Sex-specific expression of a novel gene Tmem184a during mouse testis differentiation

Identification and comparative profiling of gonadal microRNAs in the adult pigeon (Columba livia)

1. MicroRNAs are small noncoding RNA molecules that play crucial roles in gene expression. However, the comparative profiling of testicular and ovarian microRNAs in birds are rarely reported, particularly in pigeon.2. In this study, Illumina next-generation sequencing technology was used to sequence miRNA libraries of the gonads from six healthy adult utility pigeons. A total of 344 conserved known miRNAs and 32 novel putative miRNAs candidates were detected. Compared with those of ovaries, 130 differentially expressed (DE) miRNAs were identified in the testes. Among them, 70 miRNAs showed down-regulation in the ovaries, while another 60 miRNAs were up-regulated.3. Combining the results of the expression of target gene measurements and pathway enrichment analyses, it was revealed that some DEmiRNAs from the gonad samples involved in sexual differentiation and development (such as cli-miR-210-3p and cli-miR-214-3p) could down-regulate AR (androgen receptor). Cli-miR-181b-5p, cli-miR-9622-3p and cli-miR-145-5p were highly expressed in both the ovaries and testes, which could co-target HOXC9, and were related to regulation of primary metabolic processes. KEGG enrichment analysis showed that DEmiRNAs may play biological and sex-related roles in pigeon gonads.4. The expression profiles of testicular and ovarian miRNA in adult pigeon gonads are presented for the first time, and the findings may contribute to a better understanding of gonadal expression in poultry.

Toying with fate: Redirecting the differentiation of adrenocortical progenitor cells into gonadal-like tissue

Cell fate decisions are integral to zonation and remodeling of the adrenal cortex. Animal models exhibiting ectopic differentiation of gonadal-like cells in the adrenal cortex can shed light on the molecular mechanisms regulating steroidogenic cell fate. In one such model, prepubertal gonadectomy (GDX) of mice triggers the formation of adrenocortical neoplasms that resemble luteinized ovarian stroma. Transcriptomic analysis and genome-wide DNA methylation mapping have identified genetic and epigenetic markers of GDX-induced adrenocortical neoplasia. Members of the GATA transcription factor family have emerged as key regulators of cell fate in this model. Expression of Gata4 is pivotal for the accumulation of gonadal-like cells in the adrenal glands of gonadectomized mice, whereas expression of Gata6 limits the spontaneous and GDX-induced differentiation of gonadal-like cells in the adrenal cortex. Additionally, Gata6 is essential for proper development of the adrenal X-zone, a layer analogous to the fetal zone of the human adrenal cortex. The relevance of these observations to developmental signaling pathways in the adrenal cortex, to other animal models of altered adrenocortical cell fate, and to human diseases is discussed.

Transmembrane protein OSTA-1 shapes sensory cilia morphology via regulation of intracellular membrane trafficking in C. elegans

The structure and function of primary cilia are critically dependent on intracellular trafficking pathways that transport ciliary membrane and protein components. The mechanisms by which these trafficking pathways are regulated are not fully characterized. Here we identify the transmembrane protein OSTA-1 as a new regulator of the trafficking pathways that shape the morphology and protein composition of sensory cilia in C. elegans. osta-1 encodes an organic solute transporter alpha-like protein, mammalian homologs of which have been implicated in membrane trafficking and solute transport, although a role in regulating cilia structure has not previously been demonstrated. We show that mutations in osta-1 result in altered ciliary membrane volume, branch length and complexity, as well as defects in localization of a subset of ciliary transmembrane proteins in different sensory cilia types. OSTA-1 is associated with transport vesicles, localizes to a ciliary compartment shown to house trafficking proteins, and regulates both retrograde and anterograde flux of the endosome-associated RAB-5 small GTPase. Genetic epistasis experiments with sensory signaling, exocytic and endocytic proteins further implicate OSTA-1 as a crucial regulator of ciliary architecture via regulation of cilia-destined trafficking. Our findings suggest that regulation of transport pathways in a cell type-specific manner contributes to diversity in sensory cilia structure and might allow dynamic remodeling of ciliary architecture via multiple inputs.

Laser capture microdissection-reduced representation bisulfite sequencing (LCM-RRBS) maps changes in DNA methylation associated with gonadectomy-induced adrenocortical neoplasia in the mouse

DNA methylation is a mechanism for long-term transcriptional regulation and is required for normal cellular differentiation. Failure to properly establish or maintain DNA methylation patterns leads to cell dysfunction and diseases such as cancer. Identifying DNA methylation signatures in complex tissues can be challenging owing to inaccurate cell enrichment methods and low DNA yields. We have developed a technique called laser capture microdissection-reduced representation bisulfite sequencing (LCM-RRBS) for the multiplexed interrogation of the DNA methylation status of cytosine–guanine dinucleotide islands and promoters. LCM-RRBS accurately and reproducibly profiles genome-wide methylation of DNA extracted from microdissected fresh frozen or formalin-fixed paraffin-embedded tissue samples. To demonstrate the utility of LCM-RRBS, we characterized changes in DNA methylation associated with gonadectomy-induced adrenocortical neoplasia in the mouse. Compared with adjacent normal tissue, the adrenocortical tumors showed reproducible gains and losses of DNA methylation at genes involved in cell differentiation and organ development. LCM-RRBS is a rapid, cost-effective, and sensitive technique for analyzing DNA methylation in heterogeneous tissues and will facilitate the investigation of DNA methylation in cancer and organ development.

Computational analysis of the transcriptional regulation of the adenine nucleotide translocator isoform 4 gene and its role in spermatozoid glycolytic metabolism

Computational phylogenetic analysis coupled to promoter sequence alignment was used to understand mechanisms of transcriptional regulation and to identify potentially coregulated genes. Our strategy was validated on the human ANT4 gene which encodes the fourth isoform of the mitochondrial adenine nucleotide translocator specifically expressed during spermatogenesis. The movement of sperm flagella is driven mainly by ATP generated by glycolytic pathways, and the specific induction of the mitochondrial ANT4 protein presented an interesting puzzle. We analysed the sequences of the promoters, introns and exons of 30 mammalian ANT4 genes and constructed regulatory models. The whole human genome and promoter database were screened for genes that were potentially regulated by the generated models. 80% of the identified co-regulated genes encoded proteins with specific roles in spermatogenesis and with functions linked to male reproduction. Our in silico study enabled us to precise the specific role of the ANT4 isoform in spermatozoid bioenergetics.

Localization and characterization of rat transmembrane protein 225 specifically expressed in testis

Testis is the one and only location of spermatogenesis and sexual hormone production. Spermatogenesis is a complicated physiological process regulated by many genes specifically and differentially expressed in the testis. In this study, Transmembrane Protein 225 (TMEM225), which is specifically expressed in rat testis, has been identified. TMEM225 was cloned from the testis cDNA library and was mapped to chromosome 8q22 by browsing the University of California Santa Cruz genomic database. It contains an open reading frame with a length of 696 bp, encoding a protein with four putative transmembrane helices. TMEM225 mRNA expression was evaluated by reverse transcription-polymerase chain reaction and in situ hybridization. In addition, the subcellular location of TMEM225 was evaluated. The results obtained highlighted age related specific expression of TMEM225 in testis, specifically during the adult period after age of 13 months. In situ hybridization analysis indicated that TMEM225 mRNA was mainly expressed in spermatocyte cells and round spermatids. Green fluorescence protein localization analysis showed that rat TMEM225 mainly surrounded the nuclear membrane, with a minority distribution in the cytoplasm, and the distribution of TMEM225 was affected by the deletion of N-terminal transmembrane domain. As the expression phase is not related to the first wave of spermatozoon development, our data presented here suggest that TMEM225 may play an important role in sperm degeneration but not in spermatogenesis.

Mouse germ cell development: from specification to sex determination

Primordial germ cells (PGCs) are embryonic progenitors for the gametes. In the gastrulating mouse embryo, a small group of cells begin expressing a unique set of genes and so commit to the germline. Over the next 3-5 days, these PGCs migrate anteriorly and increase rapidly in number via mitotic division before colonizing the newly formed gonads. PGCs then express a different set of unique genes, their inherited epigenetic imprint is erased and an individual methylation imprint is established, and for female PGCs, the silent X chromosome is reactivated. At this point, germ cells (GCs) commit to either a female or male sexual lineage, denoted by meiosis entry and mitotic arrest, respectively. This developmental program is determined by cues emanating from the somatic environment.

The game plan: cellular and molecular mechanisms of mammalian testis development

In mammals, biological differences between males and females, which influence many aspects of their physical, social, and psychological environments, are solely determined genetically. In the presence of a Y chromosome, the gonadal primordium will differentiate into a testis, whereas in the absence of the Y chromosome an ovary will develop. Testis and ovary subsequently direct the differentiation of all secondary sex characteristics down the male and female pathway, respectively. The male-determining factor on the Y chromosome, SRY, was identified some 20 years ago. Since then, significant progress has been made toward understanding the molecular and cellular pathways that result in the formation of a testis. Here, we review what is known about testis differentiation in mice and humans, with reference to other species where appropriate.

Ex vivo magnetofection: a novel strategy for the study of gene function in mouse organogenesis

Gene function during mouse development is often studied through the production and analysis of transgenic and knockout models. However, these techniques are time- and resource-consuming, and require specialized equipment and expertise. We have established a new protocol for functional studies that combines organ culture of explanted fetal tissues with microinjection and magnetically induced transfection ("magnetofection") of gene expression constructs. As proof-of-principle, we magnetofected cDNA constructs into genital ridge tissue as a means of gain-of-function analysis, and shRNA constructs for loss-of-function analysis. Ectopic expression of Sry induced female-to-male sex-reversal, whereas knockdown of Sox9 expression caused male-to-female sex-reversal, consistent with the known functions of these genes. Furthermore, ectopic expression of Tmem184a, a gene of unknown function, in female genital ridges, resulted in failure of gonocytes to enter meiosis. This technique will likely be applicable to the study of gene function in a broader range of developing organs and tissues.

Sdmg1 is a component of secretory granules in mouse secretory exocrine tissues

Sdmg1 is a conserved eukaryotic transmembrane protein that is mainly expressed in the gonads where it may have a role in mediating signaling between somatic cells and germ cells. In this study we demonstrate that secretory exocrine cells in the pancreas, salivary gland, and mammary gland also express Sdmg1. Furthermore, we show that Sdmg1 expression is up-regulated during pancreas development when regulated secretory granules start to appear, and that Sdmg1 colocalizes with secretory granule markers in adult pancreatic acinar cells. In addition, we show that Sdmg1 co-purifies with secretory granules during subcellular fractionation of the pancreas and that Sdmg1 and the secretory granule marker Vamp2 are localized to distinct subdomains in the secretory granule membrane. These data suggest that Sdmg1 is a component of regulated secretory granules in exocrine secretory cells and that the developmental regulation of Sdmg1 expression is related to a role for Sdmg1 in post-Golgi membrane trafficking.

The cerebellin 4 precursor gene is a direct target of SRY and SOX9 in mice

In most mammals, the expression of SRY (sex-determining region on the Y chromosome) initiates the development of testes, and thus determines the sex of the individual. However, despite the pivotal role of SRY, its mechanism of action remains elusive. One important missing piece of the puzzle is the identification of genes regulated by SRY. In this study we used chromatin immunoprecipitation to identify direct SRY target genes. Anti-mouse SRY antibody precipitated a region 7.5 kb upstream of the transcriptional start site of cerebellin 4 precursor (Cbln4), which encodes a secreted protein. Cbln4 is expressed in Sertoli cells in the developing gonad, with a profile mimicking that of the testis-determining gene SRY-box containing gene 9 (Sox9). In transgenic XY mouse embryos with reduced Sox9 expression, Cbln4 expression also was reduced, whereas overexpression of Sox9 in XX mice caused an upregulation of Cbln4 expression. Finally, ectopic upregulation of SRY in vivo resulted in ectopic expression of Cbln4. Our findings suggest that both SRY and SOX9 contribute to the male-specific upregulation of Cbln4 in the developing testis, and they identified a direct in vivo target gene of SRY.

Sdmg1 is a conserved transmembrane protein associated with germ cell sex determination and germline-soma interactions in mice

In mammals, the supporting cell lineage in an embryonic gonad communicates the sex-determining decision to various sexually dimorphic cell types in the developing embryo, including the germ cells. However, the molecular nature of the sex-determining signals that pass from the supporting cells to the germ cells is not well understood. We have identified a conserved transmembrane protein, Sdmg1, owing to its male-specific expression in mouse embryonic gonads. Sdmg1 is expressed in the Sertoli cells of embryonic testes from 12.5 dpc, and in granulosa cells of growing follicles in adult ovaries. In Sertoli cells, Sdmg1 is localised to endosomes, and knock-down of Sdmg1 in Sertoli cell lines causes mis-localisation of the secretory SNARE Stx2 and defects in membrane trafficking. Upregulation of Sdmg1 appears to be part of a larger programme of changes to membrane trafficking pathways in embryonic Sertoli cells, and perturbing secretion in male embryonic gonads in organ culture causes male-to-female germ cell sex reversal. These data suggest that changes that occur in the cell biology of embryonic Sertoli cells may facilitate the communication of male sex-determining decisions to the germ cells during embryonic development.