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

Regulatory mechanisms of SoxD transcription factors and their influences on male fertility

Members of the SRY-related box (SOX) subfamily D (SoxD) of transcription factors are well conserved among vertebrate species and play important roles in different stages of male reproductive development. In mammals, the SoxD subfamily contains three members: SOX5, SOX6 and SOX13. Here, we describe their implications in testicular development and spermatogenesis, contributing to fertility. We also cover the mechanisms of action of SoxD transcription factors in gene regulation throughout male development. The specificity of activation of target genes by SoxD members depends, in part, on their post-translational modifications and interactions with other partners. Sperm production in adult males requires the coordination in the regulation of gene expression by different members of the SoxD subfamily of transcription factors in the testis. Specifically, the regulation of genes promoting adequate spermatogenesis by SoxD members is discussed in comparison between species.

mRNA expression profile reveals differentially expressed genes in splenocytes of experimental autoimmune encephalomyelitis model

Experimental autoimmune encephalomyelitis (EAE) is a mouse model that can be used to investigate aetiology, pathogenesis, and treatment approaches for multiple sclerosis (MS). A novel integrated bioinformatics approach was used to understand the involvement of differentially expressed genes (DEGs) in the spleen of EAE mice through data mining of existing microarray and RNA-seq datasets. We screened differentially expressed mRNAs using mRNA expression profile data of EAE spleens taken from Gene Expression Omnibus (GEO). Functional and pathway enrichment analyses of DEGs were performed by Database for Annotation, Visualization, and Integrated Discovery (DAVID). Subsequently, the DEGs-encoded protein-protein interaction (PPI) network was constructed. The 784 DEGs in GSE99300 A.SW PP-EAE mice spleen mRNA profiles, 859 DEGs in GSE151701 EAE mice spleen mRNA profiles, and 646 DEGs in GSE99300 SJL/J PP-EAE mice spleen mRNA profiles were explored. Functional enrichment of 55 common DEGs among 3 sub-datasets revealed several immune-related terms, such as neutrophil extravasation, leucocyte migration, antimicrobial humoral immune response mediated by an antimicrobial peptide, toll-like receptor 4 bindings, IL-17 signalling pathway, and TGF-beta signalling pathway. In the screening of 10 hub genes, including MPO, ELANE, CTSG, LTF, LCN2, SELP, CAMP, S100A9, ITGA2B, and PRTN3, and in choosing and validating the 5 DEGs, including ANK1, MBOAT2, SLC25A21, SLC43A1, and SOX6, the results showed that SLC43A1 and SOX6 were significantly decreased in EAE mice spleen. Thus this study offers a list of genes expressed in the spleen that might play a key role in the pathogenesis of EAE.

MicroRNA-499-5p promotes vascular smooth muscle cell proliferation and migration via inhibiting SOX6

Atherosclerosis (AS) is the primary etiology of cardiovascular disease, which is considered the leading cause of death all over the world. MicroRNA miR-499-5p was involved in the functional regulation of myocardial and skeletal muscle, whereas its role in atherosclerosis, especially in vascular smooth muscle cells (VSMCs), remains unclear. Our study aims to investigate the effects of miR-499-5p in the proliferation and migration of VSMCs and potential mechanisms. We used mouse aortic vascular smooth muscle cells (MOVAS) and ApoE^-/- mice to establish the models of AS in vitro and in vivo, respectively. RT-PCR was performed to detect the expression level of miR-499-5p. Subsequently, Cell Counting Kit-8 (CCK-8) assays, Transwell assays, and wound-healing assays were used to evaluate cell proliferation and migration. Dual-luciferase reporter assay was performed to validate the interaction between miR-499-5p and SOX6. miR-499-5p significantly increased in aorta tissues of mice in AS tissues and vascular smooth muscle cells treated with ox-LDL. miR-499-5p overexpression could promote the proliferation and migration of MOVAS. Bioinformatics analysis predicted and further experiments verified that miR-499-5p could directly bind to the 3'-untranslated region (UTR) region of SOX6. Further, miR-499-5p induced an increased expression of smooth muscle proliferation and migration-related genes, PCNA, cyclin D1, and matrix metalloproteinase (MMP2), as well as the decreased expression of proliferation inhibiting factor p21, which was significantly reversed by SOX6 overexpression. miR-499-5p boosts the proliferation and migration of smooth muscle cells by binding and inhibiting SOX6 expression. The miR-499-5p/SOX6 axis may present a promising therapeutic implication for the prevention and treatment of cardiovascular diseases.

Copy Number Variation of the SOX6 Gene and Its Associations with Growth Traits in Ashidan Yak

Copy number variation (CNV) is a fundamental type of structural variation of the genome affecting the economic traits of livestock. The SOX6 gene (sex-determining region Y-box 6), as a transcription factor, has multiple functions with regard to sex determination, embryonic growth, the nervous system development, as well as bone, and various organ formation. This study employed quantitative real-time fluorescence quota PCR (qPCR) for detecting the SOX6-CNV of the 311 Ashidan yaks and analyzed the correlation of the SOX6-CNV with four phenotypes (including body weight, withers height, body length, and chest girth) of the yaks aged 6, 12, 18, and 30 months using ANOVA and multiple comparisons. Furthermore, the SOX6 gene expression was identified in seven different tissues of the yaks. The experiment results demonstrated the expression of SOX6 in each tissue, and the kidney and muscle tissue were found to have higher relative expression levels. Based on the processing by IBM SPSS software, SOX6-CNV was significantly correlated with the chest girth of the 6-months old yaks (p < 0.05) and 30-months yaks (p < 0.05), and withers height of 6 months yaks (p < 0.05) and 18-months yaks (p < 0.05), as well as the normal type of CNV, was chosen for yak breeding. In conclusion, SOX6 might be prominently involved in promoting growth and development of yaks, suggesting that the SOX6 gene can be used in breeding yaks by molecular marker-assisted selection (MAS). The study also offered some important insights into the references and clues for the genetic breeding of yaks.

Systematic identification of aberrant non-coding RNAs and their mediated modules in rotator cuff tears

Background: Rotator cuff tears (RCT) is the most common cause of shoulder dysfunction, however, its molecular mechanisms remain unclear. Non-coding RNAs(ncRNAs), such as long ncRNA (lncRNA), microRNA (miRNA) and circular RNA (circRNA), are involved in a variety of diseases, but little is known about their roles in RCT. Therefore, the purpose of this study is to identify dysregulated ncRNAs and understand how they influence RCT.

Methods: We performed RNA sequencing and miRNA sequencing on five pairs of torn supraspinatus muscles and matched unharmed subscapularis muscles to identify RNAs dysregulated in RCT patients. To better comprehend the fundamental biological processes, we carried out enrichment analysis of these dysregulated mRNAs or the co-expressed genes of dysregulated ncRNAs. According to the competing endogenous RNA (ceRNA) theory, we finally established ceRNA networks to explore the relationship among dysregulated RNAs in RCT.

Results: A total of 151 mRNAs, 38 miRNAs, 20 lncRNAs and 90 circRNAs were differentially expressed between torn supraspinatus muscles and matched unharmed subscapularis muscles, respectively. We found that these dysregulated mRNAs, the target mRNAs of these dysregulated miRNAs or the co-expressed mRNAs of these dysregulated ncRNAs were enriched in muscle structure development, actin-mediated cell contraction and actin binding. Then we constructed and analyzed the ceRNA network and found that the largest module in the ceRNA network was associated with vasculature development. Based on the topological properties of the largest module, we identified several important ncRNAs including hsa_circ_0000722, hsa-miR-129-5p and hsa-miR-30c-5p, whose interacting mRNAs related to muscle diseases, fat and inflammation.

Conclusion: This study presented a systematic dissection of the expression profile of mRNAs and ncRNAs in RCT patients and revealed some important ncRNAs which may contribute to the development of RCT. Such results could provide new insights for further research on RCT.

SOX Transcription Factors as Important Regulators of Neuronal and Glial Differentiation During Nervous System Development and Adult Neurogenesis

The SOX proteins belong to the superfamily of transcription factors (TFs) that display properties of both classical TFs and architectural components of chromatin. Since the cloning of the Sox/SOX genes, remarkable progress has been made in illuminating their roles as key players in the regulation of multiple developmental and physiological processes. SOX TFs govern diverse cellular processes during development, such as maintaining the pluripotency of stem cells, cell proliferation, cell fate decisions/germ layer formation as well as terminal cell differentiation into tissues and organs. However, their roles are not limited to development since SOX proteins influence survival, regeneration, cell death and control homeostasis in adult tissues. This review summarized current knowledge of the roles of SOX proteins in control of central nervous system development. Some SOX TFs suspend neural progenitors in proliferative, stem-like state and prevent their differentiation. SOX proteins function as pioneer factors that occupy silenced target genes and keep them in a poised state for activation at subsequent stages of differentiation. At appropriate stage of development, SOX members that maintain stemness are down-regulated in cells that are competent to differentiate, while other SOX members take over their functions and govern the process of differentiation. Distinct SOX members determine down-stream processes of neuronal and glial differentiation. Thus, sequentially acting SOX TFs orchestrate neural lineage development defining neuronal and glial phenotypes. In line with their crucial roles in the nervous system development, deregulation of specific SOX proteins activities is associated with neurodevelopmental disorders (NDDs). The overview of the current knowledge about the link between SOX gene variants and NDDs is presented. We outline the roles of SOX TFs in adult neurogenesis and brain homeostasis and discuss whether impaired adult neurogenesis, detected in neurodegenerative diseases, could be associated with deregulation of SOX proteins activities. We present the current data regarding the interaction between SOX proteins and signaling pathways and microRNAs that play roles in nervous system development. Finally, future research directions that will improve the knowledge about distinct and various roles of SOX TFs in health and diseases are presented and discussed.

Role of microRNAs in myogenesis and their effects on meat quality in pig - A review

The demand for food is increasing day by day because of the increasing global population. Therefore, meat, the easiest and largely available source of protein, needs to be produced in large amounts with good quality. The pork industry is a significant shareholder in fulfilling the global meat demands. Notably, myogenesis- development of muscles during embryogenesis- is a complex mechanism which culminates in meat production. But the molecular mechanisms which govern the myogenesis are less known. The involvement of miRNAs in myogenesis and meat quality, which depends on factors such as myofiber composition and intramuscular fat contents which determine the meat color, flavor, juiciness, and water holding capacity, are being extrapolated to increase both the quantity and quality of pork. Various kinds of microRNAs (miRNAs), miR-1, miR-21, miR22, miR-27, miR-34, miR-127, miR-133, miR-143, miR-155, miR-199, miR-206, miR-208, miR-378, and miR-432 play important roles in pig skeletal muscle development. Further, the quality of meat also depends upon myofiber which is developed through the expression of different kinds of miRNAs at different stages. This review will focus on the mechanism of myogenesis, the role of miRNAs in myogenesis, and meat quality with a focus on the pig.

Association of Exon 14 of the SOX6 Gene Sequence Variations with Response to Hydroxyurea Therapy in Patients Carrying Non Transfusion-Dependent Thalassemia

Hydroxyurea (HU) activates the γ-globin gene, resulting in increased Hb F synthesis. The SOX6 gene is a member of the Sox (Sry-type HMG box) family of transcription factors, characterized by minor groove binding domain. The DNA binding domain of this gene is encoded by exon 14. We assessed the relationship between response to HU and exon 14 of the SOX6 gene sequence variations in patients with non transfusion-dependent thalassemia (NTDT). One hundred NTDT patients from southern Iran underwent HU therapy randomly participated in this cross-sectional study between February 2013 and October 2014. Based on response to HU therapy, the patients were divided into two groups: good and poor responder. Sequence variations of exon 14 of the SOX6 gene was assayed by the Sanger sequencing technique. From all evaluated single nucleotide polymorphisms (SNPs) as above, we found no significant association between sequence variations of exon 14 of the SOX6 gene and response to HU therapy (p > 0.05). It seems that no SNPs in exon 14 of the SOX6 gene is associated with response to HU in NTDT patients, but more studies are needed for further evaluation.

Emerging roles of Sox6 in the renal and cardiovascular system

The function of Sex-determining Region Y (SRY)-related high-mobility-group box (Sox) family of transcription factors in cell fate decisions during embryonic development are well-established. Accumulating evidence indicates that the Sox family of transcription factors are fundamental in adult tissue homeostasis, regeneration, and physiology. The SoxD subfamily of genes are expressed in various cell types of different organs during embryogenesis and adulthood and have been involved in cell-fate determination, cellular proliferation and survival, differentiation, and terminal maturation in a number of cell lineages. The dysregulation in the function of SoxD proteins (i.e. Sox5, Sox6, Sox13, and Sox23) have been implicated in different disease conditions such as chondrodysplasia, cancer, diabetes, hypertension, autoimmune diseases, osteoarthritis among others. In this minireview, we present recent developments related to the transcription factor Sox6, which is involved in a number of diseases such as diabetic nephropathy, adipogenesis, cardiomyopathy, inflammatory bowel disease, and cancer. Sox6 has been implicated in the regulation of renin expression and JG cell recruitment in mice during sodium depletion and dehydration. We provide a current perspective of Sox6 research developments in last five years, and the implications of Sox6 functions in cardiovascular physiology and disease conditions.

Comparative Transcriptomics Analysis of Testicular miRNA from Cryptorchid and Normal Horses

Simple Summary

The testis is an important organ for mammals, and testicular microRNA expression is associated with male fertility to a certain extent. Cryptorchidism is the failure of one or both testes to descend into the scrotal sac. It is a common congenital malformation in horses. The major clinical consequence of this abnormality is impaired fertility. The expression of testicular microRNAs is influenced by many factors, including high temperature and disease, in cryptorchid horses. Here, we investigated the microRNA expression levels of normal and retained testes. Their expression patterns showed significant differences. In addition, we obtained comprehensive expression data for equine testicular microRNA, which is fundamental information for further analysis.

Abstract

In the biological process of testicular spermatogenesis, the expression and interaction of many genes are regulated by microRNAs (miRNAs). However, comparisons of miRNA expression between descended testes (DTs) and undescended testes (UDTs) are rarely done in horses. In this study, we selected two UDTs (CKY2b and GU4b) from Chakouyi (CKY) and Guanzhong (GU) horses and eight DTs (GU1–3, CKY1, CKY3, CKY2a, GU4a, and GU5). Three groups were compared to evaluate expression patterns of testicular miRNA in stallion testes. Group 1 compared normal CKY horses and GU horses (CKY1 and CKY3 vs. GU1–3). Group 2 (CKY2a and GU4a (DTs) vs. CKY2b and GU4b (UDTs)) and group 3 (GU1–3, CKY1, CKY3 (DTs) vs. CKY2b and GU4b (UDTs)) compared the expression levels in unilateral retained testes to normal testes. The results show that 42 miRNAs (7 upregulated and 35 downregulated) had significantly different expression levels in both comparisons. The expression levels of eca-miR-545, eca-miR-9084, eca-miR-449a, eca-miR-9024, eca-miR-9121, eca-miR-8908e, eca-miR-136, eca-miR-329b, eca-miR-370, and eca-miR-181b were further confirmed by quantitative real-time PCR assay. The target genes of differentially expressed miRNAs in three comparisons were predicted, and the functions were annotated. The putative target genes of the 42 co-differentially expressed miRNAs were annotated to 15 functional terms, including metal ion binding, GTPase activator activity, zinc ion binding, intracellular, cytoplasm, and cancer pathways, and osteoclast differentiation. Our data indicate that the differentially expressed miRNAs in undescended testis suggests a potential role in male fertility and a relationship with cryptorchidism in horses. The discovery of miRNAs in stallion testes might contribute to a new direction in the search for biomarkers of stallion fertility.

SOX6 suppresses the development of lung adenocarcinoma by regulating expression of p53, p21CIPI , cyclin D1 and β-catenin

The Sry‐related high‐mobility group box6 (SOX6) has been implicated in the development of cancer, but its role in lung cancer is incompletely understood. Here, we report that SOX6 expression is frequently down‐regulated in lung adenocarcinoma tissues. Moreover, SOX6 can inhibit the proliferation and invasion of lung adenocarcinoma cells, which may occur through cell cycle arrest at G1/S due to up‐regulation of p53 and p21^CIPI and down‐regulation of cyclin D1 and β‐catenin. Univariate and multivariate analyses revealed that the expression of SOX6 is significantly associated with patient disease‐related survival and is an independent prognostic factor for lung adenocarcinoma. These data suggest that SOX6 may act as a suppressor of lung adenocarcinoma.

Metformin Promotes Neuronal Differentiation via Crosstalk between Cdk5 and Sox6 in Neuroblastoma Cells

Metformin has recently emerged as a key player in promotion of neuroblastoma differentiation and neurite outgrowth. However, molecular mechanisms of how metformin promotes cellular differentiation have not yet been fully elucidated. In this study, we investigated how metformin promotes cell differentiation, via an inhibition of cell proliferation, by culturing SH-SY5Y neuroblastoma cells with or without metformin. Pretreatment with reactive oxygen species (ROS) scavenger, NAC, revealed that ROS plays a crucial role in induction of cell differentiation. Cell differentiation was observed under various morphological criteria: extension of neuritic processes and neuronal differentiation markers. Treatment with metformin significantly increased neurite length, number of cells with neurite, and expression of neuronal differentiation markers, β-tubulin III and tyrosine hydroxylase (TH) compared with untreated control. Further investigation found that metformin significantly decreased Cdk5 but increased Sox6 during cell differentiation. Analysis of the mechanism underlying these changes using Cdk5 inhibitor, roscovitine, indicated that expressions of Cdk5 and Sox6 corresponded to metformin treatment. These results suggested that metformin produces neuronal differentiation via Cdk5 and Sox6. In addition, phosphorylated Erk1/2 was decreased while phosphorylated Akt was increased in metformin treatment. Taken together, these findings suggest that metformin promotes neuronal differentiation via ROS activation through Cdk5/Sox6 crosstalk, relating to Erk1/2 and Akt signaling.

Platelet-derived growth factor receptor α gene is regulated by multiple first exons

Transcription of the platelet-derived growth factor receptor α (PDGFRA/Pdgfra) gene is considered to be precisely regulated. We have previously reported that the PDGFRA/Pdgfra gene is regulated by a dual promoter system in human and mouse, in which a novel PDGFRA/Pdgfra transcript has a first exon (exon 1β) different from that of the canonical PDGFRA/Pdgfra transcript (exon 1α). To elucidate the function of each transcript, we first investigated the contribution of different PDGFRA transcripts to final protein levels. Notably, knockdown experiments suggested the existence of other PDGFRA transcripts, and we identified five additional first exons (exons 1γ, 1δ, 1ε, 1ζ, and 1η) in intron 1 in both the human and mouse genes. The first exons of the mouse Pdgfra gene showed unique expression patterns: exon 1α was broadly expressed; exon 1β was highly expressed in embryos; exon 1γ was observed at relatively high levels in the adult central nervous system (CNS); and exon 1δ was expressed at relatively high levels in the developing CNS. Furthermore, in silico analysis of common putative transcription factor binding sites in the upstream regions of the first exons of both human and mouse PDGFRA/Pdgfra genes predicted common (such as Sry, Mzf1, and Cdx) and unique (such as Sox5, Lmo2, and GATA) transcription factors. Our findings show the diversity of the transcriptional regulation of the PDGFRA/Pdgfra gene.

Identification of suh gene and evidence for involvement of notch signaling pathway on gonadal differentiation of Yellow River carp (Cyprinus carpio)

The suh gene is crucial in Notch pathway and regulates mammalian gonad development. In this study, the sequences of suh1 and suh2 genes in Yellow River carp (Cyprinus carpio) were verified. The partial 5'-flanking regions of suh1 and suh2 were analyzed and several potential transcription factor-binding sites were identified. Phylogenetic, gene structure, and chromosome synteny analyses revealed that carp suh1 and suh2 were orthologs and homologous to vertebrate suh. Investigation of the expression profiles of suh1 and suh2 with qPCR showed that these genes were abundant in the brain and gonad of carp, with suh1 exhibiting sexual dimorphism expression pattern in gonad. To study the relationship between gonad differentiation and Notch signaling, primordial gonads were exposed to DAPT, an inhibitor of Notch signaling, in vitro and in vivo. The results revealed a significant downregulation of suh1 and other Notch genes in vitro. In addition, expression of male-biased genes, such as amh, dmrt1, etc., was downregulated, whereas that of female-biased genes, such as foxl2, gdf9, etc., was upregulated. When the primordial gonads were subjected to long-term DAPT exposure, an increased proportion of ovary and delay in testis development were observed. These results suggest that suh gene may have a conservative function between teleosts and mammals. Furthermore, Notch signaling was found to be involved in gonad differentiation in Yellow River carp, and DAPT was noted to inhibit and enhance the expression of male- and female-biased genes, respectively, and induce the increase in number of females.

Expression profiles of Sox transcription factors within the postnatal rodent testes

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. Members of the Sox family have been identified in pre- and postnatal testis and are known to play an important role in sex determination (Sry, Sox9), male gonadal development, and fertility (Sox4, Sox8, Sox30). However, their expression profiles per cell types remain elusive. The objectives of this research were to characterize the expression profiles of Sox family members within adult testes using publically available datasets and to determine whether these findings are consistent with literature as well as immunofluorescence and in situ hybridization results. We have found that Sox4, Sox8, Sox9, and Sox12 are highly expressed in Sertoli cells, whereas Sox5, Sox6, and Sox30 were typically expressed in spermatocytes and spermatids. Spermatogonia were characterized by the expressions of Sox3, Sox4, Sox12, Sox13, and Sox18. Hence, these results suggest that Sox transcription factors may play different roles according to cell types of the adult mammalian testis.

SOX6 Downregulation Induces γ-Globin in Human β-Thalassemia Major Erythroid Cells

Background

Fetal hemoglobin (HbF; α₂γ₂) is a potent genetic modifier of the severity of β-thalassemia and sickle cell anemia. Differences in the levels of HbF that persist into adulthood affect the severity of sickle cell disease and the β-thalassemia syndromes. Sry type HMG box (SOX6) is a potent silencer of HbF. Here, we reactivated γ-globin expression by downregulating SOX6 to alleviate anemia in the β-thalassemia patients.

Methods

SOX6 was downregulated by lentiviral RNAi (RNA interference) in K562 cell line and an in vitro culture model of human erythropoiesis in which erythroblasts are derived from the normal donor mononuclear cells (MNC) or β-thalassemia major MNC. The expression of γ-globin was analyzed by qPCR (quantitative real-time PCR) and WB (western blot).

Results

Our data showed that downregulation of SOX6 induces γ-globin production in K562 cell line and human erythrocytes from normal donors and β-thalassemia major donors, without altering erythroid maturation.

Conclusions

This is the first report on γ-globin induction by downregulation of SOX6 in human erythroblasts derived from β-thalassemia major.

Unravelling pathways downstream Sox6 induction in K562 erythroid cells by proteomic analysis

The Sox6 transcription factor is crucial for terminal maturation of definitive red blood cells. Sox6-null mouse fetuses present misshapen and nucleated erythrocytes, due to impaired actin assembly and cytoskeleton stability. These defects are accompanied with a reduced survival of Sox6^−/− red blood cells, resulting in a compensated anemia. Sox6-overexpression in K562 cells and in human primary ex vivo erythroid cultures enhances erythroid differentiation and leads to hemoglobinization, the hallmark of erythroid maturation. To obtain an overview on processes downstream to Sox6 expression, we performed a differential proteomic analysis on human erythroid K562 cells overexpressing Sox6. Sox6-overexpression induces dysregulation of 64 proteins, involved in cytoskeleton remodeling and in protein synthesis, folding and trafficking, key processes for erythroid maturation. Moreover, 43 out of 64 genes encoding for differentially expressed proteins contain within their proximal regulatory regions sites that are bound by SOX6 according to ENCODE ChIP-seq datasets and are possible direct SOX6 targets. SAR1B, one of the most induced proteins upon Sox6 overexpression, shares a conserved regulatory module, composed by a double SOX6 binding site and a GATA1 consensus, with the adjacent SEC24 A gene. Since both genes encode for COPII components, this element could concur to the coordinated expression of these proteins during erythropoiesis.

An Integrative Developmental Genomics and Systems Biology Approach to Identify an In Vivo Sox Trio-Mediated Gene Regulatory Network in Murine Embryos

Embryogenesis is an intricate process involving multiple genes and pathways. Some of the key transcription factors controlling specific cell types are the Sox trio, namely, Sox5, Sox6, and Sox9, which play crucial roles in organogenesis working in a concerted manner. Much however still needs to be learned about their combinatorial roles during this process. A developmental genomics and systems biology approach offers to complement the reductionist methodology of current developmental biology and provide a more comprehensive and integrated view of the interrelationships of complex regulatory networks that occur during organogenesis. By combining cell type-specific transcriptome analysis and in vivo ChIP-Seq of the Sox trio using mouse embryos, we provide evidence for the direct control of Sox5 and Sox6 by the transcriptional trio in the murine model and by Morpholino knockdown in zebrafish and demonstrate the novel role of Tgfb2, Fbxl18, and Tle3 in formation of Sox5, Sox6, and Sox9 dependent tissues. Concurrently, a complete embryonic gene regulatory network has been generated, identifying a wide repertoire of genes involved and controlled by the Sox trio in the intricate process of normal embryogenesis.

MicroRNA-499-5p regulates porcine myofiber specification by controlling Sox6 expression

MicroRNAs (miRNAs) are a class of small non-coding RNAs that negatively regulate gene expression of target messenger RNAs (mRNAs) and miRNAs have been proven to play vital roles in skeletal muscle development. The miRNA-499-5p has been reported to be negatively related with the expression of Sox6, a critical transcription factor for the maintenance of fast-twitch skeletal muscle. In this study, we amplified a length of 2012-bp mRNA that contains a 1512-bp porcine Sox6 (pSox6) 3'UTR from skeletal muscle of a Duroc×Landrace×Yorkshire pig. By luciferase reporter assay we verified that pSox6 is a target of miR-499-5p. In extensor digitorum longus and Soleus muscles of pigs, the expression levels of miR-499-5p and pSox6 mRNA were also inversely correlated. Besides, overexpression of miR-499-5p in porcine satellite cells promoted the expression of MyHC I and MyHC IIa mRNA, along with a reduction of pSox6 mRNA. Taken together, these results indicate that miR-499-5p may facilitate the oxidative myofibers formation by downregulating pSox6 expression.

Steroidogenic genes expressions are repressed by high levels of leptin and the JAK/STAT signaling pathway in MA-10 Leydig cells

The adipose tissue is an important endocrine organ secreting numerous peptide hormones, including leptin. Increased circulating levels of leptin, as a result of hormonal resistance in obese individuals, may contribute to lower androgen production in obese males. However, the molecular mechanisms involved need to be better defined. Androgens are mainly produced by Leydig cells within the testis. In male rodents, activation of the leptin receptor modulates a cascade of intracellular signal transduction pathways which may lead to regulation of transcription factors having influences on steroidogenesis in Leydig cells. Thus, as a result of high leptin levels interacting with its receptor and modulating the activity of the JAK/STAT signaling pathway, the activity of transcription factors important for steroidogenic genes expressions may be inhibited in Leydig cells. Here we show that Lepr is increasingly expressed within Leydig cells according to postnatal development. Although high levels of leptin (corresponding to obesity condition) alone had no effect on Leydig cells' steroidogenic genes expression, it downregulated cAMP-dependent activations of the cholesterol transporter Star and of the rate-limiting steroidogenic enzyme Cyp11a1. Our results suggest that STAT transcriptional activity is downregulated by high levels of leptin, leading to reduced cAMP-dependent steroidogenic genes (Star and Cyp11a1) expressions in MA-10 Leydig cells. However, other transcription factors such as members of the SMAD and NFAT families may be involved and need further investigation to better define how leptin regulates their activities and their relevance for Leydig cells function.

Sex Change in Clownfish: Molecular Insights from Transcriptome Analysis

Sequential hermaphroditism is a unique reproductive strategy among teleosts that is displayed mainly in fish species living in the coral reef environment. The reproductive biology of hermaphrodites has long been intriguing; however, very little is known about the molecular pathways underlying their sex change. Here, we provide the first de novo transcriptome analyses of a hermaphrodite teleost´s undergoing sex change in its natural environment. Our study has examined relative gene expression across multiple groups-rather than just two contrasting conditions- and has allowed us to explore the differential expression patterns throughout the whole process. Our analysis has highlighted the rapid and complex genomic response of the brain associated with sex change, which is subsequently transmitted to the gonads, identifying a large number of candidate genes, some well-known and some novel, involved in the process. The present study provides strong evidence of the importance of the sex steroidogenic machinery during sex change in clownfish, with the aromatase gene playing a central role, both in the brain and the gonad. This work constitutes the first genome-wide study in a social sex-changing species and provides insights into the genetic mechanism governing social sex change and gonadal restructuring in protandrous hermaphrodites.

Sox6 suppression induces RA-dependent apoptosis mediated by BMP-4 expression during neuronal differentiation in P19 cells

Sox6 is a transcription factor that induces neuronal differentiation in P19 cells; its suppression not only inhibits neuronal differentiation but also induces retinoic acid (RA)-dependent apoptosis of P19 cells. In the present study, we found that Sox6 suppression-induced apoptosis was mediated by activation of caspase 9 and 3. Moreover, we noted a weak leakage of cytochrome c into the cytoplasm from the mitochondria, indicating that apoptosis occurs through a mitochondrial pathway in Sox6-suppressed P19 (P19[anti-Sox6]) cells. Sox6 suppression in the presence of RA also induced the expression and secretion of bone morphogenetic protein 4 (BMP-4). Addition of an anti-BMP-4 antibody for neutralization increased cell viability and led to RA-dependent death of P19[anti-Sox6] cells. Our results indicate that Sox6 suppression induces RA-dependent cell death of P19 cells, mediated by BMP-4 expression and secretion. Normally, high Sox6 expression leads to RA-mediated neuronal differentiation in P19 cells; however, Sox6 deficiency induces production and secretion of BMP-4, which mediates selective cell death. Our findings suggest that Sox6 contributes to cell survival by suppressing BMP-4 transcription during neuronal differentiation.

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.

Global developmental delay, progressive relapsing-remitting parkinsonism, and spinal syrinx in a child with SOX6 mutation

SOX6, a member of the SOX gene family, plays a key role in the development of several mammalian tissues and organs, including the central nervous system. Specifically, this gene modulates the differentiation and proliferation of interneurons in the medial ganglionic eminence, as well as oligodendrocytes in the spinal cord. We describe the case of a 4-year-old girl with global developmental delay and a spinal cord syrinx who presented with recurrent episodes of parkinsonian symptoms subsequent to febrile illnesses. The symptoms included gait instability, tremor, and dysarthria, with a progressive relapsing-remitting course over the span of 2 years. The patient was later found to have a large deletion-type mutation in the SOX6 gene. This case is the first report in humans implying a role for SOX6 in basal ganglia function, as well as spinal cord development.

High levels of SOX5 decrease proliferative capacity of human B cells, but permit plasmablast differentiation

Currently very little is known about the differential expression and function of the transcription factor SOX5 during B cell maturation. We identified two new splice variants of SOX5 in human B cells, encoding the known L-SOX5B isoform and a new shorter isoform L-SOX5F. The SOX5 transcripts are highly expressed during late stages of B-cell differentiation, including atypical memory B cells, activated CD21^low B cells and germinal center B cells of tonsils. In tonsillar sections SOX5 expression was predominantly polarized to centrocytes within the light zone. After in vitro stimulation, SOX5 expression was down-regulated during proliferation while high expression levels were permissible for plasmablast differentiation. Overexpression of L-SOX5F in human primary B lymphocytes resulted in reduced proliferation, less survival of CD138^neg B cells, but comparable numbers of CD138⁺CD38^hi plasmablasts compared to control cells. Thus, our findings describe for the first time a functional role of SOX5 during late B cell development reducing the proliferative capacity and thus potentially affecting the differentiation of B cells during the germinal center response.

Regulation of Sox6 by cyclin dependent kinase 5 in brain

Cyclin dependent kinase 5 (Cdk5) is a proline-directed Ser/Thr kinase involved in various biological functions during normal brain development and neurodegeneration. In brain, Cdk5 activity is specific to post-mitotic neurons, due to neuronal specific expression of its activator p35. The biological functions of Cdk5 have been ascribed to its cytoplasmic substrates, however not much is known in nucleus. Here, we show that nuclear transcription factor Sox6 is a direct nuclear target of Cdk5. Sox6 is expressed in Tuj1 positive neurons, suggesting that Sox6 is expressed in differentiating neurons. The expression of Sox6 is high in mitotic nuclei during embryonic day 12 (E12) and gradually decreases during development into adult. On the other hand, Cdk5 expression gradually increases during its development. We show that Sox6 is expressed in mitotic nuclei in embryonic day 12 (E12) and in migrating neurons of E16. Sox6 is phosphorylated in vivo. Sox6 was detected by phospho-Ser/Thr and phospho-Ser/Thr-Pro and MPM-2 (Mitotic protein #2) antibodies in brain. Furthermore, calf intestinal alkaline phosphatase (CIAP) digestion resulted in faster migration of Sox6 band. The GST-Sox6 was phosphorylated by Cdk5/p35. The mass spectrometry analysis revealed that Sox6 is phosphorylated at T119PER motif. We show that Sox6 steady state levels are regulated by Cdk5. Cdk5 knockout mice die in utero and Sox6 protein expression is remarkably high in Cdk5-/- brain, however, there is no change in mRNA expression, suggesting a post-translational regulation of Sox6 by Cdk5. Transfection of primary cortical neurons with WT Cdk5 reduced Sox6 levels, while dominant negative (DN) Cdk5 and p35 increased Sox6 levels. Thus, our results indicate that Cdk5 regulates Sox6 steady state protein level that has an important role in brain development and function.

Trip12, a HECT domain E3 ubiquitin ligase, targets Sox6 for proteasomal degradation and affects fiber type-specific gene expression in muscle cells

Background

A sophisticated level of coordinated gene expression is necessary for skeletal muscle fibers to obtain their unique functional identities. We have previously shown that the transcription factor Sox6 plays an essential role in coordinating muscle fiber type differentiation by acting as a transcriptional suppressor of slow fiber-specific genes. Currently, mechanisms regulating the activity of Sox6 in skeletal muscle and how these mechanisms affect the fiber phenotype remain unknown.

Methods

Yeast two-hybrid screening was used to identify binding partners of Sox6 in muscle. Small interfering RNA (siRNA)-mediated knockdown of one of the Sox6 binding proteins, Trip12, was used to determine its effect on Sox6 activity in C2C12 myotubes using quantitative analysis of fiber type-specific gene expression.

Results

We found that the E3 ligase Trip12, a HECT domain E3 ubiquitin ligase, recognizes and polyubiquitinates Sox6. Inhibiting Trip12 or the 26S proteasome activity resulted in an increase in Sox6 protein levels in C2C12 myotubes. This control of Sox6 activity in muscle cells via Trip12 ubiquitination has significant phenotypic outcomes. Knockdown of Trip12 in C2C12 myotubes led to upregulation of Sox6 protein levels and concurrently to a decrease in slow fiber-specific Myh7 expression coupled with an increased expression in fast fiber-specific Myh4. Therefore, regulation of Sox6 cellular levels by the ubiquitin-proteasome system can induce identity-changing alterations in the expression of fiber type-specific genes in muscle cells.

Conclusions

Based on our data, we propose that in skeletal muscle, E3 ligases have a significant role in regulating fiber type-specific gene expression, expanding their importance in muscle beyond their well-established role in atrophy.

Diagnostic role of microRNA expression profile in the serum of pregnant women with fetuses with neural tube defects

The discovery of placental microRNAs (miRNAs) in maternal serum has opened up new possibilities for non-invasive prenatal diagnosis. However, the expression of miRNAs in the serum of pregnant women with fetuses with neural tube defects (NTDs) has not been characterized. In this article, we explored serum miRNAs as potential biomarkers in the serum of pregnant women with NTD fetuses. By using a miRNA microarray that covers 887 human miRNAs, we revealed 17 miRNAs with significant change in expression in serum of pregnant women with NTD fetuses and women with normal pregnancies. Quantitative reverse-transcription PCR (qRT-PCR) analysis validated that the expression for six miRNAs (miR-142-3p, miR-144, miR-720, miR-575, miR-765, and miR-1182) was up-regulated and that for miR-1275 was down-regulated. To determine whether these miRNAs were related to pregnancy, we compared the miRNA levels in pre- and post-delivery maternal serum samples. Six of these miRNAs were rapidly reduced in post-delivery serum (p < 0.05). Moreover, by receiver operating characteristic (ROC) curve analysis, the area under the ROC curve (AUC) of combining these six miRNAs was 0.803 (p < 0.001). Thus, we reveal six pregnancy-associated miRNAs that are deregulated in the serum of pregnant women with NTD fetuses and highlight the clinical potential of serum miRNAs as biomarkers for diagnosis and prognostication of fetal NTDs.

Differential expression of oxidored nitro domain containing protein 1 (NOR1), in mouse tissues and in normal and cancerous human tissues

Oxidored nitro domain containing protein 1 (NOR1) is usually restrictively expressed in the brain and testis. Detection of altered NOR1 expression could help us to identify its functions in cell growth, differentiation, metabolism, or even carcinogenesis. In this study, NOR1 homologues were identified in multiple species through GenBank search. NOR1 is a novel protein conserved in multiple species. Mouse NOR1 shared high homology with human NOR1. Furthermore, NOR1 expression was analyzed in mouse tissues by using RT-PCR, Western blot, and immunohistochemistry. The data showed that NOR1 is broadly expressed in neurons of mouse brain and the expression profile changes during postnatal development of the mouse brain. Moreover, in non-nervous tissues, strong immunostaining for NOR1 protein was observed in the testis, epididymis and trachea. In addition, expression of human NOR1 protein in different normal and cancerous human tissues was analyzed via search of the human RNA and protein databases; the data showed that although most malignant cells weakly stained or were negative for NOR1 expression, the liver cancer cells displayed moderate to strong expression of NOR1. These data suggested that NOR1 might serve as a cancer/testis/brain antigen in cells, and that altered NOR1 expression in liver cancer may help us to elucidate the functions of NOR1 protein in liver carcinogenesis.

Endogenous tagging of the murine transcription factor Sox5 with hemaglutinin for functional studies

Gene expression is usually studied at the transcript level rather than at the protein level due to the lack of a specific and sensitive antibody. A way to overcome this is to fuse to the protein of interest an immunoreactive tag that has well-characterized antibodies. This epitope tagging approach is often used for in vitro experiments but for in vivo studies, the success rate of protein tagging has not been extensively analyzed and our study seeks to cover the void. A small epitope, hemaglutinin derived from the influenza virus was used to tag a transcription factor, Sox5 at the N-terminal via homologous recombination in the mouse. Sox5 is part of the Sry-related high-mobility-group box gene family and plays multiple roles in essential biological processes. Understanding of its molecular function in relation to its biological roles remains incomplete. In our study, we show that the longer isoform of Sox5 can be tagged endogenously with hemaglutinin without affecting its biological function in vivo. The tagged protein is easily and specifically detected with an anti-hemaglutinin antibody using immunohistochemistry with its expression matching the endogenous expression of Sox5. Immunoprecipitation of Sox5 was also carried out successfully using an anti-hemaglutinin antibody. The transgenic line generated from this study is predicted to be useful for future experiments such as co-immunoprecipitation and chromatin immunoprecipitation, allowing the further understanding of Sox5. Lastly, this approach can be easily employed for the investigation of other transcription factors and proteins in vivo to overcome technical limitations such as antibody cross-reactivity and to perform isoform-specific studies.

Concerted regulation of myofiber-specific gene expression and muscle performance by the transcriptional repressor Sox6

In response to physiological stimuli, skeletal muscle alters its myofiber composition to significantly affect muscle performance and metabolism. This process requires concerted regulation of myofiber-specific isoforms of sarcomeric and calcium regulatory proteins that couple action potentials to the generation of contractile force. Here, we identify Sox6 as a fast myofiber-enriched repressor of slow muscle gene expression in vivo. Mice lacking Sox6 specifically in skeletal muscle have an increased number of slow myofibers, elevated mitochondrial activity, and exhibit down-regulation of the fast myofiber gene program, resulting in enhanced muscular endurance. In addition, microarray profiling of Sox6 knockout muscle revealed extensive muscle fiber-type remodeling, and identified numerous genes that display distinctive fiber-type enrichment. Sox6 directly represses the transcription of slow myofiber-enriched genes by binding to conserved cis-regulatory elements. These results identify Sox6 as a robust regulator of muscle contractile phenotype and metabolism, and elucidate a mechanism by which functionally related muscle fiber-type specific gene isoforms are collectively controlled.

Sox6, jack of all trades: a versatile regulatory protein in vertebrate development

Approximately 20,000 genes are encoded in our genome, one tenth of which are thought to be transcription factors. Considering the complexity and variety of cell types generated during development, many transcription factors likely play multiple roles. Uncovering the versatile roles of Sox6 in vertebrate development sheds some light on how an organism efficiently utilizes the limited resources of transcription factors. The structure of the Sox6 gene itself may dictate its functional versatility. First, Sox6 contains no known regulatory domains; instead, it utilizes various cofactors. Second, Sox6 has a long 3'-UTR that contains multiple microRNA targets, thus its protein level is duly adjusted by cell type-specific microRNAs. Just combining these two characteristics alone makes Sox6 extremely versatile. To date, Sox6 has been reported to regulate differentiation of tissues of mesoderm, ectoderm, and endoderm origins, making Sox6 a truly multifaceted transcription factor.

Neuronal expression, cytosolic localization, and developmental regulation of the organic solute carrier partner 1 in the mouse brain

Organic solute carrier partner 1 (OSCP1) is a mammalian, transporter-related protein that is able to facilitate the uptake of structurally diverse organic compounds into the cell when expressed in Xenopus laevis oocytes. This protein has been implicated in testicular handling of organic solutes because its mRNA expression is almost exclusive in the testis. However, in this study, we demonstrated significant expression of OSCP1 protein in mouse brain, the level of which was rather higher than that in the testis, although the corresponding mRNA expression was one-tenth of the testicular level. Immunohistochemistry revealed that OSCP1 was broadly distributed throughout the brain, and various neuronal cells were immunostained, including pyramidal cells in the cerebral cortex and hippocampus. However, there was no evidence of OSCP1 expression in glia. In primary cultures of cerebral cortical neurons, double-labeling immunofluorescence localized OSCP1 to the cytosol throughout the cell body and neurites including peri-synaptic regions. This was consistent with the subcellular fractionation of brain homogenates, in which OSCP1 was mainly recovered after centrifugation both in the cytosolic fraction and the particulate fraction containing synaptosomes. Immunoelectron microscopy of brain sections also demonstrated OSCP1 in the cytosol near synapses. In addition, it was revealed that changes in the expression level of OSCP1 correlated with neuronal maturation during postnatal development of mouse brain. These results indicate that OSCP1 may have a role in the brain indirectly mediating substrate uptake into the neurons in adult animals.

Sox6 enhances erythroid differentiation in human erythroid progenitors

Sox6 belongs to the Sry (sex-determining region Y)-related high-mobility-group-box family of transcription factors, which control cell-fate specification of many cell types. Here, we explored the role of Sox6 in human erythropoiesis by its overexpression both in the erythroleukemic K562 cell line and in primary erythroid cultures from human cord blood CD34+ cells. Sox6 induced significant erythroid differentiation in both models. K562 cells underwent hemoglobinization and, despite their leukemic origin, died within 9 days after transduction; primary erythroid cultures accelerated their kinetics of erythroid maturation and increased the number of cells that reached the final enucleation step. Searching for direct Sox6 targets, we found SOCS3 (suppressor of cytokine signaling-3), a known mediator of cytokine response. Sox6 was bound in vitro and in vivo to an evolutionarily conserved regulatory SOCS3 element, which induced transcriptional activation. SOCS3 overexpression in K562 cells and in primary erythroid cells recapitulated the growth inhibition induced by Sox6, which demonstrates that SOCS3 is a relevant Sox6 effector.

Profiling spermatogenic failure in adult testes bearing Sox9-deficient Sertoli cells identifies genes involved in feminization, inflammation and stress

BACKGROUND

Sox9 (Sry box containing gene 9) is a DNA-binding transcription factor involved in chondrocyte development and sex determination. The protein's absence in testicular Sertoli nurse cells has been shown to disrupt testicular function in adults but little is known at the genome-wide level about molecular events concomitant with testicular break-down.

METHODS

To determine the genome-wide effect on mRNA concentrations triggered by the absence of Sox9 in Sertoli cells we analysed adult testicular tissue from wild-type versus mutant mice with high-density oligonucleotide microarrays and integrated the output of this experiment with regulatory motif predictions and protein-protein network data.

RESULTS

We report the genome-wide mRNA signature of adult testes lacking Sox9 in Sertoli cells before and after the onset of late spermatogenic failure as compared to fertile controls. The GeneChip data integrated with evolutionarily conserved Sox9 DNA binding motifs and regulatory network data identified genes involved in feminization, stress response and inflammation.

CONCLUSIONS

Our results extend previous observations that genes required for female gonadogenesis are up-regulated in the absence of Sox9 in fetal Sertoli cells to the adult stage. Importantly, we identify gene networks involved in immunological processes and stress response which is reminiscent of a phenomenon occurring in a sub-group of infertile men. This suggests mice lacking Sox9 in their Sertoli cells to be a potentially useful model for adult human testicular failure.

Characterization of tumor-suppressive function of SOX6 in human esophageal squamous cell carcinoma

PURPOSE

By using cDNA microarray analysis, we identified a transcriptional factor, SOX6, was frequently downregulated in esophageal squamous cell carcinoma (ESCC). The aim of this study is to investigate the role of SOX6 in human esophageal cancer development, and to examine the prevalence and clinical significance of SOX6 downregulation in ESCC.

EXPERIMENTAL DESIGN

Expressions of SOX6 mRNA in 50 ESCCs and SOX6 protein in 300 ESCCs were investigated by semiquantitative RT-PCR and immunohistochemistry, respectively. The tumor-suppressive function of SOX6 was characterized by cell growth, foci formation, wound-healing and cell invasive assays, and tumor xenograft experiment. Western blot analysis was applied to detect protein expression levels.

RESULTS

SOX6 was frequently downregulated in primary ESCCs in both mRNA level (29/50, 58%) and protein level (149/219, 68.0%), which was significantly associated with the poor differentiation (P = 0.029), lymph node metastases (P = 0.014), advanced TNM stage (P = 0.000), and disease-specific survival (P < 0.001). Multivariate analysis indicated that the downregulation of SOX6 (P = 0.000) was a significant independent prognostic factors for ESCC. Functional studies showed that SOX6 was able to suppress both in vitro and in vivo tumorigenic ability of ESCC cells. The tumor-suppressive mechanism of SOX6 was associated with its role in G1/S cell-cycle arrest by upregulating expressions of p53 and p21(WAF1/CIP1) and downregulating expressions of cyclin D1/CDK4, cyclin A, and β-catenin.

CONCLUSIONS

We provided the first evidence that SOX6 is a novel tumor-suppressor gene in ESCC development and is a potential prognostic marker in ESCC.

A highly conserved SOX6 double binding site mediates SOX6 gene downregulation in erythroid cells

The Sox6 transcription factor plays critical roles in various cell types, including erythroid cells. Sox6-deficient mice are anemic due to impaired red cell maturation and show inappropriate globin gene expression in definitive erythrocytes. To identify new Sox6 target genes in erythroid cells, we used the known repressive double Sox6 consensus within the εy-globin promoter to perform a bioinformatic genome-wide search for similar, evolutionarily conserved motifs located within genes whose expression changes during erythropoiesis. We found a highly conserved Sox6 consensus within the Sox6 human gene promoter itself. This sequence is bound by Sox6 in vitro and in vivo, and mediates transcriptional repression in transient transfections in human erythroleukemic K562 cells and in primary erythroblasts. The binding of a lentiviral transduced Sox6FLAG protein to the endogenous Sox6 promoter is accompanied, in erythroid cells, by strong downregulation of the endogenous Sox6 transcript and by decreased in vivo chromatin accessibility of this region to the PstI restriction enzyme. These observations suggest that the negative Sox6 autoregulation, mediated by the double Sox6 binding site within its own promoter, may be relevant to control the Sox6 transcriptional downregulation that we observe in human erythroid cultures and in mouse bone marrow cells in late erythroid maturation.

Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 4: intercellular bridges, mitochondria, nuclear envelope, apoptosis, ubiquitination, membrane/voltage-gated channels, methylation/acetylation, and transcription factors

As germ cells divide and differentiate from spermatogonia to spermatozoa, they share a number of structural and functional features that are common to all generations of germ cells and these features are discussed herein. Germ cells are linked to one another by large intercellular bridges which serve to move molecules and even large organelles from the cytoplasm of one cell to another. Mitochondria take on different shapes and features and topographical arrangements to accommodate their specific needs during spermatogenesis. The nuclear envelope and pore complex also undergo extensive modifications concomitant with the development of germ cell generations. Apoptosis is an event that is normally triggered by germ cells and involves many proteins. It occurs to limit the germ cell pool and acts as a quality control mechanism. The ubiquitin pathway comprises enzymes that ubiquitinate as well as deubiquitinate target proteins and this pathway is present and functional in germ cells. Germ cells express many proteins involved in water balance and pH control as well as voltage-gated ion channel movement. In the nucleus, proteins undergo epigenetic modifications which include methylation, acetylation, and phosphorylation, with each of these modifications signaling changes in chromatin structure. Germ cells contain specialized transcription complexes that coordinate the differentiation program of spermatogenesis, and there are many male germ cell-specific differences in the components of this machinery. All of the above features of germ cells will be discussed along with the specific proteins/genes and abnormalities to fertility related to each topic.

Advances in the understanding of haemoglobin switching

The study of haemoglobin switching has represented a focus in haematology due in large part to the clinical relevance of the fetal to adult haemoglobin switch for developing targeted approaches to ameliorate the severity of the beta-haemoglobinopathies. Additionally, the process by which this switch occurs represents an important paradigm for developmental gene regulation. In this review, we provide an overview of both the embryonic primitive to definitive switch in haemoglobin expression, as well as the fetal to adult switch that is unique to humans and old world monkeys. We discuss the nature of these switches and models of their regulation. The factors that have been suggested to regulate this process are then discussed. With the increased understanding and discovery of molecular regulators of haemoglobin switching, such as BCL11A, new avenues of research may lead ultimately to novel therapeutic, mechanism-based approaches to fetal haemoglobin reactivation in patients.

Uncoupling of expression of an intronic microRNA and its myosin host gene by exon skipping

The ancient MYH7b gene, expressed in striated muscle and brain, encodes a sarcomeric myosin and the intronic microRNA miR-499. We find that skipping of an exon introduces a premature termination codon in the transcript that downregulates MYH7b protein production without affecting microRNA expression. Among other genes, endogenous miR-499 targets the 3' untranslated region of the transcription factor Sox6, which in turn acts as a repressor of MYH7b transcriptional activity. Thus, concerted transcription and alternative splicing uncouple the level of expression of MYH7b and miR-499 when their coexpression is not required.

SOX6 controls dorsal progenitor identity and interneuron diversity during neocortical development

The extraordinary neuronal diversity of the central nervous system emerges largely from controlled spatial and temporal segregation of cell type-specific molecular regulators. Here, we report that the transcription factor SOX6 controls the molecular segregation of dorsal (pallial) from ventral (subpallial) telencephalic progenitors, and the differentiation of cortical interneurons, regulating forebrain progenitor and interneuron heterogeneity. During corticogenesis in mice, SOX6 and highly related SOX5 expression is largely mutually exclusive in pallial and subpallial progenitors, respectively, and remains mutually exclusive in a reverse pattern in postmitotic neuronal progeny. Loss of SOX6 from pallial progenitors causes their inappropriate expression of normally subpallium-restricted developmental controls, conferring mixed dorsal-ventral identity. In postmitotic cortical interneurons, loss of SOX6 dramatically disrupts the differentiation and diversity of cortical interneuron subtypes, analogous to SOX5 control over cortical projection neuron development. These data reveal SOX6 as a novel transcription factor regulator of both progenitor and cortical interneuron diversity during neocortical development.

The SoxD transcription factors--Sox5, Sox6, and Sox13--are key cell fate modulators

Sox5, Sox6, and Sox13 constitute the group D of sex-determining region (Sry)-related transcription factors. They are highly conserved in the family-specific high-mobility-group (HMG) box DNA-binding domain and in a group-specific coiled-coil domain. The latter mediates SoxD protein dimerization and thereby preferential binding to pairs of DNA recognition sites. The SoxD genes have overlapping expression and cell-autonomously control discrete lineages. Sox5 and Sox6 redundantly enhance chondrogenesis, but retard gliogenesis. Sox5 hinders melanogenesis, promotes neural crest generation, and controls the pace of neurogenesis. Sox6 promotes erythropoiesis, and Sox13 modulates T cell specification and is an autoimmune antigen. SoxD proteins enhance transactivation by Sox9 in chondrocytes, but antagonize Sox9 and other SoxE proteins in oligodendrocytes and melanocytes, and also repress transcription through various mechanisms in several other lineages. While their biological and molecular functions remain incompletely understood, the SoxD proteins have thus already proven that they critically modulate cell fate in major lineages.

Novel genetic markers derived from the DNA fragments of Sox genes

With the pair of degenerate primers designed against the conserved regions of HMG-box of Sox gene family, DNA fragments of different sizes were obtained by amplifying the whole genome DNA samples of many animals, including natural fish, artificial hybrid fish, Aves, reptiles, amphibians and hexapods. Each sample was identified by the specific DNA-band pattern formed by the DNA fragments with defined number and size which marked the sample's genetic characteristics. In addition, 50 DNA fragments from 22 kinds of animals were sequenced and comparatively analyzed so as to study their genetic relationships, especially that between artificial hybrids and their original parents. Based on the specific DNA-band pattern and the specific DNA sequence obtained in tissue DNA sample, we established the novel genetic DNA markers derived from the DNA fragments of Sox genes. The present results proved that the novel DNA markers provided fast and accurate markers for different animal phylogenetic branches and that these convenient markers can also distinguish closely related species and hybrids using a single gene family tool.