The Sry-related HMG box-containing gene Sox6 is expressed in the adult testis and developing nervous system of the mouse

Microarray profiling of microRNAs expressed in testis tissues of developing primates

PURPOSE

MicroRNAs (miRNAs) are small non-coding RNA molecules that have been identified as potent regulators of gene expression. Recent studies indicate that miRNAs are involved in mammalian spermatogenesis but the mechanism of regulation is largely unknown.

METHODS

miRNA microarray was employed to compare miRNA expression profiles of testis tissues from immature rhesus monkey (Sample IR), mature rhesus monkey (Sample MR), and mature human (Sample MH). Real-time RT-PCR was used to confirm the changed miRNAs.

RESULTS

Twenty-six miRNAs were shared by samples IR/MR and IR/MH with differential expression patterns greater than three-fold difference. PicTar and TargetScan prediction tools predicted a number of target mRNAs, and some of these target genes predicted by miRNAs have been shown to associate with spermatogenesis.

CONCLUSIONS

Our results indicate that miRNAs are extensively involved in spermatogenesis and provide additional information for further studies of spermatogenetic mechanisms.

Intratesticular localization of the organic solute carrier protein, OSCP1, in spermatogenic cells in mice

Organic solute carrier protein 1 (OSCP1) is a recently described human gene that facilitates the transport of various organic solutes into the cell, when expressed in frog eggs. In this study, we cloned a mouse ortholog of OSCP1 encoding 379 amino acid protein, with 94% homology to the human counterpart. The mouse OSCP1 mRNA was predominantly expressed in the testis, in which it was attributed to the spermatogenic cells, except the spermatogonia. Immunohistochemistry confirmed that OSCP1 protein is continuously expressed during spermatogenesis in a stage- and cell type-specific manner, in the leptotene spermatocytes at stage IX through step 15 spermatids. Subcellular fractionation of mouse testis homogenates indicated that OSCP1 is a 45-kDa cytosolic protein. Moreover, when green fluorescent protein-OSCP1 fusion constructs were transfected into cultured cells, the fluorescence localized evenly in the cytoplasm. These results suggest that mouse testis OSCP1 may indirectly mediate substrate uptake into meiotic and spermiogenic germ cells, within the cytosol.

Mandibular functional positioning only in vertical dimension contributes to condylar adaptation evidenced by concomitant expressions of L-Sox5 and type II collagen

OBJECTIVE

Concerted expressions of L-Sox5 and type II collagen play an important part in osteogenic transition in epiphyseal cartilage. This study was designed to elucidate the role of mandibular vertical functional positioning in condylar adaptive remodelling by examining L-Sox5 and type II collagen expressions in condylar cartilage.

DESIGN

40 female Sprague-Dawley rats at age of 5 weeks were randomly divided into the experimental (n=20) and control groups (n=20). Bite plates were fitted on the upper posterior teeth of the experimental animals to induce functional repositioning of mandible in vertical dimension. The animals in both experimental and matched control groups were sacrificed on days 3, 6, 9 and 12, respectively. Tissue sections were cut in the sagittal plane through the mandibular condyles and processed with histomorphological examination for cellular response and immunohistochemical test for expressions of L-Sox5 and type II collagen. Quantitative assessment was conducted with computer-assisted imaging system to reveal the correlation between these two factors.

RESULTS

(1) Both L-Sox5 and type II collagen were expressed in prechondroblastic cells and chondroblastic cells. (2) When mandible was downward positioned, the amount of L-Sox5 expression was significantly higher by 16.1% (day 9) and 24.2% (day 12) than that of the control (P<0.05); Similarly, type II collagen expression in the experimental group was also significantly stronger by 9.3% (day 9) and 12.3% (day 12) than control group (P<0.05), indicating an enhanced osteogenic transition occurring in condylar cartilage. (3) There was a similarity in temporospatial patterns between the expressions of these two factors, indicating their integral functions in facilitating condylar adaptation.

CONCLUSIONS

It is suggested that L-Sox5 plays a key role in adaptive remodelling of condylar cartilage resulting from downward positioning of the mandible. Integration with type II collagen enables L-Sox5 to induce osteogenic transition and consequently to encourage endochondral ossification.

Sox6 is required for normal fiber type differentiation of fetal skeletal muscle in mice

Sox6, a member of the Sox family of transcription factors, is highly expressed in skeletal muscle. Despite its abundant expression, the role of Sox6 in muscle development is not well understood. We hypothesize that, in fetal muscle, Sox6 functions as a repressor of slow fiber type-specific genes. In the wild-type mouse, differentiation of fast and slow fibers becomes apparent during late fetal stages (after approximately embryonic day 16). However, in the Sox6 null-p(100H) mutant mouse, all fetal muscle fibers maintain slow fiber characteristics, as evidenced by expression of the slow myosin heavy chain MyHC-beta. Knockdown of Sox6 expression in wild-type myotubes results in a significant increase in MyHC-beta expression, supporting our hypothesis. Analysis of the MyHC-beta promoter revealed a Sox consensus sequence that likely functions as a negative cis-regulatory element. Together, our results suggest that Sox6 plays a critical role in the fiber type differentiation of fetal skeletal muscle.

Mice deficient for RNA-binding protein brunol1 show reduction of spermatogenesis but are fertile

RNA-binding proteins are involved in post-transcriptional processes like mRNA stabilization, alternative splicing, and transport. Brunol1 is a novel mouse gene related to elav/Bruno family of genes encoding for RNA-binding proteins. We report here the expression and functional analysis of murine Brunol1. Expression analysis of Brunol1 during embryogenesis by RT-PCR showed that Brunol1 expression starts at 9.5 dpc and continues to the later stages of embryonic development. In adult mice, the Brunol1 expression is restricted to brain and testis. We also analyzed the Brunol1 expression in testes of different mutants with spermatogenesis defects: W/W(V), Tfm/y, Leyl(-/-), olt/olt, and qk/qk. Brunol1 transcript was detectable in Leyl(-/-), olt/olt, and qk/qk mutant but not in W/W(V) and Tfm/y mutants. We also showed by transfection of a fusion protein of green fluorescent protein and Brunol1 protein into NIH3T3 cells, that Brunol1 is localized in cytoplasm and nucleus. In order to elucidate the function of the Brunol1 protein in spermatogenesis, we disrupted the Brunol1 locus in mouse by homologous recombination, which resulted in a complete loss of the Brunol1 transcript. Male and female Brunol1(+/-) and Brunol1(-/-) mice from genetic backgrounds C57BL/6J x 129/Sv hybrid and 129X1/SvJ when inbred exhibited normal phenotype and are fertile, although the number and motility of sperms are significantly reduced. An intensive phenotypic analysis showed no gross abnormalities in testis morphology. Collectively our results demonstrate that Brunol1 might be nonessential protein for mouse embryonic development and spermatogenesis.

A microarray for microRNA profiling in mouse testis tissues

MicroRNAs (miRNAs) are short non-coding RNA molecules playing regulatory roles by repressing translation or cleaving RNA transcripts. Recent studies indicate that miRNAs are mechanistically involved in the development of mammalian spermatogenesis. However, little work has been done to compare the miRNA expression patterns between immature and mature mouse testes. Here, we employed a miRNA microarray to detect 892 miRNAs in order to evaluate the expression patterns of miRNA. The expression of 19 miRNAs was significantly different between immature and mature individuals. Fourteen miRNAs were significantly upregulated and five miRNAs were downregulated in immature mice and this result was further confirmed by a quantitative real-time RT-PCR assay. Many target genes involved in spermatogenesis are predicted by MiRscan performing miRNA target scanning. Our data indicated specific miRNAs expression in immature mouse testis and suggested that miRNAs have a role in regulating spermatogenesis.

Control of cell fate and differentiation by Sry-related high-mobility-group box (Sox) transcription factors

Maintain stemness, commit to a specific lineage, differentiate, proliferate, or die. These are essential decisions that every cell is constantly challenged to make in multi-cellular organisms to ensure proper development, adult maintenance, and adaptability. SRY-related high-mobility-group box (Sox) transcription factors have emerged in the animal kingdom to help cells effect such decisions. They are encoded by 20 genes in humans and mice. They share a highly conserved high-mobility-group box domain that was originally identified in SRY, the sex-determining gene on the Y chromosome, and that has derived from a canonical high-mobility-group domain characteristic of chromatin-associated proteins. The high-mobility-group box domain binds DNA in the minor groove and increases its DNA binding affinity and specificity by interacting with many types of transcription factors. It also bends DNA and may thereby confer on Sox proteins a unique and critical role in the assembly of transcriptional enhanceosomes. Sox proteins fall into eight groups. Most feature a transactivation or transrepression domain and thereby also act as typical transcription factors. Each gene has distinct expression pattern and molecular properties, often redundant with those in the same group and overlapping with those in other groups. As a whole the Sox family controls cell fate and differentiation in a multitude of processes, such as male differentiation, stemness, neurogenesis, and skeletogenesis. We review their specific molecular properties and in vivo roles, stress recent advances in the field, and suggest directions for future investigations.

Stem cell transplantation demonstrates that Sox6 represses εy globin expression in definitive erythropoiesis of adult mice

Sox6, a member of the Sox transcription factor family, is essential for the silencing of epsilon y globin gene expression in definitive erythropoiesis of mice. Homozygous Sox6-null mice are neonatally lethal, precluding analysis at later stages. We created adult mice that are deficient in Sox6 specifically in hematopoietic tissues by transplanting embryonic liver stem cells from Sox6-deficient mice into lethally irradiated congenic wild-type adult mice. The mice receiving mutant stem cells (mutant engrafted) showed high expression levels of epsilon y in bone marrow, spleen, and circulating blood compared with mice receiving wild-type and heterozygous stem cells (control engrafted). The level of expression of epsilon y in circulating blood was directly correlated with the percentage of successful mutant donor cell engraftment. Additionally, the mutant engrafted adult mice showed an increase in erythroid precursor cells in bone marrow, spleen, and blood. Thus, Sox6 continues to function as a major regulator of epsilon y in adult definitive erythropoiesis and is required for normal erythrocyte maturation. Therefore, Sox6 may provide a novel therapeutic target by reactivating epsilon y in patients with hemoglobinopathies such as sickle cell anemia and beta-thalassemia.

Preferential expression and frequent IgG responses of a tumor antigen, SOX5, in glioma patients

We previously reported to identify SOX5 as a glioma antigen by serological screening using a testis cDNA library. The present study was designed to analyze SOX5 expression, its immunoreactivity, and the correlation between SOX5 IgG responses and clinical features in glioma patients to evaluate the possibility of its use as a diagnostic marker. Quantitative RT-PCR and Western blot analysis revealed that SOX5 was expressed in glioma tissues, but not in normal adult tissues, except in the testis. An immunohistochemical analysis showed that SOX5 was expressed in glioma cells, but only a few SOX5-positive cells were detected in non-neoplastic tissues from the cerebral cortex. IgG antibodies against SOX5 were detected in sera from 8 of the 27 glioma patients (27.6%), 0 of the 14 patients with other brain diseases (0%), 1 of the 54 other cancer patients (1.9%) and 1 of the 37 healthy individuals (2.7%). Patients with glioblastoma (GBM) who showed IgG responses against SOX5 exhibited significantly better survival periods than GBM patients without SOX5 antibodies. In summary, SOX5 is aberrantly expressed in glioma and can be recognized as a glioma antigen using IgGs from the sera of glioma patients. Furthermore, there is a statistically significant correlation between the presence of SOX5 IgGs and survival in GBM patients, suggesting that the glioma antigen SOX5 may be useful not only as a diagnostic marker, but also as a prognostic marker in glioma patients.

Role of retinoic acid in the differentiation of embryonal carcinoma and embryonic stem cells

Retinoic acid (RA), the most potent natural form of vitamin A, plays an important role in many diverse biological processes such as embryogenesis and cellular differentiation. This chapter is a review of the mechanism of action of RA and the role of specific RA-regulated genes during the cellular differentiation of embryonal carcinoma (EC) and embryonic stem (ES) cells. RA acts by binding to its nuclear receptors and inducing transcription of specific target genes. The most studied mouse EC cell lines include F9 cells, which can be induced by RA to differentiate into primitive, parietal, and visceral endodermal cells; and P19 cells, which can differentiate to endodermal and neuronal cells upon RA treatment. ES cells can be induced to differentiate into a number of different cell types; many of which require RA treatment. Over the years, many RA-regulated genes have been discovered in EC and ES cells using a diverse set of techniques. Current research focuses on the elucidation how these genes affect differentiation in EC and ES cells using a variety of molecular biology approaches. However, the exact molecule events that lead from a pluripotent stem cell to a fully differentiated cell following RA treatment are yet to be determined.

Sox6 cell-autonomously stimulates erythroid cell survival, proliferation, and terminal maturation and is thereby an important enhancer of definitive erythropoiesis during mouse development

Erythropoiesis, the essential process of hematopoietic stem cell development into erythrocytes, is controlled by lineage-specific transcription factors that determine cell fate and differentiation and by the hormone erythropoietin that stimulates cell survival and proliferation. Here we identify the Sry-related high-mobility-group (HMG) box transcription factor Sox6 as an important enhancer of definitive erythropoiesis. Sox6 is highly expressed in proerythroblasts and erythroblasts in the fetal liver, neonatal spleen, and bone marrow. Mouse fetuses and pups lacking Sox6 develop erythroid cells slowly and feature misshapen, short-lived erythrocytes. They compensate for anemia by elevating the serum level of erythropoietin and progressively enlarging their erythropoietic tissues. Erythroid-specific inactivation of Sox6 causes the same phenotype, demonstrating cell-autonomous roles for Sox6 in erythroid cells. Sox6 potentiates the ability of erythropoietin signaling to promote proerythroblast survival and has an effect additive to that of erythropoietin in stimulating proerythroblast and erythroblast proliferation. Sox6 also critically facilitates erythroblast and reticulocyte maturation, including hemoglobinization, cell condensation, and enucleation, and ensures erythrocyte cytoskeleton long-term stability. It does not control adult globin and erythrocyte cytoskeleton genes but acts by stabilizing filamentous actin (F-actin) levels. Sox6 thus enhances erythroid cell development at multiple levels and thereby ensures adequate production and quality of red blood cells.

Slow and fast fiber isoform gene expression is systematically altered in skeletal muscle of the Sox6 mutant, p100H

We have previously demonstrated that p100H mutant mice, which lack a functional Sox6 gene, exhibit skeletal and cardiac muscle degeneration and develop cardiac conduction abnormalities soon after birth. To understand the role of Sox6 in skeletal muscle development, we identified muscle-specific genes differentially expressed between wild-type and p100H mutant skeletal muscles and investigated their temporal expression in the mutant muscle. We found that, in the mutant skeletal muscle, slow fiber and cardiac isoform genes are expressed at significantly higher levels, whereas fast fiber isoform genes are expressed at significantly lower levels than wild-type. Onset of this aberrant fiber type-specific gene expression in the mutant coincides with the beginning of the secondary myotube formation, at embryonic day 15-16 in mice. Together with our earlier report, demonstrating early postnatal muscle defects in the Sox6 null-p100H mutant, the present results suggest that Sox6 likely plays an important role in muscle development.

Sox6 directly silences epsilon globin expression in definitive erythropoiesis

Sox6 is a member of the Sox transcription factor family that is defined by the conserved high mobility group (HMG) DNA binding domain, first described in the testis determining gene, Sry. Previous studies have suggested that Sox6 plays a role in the development of the central nervous system, cartilage, and muscle. In the Sox6-deficient mouse, p100H, epsilony globin is persistently expressed, and increased numbers of nucleated red cells are present in the fetal circulation. Transfection assays in GM979 (erythroleukemic) cells define a 36-base pair region of the epsilony proximal promoter that is critical for Sox6 mediated repression. Electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assays demonstrate that Sox6 acts as a repressor by directly binding to the epsilony promoter. The normal expression of Sox6 in wild-type fetal liver and the ectopic expression of epsilony in p100H homozygous fetal liver demonstrate that Sox6 functions in definitive erythropoiesis. The present study shows that Sox6 is required for silencing of epsilony globin in definitive erythropoiesis and suggests a role for Sox6 in erythroid cell maturation. Thus, Sox6 regulation of epsilony globin might provide a novel therapeutical target in the treatment of hemoglobinopathies such as sickle cell anemia and thalassemia.

Generation of mice harboring aSox6 conditional null allele

Sox6 belongs to the family of Sry-related HMG box transcription factors, which determine cell fate and differentiation in various lineages. Sox6 is expressed in several tissues, including cartilage, testis, neuronal, and erythropoietic tissues. Mice lacking Sox6 have revealed critical roles for Sox6 in several of these tissues, but their multiple defects and early lethality has limited studies in specific cell types and in postnatal mice. We show here that we have generated mice harboring a Sox6 conditional null allele (Sox6(fl+)) by flanking the second coding exon with loxP sites. This allele encodes wildtype Sox6 protein, is expressed normally, and is efficiently converted into a null allele (Sox6(fl-)) by Cre-mediated recombination in somatic and germ cells. Sox6(fl+/fl+) mice are indistinguishable from wildtype mice, and Sox6(fl-/fl-) mice from Sox6(-/-) mice. These Sox6 conditional null mice will thus be valuable for further uncovering the roles of Sox6 in various processes in vivo.

Regulation of Id2 expression by CCAAT/enhancer binding protein beta

Mice deficient for Id2, a negative regulator of basic helix–loop–helix (bHLH) transcription factors, exhibit a defect in lactation due to impaired lobuloalveolar development during pregnancy, similar to the mice lacking the CCAAT enhancer binding protein (C/EBP) β. Here, we show that Id2 is a direct target of C/EBPβ. Translocation of C/EBPβ into the nucleus, which was achieved by using a system utilizing the fusion protein between C/EBPβ and the ligand-binding domain of the human estrogen receptor (C/EBPβ-ERT), demonstrated the rapid induction of endogenous Id2 expression. In reporter assays, transactivation of the Id2 promoter by C/EBPβ was observed and, among three potential C/EBPβ binding sites found in the 2.3 kb Id2 promoter region, the most proximal element was responsible for the transactivation. Electrophoretic mobility shift assay (EMSA) identified this element as a core sequence to which C/EBPβ binds. Chromatin immunoprecipitation (ChIP) furthermore confirmed the presence of C/EBPβ in the Id2 promoter region. Northern blotting showed that Id2 expression in C/EBPβ-deficient mammary glands was reduced at 10 days post coitus (d.p.c.), compared with that in wild-type mammary glands. Thus, our data demonstrate that Id2 is a direct target of C/EBPβ and provide insight into molecular mechanisms underlying mammary gland development during pregnancy.

Immunohistochemical analysis of SOX6 expression in human brain tumors

We previously demonstrated that the developmentally regulated gene, SOX6, is strongly expressed in glioma cells and in the fetal brain, but only faintly in the normal adult brain. Recent studies have indicated that brain tumor cells may share antigens, signaling systems, and behavior with neural stem/progenitor cells. To test the validity of this proposition, we analyzed the expression of SOX6 in various human central nervous system (CNS) tumors. Immunohistochemical analysis revealed that astrocytic and oligodendroglial tumors expressed SOX6; neuronal-glial cell tumors (central neurocytoma) and embryonal tumors (medulloblastoma), which arise from multipotential stem cell precursors, also showed a high intensity of SOX6 staining. In contrast, ependymal tumors (ependymoma and subependymoma), meningioma, and schwannoma, which are all well differentiated tumors, showed either no staining or only faint staining for SOX6. These results suggest that SOX6 may be expressed in bipotential or multipotential cells capable of neuronal and glial differentiation, but not in fully differentiated cells. SOX6 may be a useful marker for the diagnosis of tumors arising from immature bipotential cells that may differentiate into neuronal and glial cells.

Expression of a transcriptional factor, SOX6, in human gliomas

By screening a human testis cDNA library with glioma patients' sera, we isolated a transcriptional factor, SOX6. Here, we analyzed SOX6 expression in gliomas having a range of malignancy grades using immunostaining. Murine Sox6 is a transcriptional factor that is specifically expressed in the developing central nervous system and in the early stages of chondrogenesis in mouse embryos. The reverse transcription-polymerase chain reaction (RT-PCR) revealed that the SOX6 gene was more highly expressed in glioma tissues and fetal brain than in normal adult brain and other cancer cells, except melanoma cells. Immunohistochemical analysis with the anti-SOX6 antibody showed that all the glioma tissues analyzed (14 glioblastomas, 14 anaplastic astrocytomas, 3 anaplastic oligoastrocytomas, 5 diffuse astrocytomas, 1 oligodendroglioma, and 1 pilocytic astrocytoma) expressed SOX6 in tumor cells, but only a few SOX6-positive cells were detected in nonneoplastic tissues from the cerebral cortex. These results indicate that the developmentally regulated transcription factor SOX6 may be a potential diagnostic marker for gliomas.

Suppression of Sox6 in P19 cells leads to failure of neuronal differentiation by retinoic acid and induces retinoic acid-dependent apoptosis

The Sox6 gene is a member of the Sox gene family, which encodes transcription factors, and previous studies have suggested that it plays an important role in the development of the central nervous system. Aggregation of embryonic carcinoma P19 cells with retinoic acid (RA) results in the development of neurons, glia, and fibroblast-like cells. Sox6 mRNA increases rapidly in P19 cells during RA induction and then decreases during differentiation into neuronal cells. To investigate whether Sox6 expression is essential for neuronal differentiation, we established Sox6-suppressed P19 (P19[anti-Sox6]) cells by transfection of antisense-Sox6 cDNA. Most of the P19[anti-Sox6] cells showed no neurites and were not stained by the anti-MAP 2 antibody, while the suppression of Sox6 expression nearly totally blocked neuronal differentiation in P19 cells. Further, Sox6 suppression caused RA-dependent apoptosis by P19[anti-Sox6] cells: RA-treated P19[anti-Sox6] cells showed chromatin condensation, DNA fragmentation, and an increase in caspase-3-like activity. Thus, Sox6 is considered essential for neuronal differentiation and may play an important role in the early stages of neuronal differentiation or apoptosis.

Sox6 overexpression causes cellular aggregation and the neuronal differentiation of P19 embryonic carcinoma cells in the absence of retinoic acid

The Sox6 gene is a member of the Sox gene family that encodes transcription factors. Previous studies have suggested that Sox6 plays an important role in the development of the central nervous system. Aggregation of embryonic carcinoma P19 cells with retinoic acid (RA) results in the development of neurons, glia and fibroblast-like cells. In this report, we have shown that Sox6 mRNA increased rapidly in P19 cells during RA induction and then decreased during the differentiation of P19 into neuronal cells. To explore the possible roles of Sox6 during this process, stably Sox6-overexpressing P19 cell lines (P19[Sox6]) were established. These P19[Sox6] had acquired both characteristics of the wild-type P19 induced by RA. First, P19[Sox6] cells showed a marked cellular aggregation in the absence of RA. Second, P19[Sox6] could differentiate into microtubule-associated protein 2 (MAP2)-expressing neuronal cells in the absence of RA. Sox6 expression could cause the activation of endogenous genes including the neuronal transcription factor Mash-1, the neuronal development-related gene Wnt-1, the neuron-specific cell adhesion molecule N-cadherin, and the neuron-specific protein MAP2, resulting in neurogenesis. Moreover, E-cadherin, a major cell adhesion molecule of wild-type P19, was strongly induced by Sox6, resulting in cellular aggregation without RA. Thus Sox6 may play a critical role in cellular aggregation and neuronal differentiation of P19 cells.

Identification of a human glioma antigen, SOX6, recognized by patients' sera

To identify tumor antigens for glioma, a human testis cDNA library was screened by serological identification of antigens by recombinant expression cloning with sera from glioma patients. In this screening, the most frequently isolated antigen was SOX6, an Sry-related high-mobility group (HMG) box-containing gene. SOX6 is a transcriptional factor that is specifically expressed in the developing central nervous system and in the early stages of chondrogenesis in mouse embryos. IgG antibodies against SOX6 were detected in sera from 12 of 36 glioma patients (33.3%), 0 of 14 patients with other brain disease (0%), and one of 54 other cancer patients (1.9%). In sera from 37 healthy individuals, no IgG responses against SOX6 were detected, except in an elderly female. Furthermore, Western blot and ELISA analyses with sera from glioma patients revealed that the DNA-binding domain, the HMG box of SOX6, might be a dominant epitope of IgGs against SOX6. RT-PCR and Northern blot analysis revealed that the SOX6 gene was more highly expressed in glioma tissues than in normal adult tissues, except testis. Western blot analysis with an anti-SOX6 antibody demonstrated that the SOX6 protein was expressed in glioma tissues, but not in normal adult brain tissue. Immunohistochemical analysis with the anti-SOX6 antibody showed that all the glioma tissues analysed expressed SOX6 in tumor cells, but only a few SOX6-positive cells were detected in non-neoplastic tissues from the cerebral cortex. In summary, these results indicate that the developmentally regulated transcription factor SOX6 is aberrantly expressed in glioma and specifically recognized by IgGs from glioma patients' sera.

Sox6 regulation of cardiac myocyte development

A mouse mutation (p100H/p100H) has been identified that is associated with cardioskeletal myopathy, heart block, delayed growth and early postnatal death. The gene that is disrupted in this mutation encodes the transcription factor Sox6. P19CL6 cells were used as an in vitro cardiomyocyte differentiation system and revealed that Sox6 is expressed exclusively when the cells are committed to differentiate to beating cardiac myocytes. We used the yeast two-hybrid system to identify the Prtb (Proline-rich transcript of the brain) protein as a Sox6 interactor, and subsequently confirmed the interaction by co-immunoprecipitation. Prtb expression in P19CL6 cells increased with differentiation to beating cardiomyocytes. Using the P19CL6 cells stably transfected with noggin, an antagonist of BMP (Bone Morphogenic Protein), we found that BMP expression is required for Sox6 expression in cardiomyocyte differentiation. Surprisingly, the expression of the alpha1c-subunit gene of the L-type Ca2+ channel decreased in P19CL6 cells as they differentiated to beating cardiac cells. Ectopic expression of Sox6 or Prtb alone in P19CL6 cells caused down-regulation of L-type Ca2+ alpha1c expression, but when Sox6 and Prtb were co-transfected to the cells, L-type Ca2+ alpha1c remained at basal levels. A similar relationship of Sox6 and L-type Ca2+ alpha1c expression was seen in vivo (comparing wild-type and p(100H)/p(100H) mutant mice). Thus, Sox6 is within the BMP pathway in cardiac differentiation, interacts with Prtb and may play a critical role in the regulation of a cardiac L-type Ca2+ channel.

Molecular cloning and expression of Sox17 in gonads during sex reversal in the rice field eel, a teleost fish with a characteristic of natural sex transformation

The Sox is a large family of genes which encode transcription factors with high-mobility-group DNA binding domain related to the SRY, with diverse roles in development, and a few of them are involved in sex determination and differentiation. We report here the identification of Sox17 gene of the rice field eel, a teleost fish with a characteristic of natural sex transformation. This gene, located on chromosome 5, consists of two exons which encode a 399-amino acid protein with a conserved HMG box. Phylogenetic analysis shows that the rice field eel Sox17 fits within the Sox17 clade of vertebrates. The rice field eel Sox17 was dominantly expressed in gonads of male, female, and intersex, besides in brain and spleen. Gene expression analysis by in situ hybridization showed its expression in testis, ovary, and ovotestis, and specifically in the gonadal lamellae of ovary, ovotestis, and testis and developing spermatogenic cells of testis, suggesting that they have potentially important roles in gonadal differentiation during sex reversal in this species.

Mouse mu opioid receptor distal promoter transcriptional regulation by SOX proteins

We have identified transcription factors that bind to specific sequences in 5'-distal promoter regulatory sequences of the mouse mu opioid receptor (mor) promoter using the yeast one-hybrid system. The sequence between -746 and -707 in mor distal promoter was used as the bait because it acts as a functional promoter element and binds several DNA-binding proteins. From an adult mouse brain cDNA library, five cDNA clones encoding three Sox gene family (Sry like high mobility group (HMG) box gene) transcriptional factors, mSOX18, mSOX21, and mSOX6, were isolated. Electrophoretic mobility shift assays confirmed the presence of a binding site for SOX proteins in the -731/-725 region. Additionally, we have also established that the flanking regions outside the core Sox-binding site play an essential role in high affinity binding. DNase I footprint analysis indicates that proteins from mouse brain interact with the Sox-binding site within the mor distal promoter. Finally, we demonstrated that overexpression of mSOX18 and/or mSOX21 was able to up-regulate mouse mor distal promoter activity in mor-expressing neuronal cells (NMB). These data indicate that SOX proteins might contribute to the transcriptional activity of the mor gene and suggest that mu opioid receptor could mediate some of the developmental processes in which SOX proteins are included.

Regulation of IkappaBbeta expression in testis

IkappaBalpha and IkappaBbeta are regulators of the nuclear factor-kappaB (NF-kappaB) transcription factor family. Both IkappaBs bind to the same NF-kappaB dimers and are widely expressed in different cells and tissues. To better understand how these two IkappaB isoforms differ biologically, we have characterized the expression of IkappaBbeta in testis, a tissue in which IkappaBalpha is only minimally expressed. We have found that IkappaBbeta expression is localized within the haploid spermatid stages of spermatogenesis and follows the expression of nuclear NF-kappaB. IkappaBbeta expression in haploid spermatids is likely regulated by Sox family proteins, members of which are also expressed within spermatids. We have shown that both SRY and Sox-5 can bind to multiple Sox binding sites found within the IkappaBbeta promoter and can enhance transcription of a reporter gene in transient transfection assays. We also demonstrate that IkappaBbeta mRNA is strongly expressed in developing male gonads. These results therefore suggest that IkappaBbeta may be a novel target for transcription factors of the HMG-box SRY/Sox family and imply a potential role for NF-kappaB/IkappaBbeta in spermatogenesis.

Identification and characterization of the human long form of Sox5 (L-SOX5) gene

The Sox (Sry-type HMG box) group of transcription factors, which is defined by a high-mobility group (HMG) DNA-binding domain, is categorized into six subfamilies. Sox5 and Sox6 belong to the group D subfamily, which is characterized by conserved N-terminal domains including a leucine-zipper, a coiled-coil domain and a Q-box. Group D Sox genes are expressed as long and short transcripts that exhibit differential expression patterns. In mouse, the long form of Sox5, L-Sox5, is co-expressed and interacts with Sox6; together, these two proteins appear to play a key role in chondrogenesis and myogenesis. In humans, however, only the short form of Sox5 has previously been identified. To gain insight into Sox5 function, we have identified and characterized human L-SOX5. The human L-SOX5 cDNA encodes a 763-amino-acid protein that is 416 residues longer than the short form and contains all of the characteristic motifs of group D Sox proteins. The predicted L-SOX5 protein shares 97% amino acid identity with its mouse counterpart and 59% identity with human SOX6. The L-SOX5 gene contains 18 exons and shows similar genomic structure to SOX6. We have identified two transcription start sites in L-SOX5 and multiple alternatively spliced mRNA variants that are distinct from the short form. Unlike the short form, which shows testis-specific expression, L-SOX5 is expressed in multiple tissues. Like SOX6, L-SOX5 shows strong expression in chondrocytes and striated muscles, indicating a likely role in human cartilage and muscle development.

Testis-specific HMG-domain protein alters the responses of cells to cisplatin

Cisplatin is an effective agent for the treatment of testicular cancer. In the present study with mouse testicular teratocarcinoma cell extracts, we observed a deficiency in nucleotide excision repair (NER) of a DNA probe bearing a cisplatin 1,2-d(GpG) intrastrand cross-link. In contrast, repair of the cisplatin 1,3-d(GpTpG) intrastrand cross-link was still active in these cell extracts. A current working hypothesis is that complexes of HMG-domain proteins with the major cisplatin 1,2-intrastrand cross-links could enhance cisplatin cytotoxicity by blocking repair of these lesions on the genome. The family of HMG-domain proteins include a testis-specific protein, tsHMG, which might account for the altered NER in testicular cells. To test this possibility, a human cervical carcinoma cell line (HeLa) was constructed which ectopically expressed tsHMG under the control of an inducible promoter. Microscopic examination of tsHMG expression and cisplatin-induced apoptosis on a cellular level revealed that the nuclear protein did indeed modulate the cytotoxic consequences of cisplatin treatment. Also, tsHMG enhanced transcription inhibition by cisplatin. These results reveal that an HMG-domain protein can affect cellular responses to cisplatin and may be relevant to the clinical observation that cancer cells in specific tissues are particularly sensitive to cisplatin.

cDNA cloning of the Sry-related gene Sox6 from rat with tissue-specific expression

A cDNA encoding rat homologue of the previously characterized mouse Sox6 was isolated by a polymerase chain reaction (PCR) cloning strategy. Comparison of this eDNA with homologous mouse, human and rainbow trout cDNA exhibited an overall amino acid sequence identity of 99.6, 89.3 and 76.3% respectively. The leucine-zipper and HMG-box motif were almost completely conserved between these homologues. The expression of Sox6 was determined in rat by Northern hybridization and Real-time quantitative reverse transcription (RT)-PCR. rSox6 (rat Sox6) was specifically expressed in the neonatal brain and adult testis with Northern blotting. Real-time quantitative RT-PCR for the determination of Sox6 mRNA was examined. The rSox6 was expressed in the neonatal brain and adult testis as well as by Northern blotting and also expressed in the adult eyeball and slightly in the ovary.

Expression and characterization of Xenopus laevis SRY-related cDNAs, xSox17alpha1, xSox17alpha2, xSox18alpha and xSox18beta

Sox is a large family of genes related to the sex-determining region Y gene (designated as the SRY gene). Sox genes encoding DNA-binding transcriptional factors are found in many animals and are involved in developmental events. In this study, we newly isolated and sequenced novel Sox cDNAs from African clawed frog (Xenopus laevis). Five clones isolated here were classified into four distinct Sox genes designated as xSox17alpha1, xSox17alpha2, xSox18alpha and xSox18beta. All four belong to a subtype of SOX family, type F. The cDNA xSox17alpha1 contains essentially the same nucleotide sequence as that identified as Sox17alpha in a previous work (Cell 91 (1997) 397), whereas xSox17alpha2 is a distinct gene with high homology to xSox17alpha1. The clones, xSox18alpha and xSox18beta, are highly homologous to each other over the entire nucleotide sequences. The xSox18alpha and xSox18beta genes encode 363 and 361 amino acids, respectively. Genomic Southern hybridization analysis showed the existence of two copies of the xSox18. Northern analysis indicated that the xSox18 gene was expressed in the spleen and kidney and the size of the transcript was estimated to be 2.4 knt. Electrophoretic mobility shift assays indicated that recombinant xSox18 polypeptide was capable of binding to the HMG consensus nucleotide sequence, AACAAT.

A direct role of SRY and SOX proteins in pre-mRNA splicing

The mammalian testis determining factor SRY and its related Sox factors are critical developmental regulators. They share significant similarity in their high mobility group (HMG) domain and display discrete patterns of tissue-specific expression. Here we show that SRY and the Sox protein SOX6 colocalize with splicing factors in the nucleus and are dynamically redistributed following the blockage of splicing in living cells. Anti-SOX6 antibodies supershift the spliceosomal complex from assembled splicing reactions and inhibit splicing in vitro of multiple pre-mRNA substrates. Most importantly, SOX6-depleted nuclear extracts have impaired splicing activity, which is efficiently restored by addition of the recombinant SOX6 HMG domain and also by recombinant SRY and the SOX9 HMG domain. These results reveal an unexpected biological function of the SRY, SOX6, and SOX9 gene products and provide a functional link to the biochemical mechanisms operating in mammalian sex determination and in other developmental processes regulated by Sox genes.

Spatially precise DNA bending is an essential activity of the sox2 transcription factor

Sox proteins, a subclass of high mobility group box proteins, govern cell fate decisions by acting both as classical transcription factors and architectural components of chromatin. We aimed to demonstrate that the DNA bending activity of Sox proteins is essential to regulate gene expression. We focused on mouse Sox2, which participates in the transactivation of the Fgf4 (fibroblast growth factor 4) gene in the inner cell mass of the blastocyst. We generated six substitutions in the high mobility group box of Sox2. One mutant showed a reduced DNA bending activity on the Fgf4 enhancer (46 degrees instead of 80 degrees), which resulted in more powerful transactivation compared with the wild type protein. We then selected two single-base mutations in the Fgf4 enhancer that make the DNA less bendable by the Sox2 protein. Again, a different DNA bend (0 degrees and 42 degrees instead of 80 degrees) resulted in a different activation of transcription, but in this case reduced bending corresponded to decreased transcription. We found that the opposite effect on transcription of similar DNA bending angles is due to a 20 degrees difference in the relative orientation of the DNA bends, proving that a correct three-dimensional geometry of enhanceosome complexes is necessary to promote transcription.

Embryonic abnormalities from misexpression of cNSCL1

cNSCL1 encodes a bHLH transcription factor and is specifically expressed in the developing nervous system. We used a replication-competent retrovirus to drive misexpression of cNSCL1 in chick embryos. We found that cNSCL1 misexpression was embryonic lethal and the embryos exhibited gross abnormalities. Many skeletal bones were abnormal and some were completely absent. Expression of BMP4 was reduced. The abnormalities were due to cNSCL1 misexpression in the systemic region, since microinjection of cNSCL1 retrovirus at one hindlimb primordium severely retarded its development, while other limbs on the same animal appeared normal. Similar misexpression of cNSCL2, a closely related bHLH gene, did not produce these phenotypes. Thus, the detrimental effects on embryonic development were specific to cNSCL1. These data indicate that cNSCL1 expression must be tightly regulated during development.

SOX6 binds CtBP2 to repress transcription from the Fgf-3 promoter

Fgf-3 is expressed in a complex pattern during mouse development. Previously, an essential regulatory element PS4A was identified in the promoter region, and shown to bind at least three factors. To identify the transcription factor(s), we used a yeast one-hybrid screen and obtained a novel Sox6 cDNA (SOX6D). When introduced into cells it strongly repressed activity from both an Fgf-3 reporter gene as well as an artificial promoter containing three PS4A elements. In situ hybridisation analysis showed that Sox6 and Fgf-3 are co-expressed in the otic vesicle of E9.5 mouse embryos in a mutually exclusive pattern, consistent with a repression of Fgf-3 transcription by SOX6. To characterise additional factor(s) involved in Fgf-3 gene repression, a yeast two-hybrid screen was used with the N-terminal portion of SOX6D. Mouse CtBP2 cDNA clones were isolated and shown to bind SOX6 in yeast and mammalian cells. Furthermore, mutational analysis of SOX6 showed that binding to CtBP2, and its responsiveness to this co-repressor, were dependent on a short amino acid sequence motif PLNLSS. Co-expression studies in NIH3T3 cells showed that SOX6 and CtBP2 co-operate to repress activity from the Fgf-3 promoter through the enhancer element PS4A. These results show that SOX6 can recruit CtBP2 to repress transcription from the Fgf-3 promoter.

Transcriptional modulation of mouse mu-opioid receptor distal promoter activity by Sox18

Previously, we reported the presence of dual promoters, referred to as distal (DP) and proximal, with a negative regulatory element between them in the mouse mu-opioid receptor (mor) gene. Here we have identified a positive regulatory element influencing mor DP transcription, which contains multiple consensus binding motifs for Sox factors (sex-determining Sry-like high mobility group box-containing genes). In gel supershift assays, the Sox family member Sox18 bound directly to the multiple Sox consensus binding motifs of the mor DP enhancer. Overexpression of Sox18 cDNA increased luciferase activity regulated by the mor DP, and did so in a Sox18 concentration-dependent manner. In contrast, overexpression of another Sox member, Sox5, triggered no such trans-activation of mor DP-driven luciferase activity or DNA-protein binding activity. These results suggest that Sox18 directly and specifically stimulates mor gene expression, by trans-activating the mor DP enhancer.

Cloning, characterization and chromosome mapping of the human SOX6 gene

The Sox gene family encodes an important group of transcription factors harboring the conserved high-mobility group (HMG) box originally identified in the mouse and human testis determining gene Sry. We have cloned and sequenced SOX6, a member of the human Sox gene family. SOX6 cDNAs isolated from a human myoblast cDNA library show 94.3% amino acid identity to mouse Sox6 throughout the gene, and 100% identity in the critical HMG box and coiled-coil domains. The human SOX6 gene was localized to chromosome 11p15.2-11p15.3 in a region of shared synteny with distal mouse chromosome 7. An analysis of the genomic structure of the human SOX6 gene revealed 16 exons. We identified three SOX6 cDNAs that are generated by alternative splicing. Northern blot analysis revealed that SOX6 is expressed in a wide variety of tissues, most abundantly in skeletal muscle, suggesting an important role for SOX6 in muscle. Mice homozygous for a null mutation of Sox6 (p(100H)) die suddenly within the first 2 weeks after birth, most likely from cardiac conduction defects (Hagiwara et al., 2000). Thus, there is a possibility that human SOX6 is similarly involved in an, as yet, unidentified human cardiac disorder.

Testis hormone-sensitive lipase expression in spermatids is governed by a short promoter in transgenic mice

A testicular form of hormone-sensitive lipase (HSL(tes)), a triacylglycerol lipase, and cholesterol esterase, is expressed in male germ cells. Northern blot analysis showed HSL(tes) mRNA expression in early spermatids. Immunolocalization of the protein in human and rodent seminiferous tubules indicated that the highest level of expression occurred in elongated spermatids. We have previously shown that 0.5 kilobase pairs of the human HSL(tes) promoter directs testis-specific expression of a chloramphenicol acetyltransferase reporter gene in transgenic mice and determined regions binding nuclear proteins expressed in testis but not in liver (Blaise, R., Grober, J., Rouet, P., Tavernier, G., Daegelen, D., and Langin, D. (1999) J. Biol. Chem. 274, 9327-9334). Mutation of a SRY/Sox-binding site in one of the regions did not impair in vivo testis-specific expression of the reporter gene. Further transgenic analyses established that 95 base pairs upstream of the transcription start site were sufficient for correct testis expression. In gel retardation assays using early spermatid nuclear extracts, a germ cell-specific DNA-protein interaction was mapped between -46 and -29 base pairs. The DNA binding nuclear protein showed properties of zinc finger transcription factors. Mutation of the region abolished reporter gene activity in transgenic mice, showing that it is necessary for testis expression of HSL(tes).

A novel N-terminal domain directs membrane localization of mouse testis-specific calpastatin

Multiple isoforms of calpastatin have been identified with unique N-terminal regions followed by identical calpain inhibitory domains (II-IV). In many instances the isoforms are cell-type specific, although the precise functional differences among these N-terminal regions are largely unknown. Here we report a germ cell-specific isoform of calpastatin (tCAST) that consists of a novel N-terminal peptide of 40 amino acids (domain T) followed by domains II to IV of somatic calpastatin (sCAST). Domain T is responsible for membrane association of tCAST through a protein modification by myristylation. Mutation of the myristylation site eliminates membrane targeting. Unlike most of the isoforms of calpastatin that are generated through alternative RNA splicing or post-translational proteolysis, the testis-specific isoform is transcribed from an intronic promoter in haploid germ cells of the testis. The intronic promoter directs specific expression of a reporter transgene in developing germ cells of the mouse testis.

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.

Sox6 is a candidate gene for p100H myopathy, heart block, and sudden neonatal death

The mouse p locus encodes a gene that functions in normal pigmentation. We have characterized a radiation-induced mutant allele of the mouse p locus that is associated with a failure-to-thrive syndrome, in addition to diminished pigmentation. Mice homozygous for this mutant allele, p(100H), show delayed growth and die within 2 wk after birth. We have discovered that the mutant mice develop progressive atrioventricular heart block and significant ultrastructural changes in both cardiac and skeletal muscle cells. These observations are common characteristics described in human myopathies. The karyotype of p(100H) chromosomes indicated that the mutation is associated with a chromosome 7 inversion. We demonstrate here that the p(100H) chromosomal inversion disrupts both the p gene and the Sox6 gene. Normal Sox6 gene expression has been examined by Northern blot analysis and was found most abundantly expressed in skeletal muscle in adult mouse tissues, suggesting an involvement of Sox6 in muscle maintenance. The p(100H) mutant is thus a useful animal model in the elucidation of myopathies at the molecular level.

The pathway for perception and transduction of low-temperature signals in Synechocystis

Low temperature is an important environmental factor that has effects on all living organisms. Various low-temperature-inducible genes encode products that are essential for acclimation to low temperature, but low-temperature sensors and signal transducers have not been identified. However, systematic disruption of putative genes for histidine kinases and random mutagenesis of almost all the genes in the genome of the cyanobacterium Synechocystis sp. PCC 6803 have allowed us to identify two histidine kinases and a response regulator as components of the pathway for perception and transduction of low-temperature signals. Inactivation, by targeted mutagenesis, of the gene for each of the two histidine kinases and inactivation of the gene for the response regulator depressed the transcription of several lowtemperature-inducible genes.

Cloning and characterisation of the Sry-related transcription factor gene Sox8

SOX proteins form a large family of transcription factors related by a DNA-binding domain known as the HMG box. Some 30 Sox genes have been identified in mammals and orthologues have been found in a wide range of other metazoans. Sox genes are highly conserved and are known to play important roles in embryonic development, including roles in gonadal, central nervous system, neural crest and skeletal development. Several SOX genes have been implicated in human congenital diseases. We report here the isolation of Sox8 and its characterisation in mice and humans. This gene has a remarkably similar primary structure and genomic organisation to the campomelic dysplasia gene SOX9 and the Waardenburg-Shah syndrome gene SOX10. SOX8 protein is able to bind to canonical SOX target DNA sequences and activate transcription in vitro through two separate trans -activation regions. Further, Sox8 is expressed in the central nervous system, limbs, kidneys, gonads and craniofacial structures during mouse embryo development. Sox8 maps to the t complex on mouse chromosome 17 and to human chromosome 16p13.3, a region associated with the microphthalmia-cataract syndrome CATM and the alpha-thalassemia/mental retardation syndrome ATR-16.

Pituitary adenylate cyclase-activating polypeptide gene expression regulated by a testis-specific promoter in germ cells during spermatogenesis

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a member of the glucagon-related family of hormones that is widely expressed in various tissues. The PACAP messenger RNA (mRNA) and protein is expressed at high levels in the germ cells of the testis, where it locally activates cAMP-coupled receptors located in the somatic Sertoli cells. The PACAP mRNA expressed specifically in the testis is shorter than the mRNA expressed in hypothalamus and includes 127 nucleotides of novel sequence at the 5'-end, suggesting a different start site of transcription in the testes and the utilization of a tissue-specific promoter. Here we present evidence that a single PACAP gene uses a testis-specific promoter to express a mRNA containing a unique exon located 13.5 kb upstream from the first coding exon. As determined by RT-PCR analysis of testis mRNA, the expression of the first testis-specific exon is relatively specific for the testis, as no PACAP mRNA containing the testis-specific first exon was detected in hypothalamic mRNAs. The promoter for the testis-specific PACAP gene was cloned, and a start site for transcription was mapped by primer extension. The testis-specific promoter sequence directs germ cell-specific expression upon transfection of promoter-transcriptional reporter plasmids to populations of testicular cells in vitro and upon expression of a promoter-reporter transgene in mice. Analyses of PACAP gene expression during the spermatogenic cycle, accomplished by RT-PCR of segments of isolated seminiferous tubules, identified intense expression in the postmeiotic round spermatids during developmental stages I-VIII. These observations establish the existence of a specialized PACAP gene promoter whose activity is highly regulated during the spermatogenic cycle.

Expression and hormonal regulation of the Sox4 gene in mouse female reproductive tissues

The SOX genes define a family of transcriptional regulators whose diverse patterns and tightly controlled temporal profiles of expression suggest that they play key roles in determination of cell fate during development. One of the family members, Sox4, is expressed in the gonads of adult mice, but expression in the reproductive tissues has not been studied. As previous studies in this laboratory had shown that the SOX4 gene was regulated by ovarian hormones in breast cancer cells, murine Sox4 expression was analyzed in the reproductive tissues of mice by Northern blot analysis and ribonuclease protection assays. Sox4 mRNA expression was detected in the uterus and, at a lower level, in the mammary glands of pubertal and adult mice. Expression was modulated in the uterus of intact mice at various stages of the estrous cycle and was reduced by estradiol treatment of ovariectomized mice. Progesterone treatment partially reversed the estradiol effect. Although no modulation of Sox4 expression in the mammary glands was detected by Northern blot analysis, further evaluation of Sox4 protein expression at a cellular level is required. No modulation of Sox4 levels was observed in the thymus. The results presented here suggest that expression of the Sox4 gene is under ovarian hormone control in the uterus and implicate Sox4 in the complex effects controlled by ovarian hormones in the female reproductive system.

Isolation and characterization of a mouse SRY-related cDNA, mSox7

SOX is a family of SRY-related genes, which encode transcriptional factors involved in development. In this study, we newly isolated and sequenced mouse cDNA clones for mSox7. The mSox7 gene encodes 380 amino acids containing an SRY-type HMG box. Genomic Southern analysis suggested that the mSox7 gene was a single-copy gene. Tissue specific expression of mSox7 was investigated by Northern analysis. The expression was restricted to the ovary and heart, and the size of the transcripts was estimated to be 3.6 knt. Electrophoretic mobility shift assay indicated that recombinant mSox7 polypeptide was capable of binding to a nucleotide sequence, AACAAT. Immunohistochemical study revealed that mSox7 protein was localized in oocytes in the mouse ovary.

Trans-activation of the mouse cartilage-derived retinoic acid-sensitive protein gene by Sox9

The transcription factor Sox9 is capable of enhancing type II collagen gene expression and may play a crucial role in chondrogenesis. To determine whether Sox9 is an inducer of the chondrocyte phenotype, we investigated the role of Sox9 in transcription of another cartilage gene encoding the cartilage-derived retinoic acid-sensitive protein (CD-RAP). CD-RAP is specifically expressed during chondrogenesis. We show here that Sox9 protein is able to bind to a SOX consensus sequence in the CD-RAP promoter. Mutation of the SOX motif led to decreased transcription of a CD-RAP promoter construct in chondrocytes. Overexpression of SOX9 resulted in a dose-dependent increased activity of CD-RAP promoter-driven reporter gene in both chondrocytes and nonchondrogenic cells. A truncated SOX9, which contains a binding domain but no trans-activation function, inhibited CD-RAP promoter activity. Overexpression of SOX9 increased the level of endogenous CD-RAP mRNA in chondrocytes, but was unable to induce endogenous gene expression in 10T1/2 mesenchymal cells or BALB/c-3T3 fibroblasts. These results suggest that Sox9 is a general transcriptional regulator of cartilage-specific genes. However, Sox9 does not appear to be able to induce the chondrocyte phenotype in nonchondrogenic cells, implying that other factors are involved in chondrogenesis.

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.

Testis expression of hormone-sensitive lipase is conferred by a specific promoter that contains four regions binding testicular nuclear proteins

The testicular isoform of hormone-sensitive lipase (HSLtes) is encoded by a testis-specific exon and 9 exons common to the testis and adipocyte isoforms. In mouse, HSLtes mRNA appeared during spermiogenesis in round spermatids. Two constructs containing 1.4 and 0.5 kilobase pairs (kb) of the human HSLtes gene 5'-flanking region cloned upstream of the chloramphenicol acetyltransferase gene were microinjected into mouse oocytes. Analyses of enzyme activity in male and female transgenic mice showed that 0.5 kb of the HSLtes promoter was sufficient to direct expression only in testis. Cell transfection experiments showed that CREMtau, a testis-specific transcriptional activator, does not transactivate the HSLtes promoter. Using gel retardation assays, four testis-specific binding regions (TSBR) were identified using testis and liver nuclear extracts. The testis-specific protein binding on TSBR4 was selectively competed by a probe containing a SRY/Sox protein DNA recognition site. Sox5 and Sox6 which are expressed in post-meiotic germ cells bound TSBR4. Mutation of the AACAAAG motif in TSBR4 abolished the binding. Moreover, binding of the high mobility group domain of Sox5 induced a bend within TSBR4. Together, our results showed that 0.5 kb of the human HSLtes promoter bind Sox proteins and contain cis-acting elements essential for the testis specificity of HSL.

Mechanism of regulatory target selection by the SOX high-mobility-group domain proteins as revealed by comparison of SOX1/2/3 and SOX9

SOX proteins bind similar DNA motifs through their high-mobility-group (HMG) domains, but their action is highly specific with respect to target genes and cell type. We investigated the mechanism of target selection by comparing SOX1/2/3, which activate delta-crystallin minimal enhancer DC5, with SOX9, which activates Col2a1 minimal enhancer COL2C2. These enhancers depend on both the SOX binding site and the binding site of a putative partner factor. The DC5 site was equally bound and bent by the HMG domains of SOX1/2 and SOX9. The activation domains of these SOX proteins mapped at the distal portions of the C-terminal domains were not cell specific and were independent of the partner factor. Chimeric proteins produced between SOX1 and SOX9 showed that to activate the DC5 enhancer, the C-terminal domain must be that of SOX1, although the HMG domains were replaceable. The SOX2-VP16 fusion protein, in which the activation domain of SOX2 was replaced by that of VP16, activated the DC5 enhancer still in a partner factor-dependent manner. The results argue that the proximal portion of the C-terminal domain of SOX1/2 specifically interacts with the partner factor, and this interaction determines the specificity of the SOX1/2 action. Essentially the same results were obtained in the converse experiments in which COL2C2 activation by SOX9 was analyzed, except that specificity of SOX9-partner factor interaction also involved the SOX9 HMG domain. The highly selective SOX-partner factor interactions presumably stabilize the DNA binding of the SOX proteins and provide the mechanism for regulatory target selection.

Ma1, a novel neuron- and testis-specific protein, is recognized by the serum of patients with paraneoplastic neurological disorders

The identification of antineuronal antibodies has facilitated the diagnosis of paraneoplastic neurological disorders and the early detection of the associated tumours. It has also led to the cloning of possibly important neuron-specific proteins. In this study we wanted to identify novel antineuronal antibodies in the sera of patients with paraneoplastic neurological disorders and to clone the corresponding antigens. Serological studies of 1705 sera from patients with suspected paraneoplastic neurological disorders resulted in the identification of four patients with antibodies that reacted with 37 and 40 kDa neuronal proteins (anti-Ma antibodies). Three patients had brainstem and cerebellar dysfunction, and one had dysphagia and motor weakness. Autopsy of two patients showed loss of Purkinje cells, Bergmann gliosis and deep cerebellar white matter inflammatory infiltrates. Extensive neuronal degeneration, gliosis and infiltrates mainly composed of CD8+ T cells were also found in the brainstem of one patient. In normal human and rat tissues, the anti-Ma antibodies reacted exclusively with neurons and with testicular germ cells; the reaction was mainly with subnuclear elements (including the nucleoli) and to a lesser degree the cytoplasm. Anti-Ma antibodies also reacted with the cancers (breast, colon and parotid) available from three anti-Ma patients, but not with 66 other tumours of varying histological types. Preincubation of tissues with any of the anti-Ma sera abrogated the reactivity of the other anti-Ma immunoglobulins. Probing of a human complementary DNA library with anti-Ma serum resulted in the cloning of a gene that encodes a novel 37 kDa protein (Mal). Recombinant Mal was specifically recognized by the four anti-Ma sera but not by 337 control sera, including those from 52 normal individuals, 179 cancer patients without paraneoplastic neurological symptoms, 96 patients with paraneoplastic syndromes and 10 patients with non-cancer-related neurological disorders. The expression of Mal mRNA is highly restricted to the brain and testis. Subsequent analysis suggested that Mal is likely to be a phosphoprotein. Our study demonstrates that some patients with paraneoplastic neurological disorders develop antibodies against Mal, a new member of an expanding family of 'brain/testis' proteins.