cDNA cloning of a novel rainbow trout SRY-type HMG box protein, rtSox23, and its functional analysis

Expressions of Sox9, Sox5, and Sox13 transcription factors in mice testis during postnatal development

SRY-related box (Sox) transcription factors are conserved among vertebrate species. These proteins regulate multiple processes including sex determination and testis differentiation of the male embryo. Although members of the Sox family have been identified in pre- and postnatal Sertoli cells, they have never been characterized in adult Leydig cells. The objectives of this research were to identify expressions of Sox9, Sox5, and Sox13 in mice Leydig cell cultures and to establish their expression profiles in postnatal mice testes at different developmental stages. Methods used include Western blots and qPCR of stimulated MA-10 cell cultures and whole mice testes. Sox9, Sox5, and Sox13 proteins were detected in MA-10 cells as well as whole mouse testis. Although Sox9, Sox5, and Sox13 mRNA levels from whole mice testes tended to increase according to postnatal development, these results were not significant. Sox members were also detected in whole mice testis by Western Blot. However, Sox9, Sox5, and Sox13 protein expressions remained relatively constant during postnatal development from postnatal (P) day 60 to P365. Being newly characterized in the mouse testis, Sox13 was mainly localized by immunofluorescence within the nuclei of cells from seminiferous tubules, possibly spermatocytes and Sertoli cells. In addition, Sox9, Sox5, and Sox13 proteins were characterized in the nuclei of MA-10 Leydig cell cultures. Their expressions and transcriptional activities remained unaffected by activators of the cAMP/PKA pathway. Thus, Sox9, Sox5, and Sox13 transcription factors are expressed in postnatal testis and may regulate multiple functions such as steroidogenesis and spermatogenesis.

Mapping of DNA sex-specific markers and genes related to sex differentiation in turbot (Scophthalmus maximus)

Production of all-female populations in turbot can increase farmer's benefits since sexual dimorphism in growth in this species is among the highest within marine fish, turbot females reaching commercial size 3-6 months earlier than males. Puberty in males occurs earlier than in females, which additionally slows their growth. Thus, elucidating the mechanisms of sex determination and gonad differentiation is a relevant goal for turbot production. A ZZ/ZW sex determination mechanism has been suggested for this species, and four sex-related quantitative trait loci (QTL) were detected, the major one located in linkage group (LG) 5 and the three minor ones in LG6, LG8, and LG21. In the present work, we carried out a linkage analysis for several sex-related markers: (1) three anonymous sex-associated RAPD and (2) several candidate genes related to sex determination and gonad differentiation in other species (Sox3, Sox6, Sox8, Sox9, Sox17, Sox19, Amh, Dmrta2, Cyp19a, Cyp19b). We focused our attention on their co-localization with the major and minor sex-related QTL trying to approach to the master sex-determining gene of this species. Previously described growth-related QTL were also considered since the association observed between growth and sex determination in fish. Amh, Dmrta2, and one RAPD were located in LG5, while Sox9 and Sox17 (LG21), Cyp19b (LG6), and a second RAPD (LG8) co-mapped with suggestive sex-related QTL, thus supporting further analyses on these genes to elucidate the genetic basis of this relevant trait for turbot farming.

Different sox17 transcripts during sex differentiation in sea bass, Dicentrarchus labrax

Sox genes participate in several developmental processes, including sex determination and differentiation. In this study, the genomic structure of sox17 was characterized in the sea bass (sb). Two transcripts, one producing a normal protein (sb Sox17) and another producing a truncated protein (sb t-Sox17) were detected. A third, novel transcript, originated by intron retention (sb i-sox17) was also observed. Sb sox17 was widely distributed, whereas sb i-sox17 was predominantly found in skin and brain. In gonads, sb sox17 expression first increased at 150 days of age, coinciding with the onset of sex differentiation. At 250 days and onwards, sb sox17 expression was significantly higher in females, and mRNA levels correlated with those of gonadal aromatase. Thus, this study provides the first evidence for the presence of alternative splicing by intron retention in a Sox17 gene, and for sex-related differences in expression, implicating sox17 in ovarian development and function in fish.

Expression profiling of candidate genes during ovary-to-testis trans-differentiation in rainbow trout masculinized by androgens

Fish gonadal phenotype is very sensitive to sex steroid and functional masculinizations can be obtained in most species using androgen treatments. To gain insight into the molecular effects of androgen-induced masculinization we characterized, in the rainbow trout, the gonadal expression profiles of 103 candidate genes involved in sex differentiation and early gametogenesis. The androgen treatment (11beta-hydroxyandrostenedione, 10 mg/kg of food for 3 months) was administered in a genetic all-female population. Gonads were sampled at different time points in genetic all-male and all-female control populations and in the androgen-treated group. Gene expression profiles were recorded by real-time RT-PCR and biological samples and gene expressions were compared using a global clustering analysis. This analysis revealed that masculinization with androgens acts firstly by repressing granulosa cell related genes, including genes involved in ovarian differentiation (foxl2a, fst, cyp19a1a), and subsequently by repressing genes important for early oogenesis (gdf9, bcl2lb, fancl, gcl, fshb, lhb, sox23, sox24, nup62 and vtgr). However, this masculinizing treatment did not induce a testicular differentiation similar to what was observed in the control male population. This was especially noticeable for many Leydig cell genes encoding proteins involved in steroidogenesis or its control (hsd3b1, star, cyp17a1, cyp11b2.1 and nr5a1b) that were down-regulated in the androgen-treated group. Concomitantly some Sertoli cells marker genes were up-regulated by the androgen treatment (sox9a.1, nr0b1, cldn11, dmrt1) whereas others were down-regulated (amh, sox9a.2), suggesting a partial differentiation of the Sertoli cell lineage. Overall, this suggests that the crucial step of this masculinization process is the de-differentiation of the granulosa cells.

Nucleoporins NPP-1, NPP-3, NPP-4, NPP-11 and NPP-13 are required for proper spindle orientation in C. elegans

Nucleoporins are components of the nuclear pore, which is required for nucleo-cytoplasmic transport. We report a role for a subclass of nucleoporins in orienting the mitotic spindle in C. elegans embryos. RNAi-mediated depletion of any of five putative nucleoporins npp-1, npp-3, npp-4, npp-11, and npp-13 leads to indistinguishable spindle orientation defects. Transgenic worms expressing NPP-1::GFP or NPP-11::GFP show GFP localization at the nuclear envelope, consistent with their predicted function. NPP-1 interacts with the other nucleoporins in yeast two-hybrid assays, suggesting that the proteins affect spindle orientation by a common process. The failed orientation phenotype of npp-1(RNAi) is at least partially epistatic to the ectopic spindle rotation in the AB blastomere of par-3 mutant embryos. This suggests that NPP-1 contributes to the mechanics of spindle orientation. However, NPP-1 is also required for PAR-6 asymmetry at the two-cell stage, indicating that nucleoporins may be required to define cortical domains in the germ line blastomere P1. Nuclear envelope structure is abnormal in npp-1(RNAi) embryos, but the envelope maintains its integrity, and most nuclear proteins we assayed accumulate normally. These findings raise the possibility that these nucleoporins may have direct roles in orienting the mitotic spindle and the maintenance of cell polarity.

Large-Scale Temporal Gene Expression Profiling During Gonadal Differentiation and Early Gametogenesis in Rainbow Trout1

The overall understanding of the sex differentiation cascade in vertebrates is still growing slowly, probably because of the variety of vertebrate models used and the number of molecular players yet to be discovered. Finding conserved mechanisms among vertebrates should provide a better view of the key factors involved in this process. To this end, we used real-time reverse transcription-polymerase chain reaction to produce a temporal map of fluctuations in mRNA expression of 102 genes during sex differentiation and early gametogenesis in the rainbow trout (Oncorhynchus mykiss). We used these 102 temporal gene expression patterns as a basis for a hierarchical clustering analysis to find characteristic clusters of coexpressed genes. Analysis of some of these gene clusters suggested a conserved overall expression profile between the sex differentiation cascade in fish and mammals. Among these conserved molecular mechanisms, sox9, dmrt1, amh, nr5a1, nr0b1, igf1, and igf1ra are, for instance, characterized as early expressed genes involved in trout testicular differentiation as it is known or suggested in mammals. On the contrary, foxl2, fst, and lhr are characterized as early expressed genes during trout ovarian differentiation, as also found in mammals. Apart from this high conservation, our analysis suggests some potential new players, such as the fshb subunit gene, which is detected here for the first time, to our knowledge, in the female differentiating gonad of a vertebrate species and displays a specific overexpression that coincides in timing with the occurrence of first oocyte meioses, or the pax2 gene, which displays an early and testis-specific expression profile.

Phylogeny of the SOX family of developmental transcription factors based on sequence and structural indicators

Members of the SOX family of transcription factors are found throughout the animal kingdom, are characterized by the presence of a DNA-binding HMG domain, and are involved in a diverse range of developmental processes. Previous attempts to group SOX genes and deduce their structural, functional, and evolutionary relationships have relied largely on complete or partial HMG box sequence of a limited number of genes. In this study, we have used complete HMG domain sequence, full-length protein structure, and gene organization data to study the pattern of evolution within the family. For the first time, a substantial number of invertebrate SOX sequences have been included in the analysis. We find support for subdivision of the family into groups A-H, as has been suggested in some previous studies, and for the assignment of two new groups, I and J. For vertebrate genes, it appears that relatedness as suggested by HMG domain sequence is congruent with relatedness as indicated by overall structure of the full-length protein and intron-exon structure of the genes. Most of the SOX groups identified in vertebrates were represented by a single SOX sequence in each invertebrate species studied. We have named anonymous sequences and, where appropriate, have suggested systematic names for some previously identified sequences. In addition, we identify an HMG domain signature motif which may be considered representative of the SOX family. Based on our data, we propose a robust phylogeny of SOX genes that reflects their evolutionary history in metazoans.

Characterization of Solt, a novel SoxLZ/Sox6 binding protein expressed in adult mouse testis

SoxLZ/Sox6, a member of the Sox protein family, contains a leucine zipper motif in addition to an HMG box, which is its DNA binding domain. Here we have identified a novel SoxLZ/Sox6 binding protein, termed Solt, which we obtained independently using both a far-Western blot and a yeast two-hybrid screen. Like SoxLZ/Sox6 mRNA, Solt mRNA was exclusively expressed in the testis in mouse. Solt contains an unusual leucine zipper, which bound to the leucine zipper region of SoxLZ/Sox6 in vitro. In transient transfection assays in CHO cells with SoxLZ/Sox6 containing the transactivational region of herpes simplex virus VP16, expression of a reporter gene that carries a cis binding region for Sox proteins was significantly enhanced by the co-expression of Solt and Ca(2+)/calmodulin-dependent protein kinase IV.

The glial transcription factor Sox10 binds to DNA both as monomer and dimer with different functional consequences

Sox10 is an important transcriptional regulator in the neural crest and various neural-crest derived lineages, such as the Schwann cells of the peripheral nervous system. Recently, we identified the gene for myelin Protein zero (P(0)) as a transcriptional target of Sox10 in Schwann cells, allowing for the first time a detailed analysis of Sox10 responsive elements and their functional interaction with Sox10. Here we show that Sox10 functions through two different types of DNA response elements, one that allows binding of monomers, and a second that favors cooperative binding of two molecules. This dimeric binding required the presence of two heptameric Sox binding sites in a specific orientation and spacing, and was mediated by an N-terminal region of Sox10 with high conservation in the related Sox9, which also exhibited dimeric binding. This argues that the conserved region has the capacity to function as a DNA-dependent dimerization domain. The interaction between Sox10 dimers and DNA differed dramatically from that of Sox10 monomers, as it drastically reduced the protein's off-rate and increased the protein-induced angle of DNA bending. These results indicate that functionally relevant interactions between Sox10 and DNA occur through completely different modes of binding.

Genomic characterisation and fine mapping of the human SOX13 gene

SOX13 is the member of the SOX (Sry related HMG BOX) family of transcription factors which encodes the type-1 diabetes autoantigen, ICA12, and is expressed in a number of tissues including pancreatic islets and arterial walls. By fluorescence in situ hybridisation, radiation hybrid mapping and YAC analysis we determined that the human SOX13 gene maps to Chromosome 1q31.3-32.1 near the marker D1S504, a region associated with type-1 diabetes susceptibility and familial dilated cardiomyopathy. Mouse Sox13 maps to the syntenic region near the marker D1Mit57. The human SOX13 gene spans >15.5kb of genomic DNA and is composed of 14 exons with introns interrupting regions encoding the HMG DNA binding domain and the leucine zipper/glutamine-rich dimerisation domain. Comparison with the mouse Sox13 gene suggests the existence of long and short forms of the SOX13 protein which may arise by differential splicing during different stages in embryogenesis. The high sequence conservation between human SOX13 and mouse, Xenopus and trout orthologues implies a conserved function in vertebrates. SOX13 belongs to SOX Group D members which contain a leucine zipper/glutamine-rich region. Phylogenetic analyses of SOX proteins suggest that such domains were acquired after the initial divergence of groups A to G.

The Sox-13 gene: structure, promoter characterization, and chromosomal localization

We have recently identified the HMG box transcription factor Sox-13 and described its expression during murine embryogenesis. Here we describe the structure of the murine Sox-13 gene. This gene spans approximately 12 kb and consists of 13 exons. The HMG domain is encoded by exons XI and XII, separated by an intron that is conserved among Sox-5, Sox-13, and Sox-17. A single major transcription initiation site was identified. Deletion analysis of the 3-kb promoter region revealed a 400-bp fragment driving transcription of a luciferase reporter in a Sox-13-expressing cell line. To determine the chromosomal localization of the human gene, a human SOX13 cDNA was isolated with 75% homology to the mouse Sox-13. FISH analysis mapped the human SOX13 gene to chromosome 1 band q32.

Localization of a human nucleoporin 155 gene (NUP155) to the 5p13 region and cloning of its cDNA

Nucleoporins are the main components of nuclear pore complexes (NPCs) involved in nucleo-cytoplasmic transport. Starting with an expressed DNA fragment retrieved by exon trapping from pooled human BAC clones mapped to the short arm of chromosome 5, we identified a human nucleoporin cDNA sequence by PCR from a human testis cDNA library. The coding sequence showed high homology to that of the rat nucleoporin 155 (Nup155) cDNA. FISH analysis with the human BAC clone as probe localized the human NUP155 gene to chromosome band 5p13. Northern analysis showed that the human NUP155 gene was expressed at different levels in all tissues tested. Two species of transcripts were observed with estimated lengths of 5.4 and 4.7 kb, respectively, in concordance with the finding of two alternative polyadenylation sites in the cDNA. The genomic location of the human NUP155 gene suggests a possible role in the mental and developmental retardation associated with hemizygous deletions of the 5p13 region.

Further complexity of the human SOX gene family revealed by the combined use of highly degenerate primers and nested PCR

SOX proteins contain a conserved HMG-related DNA-binding domain. They fulfill essential functions during the development of animals. Mutations in several SOX genes have been implicated in human diseases. We present here a new set of PCR primers designed to amplify a broad range of SOX HMG-box sequences. These primers facilitated the cloning of several new SOX HMG boxes from human genomic DNA, revealing unexpected complexity of the SOX gene family.

A new long form of Sox5 (L-Sox5), Sox6 and Sox9 are coexpressed in chondrogenesis and cooperatively activate the type II collagen gene

Transcripts for a new form of Sox5, called L-Sox5, and Sox6 are coexpressed with Sox9 in all chondrogenic sites of mouse embryos. A coiled-coil domain located in the N-terminal part of L-Sox5, and absent in Sox5, showed >90% identity with a similar domain in Sox6 and mediated homodimerization and heterodimerization with Sox6. Dimerization of L-Sox5/Sox6 greatly increased efficiency of binding of the two Sox proteins to DNA containing adjacent HMG sites. L-Sox5, Sox6 and Sox9 cooperatively activated expression of the chondrocyte differentiation marker Col2a1 in 10T1/2 and MC615 cells. A 48 bp chondrocyte-specific enhancer in this gene, which contains several HMG-like sites that are necessary for enhancer activity, bound the three Sox proteins and was cooperatively activated by the three Sox proteins in non-chondrogenic cells. Our data suggest that L-Sox5/Sox6 and Sox9, which belong to two different classes of Sox transcription factors, cooperate with each other in expression of Col2a1 and possibly other genes of the chondrocytic program.