Female Sex Chromosome Research Articles

Integration of long-read sequencing, DNA methylation and gene expression reveals heterogeneity in Y chromosome segment lengths in phenotypic males with 46,XX testicular disorder/difference of sex development.

46,XX testicular disorder/difference of sex development (46,XX DSD) is a rare congenital condition, characterized by a combination of the typical female sex chromosome constitution, 46,XX, and a variable male phenotype. In the majority of individuals with 46,XX DSD, a Y chromosome segment containing the sex-determining region gene (SRY) has been translocated to the paternal X chromosome. However, the precise genomic content of the translocated segment and the genome-wide effects remain elusive. We performed long-read DNA sequencing, RNA sequencing and DNA methylation analyses on blood samples from 46,XX DSD (n = 11), male controls (46,XY; variable cohort sizes) and female controls (46,XX; variable cohort sizes), in addition to RNA sequencing and DNA methylation analysis on blood samples from males with Klinefelter syndrome (47,XXY, n = 22). We also performed clinical measurements on all 46,XX DSD and a subset of 46,XY (n = 10). We identified variation in the translocated Y chromosome segments, enabling subcategorization into 46,XX DSD (1) lacking Y chromosome material (n = 1), (2) with short Yp arms (breakpoint at 2.7-2.8Mb, n = 2), (3) with medium Yp arms (breakpoint at 7.3Mb, n = 1), and (4) with long Yp arms (n = 7), including deletions of AMELY, TBLY1 and in some cases PRKY. We also identified variable expression of the X-Y homologues PRKY and PRKX. The Y-chromosomal transcriptome and methylome reflected the Y chromosome segment lengths, while changes to autosomal and X-chromosomal regions indicated global effects. Furthermore, transcriptional changes tentatively correlated with phenotypic traits of 46,XX DSD, including reduced height, lean mass and testicular size. This study refines our understanding of the genetic composition in 46,XX DSD, describing the translocated Y chromosome segment in more detail than previously and linking variability herein to genome-wide changes in the transcriptome and methylome.

8320 Integration of long-read sequencing, DNA methylation and gene expression reveals heterogeneity in Y-chromosome segment lengths in phenotypic males with 46,XX testicular disorder of sex development

Abstract Disclosure: E.B. Johannsen: None. A. Berglund: None. A. Skakkebæk: None. S. Chang: None. J. Rohayem: None. S. Laurentino: None. A. Hørlyck: None. S.O. Drue: None. E.N. Bak: None. J. Fedder: None. F. Tuttelmann: None. J. Gromoll: None. J. Just: None. C.H. Gravholt: None. Background: 46,XX testicular disorder of sex development is a rare congenital condition affecting approximately three per 100,000 newborn males. It is characterized by a combination of the typical female sex chromosome constitution, 46,XX, and a variable male phenotype. In the majority of XX males, a Y chromosome segment containing the sex-determining region gene (SRY) has been translocated to the paternal X chromosome. However, the precise genomic content of the translocated segment, breakpoints, genome-wide effects, and the effect on other biological pathways essential for the phenotype remain unknown. Methods: We performed long-read DNA sequencing (Oxford Nanopore), RNA sequencing (paired-end, 100 bp) and DNA methylation (Infinium EPIC) analysis on blood samples from males with 46,XX testicular disorder of sex development (XX males; n = 11), male controls (46,XY; n = 12 for long-read DNA sequencing, n = 26 for RNA sequencing and DNA methylation) and female controls (46,XX; n = 12 for long-read DNA sequencing, n = 32 for RNA sequencing and DNA methylation), in addition to RNA sequencing and DNA methylation analysis on blood samples from males with Klinefelter syndrome (47,XXY, n = 22). We also performed clinical measures on all XX males and a subset of male controls (n = 10). Results: We identified variation in the translocated Y-chromosome segment of our XX male cohort, allowing for subcategorization into 1) XX males without Y chromosome material (n = 1), 2) those with short Yp arms (breakpoint at 2.7-2.8 Mbp, n = 2), 3) those with medium Yp arms (breakpoint at 7.3 Mbp, n = 1) and 4) those with long Yp arms, including AMELY, TBLY1 deletions, and in some cases PRKY deletions (n = 7). We also identified variable expression of the X-Y homologues PRKY and PRKX, appeared to have balanced expression level resulting in overall equilibrium. The Y-chromosomal transcriptome and methylome were affected, reflecting the Y-chromosome segment length. Genomic changes induced by the translocated Yp segment were evident in the transcriptome and methylome of autosomal and X-chromosomal regions, indicating global effects. Furthermore, the transcriptional changes in XX males correlated with phenotypic traits of the XX males, including lower height, decreased lean mass and smaller testicular size. Conclusion: Integration of long-read DNA sequencing, DNA methylation, and RNA sequencing analysis allowed for the identification of a heterogenous translocation process in XX males that exerted widespread effects on methylation and transcription. Presentation: 6/2/2024

8320 Integration of long-read sequencing, DNA methylation and gene expression reveals heterogeneity in Y-chromosome segment lengths in phenotypic males with 46,XX testicular disorder of sex development

Abstract Disclosure: E.B. Johannsen: None. A. Berglund: None. A. Skakkebæk: None. S. Chang: None. J. Rohayem: None. S. Laurentino: None. A. Hørlyck: None. S.O. Drue: None. E.N. Bak: None. J. Fedder: None. F. Tuttelmann: None. J. Gromoll: None. J. Just: None. C.H. Gravholt: None. Background: 46,XX testicular disorder of sex development is a rare congenital condition affecting approximately three per 100,000 newborn males. It is characterized by a combination of the typical female sex chromosome constitution, 46,XX, and a variable male phenotype. In the majority of XX males, a Y chromosome segment containing the sex-determining region gene (SRY) has been translocated to the paternal X chromosome. However, the precise genomic content of the translocated segment, breakpoints, genome-wide effects, and the effect on other biological pathways essential for the phenotype remain unknown. Methods: We performed long-read DNA sequencing (Oxford Nanopore), RNA sequencing (paired-end, 100 bp) and DNA methylation (Infinium EPIC) analysis on blood samples from males with 46,XX testicular disorder of sex development (XX males; n = 11), male controls (46,XY; n = 12 for long-read DNA sequencing, n = 26 for RNA sequencing and DNA methylation) and female controls (46,XX; n = 12 for long-read DNA sequencing, n = 32 for RNA sequencing and DNA methylation), in addition to RNA sequencing and DNA methylation analysis on blood samples from males with Klinefelter syndrome (47,XXY, n = 22). We also performed clinical measures on all XX males and a subset of male controls (n = 10). Results: We identified variation in the translocated Y-chromosome segment of our XX male cohort, allowing for subcategorization into 1) XX males without Y chromosome material (n = 1), 2) those with short Yp arms (breakpoint at 2.7-2.8 Mbp, n = 2), 3) those with medium Yp arms (breakpoint at 7.3 Mbp, n = 1) and 4) those with long Yp arms, including AMELY, TBLY1 deletions, and in some cases PRKY deletions (n = 7). We also identified variable expression of the X-Y homologues PRKY and PRKX, appeared to have balanced expression level resulting in overall equilibrium. The Y-chromosomal transcriptome and methylome were affected, reflecting the Y-chromosome segment length. Genomic changes induced by the translocated Yp segment were evident in the transcriptome and methylome of autosomal and X-chromosomal regions, indicating global effects. Furthermore, the transcriptional changes in XX males correlated with phenotypic traits of the XX males, including lower height, decreased lean mass and smaller testicular size. Conclusion: Integration of long-read DNA sequencing, DNA methylation, and RNA sequencing analysis allowed for the identification of a heterogenous translocation process in XX males that exerted widespread effects on methylation and transcription. Presentation: 6/2/2024

Abstract P228: Kdm6a Regulates Extracellular Matrix Genes During Arterial Stiffening and High Blood Pressure in Female Mice

Arterial stiffness measured by pulse wave velocity (PWV) increases steeply during menopause due to estradiol decline. Longitudinal studies show higher PWV in postmenopausal women compared to age-matched men. Previously, we have demonstrated increased PWV in ovariectomized (OVX) and middle-aged female mice. However, the impact of sex chromosomes on PWV is unknown in female mice. We hypothesize that a decline in estradiol unleashes the female sex chromosomes effect that promotes arterial stiffening. This study used four core genotype mice (n=6-10/group) of XX or XY sex chromosomes left intact or OVX for 8 weeks. Arterial stiffening was assessed with pulse wave Doppler and 24-hour blood pressure by radiotelemetry. Carotid artery passive myography and vascular reactivity of 2 nd order mesenteric artery were assessed by pressure myography. To induce hypertension, XX and XY mice were treated with deoxycorticosterone acetate (DOCA; 50 mg/pellet) for 21 days and 1% saline. In vitro, isolated aortic vascular smooth muscle cells (VSMC) were stretched on collagen matrix or treated with Kdm6a inhibitor GSKJ-1. PWV was significantly increased in OVX than in gonadal intact XX and XY mice (P<0.001). However, an interaction effect was indicated with higher PWV in XX than XY OVX mice (4.9±0.1 vs. 4.2±0.2 m/s; P<0.001), indicating a sex chromosome effect. Carotid artery stress-strain curves showed a leftward shift of XX than XY mice, suggesting increased structural stiffness. Masson’s trichrome staining of the aorta showed increased collagen in the adventitia of XX than XY (30% vs. 26%; P=0.005) mice. Higher systolic blood pressure (SBP) was indicated in XX than in XY mice (Baseline; 123±3 vs. 116±4 mmHg; P=0.02). Aortic RNAseq showed increased X-linked genes, including Kdm6a, in XX compared to XY mice. Stretched aortic VSMC showed increased Col1a1 and decreased Itga4 and Lama2 genes reversed by GSKJ-1. DOCA-induced hypertension blunted the PWV difference between XX and XY mice; however, SBP was higher in XX than in XY mice (Week 1: 135±13 vs.127±3 mmHg; P=0.03), but not weeks 2 and 3. We observed impaired acetylcholine-mediated relaxation in hypertensive XX than XY mice (47% vs. 24%; P=0.03). Our data suggested that OVX mice with XX sex chromosomes promote arterial stiffening and high blood pressure, and Kdm6a regulates extracellular matrix genes in XX female VSMC. DOCA-induced hypertension promotes endothelial dysfunction and blunts PWV in ovariectomized XX and XY mice.

A second X chromosome improves cognition in aging male and female mice.

Women show resilience to cognitive aging, in the absence of dementia, in many populations. To dissect sex differences, we utilized the FCG and XY* mouse models. Female gonads and sex chromosomes improved cognition in aging mice of both sexes. Further, presence of a second X in male and female mice conferred cognitive resilience while its absence in females blocked it. In the hippocampal proteome of aging female mice, the second X increased proteins involved in synaptogenesis signaling - a potential pathway to improved cognition.

One-factor sex determination evolves without linkage between feminizing and masculinizing mutations.

The evolution of separate sexes from cosexuality requires at least two mutations: a feminizing allele to cause female development and a masculinizing allele to cause male development. Classically, the double mutant is assumed to be sterile, which leads to two-factor sex determination where male and female sex chromosomes differ at two loci. However, several species appear to have one-factor sex determination where sexual development depends on variation at a single locus. We show that one-factor sex determination evolves when the double mutant develops as a male or a female. The feminizing allele fixes when the double mutant is male, and the masculinizing allele fixes when the double mutant is female. The other locus then gives XY or ZW sex determination based on dominance: for example, a dominant masculinizer becomes a Y chromosome. Although the resulting sex determination system differs, the conditions required for feminizers and masculinizers to spread are the same as in classical models, with the important difference that the two alleles do not need to be linked. Thus, we reveal alternative pathways for the evolution of sex determination and discuss how they can be distinguished using new data on the genetics of sex determination.

XX Sex Chromosome Complement Promotes Arterial Stiffening and High Blood Pressure in Female Mice

Arterial stiffness measured by pulse wave velocity (PWV) increases precipitously during menopausal transition due to estradiol decline. Longitudinal studies show a steep increase in PWV of postmenopausal women compared to age-matched men. Previously, we have demonstrated increased PWV in ovariectomized and middle-aged female mice. Additionally, we showed increased oxidative stress in female than male vascular cells treated with angiotensin II in hormone-free charcoal-stripped media. We hypothesize that a decline in estradiol unleashes the female sex chromosomes effect that promotes arterial stiffening. In this study, we used the four core genotype mice (n=6-10/group) comprising females with either XX or XY sex chromosome complement that were left intact or ovariectomized for 8 weeks. Arterial stiffening was assessed with pulse wave Doppler and 24-hour blood pressure by radiotelemetry. Carotid artery passive myography and vascular reactivity of 2nd order mesenteric artery were assessed by pressure myography. To induce hypertension, ovariectomized XX and XY mice were treated with deoxycorticosterone acetate (DOCA; 50 mg/pellet) for 21 days and 1% saline as drinking water. PWV was significantly increased in ovariectomized than in gonadal intact XX and XY mice (main effect: p<0.001). However, an interaction effect was indicated with higher PWV in XX than XY ovariectomized mice (4.9±0.1 vs. 4.2±0.2 m/s; p<0.001), indicating a sex chromosome effect. Carotid artery stress-strain curves showed a leftward shift of XX than XY ovariectomized mice, suggesting increased structural stiffness. Masson’s trichrome staining of the aorta showed increased collagen in the adventitia of XX than XY ovariectomized mice (30±0.01 vs. 26±0.02 %; P=0.005). Higher systolic blood pressure (SBP) was indicated in ovariectomized XX than in XY mice (Baseline; 123±3 vs. 116±4 mmHg; P=0.02). DOCA-induced hypertension blunted the PWV difference between OVX XX and XY mice; however, SBP was higher in XX than in XY mice (Week 1: 135±13 vs.127±3 mmHg; P=0.3), (Week 2: 148±4 vs.140±1 mmHg; P=0.08), and (Week 3: 137±9 vs.127±4 mmHg; P=0.4). We observed impaired acetylcholine-mediated relaxation in mesenteric arteries of hypertensive ovariectomized XX than XY mice (47±6 % vs. 24±6 %; P=0.03). Our data suggested that ovariectomized female mice with XX sex chromosome complement promote arterial stiffening and blood pressure. However, DOCA-induced hypertension promotes endothelial dysfunction and blunts PWV in ovariectomized XX and XY mice. Future studies will identify elements in the XX sex chromosome complement contributing to arterial stiffening and high blood pressure. R00HL155841 and R25HL105400. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Interactions between U and V sex chromosomes during the life cycle of Ectocarpus.

In many animals and flowering plants, sex determination occurs in the diploid phase of the life cycle with XX/XY or ZW/ZZ sex chromosomes. However, in early diverging plants and most macroalgae, sex is determined by female (U) or male (V) sex chromosomes in a haploid phase called the gametophyte. Once the U and V chromosomes unite at fertilization to produce a diploid sporophyte, sex determination no longer occurs, raising key questions about the fate of the U and V sex chromosomes in the sporophyte phase. Here, we investigate genetic and molecular interactions of the UV sex chromosomes in both the haploid and diploid phases of the brown alga Ectocarpus. We reveal extensive developmental regulation of sex chromosome genes across its life cycle and implicate the TALE-HD transcription factor OUROBOROS in suppressing sex determination in the diploid phase. Small RNAs may also play a role in the repression of a female sex-linked gene, and transition to the diploid sporophyte coincides with major reconfiguration of histone H3K79me2, suggesting a more intricate role for this histone mark in Ectocarpus development than previously appreciated.

U2 and U4 snDNA Comparative Chromosomal Mapping in the Neotropical Fish Genera Apareiodon and Parodon (Characiformes: Parodontidae).

Small nuclear DNA (snDNA) are valuable cytogenetic markers for comparative studies in chromosome evolution because different distribution patterns were found among species. Parodontidae, a Neotropical fish family, is known to have female heterogametic sex chromosome systems in some species. The U2 and U4 snDNA sites have been found to be involved in Z and W chromosome differentiation in Apareiodon sp., Apareiodon affinis, and Parodon hilarii. However, few studies have evaluated snDNA sites as propulsors of chromosome diversification among closely related fish species. In this study, we investigated the distribution of U2 and U4 snDNA clusters in the chromosomes of 10 populations/species belonging to Apareiodon and Parodon, aiming to identify chromosomal homeologies or diversification. In situ localization data revealed a submetacentric pair carrying the U2 snDNA site among the populations/species analyzed. Furthermore, all studied species demonstrated homeology in the location of U4 snDNA cluster in the proximal region of metacentric pair 1, besides an additional signal showing up with a divergence in Apareiodon. Comparative chromosomal mapping of U4 snDNA also helped to reinforce the proposal of the ZZ/ZW1W2 sex chromosome system origin in an A. affinis population. According to cytogenetic data, the study corroborates the diversification in Parodontidae paired species with uncertain taxonomy.

Why Is Multiple Sclerosis More Frequent in Women? Role of the Immune System and of Oral and Gut Microbiota

Multiple sclerosis (MS) is the most prevalent demyelinating disease of the central nervous system (CNS) with an autoimmune component affecting young adults in their third decade of life. The etiology is still undefined, but myelin damage is mainly due to an aberrant immune response of lymphocyte cells against myelin components. Therefore, inflammation, demyelination, and axonal degeneration represent the major pathologic hallmarks of the disease. There are many risk factors associated with MS, and probably the most relevant is gender-related. Women are up to four times more affected than men are. Although the female prevalence in MS is epidemiologically evident, the identification of key factors involved in this difference is under investigation. On the other side, if women are more affected, men show late onset and worse prognosis. This sexual dimorphism derives from many sources, including sex hormones, different genes on female sex chromosomes, and differences in bacterial species. Indeed, accumulating evidence proves a link among MS and gut microbiota where its dysbiosis could help the immune system to trigger neuroinflammation. In this context, oral biology alteration should be considered, too. This work is intended to explore current knowledge inside MS gender differences with a look towards oral–gut–brain axis involvement.

XX/XY Chimerism in Internal Genitalia of a Virilized Heifer.

Five DSD heifers underwent genetic analysis in the present study. We cytogenetically analyzed in vitro cultured leukocytes and searched for SRY, AMELX/AMELY and ZFX/ZFY genes in leukocytes and hair follicles, finding that four of the studied heifers were freemartins (XX/XY leukocyte chimerism). The fifth case had an underdeveloped vulva localized ventrally and cranially to the mammary gland, a normal female sex chromosome complement (60,XX) in the leukocytes, and a lack of Y-chromosome-derived genes in the leukocytes and hair follicles. Postmortem anatomical examination of this heifer revealed the presence of normal ovaries with follicles, uterus, and oviducts, but molecular detection of the SRY, ZFX, ZFY,AMELX, and AMELY genes in these organs indicated the presence of a cell line carrying the Y chromosome. Further analysis of twelve microsatellite markers revealed the presence of additional variants at six loci in DNA samples derived from the reproductive organs; XX/XY chimerism was thus suspected in these samples. On the basis of the detection of AMELY (Y-linked) versus AMELX (X-linked) and SOX9 (autosomal) versus AMELY genes by droplet digital PCR (ddPCR), the Y/X and Y/autosome ratios were evaluated; they indicated the presence of XX and XY cell lines in the reproductive tissues. Our study showed that XX/XY chimerism can be present in the internal reproductive organs of the virilized heifers with a normal female set of sex chromosomes (60,XX) and a lack of Y-chromosome-derived genes in the leukocytes. The etiology of this phenomenon remains unknown.

Salt Sensitivity of Blood Pressure in Women.

Several clinical and large population studies indicate that women are more salt-sensitive than men, yet the precise mechanisms by which the sexually dimorphic onset manifests remains incompletely understood. Here, we evaluate recent epidemiological data and highlight current knowledge from studies investigating sex-specific mechanisms of salt-sensitive blood pressure (SSBP). Emerging evidence indicates that women of all ethnicities are more salt-sensitive than men, at all ages both premenopausal and postmenopausal. However, menopause exacerbates severity and prevalence of SSBP, suggesting that female sex chromosomes predispose to and female sex hormones mitigate SSBP. Results from both human and rodent studies support the contribution of enhanced and inappropriate activation of the aldosterone-ECMR (endothelial cell mineralocorticoid receptor) axis promoting vascular dysfunction in females. Increases in adrenal response to angiotensin II, in association with higher ECMR expression and activation of endothelial ENaC (epithelial sodium channel) in females compared to males, are emerging as central players in the development of endothelial dysfunction and SSBP in females. Female sex increases the prevalence and susceptibility of SSBP and sex hormones and sex chromosome complement may exert antagonistic effects in the development of the female heightened SSBP.

Impact of temperature-induced sex reversal on behavior and sound production in Nile tilapia (Oreochromis niloticus)

In some fish species, sex is determined by the combination of genetic and environmental factors. In most species concerned, extreme temperatures during the sensitive period of sex differentiation drives masculinization, independently of the female sex chromosomes. In Nile tilapia (XY male heterogamety), XX juveniles exposed to high temperatures (>32 °C) can masculinize and become phenotypical males (neomales). Whether these neomales exhibit a different behavior than XY males remains however unclear. Sex reversal being naturally relevant, we investigated the agonistic behavior of neomales during dyadic fights and the preference of gravid females for one of the two male types. We quantified the behavior, size of the nest, hormone circulating levels (testosterone, 11-ketotestosterone and cortisol) and sound production of the two male types in both contexts. Independently of the individual they face, neomales seem to display more aggressive behaviors than XY males but often fail to become dominant. Agonistic interactions were mainly silent, suggesting that sounds are unnecessary for the establishment of social hierarchy. Although males and neomales produce different kinds of sounds when facing a gravid female, the female does not exhibit a preference. Overall, no differences were observed for hormone circulating concentrations between the two male types. We suggest that the sex chromosomes and/or the sex reversal procedure may have differently shaped the brain of neomales, resulting in differences in the expression of behavior.

Pubertal induction in girls with Turner Syndrome.

Turner Syndrome (TS) is the most common female sex chromosome aneuploidy in females, and patients may present with hypergonadotropic hypogonadism due to gonadal dysgenesis. Timing and modalities of pubertal induction in these patients is still a matter of debate. Aim of this review was to focus on the latest update on pubertal induction in TS. Based on literature data, the following practical approach to this issue is recommended. Pubertal induction should begin between 11 and 12 years of age, starting with low doses of estradiol to preserve height potential. Transdermal 17β-Estradiol (17β-E2) could represent the first-choice induction regimen as it is more physiologic compared to an oral regimen and avoids the first-pass mechanism in the liver. In the case of poor compliance, administration of oral 17β-E2 or ethinyl estradiol could be offered. Incremental dose increases, approximately every 6 months, can contribute to mimic normal pubertal progression until adult dosing is reached over a 2- to 3-year period. Progestin should be added once breakthrough bleeding occurs or after 2 to 3 years of estrogen therapy or if ultrasound shows a mature uterus with thick endometrium. Treatment needs to be individualized and monitored by clinical assessment in relation to patient compliance and satisfaction. Well-designed prospective randomized clinical trials aimed to identify the best estrogen regimen for pubertal induction in TS girls are needed.

Two transcriptionally distinct pathways drive female development in a reptile with both genetic and temperature dependent sex determination.

How temperature determines sex remains unknown. A recent hypothesis proposes that conserved cellular mechanisms (calcium and redox; ‘CaRe’ status) sense temperature and identify genes and regulatory pathways likely to be involved in driving sexual development. We take advantage of the unique sex determining system of the model organism, Pogona vitticeps, to assess predictions of this hypothesis. P. vitticeps has ZZ male: ZW female sex chromosomes whose influence can be overridden in genetic males by high temperatures, causing male-to-female sex reversal. We compare a developmental transcriptome series of ZWf females and temperature sex reversed ZZf females. We demonstrate that early developmental cascades differ dramatically between genetically driven and thermally driven females, later converging to produce a common outcome (ovaries). We show that genes proposed as regulators of thermosensitive sex determination play a role in temperature sex reversal. Our study greatly advances the search for the mechanisms by which temperature determines sex.

Transcriptional regulation of dosage compensation in Carica papaya

Sex chromosome evolution results in the disparity in gene content between heterogametic sex chromosomes and creates the need for dosage compensation to counteract the effects of gene dose imbalance of sex chromosomes in males and females. It is not known at which stage of sex chromosome evolution dosage compensation would evolve. We used global gene expression profiling in male and female papayas to assess gene expression patterns of sex-linked genes on the papaya sex chromosomes. By analyzing expression ratios of sex-linked genes to autosomal genes and sex-linked genes in males relative to females, our results showed that dosage compensation was regulated on a gene-by-gene level rather than whole sex-linked region in papaya. Seven genes on the papaya X chromosome exhibited dosage compensation. We further compared gene expression ratios in the two evolutionary strata. Y alleles in the older evolutionary stratum showed reduced expression compared to X alleles, while Y alleles in the younger evolutionary stratum showed elevated expression compared to X alleles. Reduced expression of Y alleles in the older evolutionary stratum might be caused by accumulation of deleterious mutations in regulatory regions or transposable element-mediated methylation spreading. Most X-hemizygous genes exhibited either no or very low expression, suggesting that gene silencing might play a role in maintaining transcriptional balance between females and males.

Centromere organization and UU/V sex chromosome behavior in a liverwort.

In 1917, sex chromosomes in plants were discovered in a liverwort with hetermorphic U and V chromosomes. Such heteromorphy is unexpected because, unlike the XY chromosomes in diploid-dominant plants, in haploid-dominant plants the female U and the male V chromosomes experience largely symmetrical potential recombination environments. Here we use molecular cytogenetics and super-resolution microscopy to study Frullania dilatata, a liverwort with one male and two female sex chromosomes. We applied a pipeline to Illumina sequences to detect abundant types of repetitive DNA and developed FISH probes to microscopically distinguish the sex chromosomes. We also determined the phenotypic population sex ratio because biased ratios have been reported from other liverworts with heteromorphic sex chromosomes. Populations had male-biased sex ratios. The sex chromosomes are monocentric, and of 14 probes studied (eight satellites, five transposable elements and one plastid region), four resulted in unique signals that differentiated the sex chromosomes from the autosomes and from each other. One FISH probe selectively marked the centromeres of both U chromosomes, so we could prove that during meiosis each U chromosome associates with one of the opposite telomeres of the V chromosome, resulting in a head-to-head trivalent. The similarity of the two U chromosomes to each other in size and in their centromere FISH signal positions points to their origin via a non-disjunction event (aneuploidy), which would fit with the general picture of sex chromosomes rarely crossing-over and being prone to suffer from non-disjunction.

Classical and molecular cytogenetics of Belontia hasselti (Perciformes: Osphronemidae): Insights into the ZZ/ZW sex chromosome system

Abstract. Chaiyasan P, Mingkwan B, Jantarat S, Suwannapoom C, Cioffi MDB, Liehr T, Talumphai S, Tanomtong A, Supiwong W. 2021. Classical and molecular cytogenetics of Belontia hasselti (Perciformes: Osphronemidae): Insights into the ZZ/ZW sex chromosome system. Biodiversitas 22: 546-554. Karyotype of Java combtail fish, Belontia hasselti, from To Daeng peat swamp forest, Narathiwat Province, southern Thailand, was studied for the first time. Mitotic chromosome preparations were prepared directly from kidney cells from ten male and ten female fish. Conventional staining, NOR banding, and molecular cytogenetics with fluorescence in situ hybridization (FISH) using 5S and 18S rDNAs, as well as microsatellites d(CA)15 and d(CAC)10 as probes were applied. The diploid chromosome number (2n) was 48 and a female heterogametic sex chromosome system (ZZ/ZW) is suggested. The fundamental numbers (NF) were 48 and 49 in males and females, respectively. The karyotype of males comprised 48 telocentric chromosomes while the female ones were composed of one metacentric and 47 telocentric chromosomes. A single Ag-NOR-bearing chromosomal pair was identified. The NOR positions were characterized at the interstitial sub-centromeric region of pair 13, which coincided with signals of 18S rDNA and d(CAC)10 probes. The 5S rDNA signals were located at interstitial sites of the largest telocentric pair. Microsatellite d(CA)15 repeats were highly distributed throughout almost all entire chromosomes except for centromeric regions on some chromosome pairs, including sex chromosomes. The present study is a novel report for a ZZ/ZW sex chromosome system of this fish family in Thailand.

Exogenous Progesterone for Offspring Sex Ratio Manipulation in Arabic Chickens (Gallus turcicus) Leading to Increasing Female Chicks Proportion

Female birds of egg-laying hens are more valuable than males, because males bird have no commercial value. The opportunity to manipulate offspring sex ratio in poultry has been observed in female birds; hence, female birds have heterogametic ZW chromosomes. High progesterone concentration 2-5 h before ovulation is thought to affect the segregation of female sex chromosomes as the basis for determining the sex of offspring. This study aimed to investigate the effect of progesterone induction in Arabic hens, which was conducted 5 h before ovulation, along with the time of the first meiosis; therefore, segregation of sex chromosomes leading to an increase in female offspring. The study utilized on 60 Arabic hens divided into three treatment groups: Without injection (P0), progesterone injection 1 mg/hen, (P1), progesterone injection 2 mg/hen (P2). The results showed that the percentage of female offspring at P0 and P1 was 54.74 and 53.33%, respectively, while P2 hens resulted in 62.92% females, the highest female offspring rate than the other groups. Chi-square analysis of sex ratio showed that P0 and P1 hens had no significant effect (P>0.05) while P2 hens being significant (P<0.05) from the expected sex ratio (50:50). Progesterone concentration of hens produced female offspring in the P2 group was 7.15 ng/ml being highly significant (P<0.05) than that found in the hens produced male offspring (4.53 ng/ml). Progesterone 5 h preceding ovulation in the Arabic hens with a 2 mg/hen dose can increase the proportion of female offspring; therefore, an opportunity for sex ratio manipulation in Arabic chickens.

Pubertal induction in girls with Turner syndrome

Turner Syndrome (TS) is the most common female sex chromosome aneuploidy in females, and patients may present with hypergonadotropic hypogonadism due to gonadal dysgenesis. Timing and modalities of pubertal induction in these patients is still a matter of debate. Aim of this review was to focus on the latest update on pubertal induction in TS. Based on literature data, the following practical approach to this issue is recommended. Pubertal induction should begin between 11 and 12 years of age, starting with low doses of estradiol to preserve height potential. Transdermal 17β-Estradiol (17β-E2) could represent the first-choice induction regimen as it is more physiologic compared to an oral regimen and avoids the first-pass mechanism in the liver. In the case of poor compliance, administration of oral 17β-E2 or ethinyl estradiol could be offered. Incremental dose increases, approximately every 6 months, can contribute to mimic normal pubertal progression until adult dosing is reached over a 2- to 3-year period. Progestin should be added once breakthrough bleeding occurs or after 2 to 3 years of estrogen therapy or if ultrasound shows a mature uterus with thick endometrium. Treatment needs to be individualized and monitored by clinical assessment in relation to patient compliance and satisfaction. Well-designed prospective randomized clinical trials aimed to identify the best estrogen regimen for pubertal induction in TS girls are needed.