Specific interaction with the nuclear transporter importin α2 can modulate paraspeckle protein 1 delivery to nuclear paraspeckles.

Importin (IMP) superfamily members mediate regulated nucleocytoplasmic transport, which is central to key cellular processes. Although individual IMPα proteins exhibit dynamic synthesis and subcellular localization during cellular differentiation, including during spermatogenesis, little is known of how this affects cell fate. To investigate how IMPαs control cellular development, we conducted a yeast two-hybrid screen for IMPα2 cargoes in embryonic day 12.5 mouse testis, a site of peak IMPα2 expression coincident with germ-line masculization. We identified paraspeckle protein 1 (PSPC1), the original defining component of nuclear paraspeckles, as an IMPα2-binding partner. PSPC1-IMPα2 binding in testis was confirmed in immunoprecipitations and pull downs, and an enzyme-linked immunosorbent assay-based assay demonstrated direct, high-affinity PSPC1 binding to either IMPα2/IMPß1 or IMPα6/IMPß1. Coexpression of full-length PSPC1 and IMPα2 in HeLa cells yielded increased PSPC1 localization in nuclear paraspeckles. High-throughput image analysis of >3500 cells indicated IMPα2 levels can directly determine PSPC1-positive nuclear speckle numbers and size; a transport-deficient IMPα2 isoform or small interfering RNA knockdown of IMPα2 each reduced endogenous PSPC1 accumulation in speckles. This first validation of an IMPα2 nuclear import cargo in fetal testis provides novel evidence that PSPC1 delivery to paraspeckles, and consequently paraspeckle function, may be controlled by modulated synthesis of specific IMPs.

Effects of TGFbeta2 on wild-type and Tgfbr3 knockout mouse fetal testis.

TGFBR3 (betaglycan), a TGFbeta superfamily coreceptor, is essential for normal seminiferous cord and Leydig cell development in the fetal mouse testis and has been associated with testicular dysgenesis syndrome in men. However, the mechanisms underlying TGFBR3-regulated testis development are unclear. We tested the hypothesis that loss of Tgfbr3 compromises the functions of TGFbeta2 in the differentiating fetal testis. Analysis of expression of transcripts encoding the TGFbeta superfamily members showed a predominance of TGFbeta mRNAs during the critical window of development when testis structure is established (11.5-14.5 days postcoitum [dpc]). When cultured under basal conditions for 2 days, explants of 13.5 dpc wild-type fetal testis/mesonephros complexes exhibited structure and gene expression profiles resembling those observed in vivo between 13.5-15.5 dpc. Similarly, development of Tgfbr3 knockout testis explants recapitulated the dysgenesis and decreased somatic cell marker expression previously observed in vivo. TGFbeta2 treatment partially rescued cord development in 11.5-13.5 dpc Tgfbr3 knockout explants but did not significantly alter somatic or germ cell gene expression. In contrast, TGFbeta2 treatment of wild-type explants disrupted cord structure and significantly downregulated the somatic and steroidogenic cell markers Amh, Sf1, Star, Cyp11a, Hsd3b1, and Cyp17a1. We conclude that 1) the compromised cord development in Tgfbr3 null fetal testis is due to, at least in part, disrupted TGFbeta2 function; 2) the reduction in steroidogenesis observed in the Tgfbr3 null testis may be regulated by additional TGFBR3 ligands, rather than TGFbeta2; and 3) both cord maintenance and somatic cell development are highly sensitive to the levels of TGFbeta2.

Expression patterns of activin, inhibin and follistatin variants in the adult male mouse reproductive tract suggest important roles in the epididymis and vas deferens.

Activin A and its inhibitors follistatin and inhibin play key roles in development and function of the male reproductive tract. Quantitative (q) polymerase chain reaction (PCR) was used to evaluate the expression of Inhba (the gene encoding activin A subunits), Inha and Inhbb (genes encoding the inhibin B subunits), as well as the genes for follistatin (Fst) and follistatin-like 3 (Fstl3) and the activin receptor subunits, in the male mouse reproductive tract. A qPCR assay that discriminated between the two follistatin variants of Fst288 (tissue-bound form) and Fst315 (circulating) was established. Activin A protein was measured by ELISA, whereas the inhibin α-subunit and total follistatin proteins were measured by radioimmunoassay (RIA). A screen of 22 tissues demonstrated tissue-specific regulation of the follistatin variants, with Fst288 highly expressed in the vas deferens and Fst315 most highly expressed in the skin. The expression of Fst288 and Fst315 and follistatin protein levels increased progressively from the testis through to the distal vas deferens. Inhba and the activin receptors were highly expressed in the epididymis, but activin A protein was elevated in both the epididymis and vas deferens. Inhibin α-subunit mRNA and protein and Inhbb expression were highest in the testis. These results indicate a role for activin A within the epididymis, but also that activin A bioactivity may be increasingly inhibited by follistatin distally along the male reproductive tract.

Mammalian foetal ovarian development: consequences for health and disease.

The development of a normal ovary during foetal life is essential for the production and ovulation of a high-quality oocyte in adult life. Early in embryogenesis, the primordial germ cells (PGCs) migrate to and colonise the genital ridges. Once the PGCs reach the bipotential gonad, the absence of the sex-determining region on the Y chromosome (SRY) gene and the presence of female-specific genes ensure that the indifferent gonad takes the female pathway and an ovary forms. PGCs enter into meiosis, transform into oogonia and ultimately give rise to oocytes that are later surrounded by granulosa cells to form primordial follicles. Various genes and signals are implicated in germ and somatic cell development, leading to successful follicle formation and normal ovarian development. This review focuses on the differentiation events, cellular processes and molecular mechanisms essential for foetal ovarian development in the mice and humans. A better understanding of these early cellular and morphological events will facilitate further study into the regulation of oocyte development, manifestation of ovarian disease and basis of female infertility.

Betaglycan is required for the establishment of nephron endowment in the mouse.

Betaglycan is an accessory receptor for the transforming growth factor-ß (TGFß) superfamily, many members of which play key roles in kidney development. The purpose of this study was to define the role of this co-receptor on fetal murine kidney development. Stereological examination of embryonic and adult betaglycan heterozygous kidneys revealed augmented nephron number relative to littermate controls. Fetal heterozygous kidneys exhibited accelerated ureteric branching, which correlated with augmented nephron development at embryonic day (e) 15.5. In contrast, betaglycan null kidneys exhibited renal hypoplasia from e13.5 and reduced nephron number at e15.5. Quantitative real-time PCR analysis of e11.5-e14.5 kidneys demonstrated that heterozygous kidneys exhibited a transient decrease in Bmp4 expression at e11.5 and a subsequent cascade of changes in the gene regulatory network that governs metanephric development, including significant increases in Pax2, Eya1, Gdnf, Ret, Wnt4, and Wt1 expression. Conversely, gene expression in null kidneys was normal until e13.5, when significant reductions were detected in the expression of Bmp4 as well as other key metanephric regulatory genes. Tgfb1 and Tgfb2 mRNA expression was down-regulated in both nulls and heterozygotes at e13.5 and e14.5. The opposing morphological and molecular phenotypes in betaglycan heterozygote and null mutants demonstrate that the levels of betaglycan must be tightly regulated for optimal kidney development.

Estrogen-dependent gene expression in the mouse ovary.

Estrogen (E) plays a pivotal role in regulating the female reproductive system, particularly the ovary. However, the number and type of ovarian genes influenced by estrogen remain to be fully elucidated. In this study, we have utilized wild-type (WT) and aromatase knockout (ArKO; estrogen free) mouse ovaries as an in vivo model to profile estrogen dependent genes. RNA from each individual ovary (n = 3) was analyzed by a microarray-based screen using Illumina Sentrix Mouse WG-6 BeadChip (45,281 transcripts). Comparative analysis (GeneSpring) showed differential expression profiles of 450 genes influenced by E, with 291 genes up-regulated and 159 down-regulated by 2-fold or greater in the ArKO ovary compared to WT. Genes previously reported to be E regulated in ArKO ovaries were confirmed, in addition to novel genes not previously reported to be expressed or regulated by E in the ovary. Of genes involved in 5 diverse functional processes (hormonal processes, reproduction, sex differentiation and determination, apoptosis and cellular processes) 78 had estrogen-responsive elements (ERE). These analyses define the transcriptome regulated by E in the mouse ovary. Further analysis and investigation will increase our knowledge pertaining to how E influences follicular development and other ovarian functions.

Activin A balances Sertoli and germ cell proliferation in the fetal mouse testis.

Activin affects many aspects of cellular development, including those essential for reproductive fitness. This study examined the contribution of activin A to murine fetal testicular development, revealing contrasting outcomes of activin actions on Sertoli cells and gonocytes. Shortly after sex determination, from Embryonic Day 12.5 (E12.5) through to birth (0 dpp), the activin A subunit transcript (Inhba) level rises in testis but not ovary, followed closely by the Inha transcript (encoding the inhibitory inhibin alpha subunit). Activin receptor transcript levels also change, with Acvr1 (encoding ALK2) and Acvr2b (ActRIIB) significantly higher and lower, respectively, at 0 dpp compared with E13.5 and E15.5. Transcripts encoding the signaling mediators Smad1, Smad3, and Smad4 were higher at 0 dpp compared with E13.5 and E15.5, whereas Smad2, Smad5, and Smad7 were lower. Detection of phosphorylated (P-)SMAD2/3 in nearly all testis cell nuclei indicated widespread transforming growth factor beta (TGFB) and/or activin ligand signaling activity. In contrast to wild-type littermates, activin betaA subunit knockout (Inhba(-/-)) mice have significantly smaller testes at birth, attributable to a 50% lower Sertoli cell number and decreased Sertoli cell proliferation from E13.5. Inhba(-/-) testes contained twice the normal gonocyte number at birth, with some appearing to bypass quiescence. Persistence of widespread P-SMAD2/3 in Inhba(-/-) cells indicates other TGFB superfamily ligands are active in fetal testes. Significant differences in Smad and cell cycle regulator transcript levels correlating to Inhba gene dosage correspond to differences in Sertoli and germ cell numbers. In Inhba(-/-) testes, Cdkn1a (encoding p21(cip1)), identified previously in fetal gonocytes, was lower at E13.5, whereas Cdkn1b (encoding p(27kip1) in somatic cells) was lower at birth, and cyclin D2 mRNA and protein were lower at E15.5 and 0 dpp. Thus, activin A dosage contributes to establishing the balance between Sertoli and germ cell number that is ultimately required for adult male fertility.

Fetal testis dysgenesis and compromised Leydig cell function in Tgfbr3 (beta glycan) knockout mice.

Betaglycan (Tgfbr3) is a coreceptor for transforming growth factor-beta (TGFB) superfamily ligands. In the current study, a defect in seminiferous cord formation was detected in 12.5-13.5 days postcoitum (dpc) beta glycan null murine testis. Immunohistochemistry with antibodies against cell-specific markers revealed defects in somatic cell populations. To confirm these data, quantitative real-time PCR was performed to determine changes in the expression levels of genes involved in fetal testis cell differentiation and function. The expression levels of the Leydig cell markers Insl3, Cyp17a1, Cyp11a1, Star, and Hsd3b1 were reduced in knockout testis compared to wild-type testis, beginning at 12.5 dpc. Whole mount in situ hybridization confirmed that Cyp11a1 expression was reduced in the null testis, but its distribution pattern was unchanged. Apoptosis was not affected by the loss of beta glycan, but proliferation within the interstitium was reduced at 14.5 dpc. However, morphometric analysis showed no changes in Leydig cell counts between the wild-type and the knockout testes at 14.5 dpc, indicating that fetal Leydig function, rather than number, was affected by the loss of beta glycan. The expression levels of Sertoli cell markers Dhh, Sox9, and Amh were also reduced in the knockout testis at 14.5 dpc. However, the expression of fetal germ cell markers Pou5f1 and DDX4 were not changed across the genotypes at any age examined. Our data show that the presence of beta glycan is required for normal cord formation, normal fetal Leydig cell development, and the establishment of fetal testis endocrine function, thus implicating TGFB superfamily members as regulators of early fetal testis structure and function.

Differential expression of TGFBR3 (betaglycan) in mouse ovary and testis during gonadogenesis.

TGFBR3 is an accessory receptor that binds to and modulates the activities of both transforming growth factor-beta (TGFbeta) and inhibin, two members of the TGFbeta superfamily of growth factors that regulate many aspects of reproductive biology. Tgfbr3 is known to be expressed in adult testis and ovary, but little is known about this receptor during gonadogenesis. Herein, we describe Tgfbr3 expression in the male and female fetal and neonatal murine gonad. Real-time PCR analysis revealed that Tgfbr3 mRNA was expressed at higher levels in the developing testis compared to ovary. TGFBR3 was expressed within the fetal testis interstitium, predominantly by Leydig cells, but expression shifted inside the seminiferous cords at birth. In contrast, TGFBR3 was detected in both the somatic and germ cell lineages in the fetal and neonatal ovary. This differential expression pattern suggests divergent roles for this TGFBR3 in developing testis and ovary.

Eki2 is upregulated specifically in the testis during mouse sex determination.

We have identified a gene with gonad restricted expression throughout mouse development, which is orthologous to human EKI2 (ethanolamine kinase 2). Our studies showed that mouse Eki2 expression became upregulated in the male gonad during the period of sex determination. Expression was restricted to the Sertoli cells of the developing testis. Eki2 has sequence similarity to ethanolamine (73%) and choline kinases (54%).

Sox15 is up regulated in the embryonic mouse testis.

The mammalian sex determining region on the Y chromosome, SRY, is the founding member of the SOX gene family. SOX genes share a common DNA-binding motif termed the HMG box and have diverse roles in vertebrate embryonic development and tissue differentiation. Sox15 expression was analysed during mouse embryogenesis by whole-mount in situ hybridisation and Real Time RT-PCR. Sox15 was found to be expressed in developing mouse gonads from 11.5 dpc to 13.5 dpc with a peak of expression at 12.5 dpc. Expression was approximately twice as high in the male gonad as in the female gonad.