Estrogenic-like compounds severely disturb germ cell formation in Japanese quail.

During avian germ cell formation, primordial germ cells (PGCs) differentiate into prospermatogonia in testicular seminiferous tubules or into oogonia in the ovarian cortex in late-stage embryos. Although estrogenic endocrine-disrupting chemicals (EDCs) have been suggested to affect the differential fate of avian germ cells, there is currently no established method to examine the effects of EDCs on the differentiation potential of germline cells due to large amount of unidentified proteins present in avian germ cells. Regarding reliable molecular probes for the detection of germ cells that differentiated from the PGCs of Japanese quail, the prospermatogonium and oogonium, respectively, integrin beta1 (ITGB1), insulin-like growth factor 2-binding protein 1 (IGF2BP1), and stimulated by retinoic acid 8 (STRA8) were identified as marker proteins by RNA-seq and liquid chromatography tandem mass spectrometry analyses.

Initial formation of and sex differences in primordial germ cells in Japanese quail.

DEAD-box RNA helicase 4 (DDX4) is posited to be a key maternal germ cell factor regulating avian germ cell formation. We herein showed that the DDX4 gene product of zygotic genome activation associated with the nuclear localization of the cyclin D1 protein in presumptive primordial germ cells (PGCs) plays an essential role in the proliferation of PGCs using a CRISPR/Cas9 system approach combined with in vitro fertilization techniques in Japanese quail. A proteome analysis also revealed molecular-based differences in the features of early male and female PGCs.

Loss of One X and the Y Chromosome Changes the Configuration of the X Inactivation Center in the Genus Tokudaia.

Introduction: X chromosome inactivation (XCI) is an essential mechanism for dosage compensation between females and males in mammals. In females, XCI is controlled by a complex, conserved locus termed the X inactivation center (Xic), in which the lncRNA Xist is the key regulator. However, little is known about the Xic in species with unusual sex chromosomes.

Identification of a New Enhancer That Promotes Sox9 Expression by a Comparative Analysis of Mouse and Sry-Deficient Amami Spiny Rat.

Introduction: Testis differentiation is initiated by the SRY gene on the Y chromosome in mammalian species. However, the Amami spiny rat, Tokudaia osimensis, lacks both the Y chromosome and the Sry gene and acquired a unique Sox9 regulatory mechanism via a male-specific duplication upstream of Sox9, without Sry. In general mammalian species, the SRY protein binds to a testis-specific enhancer to promote SOX9 gene expression.

Research Note: Diethylstilbestrol reduces primordial germ cells in male Japanese quail.

This study investigated the detrimental effects of diethylstilbestrol (DES), an estrogenic endocrine-disrupting chemical, on the viability of primordial germ cells (PGCs), embryonic precursors of germ cells, in Japanese quail. We injected 50 or 100 nmol DES solubilized in sesame oil into the yolk of stage X embryos and assessed changes in the population and cell cycle properties of circulating PGCs in blood vessels and gonadal PGCs after 2.5- and 7-day incubations, respectively.

The Neo-X Does Not Form a Barr Body but Shows a Slightly Condensed Structure in the Okinawa Spiny Rat (Tokudaia muenninki).

X chromosome inactivation (XCI) is an essential mechanism for gene dosage compensation between male and female cells in mammals. The Okinawa spiny rat (Tokudaia muenninki) is a native rodent in Japan with XX/XY sex chromosomes, like most mammals; however, the X chromosome has acquired a neo-X region (Xp) by fusion with an autosome. We previously reported that dosage compensation has not yet evolved in the neo-X region; however, X-inactive-specific transcript (Xist) RNA (long non-coding RNA required for the initiation of XCI) is partially localized in the region.

Current Approaches to and the Application of Intracytoplasmic Sperm Injection (ICSI) for Avian Genome Editing.

Poultry are one of the most valuable resources for human society. They are also recognized as a powerful experimental animal for basic research on embryogenesis. Demands for the supply of low-allergen eggs and bioreactors have increased with the development of programmable genome editing technology.

Turnover of mammal sex chromosomes in the -deficient Amami spiny rat is due to male-specific upregulation of .

Mammalian sex chromosomes are highly conserved, and sex is determined by on the Y chromosome. Two exceptional rodent groups in which some species lack a Y chromosome and offer insights into how novel sex genes can arise and replace , leading to sex chromosome turnover. However, intensive study over three decades has failed to reveal the identity of novel sex genes in either of these lineages.

Inositol-1,4,5-Trisphosphate Receptor-1 and -3 and Ryanodine Receptor-3 May Increase Ooplasmic Ca During Quail Egg Activation.

We previously reported that egg activation in Japanese quail is driven by two distinct types of intracellular Ca ([Ca]): transient elevations in [Ca] induced by phospholipase Czeta 1 (PLCZ1) and long-lasting spiral-like Ca oscillations by citrate synthase (CS) and aconitate hydratase 2 (ACO2). Although the blockade of inositol 1,4,5-trisphosphate receptors (ITPRs) before microinjections of , and cRNAs only prevented transient increases in [Ca], a microinjection of an agonist of ryanodine receptors (RYRs) induced spiral-like Ca oscillations, indicating the involvement of both ITPRs and RYRs in these events. In this study, we investigated the isoforms of ITPRs and RYRs responsible for the expression of the two types of [Ca] increases.

Analysis of Sex Chromosome Evolution in the Clade Palaeognathae from Phased Genome Assembly.

Birds in the clade Palaeognathae, excluding Tinamiformes, have morphologically conserved karyotypes and less differentiated ZW sex chromosomes compared with those of other birds. In particular, the sex chromosomes of the ostrich and emu have exceptionally large recombining pseudoautosomal regions (PARs), whereas non-PARs are classified into two strata according to the date of their origins: stratum 0 and stratum 1 (S1). However, the construction and analysis of the genome sequences in these regions in the clade Palaeognathae can be challenging because assembling the S1 region is difficult owing to low sequence diversity between gametologs (Z-linked and W-linked sequences).

Cyclin D1 gene expression is essential for cell cycle progression from the maternal-to-zygotic transition during blastoderm development in Japanese quail.

Embryogenesis proceeds by a highly regulated series of events. In animals, maternal factors that accumulate in the egg cytoplasm control cell cycle progression at the initial stage of cleavage. However, cell cycle regulation is switched to a system governed by the activated nuclear genome at a specific stage of development, referred to as maternal-to-zygotic transition (MZT).

Diversification of mineralocorticoid receptor genes in a subterranean rodent, the naked mole-rat.

Naked mole-rats (Heterocephalus glaber) inhabit subterranean burrows in savannas and are, thus, unable to access free water. To identify their mechanism of osmoregulation in xeric environments, we molecularly cloned and analyzed the nuclear receptor subfamily 3 group C member 2 (NR3C2) gene encoding the mineralocorticoid receptor (MR), required for hormone-dependent regulation of genes contributing to body fluid homeostasis. Most vertebrates harbor a single MR homolog.

Expression profiling of sexually dimorphic genes in the Japanese quail, Coturnix japonica.

Research on avian sex determination has focused on the chicken. In this study, we established the utility of another widely used animal model, the Japanese quail (Coturnix japonica), for clarifying the molecular mechanisms underlying gonadal sex differentiation. In particular, we performed comprehensive gene expression profiling of embryonic gonads at three stages (HH27, HH31 and HH38) by mRNA-seq.

Regulation of the Sox3 Gene in an X0/X0 Mammal without Sry, the Amami Spiny Rat, Tokudaia osimensis.

Two species of spiny rats, Tokudaia osimensis and Tokudaia tokunoshimensis, show an X0/X0 sex chromosome constitution due to the lack of a Y chromosome. The Sry gene has been completely lost from the genome of these species. We hypothesized that Sox3, which is thought to be originally a homologue of Sry, could function in sex determination in these animals in the absence of Sry.

Spiny rat SRY lacks a long Q-rich domain and is not stable in transgenic mice.

Background: Although Tokudaia muenninki has multiple extra copies of the Sry gene on the Y chromosome, loss of function of these sequences is indicated. To examine the Sry gene function for sex determining in T. muenninki, we screened a BAC library and identified a clone (SRY26) containing complete SRY coding and promoter sequences.

Sexual dimorphism in brain transcriptomes of Amami spiny rats (Tokudaia osimensis): a rodent species where males lack the Y chromosome.

Background: Brain sexual differentiation is sculpted by precise coordination of steroid hormones during development. Programming of several brain regions in males depends upon aromatase conversion of testosterone to estrogen. However, it is not clear the direct contribution that Y chromosome associated genes, especially sex-determining region Y (Sry), might exert on brain sexual differentiation in therian mammals.

Knockdown of DEAD-box helicase 4 (DDX4) decreases the number of germ cells in male and female chicken embryonic gonads.

DEAD-box helicase 4 (DDX4; also known as vasa) is essential for the proper formation and maintenance of germ cells. Although DDX4 is conserved in a variety of vertebrates and invertebrates, its roles differ between species. This study investigated the function of DDX4 in chicken embryos by knocking down its expression using retroviral vectors that encoded DDX4-targeting microRNAs.

Sex-Determining Mechanism in Avians.

The sex of birds is determined by inheritance of sex chromosomes at fertilization. The embryo with two Z chromosomes (ZZ) develops into a male; by contrast, the embryo with Z and W chromosomes (ZW) becomes female. Two theories are hypothesized for the mechanisms of avian sex determination that explain how genes carried on sex chromosomes control gonadal differentiation and development during embryogenesis.

Unique XCI evolution in Tokudaia: initial XCI of the neo-X chromosome in Tokudaia muenninki and function loss of XIST in Tokudaia osimensis.

X chromosome inactivation (XCI) is an essential mechanism to compensate gene dosage in mammals. Here, we show that XCI has evolved differently in two species of the genus Tokudaia. The Amami spiny rat, Tokudaia osimensis, has a single X chromosome in males and females (XO/XO).

Flexible adaptation of male germ cells from female iPSCs of endangered .

In mammals, the Y chromosome strictly influences the maintenance of male germ cells. Almost all mammalian species require genetic contributors to generate testes. An endangered species, , has a unique sex chromosome composition XO/XO, and genetic differences between males and females have not been confirmed.

Androgens and androgen receptor signaling contribute to ovarian development in the chicken embryo.

Androgens and androgen receptor (AR) signaling play important roles throughout development. In the chicken, AR signaling is involved in reproduction; however, its specific role is unclear. We show that AR signaling is involved in the normal development of the female embryonic gonads.

Molecular mechanism of male differentiation is conserved in the SRY-absent mammal, Tokudaia osimensis.

The sex-determining gene SRY induces SOX9 expression in the testes of eutherian mammals via two pathways. SRY binds to testis-specific enhancer of Sox9 (TESCO) with SF1 to activate SOX9 transcription. SRY also up-regulates ER71 expression, and ER71 activates Sox9 transcription.

Ancestral Y-linked genes were maintained by translocation to the X and Y chromosomes fused to an autosomal pair in the Okinawa spiny rat Tokudaia muenninki.

Two species of the genus Tokudaia lack the Y chromosome and SRY, but several Y-linked genes have been rescued by translocation or transposition to other chromosomes. Tokudaia muenninki is the only species in the genus that maintains the Y owing to sex chromosome-autosome fusions. According to previous studies, many SRY pseudocopies and other Y-linked genes have evolved by excess duplication in this species.

The cryptic Y-autosome translocation in the small Indian mongoose, Herpestes auropunctatus, revealed by molecular cytogenetic approaches.

In initial studies of the eutherian small Indian mongoose (Herpestes auropunctatus), the Y chromosome could not be identified in somatic cells. The male chromosome number is uniquely odd, 2n = 35, whereas that of females is 2n = 36. Previous reports indicated that this unique karyotype resulted from a translocation of the ancestral Y chromosome to an autosome.