Partial sex linkage and linkage disequilibrium on the guppy sex chromosome

The guppy Y chromosome has been considered a model system for the evolution of suppressed recombination between sex chromosomes, and it has been proposed that complete sex-linkage has evolved across about 3 Mb surrounding the sex-determining locus of this fish, followed by recombination suppression across a further 7 Mb of the 23 Mb XY pair, forming younger evolutionary strata. Sequences of the guppy genome show that Y is very similar to the X chromosome, making it important to understand which parts of the Y are completely non-recombining, and whether there is indeed a large completely non-recombining region. Here, we describe new evidence that supports a different interpretation of the data that suggested the presence of such a region. We analysed PoolSeq data in samples from multiple natural populations from Trinidad. This yields evidence for linkage disequilibrium (LD) between sequence variants and the sex-determining locus. Downstream populations have higher diversity than upstream ones (which display the expected signs of bottlenecks). The associations we observe conform to predictions for a genome region with infrequent recombination that carries one or more sexually antagonistic polymorphisms. They also suggest the region in which the sex-determining locus must be located. However, no consistently male-specific variants were found, supporting the suggestion that any completely sex-linked region may be very small.

An ancient truncated duplication of the anti-Mullerian hormone receptor type 2 gene is a potential conserved master sex determinant in the Pangasiidae catfish family

The evolution of sex determination (SD) mechanisms in teleost fishes is amazingly dynamic, as reflected by the variety of different master sex-determining genes identified, even sometimes among closely related species. Pangasiids are a group of economically important catfishes in many South-Asian countries, but little is known about their sex determination system. Here, we generated novel genomic resources for 12 Pangasiid species and provided a first characterization of their SD system. Based on an Oxford Nanopore long-read chromosome-scale high quality genome assembly of the striped catfish Pangasianodon hypophthalmus, we identified a duplication of the anti-Mullerian hormone receptor type II gene (amhr2), which was further characterized as being sex-linked in males and expressed only in testicular samples. These first results point to a male-specific duplication on the Y chromosome (amhr2by) of the autosomal amhr2a. Sequence annotation revealed that the P. hypophthalmus Amhr2by is truncated in its N-terminal domain, lacking the cysteine-rich extracellular part of the receptor that is crucial for ligand binding, suggesting a potential route for its neofunctionalization. Short-read genome sequencing and reference-guided assembly of 11 additional Pangasiid species, along with sex-linkage studies, revealed that this truncated amhr2by duplication is also conserved as a male-specific gene in many Pangasiids. Reconstructions of the amhr2 phylogeny suggested that amhr2by arose from an ancient duplication / insertion event at the root of the Siluroidei radiation that is dated around 100 million years ago. Altogether these results bring multiple lines of evidence supporting that amhr2by is an ancient and conserved master sex-determining gene in Pangasiid catfishes, a finding that highlights the recurrent usage of the transforming growth factor β pathway in teleost sex determination and brings another empirical case towards the understanding of the dynamics or stability of sex determination systems.

Paternally expressed gene 3 (Pw1/Peg3) promotes sexual dimorphism in metabolism and behavior

The paternally expressed gene 3 (Pw1/Peg3) is a mammalian-specific parentally imprinted gene expressed in stem/progenitor cells of the brain and endocrine tissues. Here, we compared phenotypic characteristics in Pw1/Peg3 deficient male and female mice. Our findings indicate that Pw1/Peg3 is a key player for the determination of sexual dimorphism in metabolism and behavior. Mice carrying a paternally inherited Pw1/Peg3 mutant allele manifested postnatal deficits in GH/IGF dependent growth before weaning, sex steroid dependent masculinization during puberty, and insulin dependent fat accumulation in adulthood. As a result, Pw1/Peg3 deficient mice develop a sex-dependent global shift of body metabolism towards accelerated adiposity, diabetic-like insulin resistance, and fatty liver. Furthermore, Pw1/Peg3 deficient males displayed reduced social dominance and competitiveness concomitant with alterations in the vasopressinergic architecture in the brain. This study demonstrates that Pw1/Peg3 provides an epigenetic context that promotes male-specific characteristics through sex steroid pathways during postnatal development.

Y chromosome is moving out of sex determination shadow

Although sex hormones play a key role in sex differences in susceptibility, severity, outcomes, and response to therapy of different diseases, sex chromosomes are also increasingly recognized as an important factor. Studies demonstrated that the Y chromosome is not a ‘genetic wasteland’ and can be a useful genetic marker for interpreting various male-specific physiological and pathophysiological characteristics. Y chromosome harbors male‑specific genes, which either solely or in cooperation with their X-counterpart, and independent or in conjunction with sex hormones have a considerable impact on basic physiology and disease mechanisms in most or all tissues development. Furthermore, loss of Y chromosome and/or aberrant expression of Y chromosome genes cause sex differences in disease mechanisms. With the launch of the human proteome project (HPP), the association of Y chromosome proteins with pathological conditions has been increasingly explored. In this review, the involvement of Y chromosome genes in male-specific diseases such as prostate cancer and the cases that are more prevalent in men, such as cardiovascular disease, neurological disease, and cancers, has been highlighted. Understanding the molecular mechanisms underlying Y chromosome-related diseases can have a significant impact on the prevention, diagnosis, and treatment of diseases.

Salsolaius gen. nov. a new genus of Apalochrini (Coleoptera, Melyridae, Malachiinae) from the salt Lake Way of Western Australia

Apalochrini comprises nearly half of the genera of Australian Melyridae, which are all recognized by male specific characters, and are commonly found on grasses, flowers and riverside or seashore rocks. Here we describe a new genus Salsolaius gen. nov. from Lake Way of Western Australia, representing the first known genus of Australian Melyridae inhabitating in salt lakes. The new genus can be easily distinguished by asymmetrically biserrate antennae and exposed apical abdomen from above in both male and female, the former characters is firstly found in Melyridae. Consequently, Salsolaius biserratus sp. nov. was described as the type species of this genus. An updated key to genera of Australian Apalochrini is provided.

Prediction of the Sex-Associated Genomic Region in Tunas (Thunnus Fishes)

Fish species have a variety of sex determination systems. Tunas (genus Thunnus) have an XY genetic sex determination system. However, the Y chromosome or responsible locus has not yet been identified in males. In a previous study, a female genome of Pacific bluefin tuna (T. orientalis) was sequenced, and candidates for sex-associated DNA polymorphisms were identified by a genome-wide association study using resequencing data. In the present study, we sequenced a male genome of Pacific bluefin tuna by long-read and linked-read sequencing technologies and explored male-specific loci through a comparison with the female genome. As a result, we found a unique region carrying the male-specific haplotype, where a homolog of estrogen sulfotransferase gene was predicted to be encoded. The genome-wide mapping of previously resequenced data indicated that, among the functionally annotated genes, only this gene, named sult1st6y, was paternally inherited in the males of Pacific bluefin tuna. We reviewed the RNA-seq data of southern bluefin tuna (T. maccoyii) in the public database and found that sult1st6y of southern bluefin tuna was expressed in all male testes, but absent or suppressed in the female ovary. Since estrogen sulfotransferase is responsible for the inactivation of estrogens, it is reasonable to assume that the expression of sult1st6y in gonad cells may inhibit female development, thereby inducing the individuals to become males. Thus, our results raise a promising hypothesis that sult1st6y is the sex determination gene in Thunnus fishes or at least functions at a crucial point in the sex-differentiation cascade.

Resveratrol Relieved Acute Liver Damage in Ducks (Anas platyrhynchos) Induced by AFB1 via Modulation of Apoptosis and Nrf2 Signaling Pathways

The presence of aflatoxin B1 (AFB1) in feed is a serious threat to livestock and poultry health and to human food safety. Resveratrol (Res) is a polyphenolic compound with antioxidant, anti-apoptotic and other biological activities; however, it is not clear whether it can improve AFB1 induced hepatotoxicity. Therefore, this study was conducted to investigate the effects of dietary Res on liver injury induced by AFB1 and its mechanisms. A total of 270 one-day-old male specific pathogen free (SPF) ducks, with no significant difference in weight, were randomly assigned to three groups: the control group, the AFB1 group and the AFB1 + Res group, which were fed a basic diet, a basic diet and a basic diet containing 500 mg/kg Res, respectively. On the 70th day, the ducks in theAFB1 group and the AFB1+ 500 mg/kg Res group were given 60 μg/kg AFB1 via gavage. When comparing the AFB1 group and the AFB1 + Res group and also with the control group, AFB1 significantly increased liver damage, cytochrome P450 (CYP450) and AFB1-DNA adduct content, increased oxidative stress levels and induced liver apoptosis, which was improved by Res supplementation. In sum, the addition of Res to feed can increase the activity of the II-phase enzyme, activate the nuclear factor E2-related factor 2 (Nrf2) signal pathway, and protect ducks’ livers from the toxicity, oxidative stress and inflammatory reaction induced by AFB1.

MSL3 promotes germline stem cell differentiation in female Drosophila

Gamete formation from germline stem cells (GSCs) is essential for sexual reproduction. However, the regulation of GSC differentiation are incompletely understood. Set2, which deposits H3K36me3 modifications, is required for GSC differentiation during Drosophila oogenesis. We discovered that the H3K36me3 reader Male-specific lethal 3 (MSL3) and histone acetyltransferase complex Ada2a-containing (ATAC) cooperate with Set2 to regulate GSC differentiation in female Drosophila. MSL3, acting independent from the rest of the male specific lethal complex, promotes transcription of genes including a germline enriched ribosomal protein S19 paralog, RpS19b. RpS19b upregulation is required for translation of RNA-binding Fox protein 1 (Rbfox1), a known meiotic cell cycle entry factor. Thus, MSL3 regulates GSC differentiation by modulating translation of a key factor that promotes transition to an oocyte fate.

Multiple Indicators of Wastewater Contamination to Shellfish Farms Near a Tidal River

Wastewater contamination threatens the shellfish aquaculture industry by posing risks to public health. Multiple indicators of wastewater contamination, including fecal coliforms (fc), male-specific coliphage (MSC), dissolved nutrients, stable isotope ratios, and artificial sweeteners were analyzed to determine possible sources of wastewater to local shellfish farms. Samples were collected at a wastewater treatment plant outfall (WTPO), nonpoint residential, and agricultural areas of a tidal river, and tidal creek inflows adjacent to farms. To capture seasonal variation, we sampled under warm and cold, and wet and dry conditions. Fc ranged < 5–5250 CFU 100 mL−1, NH4+ concentrations ranged up to 9.58 μM, and δ15N ranged 1.4–7.8‰ across all sites and time periods. Fc and NH4+ were higher, and δ15N was lower in the cold wet period and near residential and agricultural areas. Acesulfame and sucralose concentrations ranged 0.004–0.05 μg L−1 and up to > 0.8 μg L−1, respectively, and did not correlate with other indicators but tended to be higher in residential areas and at the WTPO, supporting their value in differentiating human sewage from other sources. Shoreline disturbance during septic system upgrades may have inadvertently contributed bacterial indicators to shellfish farms. Overall, indicator source dominance depended on environmental conditions, with WTPO and residential sources conveying human-specific indicators to farms year-round, while agricultural and industrial sites contributed additional fc during cold wet periods. The use of multiple indicators will aid managers to detect and define wastewater sources, identify targets for monitoring or remediation, and manage shellfish areas in estuaries with a mosaic of land-derived wastewater sources.