a robust and unexpected pattern.

Body Height

Prenatal flutamide alters sexually dimorphic nuclei in the spinal cord of male rats.

The effects of prenatal exposure to the antiandrogen flutamide on two sexually dimorphic nuclei of the lumbar spinal cord, the dorsolateral nucleus (DLN) and the spinal nucleus of the bulbocavernosus (SNB), were investigated. Rat dams were given daily injections of 5 mg flutamide or vehicle alone from day 11 through 21 of pregnancy. The spinal cords and perineal morphology of their male and female offspring were examined in adulthood. Flutamide reduced the number of SNB and DLN neurons, reduced the somal and nuclear area of SNB neurons, and reduced the weight of the perineal muscles in males. Flutamide produced no effect in females. No sexual dimorphism was found in the mean somal area of DLN neurons, but a sexual dimorphism was found in the distribution of somal areas in our samples; females had proportionately more large neurons than males. Flutamide-treated males also had proportionately more large neurons than control males but fewer than females. A sexual dimorphism was found in the nuclear areas of DLN neurons but flutamide did not influence this trait.

Animals

Sexual dimorphism and growth hormone regulation of a hybrid gene in transgenic mice.

The sexually dimorphic expression of the urinary protein genes of mice (Mup genes) in the liver is mediated by the different male and female temporal patterns of circulating GH. Normal females were induced to male levels when GH was administered by injection to mimic the male GH pattern, showing that expression at the male level does not require a male sex steroid status in addition to intermittent GH. Two Mup-alpha 2u-globulin hybrid transgenes with different Mup gene promoters showed sexually dimorphic expression, and their expression in females increased to male levels upon testosterone treatment. GH-deficient (lit/lit) mice did not express these transgenes, and GH-deficient females did not respond to testosterone treatment, showing that GH was required for induction. Both normal and GH-deficient females were induced to male levels when GH was administered by injection. This is the first report of a transgene responsive to GH. A transgene consisting of a Mup promoter fused to a Herpes simplex virus thymidine kinase reporter sequence also showed sexual dimorphism, although to a lesser degree. It was expressed at the same level in normal females and GH-deficient mice of both sexes and was induced when GH-deficient mice were treated with GH. We propose that this transgene has a basal constitutive expression, possibly due to the absence of any rodent DNA downstream of the promoter. Since expression of the transgene was significantly induced by GH, the GH response is due at least in part to sequences in the promoter region.

Alpha-Globulins

Sexual dimorphism in the growth of the cranium.

The major sexual dimorphisms in body size appear at puberty but, by then, 95% of the growth of the cranium is completed. As sexual dimorphism in the cranium is as great as for other parts of the body, this suggests that it must appear at an earlier age, and that cranium/body size ratios for the two sexes will vary during growth. Results from a longitudinal study of Montreal children are used to investigate this phenomenon. The effect is expressed quantitatively by proportional growth and growth velocity curves, based on the final size of boys, which show that the dimorphism indeed makes an early appearance. The data are also analyzed on an age scale relative to the ages of peak growth velocity in stature, derived from the individual growth curves. This shows that although there is a minor pubertal spurt in growth for the external cranial dimensions of boys, it contributes relatively little to the final dimorphism in cranial size. To summarize this aspect of growth, an index of cephalization is calculated: head length X head width/stature. Cross-sectional standards for the change of the mean index with age show a linear decline for boys and girls until puberty, with a constant difference between them. After puberty, the index becomes equal in the two sexes. Individual development curves for the index are however not linear.

Adolescent

Sexual dimorphism of bone robusticity in different strains of rats.

A quantitative method was used to establish the sexual dimorphism of bone robusticity in 10 domesticated strains of rats and in wild rats. Sexual dimorphism had its highest frequency in the pelvis, followed by the ulna, the skull, and the femur and tibia. Humerus and tail showed the lowest frequency of such sexual dimorphism. This distribution in an unspecialized mammal such as the rat, in which selective pressures are at their minimum becauses of the factor of domestication, can serve as a baseline for comparison with taxa in which selective forces are more strongly active.

Animals

Corpus callosum in sexually dimorphic and nondimorphic primates.

The midsagittal area and other morphological measures were taken on the corpus callosum of four different species of primate: Macaca mulatta, M. fascicularis, Callithrix jacchus, and Saguinus oedipus. The first two species are strongly dimorphic, whereas the New World forms show little dimorphism with regard to overall body size, canines, and brain weight. Neither total corpus callosal area (TOTALCC), or other parts of the corpus callosum (CC) showed any significant sexual dimorphism in any of the primate species sampled. Only in M. mulatta did a sexual dimorphism appear to be significant. In males of this species, the dorsoventral width of the splenium was larger than in females. In addition, the anterior commissure (ANTCOMM) evinced no sexual dimorphism in the different species. Brain weight was significantly dimorphic in only M. mulatta, and when ratio data were used to correct for brain weight, no significant differences were found in the corpus callosum. This is in contrast to Homo sapiens, where the relative size of the CC has been reported to be larger in females, and particularly so in the posterior, or splenial portion of the CC. Correlation coefficients were calculated for the various variables within each species. In general, most of the callosal measures are significantly inter-correlated, although the exact pattern varies for each species. Thus, unlike Homo sapiens, or pongids such as Gorilla and Pan, neither New nor Old World monkeys show any striking evidence for sexual dimorphism in the corpus callosum.

Animals

Single-cell spatial transcriptomic atlas of the mouse adrenal gland reveals sexual dimorphism in steroidogenic enzyme and hormone receptor expression.

The adrenal cortex shows sexual dimorphism in structure and function. We analysed adrenal glands from 7-week-old male and female BALB/c mice using Visium HD with Cellpose 3 segmentation, comprising 236,077 cells across eleven populations, including four cortical zones. Using curated marker-gene-based zonal annotation, we focused on steroidogenic enzymes and hormone receptors, complementing our companion study based on the same primary dataset. The X-zone was nearly absent in males but prominent in females. Females showed higher Hsd3b1 expression across cortical zones and higher Cyp11b1 expression in outer cortical compartments. The strongest sex difference involved Srd5a2, with markedly higher expression in male zona fasciculata (inner: 77.1% vs. 28.9%), independently supported by RNAscope and immunohistochemistry. Mc2r and Mrap showed discordant spatial distributions, with limited co-expression, suggesting potential MC2R-independent MRAP roles. Agtr1a dominated angiotensin II receptor expression in zona glomerulosa without major sex differences, providing a zone-resolved reference for adrenal sexual dimorphism.

Adrenal cortex

The effects of serotonin manipulation during the postnatal period on the development of sexually dimorphic and non-dimorphic lumbosacral motor neuron groups in the albino Swiss rat.

Serotonin (5-HT) may act during development as a neurotrophic agent. Evidence suggests that sexually dimorphic regions of the mammalian nervous system (which often possess sexually dimorphic patterns of 5-HT innervation) could provide a model for this aspect of 5-HT action. Albino Swiss rat pups were treated with p-chlorophenyl alanine (pCPA, 200 mg/kg) or 5-hydroxytryptophan (5-HTP, 75 mg/kg) for 14 days after birth. As adults, the number of motor neurons in the sexually dimorphic spinal nucleus of bulbocavernosus (SNB) and dorsolateral nucleus (DLN), together with the non-dimorphic ventromedial nucleus (VM) were analysed. Postnatal treatment with 5-HTP had a general effect of increasing motor neuron numbers in all three groups. However, pCPA treatment had a marked and specific effect on SNB neuron numbers, increasing these in both sexes (+250% in females and +60% in males) compared with control animals. The results suggest that the postnatal innervation of ventral horn motor neurons by 5-HT-containing terminals may affect cell death at this time.

Animals

Sexual dimorphism of skeletal robusticity in several mammalian orders.

This study tries to determine whether a phylogenetic trend exists in the sexual dimorphism of skeletal robusticity and whether domestication has an effect on it. The problems were studied in the metatarsals of marsupials, insectivores, rodents and primates including Homo, and in various skeletal sections of wild and domesticated rats and dogs. No clear phylogenetic trend could be found and domestication cannot be shown to have an effect on diminishing skeletal robusticity. Sexual dimorphism of skeletal robusticity seems to be highly species-specific and to have a mosaic distribution in a given taxon. Conclusions on phylogenetic trends of sexual dimorphism of skeletal robusticity and the effect of culture on it seem to be premature.

Animals