Gadd45g is essential for primary sex determination, male fertility and testis development

GADD45A: With or without you

The growth arrest and DNA damage inducible (GADD)45 family includes three small and ubiquitously distributed proteins (GADD45A, GADD45B, and GADD45G) that regulate numerous cellular processes associated with stress signaling and injury response. Here, we provide a comprehensive review of the current literature investigating GADD45A, the first discovered member of the family. We first depict how its levels are regulated by a myriad of genotoxic and non-genotoxic stressors, and through the combined action of intricate transcriptional, posttranscriptional, and even, posttranslational mechanisms. GADD45A is a recognized tumor suppressor and, for this reason, we next summarize its role in cancer, as well as the different mechanisms by which it regulates cell cycle, DNA repair, and apoptosis. Beyond these most well-known actions, GADD45A may also influence catabolic and anabolic pathways in the liver, adipose tissue and skeletal muscle, among others. Not surprisingly, GADD45A may trigger AMP-activated protein kinase activity, a master regulator of metabolism, and is known to act as a transcriptional coregulator of numerous nuclear receptors. GADD45A has also been reported to display a cytoprotective role by regulating inflammation, fibrosis and oxidative stress in several organs and tissues, and is regarded an important contributor for the development of heart failure. Overall data point to that GADD45A may play an important role in metabolic, neurodegenerative and cardiovascular diseases, and also autoimmune-related disorders. Thus, the potential mechanisms by which dysregulation of GADD45A activity may contribute to the progression of these diseases are also reviewed below.

Complete male-to-female sex reversal in XY mice lacking the miR-17~92 cluster

Mammalian sex determination is controlled by antagonistic gene cascades operating in embryonic undifferentiated gonads. The expression of the Y-linked gene SRY is sufficient to trigger the testicular pathway, whereas its absence in XX embryos leads to ovarian differentiation. Yet, the potential involvement of non-coding regulation in this process remains unclear. Here we show that the deletion of a single microRNA cluster, miR-17~92, induces complete primary male-to-female sex reversal in XY mice. Sry expression is delayed in XY knockout gonads, which develop as ovaries. Sertoli cell differentiation is reduced, delayed and unable to sustain testicular development. Pre-supporting cells in mutant gonads undergo a transient state of sex ambiguity which is subsequently resolved towards the ovarian fate. The miR-17~92 predicted target genes are upregulated, affecting the fine regulation of gene networks controlling gonad development. Thus, microRNAs emerge as key components for mammalian sex determination, controlling Sry expression timing and Sertoli cell differentiation.

Mixture toxicity of 6PPD-quinone and polystyrene nanoplastics in zebrafish

Plastic pollution, including micro- and nanoplastics, is a growing concern. Tyre-wear particles (TWPs) are the second largest source of microplastics in the ocean following abrasion of synthetic fibres. In addition to the particles themselves, TWPs contain many harmful chemicals, including 6PPD. This chemical reacts with atmospheric ozone and forms the toxic compound 6PPD-quinone (6PPDq), which poses a danger to aquatic life. There is a knowledge gap in understanding risks associated with the combined toxicity of nanoplastics (NPs) and 6PPDq. The present study aimed to investigate the toxicity of NPs and 6PPDq on adult zebrafish using phenotypic (behaviour, histology) and transcriptomic endpoints. Zebrafish were exposed to four treatments: control (contaminant-free), 50 μg/L 6PPDq, 3 mg/L polystyrene (PS)-NPs, and a combination of 50 μg/L 6PPDq and 3 mg/L PS-NPs. We did not observe locomotory dysregulation in zebrafish exposed to NPs. However, we found significant hyperlocomotion in zebrafish exposed to 6PPDq and this effect was even more substantial after co-exposure with PS-NPs. This study explores the molecular mechanisms behind these effects, identifying genes associated with neurotransmitters and fatty acid metabolism that were dysregulated by the co-exposure. Transcriptomic analysis further showed that both 6PPDq and PS-NPs impacted cellular processes associated with sterol biosynthesis, cholesterol metabolism, and muscle tissue development. The effects on these mechanisms were stronger in co-exposed zebrafish, indicating a heightened risk to cellular integrity and mitochondrial dysfunction. These results highlight the significance of mixture toxicity when studying the effects of NPs and associated chemicals like 6PPDq.

FOXL2 interaction with different binding partners regulates the dynamics of ovarian development

The transcription factor FOXL2 is required in ovarian somatic cells for female fertility. Differential timing of Foxl2 deletion, in embryonic versus adult mouse ovary, leads to distinctive outcomes, suggesting different roles across development. Here, we comprehensively investigated FOXL2's role through a multi-omics approach to characterize gene expression dynamics and chromatin accessibility changes, coupled with genome-wide identification of FOXL2 targets and on-chromatin interacting partners in somatic cells across ovarian development. We found that FOXL2 regulates more targets postnatally, through interaction with factors regulating primordial follicle formation and steroidogenesis. Deletion of one interactor, ubiquitin-specific protease 7 (Usp7), results in impairment of somatic cell differentiation, germ cell nest breakdown, and ovarian development, leading to sterility. Our datasets constitute a comprehensive resource for exploration of the molecular mechanisms of ovarian development and causes of female infertility.

Role of glucocorticoid and mineralocorticoid receptors in rainbow trout (Oncorhynchus mykiss) skeletal muscle: A transcriptomic perspective of cortisol action

Cortisol is an essential regulator of neuroendocrine stress responses in teleost. Cortisol performs its effects through the modulation of glucocorticoid receptor (GR) and mineralocorticoid receptor (MR), activating gene expression. Until now the contribution of both receptors in the global transcriptional response in teleost skeletal muscle has not been explored. To understand in a comprehensive and global manner how GR and MR modulates the skeletal muscle transcriptomic response, we performed RNA-seq analysis. Juvenile rainbow trout (Oncorhynchus mykiss) pretreated with a suppressor of endogenous cortisol production were intraperitoneally injected with cortisol (10 mg/kg). We also included a treatment with mifepristone (GR antagonist) and eplerenone (MR antagonist) in the presence or absence of cortisol. cDNA libraries were constructed from the skeletal muscle of rainbow trout groups: vehicle, cortisol, mifepristone, eplerenone, mifepristone/cortisol and eplerenone/cortisol. RNA-seq analysis revealed that 135 transcripts were differentially expressed in cortisol vs. mifepristone/cortisol group, mainly associated to inflammatory response, ion transmembrane transport, and proteolysis. In the other hand, 68 transcripts were differentially expressed in cortisol vs. eplerenone/cortisol group, mainly associated to muscle contraction, and regulation of cell cycle. To validate these observations, we performed in vitro experiments using rainbow trout myotubes. In myotubes treated with cortisol, we found increased expression of cxcr2, c3, and clca3p mediated by GR, associated with inflammatory response, proteolysis, and ion transmembrane transport, respectively. Contrastingly, MR modulated the expression of myh2 and gadd45g mainly associated with muscle contraction and regulation of cell cycle, respectively. These results suggest that GR and MR have a differential participation in the physiological response to stress in teleost skeletal muscle.

Gonadal Sex Differentiation and Ovarian Organogenesis along the Cortical-Medullary Axis in Mammals

In most mammals, the sex of the gonads is based on the fate of the supporting cell lineages, which arises from the proliferation of coelomic epithelium (CE) that surfaces on the bipotential genital ridge in both XY and XX embryos. Recent genetic studies and single-cell transcriptome analyses in mice have revealed the cellular and molecular events in the two-wave proliferation of the CE that produce the supporting cells. This proliferation contributes to the formation of the primary sex cords in the medullary region of both the testis and the ovary at the early phase of gonadal sex differentiation, as well as to that of the secondary sex cords in the cortical region of the ovary at the perinatal stage. To support gametogenesis, the testis forms seminiferous tubules in the medullary region, whereas the ovary forms follicles mainly in the cortical region. The medullary region in the ovary exhibits morphological and functional diversity among mammalian species that ranges from ovary-like to testis-like characteristics. This review focuses on the mechanism of gonadal sex differentiation along the cortical-medullary axis and compares the features of the cortical and medullary regions of the ovary in mammalian species.

Early Gonadal Development and Sex Determination in Mammal

Sex determination is crucial for the transmission of genetic information through generations. In mammal, this process is primarily regulated by an antagonistic network of sex-related genes beginning in embryonic development and continuing throughout life. Nonetheless, abnormal expression of these sex-related genes will lead to reproductive organ and germline abnormalities, resulting in disorders of sex development (DSD) and infertility. On the other hand, it is possible to predetermine the sex of animal offspring by artificially regulating sex-related gene expression, a recent research hotspot. In this paper, we reviewed recent research that has improved our understanding of the mechanisms underlying the development of the gonad and primordial germ cells (PGCs), progenitors of the germline, to provide new directions for the treatment of DSD and infertility, both of which involve manipulating the sex ratio of livestock offspring.

GADD45 in Stress Signaling, Cell Cycle Control, and Apoptosis

GADD45 is a gene family consisting of GADD45A, GADD45B, and GADD45G that is often induced by DNA damage and other stress signals associated with growth arrest and apoptosis. Many of these roles are carried out via signaling mediated by p38 mitogen-activated protein kinases (MAPKs). The GADD45 proteins can contribute to p38 activation either by activation of upstream kinase(s) or by direct interaction, as well as suppression of p38 activity in certain cases. In vivo, there are important tissue and cell type specific differences in the roles for GADD45 in MAPK signaling. In addition to being p53-regulated, GADD45A has also been found to contribute to p53 activation via p38. Like other stress and signaling proteins, GADD45 proteins show complex regulation and numerous effectors. More recently, aberrant GADD45 expression has been found in several human cancers, but the mechanisms behind these findings largely remain to be understood.

Gadd45g is required for timely Sry expression independently of RSPO1 activity

Sex determination in mammals is controlled by the dominance of either pro-testis (SRY-SOX9-FGF9) or pro-ovary (RSPO1-WNT4-FOXL2) genetic pathways during early gonad development in XY and XX embryos, respectively. We have previously shown that early, robust expression of mouse Sry is dependent on the nuclear protein GADD45g. In the absence of GADD45g, XY gonadal sex reversal occurs, associated with a major reduction of Sry levels at 11.5 dpc. Here, we probe the relationship between Gadd45g and Sry further, using gain- and loss-of-function genetics. First, we show that transgenic Gadd45g overexpression can elevate Sry expression levels at 11.5 dpc in the B6.YPOS model of sex reversal, resulting in phenotypic rescue. We then show that the zygosity of pro-ovarian Rspo1 is critical for the degree of gonadal sex reversal observed in both B6.YPOS and Gadd45g-deficient XY gonads, in contrast to that of Foxl2. Phenotypic rescue of sex reversal is observed in XY gonads lacking both Gadd45g and Rspo1, but this is not associated with rescue of Sry expression levels at 11.5 dpc. Instead, Sox9 levels are rescued by around 12.5 dpc. We conclude that Gadd45g is absolutely required for timely expression of Sry in XY gonads, independently of RSPO1-mediated WNT signalling, and discuss these data in light of our understanding of antagonistic interactions between the pro-testis and pro-ovary pathways.

Levonorgestrel and dydrogesterone affect sex determination via different pathways in zebrafish

Levonorgestrel (LNG) and dydrogesterone (DDG) are two commonly used synthetic progestins that have been detected in aquatic environments. They could affect fish sex differentiation, but the underlying mechanisms remain unknown. Here we investigated the effects of LNG (5 ng L^-1 and 50 ng L^-1), DDG (100 ng L^-1) and their mixtures on gonadal differentiation and sex determination in zebrafish at transcriptomic and histological levels from 2 hours post-fertilization (eleutheroembryos) to 144 days post-fertilization (sexual maturity). Germ cell development and oogenesis pathways were significantly enriched in LNG and the mixture of LNG and DDG treatments, while insulin and apoptosis pathways in the DDG treatment. LNG and the mixture of LNG and DDG strongly decreased transcripts of germ cell development and oogenesis related genes, while DDG increased the transcripts of insulin and apoptosis related genes at 28 days post fertilization (dpf) and 35 dpf. Furthermore, DDG caused ∼ 90% males, and LNG and the mixture of LNG and DDG resulted in 100% males on all sampling dates. Specifically, most males in LNG and the mixture of LNG and DDG treatments were "Type I" males without juvenile oocytes at 28 dpf and 35 dpf, while those in DDG treatment were "Type II" and "Type III" males with a few juvenile oocytes. These results indicated that LNG and DDG promoted testicular differentiation via different pathways to cause male bias. LNG and DDG mixtures have similar effect on testicular differentiation to LNG alone. The findings from this study could have significant ecological implications to fish populations.

Gadd45g initiates embryonic stem cell differentiation and inhibits breast cell carcinogenesis

Many self-renewal-promoting factors of embryonic stem cells (ESCs) have been implicated in carcinogenesis, while little known about the genes that direct ESCs exit from pluripotency and regulate tumor development. Here, we show that the transcripts of Gadd45 family genes, including Gadd45a, Gadd45b, and Gadd45g, are gradually increased upon mouse ESC differentiation. Upregulation of Gadd45 members decreases cell proliferation and induces endodermal and trophectodermal lineages. In contrast, knockdown of Gadd45 genes can delay mouse ESC differentiation. Mechanistic studies reveal that Gadd45g activates MAPK signaling by increasing expression levels of the positive modulators of this pathway, such as Csf1r, Igf2, and Fgfr3. Therefore, inhibition of MAPK signaling with a MEK specific inhibitor is capable of eliminating the differentiation phenotype caused by Gadd45g upregulation. Meanwhile, GADD45G functions as a suppressor in human breast cancers. Enforced expression of GADD45G significantly inhibits tumor formation and breast cancer metastasis in mice through limitation of the propagation and invasion of breast cancer cells. These results not only expand our understanding of the regulatory network of ESCs, but also help people better treatment of cancers by manipulating the prodifferentiation candidates.

Acute heat stress reduces viability but increases lactate secretion of porcine immature Sertoli cells through transcriptome reprogramming

Sertoli cells, important constituents of the somatic niche, supports the growth and development of spermatogonia. Heat stress (HS), among multiple intrinsic and external factors, can induce physiological and biochemical changes in Sertoli cells. However, the underlying molecular mechanism remains largely unclear. Here, we showed that acute heat stress (43 °C, 0.5 h) could reduce cell viability, promote apoptosis, and increase the lactate production of porcine immature Sertoli cells (iSCs) cultured in vitro. Then, transcriptome sequencing identified 126 immediately and 3372 prolonged responded differentially expressed genes (DEGs) after acute heat stress (43 °C, 0.5 h) (HS0.5), and 36 h recovery culture following heat stress (HS0.5-R36), respectively. Enrichment analyses found different signaling pathways: immediate changes including cell response to heat, regulation of cellular response to stress, heat shock protein binding, chaperon-mediated protein folding, and sterol biosynthetic process, but prolonged changes mainly involving cell cycle, regulation of apoptotic process/cell proliferation, reproductive process, P53, PI3K-Akt and Glycolysis/Gluconeogenesis. Furthermore, transcriptional patterns of 9 DEGs (Dnajb1, Traf6, Insig1, Gadd45g, Hdac6, Fkbp4, Serpine1, Pfkp and Galm), and 6 heat shock proteins (HSPs) (Hspa6, Hspb1, Hspd1, HSP90aa1, HSP90ab1 and Hsph1) were validated, as well as the protein pattern of HSP90AA1 via immunostaining and western blot. Taken together, heat stress could initiate immediate changes of heat shock-related genes, and reprogram transcriptome and signaling pathways affecting the viability, apoptosis and metabolite production of pig iSCs.

New Anti-Müllerian Hormone Target Genes Involved in Granulosa Cell Survival in Women With Polycystic Ovary Syndrome

PURPOSE

A protective effect of anti-Müllerian hormone (AMH) on follicle atresia was recently demonstrated using long-term treatments, but this effect has never been supported by mechanistic studies. This work aimed to gain an insight into the mechanism of action of AMH on follicle atresia and on how this could account for the increased follicle pool observed in women with polycystic ovary syndrome (PCOS).

METHODS

In vivo and in vitro experiments were performed to study the effects of AMH on follicle atresia and on the proliferation and apoptosis of granulosa cells (GCs). RNA-sequencing was carried out to identify new AMH target genes in GCs. The expression of some of these genes in GCs from control and PCOS women was compared using microfluidic real time quantitative RT-PCR.

RESULTS

A short-term AMH treatment prevented follicle atresia in prepubertal mice. Consistent with this result, AMH inhibited apoptosis and promoted proliferation of different models of GCs. Moreover, integrative biology analyses of 965 AMH target genes identified in 1 of these GC models, confirmed that AMH had initiated a gene expression program favoring cell survival and proliferation. Finally, on 43 genes selected among the most up- and down-regulated AMH targets, 8 were up-regulated in GCs isolated from PCOS women, of which 5 are involved in cell survival.

MAIN CONCLUSIONS

Our results provide for the first time cellular and molecular evidence that AMH protects follicles from atresia by controlling GC survival and suggest that AMH could participate in the increased follicle pool of PCOS patients.

miR-4270 regulates cell proliferation and apoptosis in patients with Sertoli cell-only syndrome by targeting GADD45A and inactivating the NOTCH signaling pathway

In recent decades, growing data has suggested that microRNAs (miRNAs, miRs) play a critical role in the development of Sertoli cells (SC), including regulating SC maturation, synthesis, proliferation, and apoptosis. Previous reports of miRNA microarray have identified aberrant miR-4270 expression in patients with Sertoli-cell-only syndrome (SCOS). However, it is not known whether miR-4270 is associated with the pathogenesis of SCOS. In this study, we aimed to further investigate the roles and potential mechanisms of miR-4270 on SC proliferation and apoptosis. Our data confirmed that miR-4270 was significantly upregulated in SC of SCOS patients compared with healthy controls. EdU and CCK-8 assays showed silencing of miR-4270 by specific inhibitor significantly enhanced human SC and TM4 cells proliferation. ELISA and flow cytometry assays indicated that miR-4270 knockdown prominently suppressed the apoptosis of human SC and TM4 cells. Furthermore, expression of cell cycle genes, including CCNE1 (cyclin E1), CCND1 (cyclin D1) and CDK4 (cyclin dependent kinase 4), were obviously upregulated in human SC and TM4 cells by qRT-PCR assay after knockdown of miR-4270, while expression of cell apoptotic factors, including CASP3 (caspase 3), CASP6 (caspase 6) and CASP7 (caspase 7), were all markedly decreased. Notably, GADD45A (growth arrest and DNA damage inducible alpha) mRNA was downregulated in SC of SCOS patients, and negatively corrected with miR-4270 expression. Moreover, bioinformatics tools and dual-luciferase reporter assay identified that miR-4270 directly bound the 3'-UTR of GADD45A mRNA to inhibit GADD45A expression. Meanwhile, Western blots analysis validated that the protein expression levels of NOTCH1 (notch receptor 1) and HES1 (hes family bHLH transcription factor 1) were significantly increased in SC and TM4 cells after miR-4270 silencing or GADD45A overexpression. Taken together, our data demonstrated that miR-4270 regulates proliferation and apoptosis in SC of SCOS patients by inactivating NOTCH signaling pathway via GADD45A gene, which may offer a new insight into the development of human SC and provide a promising biomarker for the treatment of SCOS.

Sex-Dependent RNA Editing and N6-adenosine RNA Methylation Profiling in the Gonads of a Fish, the Olive Flounder (Paralichthys olivaceus)

Adenosine-to-inosine (A-to-I) editing and N6-methyladenosine (m6A) are two of the most abundant RNA modifications. Here, we examined the characteristics of the RNA editing and transcriptome-wide m6A modification profile in the gonads of the olive flounder, Paralichthys olivaceus, an important maricultured fish in Asia. The gonadal differentiation and development of the flounder are controlled by genetic as well as environmental factors, and the epigenetic mechanism may play an important role. In total, 742 RNA editing events were identified, 459 of which caused A to I conversion. Most A-to-I sites were located in 3′UTRs, while 61 were detected in coding regions (CDs). The number of editing sites in the testis was higher than that in the ovary. Transcriptome-wide analyses showed that more than one-half of the transcribed genes presented an m6A modification in the flounder gonads, and approximately 60% of the differentially expressed genes (DEGs) between the testis and ovary appeared to be negatively correlated with m6A methylation enrichment. Further analyses revealed that the mRNA expression of some sex-related genes (e.g., dmrt1 and amh) in the gonads may be regulated by changes in mRNA m6A enrichment. Functional enrichment analysis indicated that the RNA editing and m6A modifications were enriched in several canonical pathways (e.g., Wnt and MAPK signaling pathways) in fish gonads and in some pathways whose roles have not been investigated in relation to fish sex differentiation and gonadal development (e.g., PPAR and RNA degradation pathways). There were 125 genes that were modified by both A-to-I editing and m6A, but the two types of modifications mostly occurred at different sites. Our results suggested that the presence of sex-specific RNA modifications may be involved in the regulation of gonadal development and gametogenesis.

RNA-Seq transcriptome reveals different molecular responses during human and mouse oocyte maturation and fertilization

BACKGROUND

Female infertility is a worldwide concern and the etiology of infertility has not been thoroughly demonstrated. Although the mouse is a good model system to perform functional studies, the differences between mouse and human also need to be considered. The objective of this study is to elucidate the different molecular mechanisms underlying oocyte maturation and fertilization between human and mouse.

RESULTS

A comparative transcriptome analysis was performed to identify the differentially expressed genes and associated biological processes between human and mouse oocytes. In total, 8513 common genes, as well as 15,165 and 6126 uniquely expressed genes were detected in human and mouse MII oocytes, respectively. Additionally, the ratios of non-homologous genes in human and mouse MII oocytes were 37 and 8%, respectively. Functional categorization analysis of the human MII non-homologous genes revealed that cAMP-mediated signaling, sister chromatid cohesin, and cell recognition were the major enriched biological processes. Interestingly, we couldn't detect any GO categories in mouse non-homologous genes.

CONCLUSIONS

This study demonstrates that human and mouse oocytes exhibit significant differences in gene expression profiles during oocyte maturation, which probably deciphers the differential molecular responses to oocyte maturation and fertilization. The significant differences between human and mouse oocytes limit the generalizations from mouse to human oocyte maturation. Knowledge about the limitations of animal models is crucial when exploring a complex process such as human oocyte maturation and fertilization.

Molecular correlates of hypothalamic development in songbird ontogeny in comparison with the telencephalon

Development of the songbird brain provides an excellent experimental model for understanding the regulation of sex differences in ontogeny. Considering the regulatory role of the hypothalamus in endocrine, in particular reproductive, physiology, we measured the structural (volume) and molecular correlates of hypothalamic development during ontogeny of male and female zebra finches. We quantified by relative quantitative polymerase chain reaction (rqPCR) the expression of 14 genes related to thyroid and steroid hormones actions as well as 12 genes related to brain plasticity at four specific time points during ontogeny and compared these expression patterns with the expression of the same genes as detected by transcriptomics in the telencephalon. These two different methodological approaches detected specific changes with age and demonstrated that in a substantial number of cases changes observed in both brain regions are nearly identical. Other genes however had a tissue-specific developmental pattern. Sex differences or interactions of sex by age were detected in the expression of a subset of genes, more in hypothalamus than telencephalon. These results correlate with multiple known aspects of the developmental and reproductive physiology but also raise a number of new functional questions.

Validation of Suitable Reference Genes for Gene Expression Studies on Yak Testis Development

Simple Summary

Yak (Bos grunniens) provides life materials for herdsmen in high-plateau areas. Improving their low fertility is necessary to meet the demands of the development of the yak industry. The testis is an important organ for male fertility, its development is controlled by a large number of genes. Using real-time reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) to explore the quantitative expression of genes can provide insights for illuminating the molecular mechanisms of testis development, but the RT-qPCR data are influenced by the stability of reference genes (RGs). Unfortunately, no available RGs can normalize the gene expression in yak testis development. In this study, the expression stability of 13 candidate genes in yak testis at different developmental stages was evaluated using five different pieces of software. The results showed that the TATA box-binding protein (TBP) and ubiquitously expressed transcript protein (UXT) exhibited high stability across various developmental stages, TBP and hydroxymethylbilane synthase (HMBS) were the most stably expressed genes in immature stages, and mitochondrial ribosomal protein L39 (MRPL39) and TBP exhibited the most stable expression across mature stages. This study provided suitable RGs for gene expression studies in yak testis development.

Abstract

Testis has an important function in male reproduction. Its development is regulated by a large number of genes. The real-time reserve transcriptase-quantitative polymerase chain reaction (RT-qPCR) is a useful tool to evaluate the gene expression levels. However, unsuitable reference genes (RGs) can cause the misinterpretation of gene expression levels. Unfortunately, the ideal RGs for yak testis development are yet to be studied. In this study, 13 commonly used RGs were selected to identify the most stable RGs in yak testis at four different developmental stages, including two immature stages (6 months and 18 months) and two mature stages (30 months and 6 years). This study used GeNorm, NormFinder, BestKeeper, ∆Ct, and RefFinder programs to evaluate the stability of 13 candidate genes. The results of RefFinder showed that the stabilities of TATA box-binding protein (TBP) and ubiquitously expressed transcript protein (UXT) were ranked the top two across all developmental stages. TBP and hydroxymethylbilane synthase (HMBS) were stably expressed in immature stages, while mitochondrial ribosomal protein L39 (MRPL39) and TBP had higher stability than other candidate genes in mature stages. This study provided valuable information for gene expression studies to assist further investigation on the molecular mechanisms in underlying yak testis development.

Mapping of the Sex Determining Region on Linkage Group 12 of Guppy (Poecilia reticulata)

Poecilia reticulata is one of the most popular ornamental fish species with a higher demand for males due to their large colorful fins. The objectives of this study were mapping of the sex-determining (SD) region on linkage group 12 of guppy, and identification of a sex specific marker. We generated eight polymorphic microsatellite markers distributed along the distal 5.4 Mbp sequence of the previously identified SD region on linkage group (LG) 12. The markers were tested for association with sex in 156 individuals of the Red Blonde and Flame strains, and 126 progeny of four full-sibs Red Blonde families. A male-specific allele was found for microsatellite gu1066 at position of 25.3 Mbp on LG12 for both strains, and gu832 at position 24.4 Mbp for the Flame strain. Thus, a region of 0.9 Mbp between these markers, harboring 27 annotated genes, was selected for analysis. Based on association of copy number variation and sex determination we mapped a duplicated region between LGs 9 and 12, of 1.26 Mbp, containing 59 genes on LG12. The common interval between the segment bounded by gu1066 and gu832, and the duplicated region of 0.43 Mbp on LG12 harbors 11 genes of which 6 have multiple copies (54%). Growth arrest and DNA damage inducible gamma-like (GADD45G-like) is a plausible positional and functional candidate gene for its role in male fertility. We characterized the genomic structure of the gene in guppy, and found two isoforms; but no sex-biased differences were evident in genomic sequence and gene expression.

Mutations of GADD45G in rabbits cause cleft lip by the disorder of proliferation, apoptosis and epithelial-mesenchymal transition (EMT)

The cleft lip with or without cleft palate (CL/P) is one of the most common congenital defects in humans. Genome-wide association studies (GWAS) have been widely used for identifying candidate genes, and different genes or chromosomal regions have shown strong evidence for the presence of causal genes in CL/P. To date, two independent GWAS have identified GADD45G as influencing risk for CL/P. However, there is no animal model evidence about GADD45G related to CL/P. Here, we reported the generation of a novel GADD45G mutated rabbit model by CRISPR/Cas9 and CRISPR-based BE4-Gam systems. The homozygous (GADD45G-/-) while not heterozygous (GADD45G+/-) pups died after birth due to severe craniofacial defects of unilateral or bilateral cleft lip (CL). Moreover, the disorder of proliferation, apoptosis and epithelial-mesenchymal transition (EMT) were also determined in the medial and lateral nasal processes (MNP and LNP) of the embryonic day 13 (E13) GADD45G-/- rabbits, which compared with the normal wild type (WT) rabbits. Thus, our study confirmed for the first time that loss of GADD45G lead to CL at the animal level and provided new insights into the crucial role of GADD45G for upper lip formation and fusion.

Characterisation and use of a functional Gadd45g bacterial artificial chromosome

Bacterial artificial chromosomes (BACs) offer a means of manipulating gene expression and tagging gene products in the mammalian genome without the need to alter endogenous gene structure and risk deleterious phenotypic consequences. However, for a BAC clone to be useful for such purposes it must be shown to contain all the regulatory elements required for normal gene expression and allow phenotypic rescue in the absence of an endogenous gene. Here, we report identification of a functional BAC containing Gadd45g, a gene implicated in DNA repair, DNA demethylation and testis determination in mice and exhibiting a broad pattern of embryonic expression. Mouse fetuses lacking the endogenous Gadd45g gene undergo normal testis development in the presence of the Gadd45g BAC transgene. Moreover, a survey of embryonic Gadd45g expression from the BAC reveals that all reported sites of expression are maintained. This functional BAC can now be used for subsequent manipulation of the Gadd45g gene with the confidence that regulatory elements required for embryonic expression, including testis determination, are present. We describe the generation and characterisation of a Gadd45g-mCherry fluorescent reporter exhibiting strong expression in developing gonads and neural tissue, recapitulating endogenous gene expression, as evidence of this.

The molecular pathways underlying early gonadal development

The body of knowledge surrounding reproductive development spans the fields of genetics, anatomy, physiology and biomedicine, to build a comprehensive understanding of the later stages of reproductive development in humans and animal models. Despite this, there remains much to learn about the bi-potential progenitor structure that the ovary and testis arise from, known as the genital ridge (GR). This tissue forms relatively late in embryonic development and has the potential to form either the ovary or testis, which in turn produce hormones required for development of the rest of the reproductive tract. It is imperative that we understand the genetic networks underpinning GR development if we are to begin to understand abnormalities in the adult. This is particularly relevant in the contexts of disorders of sex development (DSDs) and infertility, two conditions that many individuals struggle with worldwide, with often no answers as to their aetiology. Here, we review what is known about the genetics of GR development. Investigating the genetic networks required for GR formation will not only contribute to our understanding of the genetic regulation of reproductive development, it may in turn open new avenues of investigation into reproductive abnormalities and later fertility issues in the adult.

Loss of p300 and CBP disrupts histone acetylation at the mouse Sry promoter and causes XY gonadal sex reversal

CREB-binding protein (CBP, CREBBP, KAT3A) and its closely related paralogue p300 (EP300, KAT3B), together termed p300/CBP, are histone/lysine acetyl-transferases that control gene expression by modifying chromatin-associated proteins. Here, we report roles for both of these chromatin-modifying enzymes in mouse sex determination, the process by which the embryonic gonad develops into a testis or an ovary. By targeting gene ablation to embryonic gonadal somatic cells using an inducible Cre line, we show that gonads lacking either gene exhibit major abnormalities of XY gonad development at 14.5 dpc, including partial sex reversal. Embryos lacking three out of four functional copies of p300/Cbp exhibit complete XY gonadal sex reversal and have greatly reduced expression of the key testis-determining genes Sry and Sox9. An analysis of histone acetylation at the Sry promoter in mutant gonads at 11.5 dpc shows a reduction in levels of the positive histone mark H3K27Ac. Our data suggest a role for CBP/p300 in testis determination mediated by control of histone acetylation at the Sry locus and reveal a novel element in the epigenetic control of Sry and mammalian sex determination. They also suggest possible novel causes of human disorders of sex development (DSD).

Cyp1b1 deletion and retinol deficiency coordinately suppress mouse liver lipogenic genes and hepcidin expression during post-natal development

Cyp1b1 deletion and gestational vitamin A deficiency (GVAD) redirect adult liver gene expression. A matched sufficient pre- and post-natal diet, which has high carbohydrate and normal iron content (LF12), increased inflammatory gene expression markers in adult livers that were suppressed by GVAD and Cyp1b1 deletion. At birth on the LF12 diet, Cyp1b1 deletion and GVAD each suppress liver expression of the iron suppressor, hepcidin (Hepc), while increasing stellate cell activation markers and suppressing post-natal increases in lipogenesis. Hepc was less suppressed in Cyp1b1-/- pups with a standard breeder diet, but was restored by iron supplementation of the LF12 diet.

CONCLUSIONS

The LF12 diet delivered low post-natal iron and attenuated Hepc. Hepc decreases in Cyp1b1-/- and GVAD mice resulted in stellate activation and lipogenesis suppression. Endothelial BMP6, a Hepc stimulant, is a potential coordinator and Cyp1b1 target. These neonatal changes in Cyp1b1-/- mice link to diminished adult obesity and liver inflammation.

The Genome of the Trinidadian Guppy, Poecilia reticulata, and Variation in the Guanapo Population

For over a century, the live bearing guppy, Poecilia reticulata, has been used to study sexual selection as well as local adaptation. Natural guppy populations differ in many traits that are of intuitively adaptive significance such as ornamentation, age at maturity, brood size and body shape. Water depth, light supply, food resources and predation regime shape these traits, and barrier waterfalls often separate contrasting environments in the same river. We have assembled and annotated the genome of an inbred single female from a high-predation site in the Guanapo drainage. The final assembly comprises 731.6 Mb with a scaffold N50 of 5.3 MB. Scaffolds were mapped to linkage groups, placing 95% of the genome assembly on the 22 autosomes and the X-chromosome. To investigate genetic variation in the population used for the genome assembly, we sequenced 10 wild caught male individuals. The identified 5 million SNPs correspond to an average nucleotide diversity (π) of 0.0025. The genome assembly and SNP map provide a rich resource for investigating adaptation to different predation regimes. In addition, comparisons with the genomes of other Poeciliid species, which differ greatly in mechanisms of sex determination and maternal resource allocation, as well as comparisons to other teleost genera can begin to reveal how live bearing evolved in teleost fish.

Dynamic changes in the expression of apoptosis-related genes in differentiating gonocytes and in seminomas

Apoptosis is an integral part of the spermatogenic process, necessary to maintain a proper ratio of Sertoli to germ cell numbers and provide an adequate microenvironment to germ cells. Apoptosis may also represent a protective mechanism mediating the elimination of abnormal germ cells. Extensive apoptosis occurs between the first and second postnatal weeks, at the point when gonocytes, precursors of spermatogonial stem cells, should have migrated toward the basement membrane of the tubules and differentiated into spermatogonia. The mechanisms regulating this process are not well-understood. Gonocytes undergo phases of proliferation, migration, and differentiation which occur in a timely and closely regulated manner. Gonocytes failing to migrate and differentiate properly undergo apoptosis. Inadequate gonocyte differentiation has been suggested to lead to testicular germ cell tumor (TGCT) formation. Here, we examined the expression levels of apoptosis-related genes during gonocyte differentiation by quantitative real-time polymerase chain reaction, identifying 48 pro- and anti-apoptotic genes increased by at least two-fold in rat gonocytes induced to differentiate by retinoic acid, when compared to untreated gonocytes. Further analysis of the most highly expressed genes identified the pro-apoptotic genes Gadd45a and Cycs as upregulated in differentiating gonocytes and in spermatogonia compared with gonocytes. These genes were also significantly downregulated in seminomas, the most common type of TGCT, compared with normal human testicular tissues. These results indicate that apoptosis-related genes are actively regulated during gonocyte differentiation. Moreover, the down-regulation of pro-apoptotic genes in seminomas suggests that they could represent new therapeutic targets in the treatment of TGCTs.

Molecular characterization and functional divergence of two Gadd45g homologs in sex determination in half-smooth tongue sole (Cynoglossus semilaevis)

The growth arrest and DNA-damage-inducible protein 45 gamma (Gadd45g) is known to play a major role in embryonic development and sex determination. In this study, two Gadd45g genes were isolated from half-smooth tongue sole (Cynoglossus semilaevis). Using chromosomal fluorescence in situ hybridization (FISH), Gadd45g1 and Gadd45g2 were located on the W and Z chromosomes, respectively. The full-length cDNA sequences of Gadd45g1 (1270bp) and Gadd45g2 (1181bp) were predicted to contain a 480-bp coding sequence that could encode a protein of 159 amino acids residues. A phylogenetic tree showed that the predicted Gadd45g1 and Gadd45g2 amino acid sequences clustered closely in one branch. It is proposed that Gadd45g1 and Gadd45g2 are paralogous genes derived from the divergence of the sex chromosome. Ka/Ks ratios indicated that Gadd45g1 and Gadd45g2 may have undergone a high number of mutations and have a divergence time of only about 68,000years, although Gadd45g homologs are highly conserved. The qRT-PCR demonstrated that Gadd45g1 and Gadd45g2 were highly expressed in ovary, and negligibly expressed in testis of male and neo-male. During development of the ovary (from 80 to 150days), the expression levels of both genes reached high levels. Gadd45g1 was also highly expressed at 50days, the stage just before gonad differentiation in C. semilaevis. All these findings imply functional divergence of the two Gadd45g homologs; Gadd45g1 may be necessary for sex differentiation in the early stage of gonad development, and then Gadd45g1 and Gadd45g2 maintain ovary development and the female character of half-smooth tongue sole.

Switching on sex: transcriptional regulation of the testis-determining gene Sry

Mammalian sex determination hinges on the development of ovaries or testes, with testis fate being triggered by the expression of the transcription factor sex-determining region Y (Sry). Reduced or delayed Sry expression impairs testis development, highlighting the importance of its accurate spatiotemporal regulation and implying a potential role for SRY dysregulation in human intersex disorders. Several epigenetic modifiers, transcription factors and kinases are implicated in regulating Sry transcription, but it remains unclear whether or how this farrago of factors acts co-ordinately. Here we review our current understanding of Sry regulation and provide a model that assembles all known regulators into three modules, each converging on a single transcription factor that binds to the Sry promoter. We also discuss potential future avenues for discovering the cis-elements and trans-factors required for Sry regulation.

Gadd45 in stress signaling, cell cycle control, and apoptosis

The first identified Gadd45 gene, Gadd45a, encodes a ubiquitously expressed protein that is often induced by DNA damage and other stress signals associated with growth arrest and apoptosis. This protein and the other two members of this small gene family, Gadd45b and Gadd45g, have been implicated in a variety of the responses to cell injury including cell cycle checkpoints, apoptosis, and DNA repair. In vivo, many of the prominent roles for the Gadd45 proteins are associated with signaling mediated by p38 mitogen-activated protein kinases (MAPK). Gadd45 proteins can contribute to p38 activation either by activation of upstream kinase(s) or by direct interaction. In vivo, there are important tissue and cell-type-specific differences in the roles for Gadd45 in MAPK signaling. In addition to being p53-regulated, Gadd45a has been found to contribute to p53 activation via p38. Like other stress and signaling proteins, Gadd45 proteins show complex regulation and numerous effectors.

Genome-wide association study for poor sperm motility in Holstein-Friesian bulls

The aim of the study was to screen the whole bull genome to identify markers and candidate genes underlying poor sperm motility. The analyzed data set originates from the Polish Holstein-Friesian bull population and consists of 41 Case and 279 Control bulls (selected from 1581 bulls). The most distinguishing trait of case group was very poor sperm motility (average 25.61%) when compared to control samples (average 72.95%). Each bull was genotyped using the Illumina BovineSNP50 BeadChip. Genome-wide association analysis was performed with the use of GoldenHelix SVS7 software. An additive model with a Cohran-Armitage test, Correlation/Trend adjusted by Bonferroni test were used to estimate the effect of Single Nucleotide Polymorphism (SNP) marker for poor sperm motility. Markers (n=34) reached genome-wide significance. The most significant SNP were located on chromosome 24 (rs110876480), 5 (rs110827324 and rs29011704), and 1 (rs110596818), in the close vicinity of melanocortin 4 receptor (MC4R), PDZ domain containing ring finger 4 (PDZRN4) and ethanolamine kinase 1 (ETNK1), olfactory receptor 5K3-like (LOC785875) genes, respectively. For five other candidate genes located close to significant markers (in distance of ca. 1 Mb), namely alkaline phosphatase, liver/bone/kidney (ALPL), tripartite motif containing 36 (TRIM36), 3-hydroxyisobutyrate dehygrogenase (HIBADH), kelch-like 1 (KLHL1), protein kinase C, beta (PRKCB), their potential role in sperm motility was confirmed in the earlier studies. Five additional candidate genes, cystic fibrosis transmembrane conductance regulator (CFTR), insulin-like growth factor 1 receptor (IGF1R), steroid-5-alpha-reductase, alpha polypeptide 2 (SRD5A2), cation channel, sperm associated 1 (CATSPER1) calpain 1 (mu/I) large subunit (CAPN1) were suggested to be significantly associated with sperm motility or semen biochemistry. Results of the present study indicate there is a genetic complexity of poor sperm motility but also indicate there might be a causal polymorphism useful in marker-assisted selection. Identifying genomic regions associated with poor sperm motility may be very important for early recognition of a young sire as unsuitable for effective semen production in artificial insemination centers.