The transcription factor Sox5 modulates Sox10 function during melanocyte development

Identification of candidate genes associated with primary feathers of tianfu nonghua ducks based on Genome-wide association studies

The primary feathers of ducks have important economic value in the poultry industry. This study quantified the primary feather phenotype of Nonghua ducks, including the primary feathers' length, area, distribution of black spots, and feather symmetry. And genome-wide association analysis was used to screen candidate genes that affect the primary feather traits. The genome-wide association study (GWAS) results identified the genetic region related to feather length (FL) on chromosome 2. Through Linkage disequilibrium (LD) analysis, candidate regions (chr2: 115,246,393-116,501,448 bp) were identified and were further annotated to 5 genes: MRS2, GPLD1, ALDH5A1, KIAA0319, and ATP9B. Secondly, candidate regions related to feather black spots were identified on chromosome 21. Through LD analysis, the candidate regions (chr21: 163,552-2,183,853 bp) were screened and further annotated to 47 genes. Among them, STK4, CCN5, and YWHAB genes were related to melanin-related pathways or pigment deposition, which may be key genes affecting the distribution of black spots on feathers. In addition, we also screened 125 genes on multiple chromosomes that may be related to feather symmetry. Among them, significant SNPs on chromosome 1 were further identified as candidate regions (chr1: 142,118,209-142,223,605 bp) through LD analysis and annotated into 2 genes, TGFBRAP1 and LOC113839965. These results reported the genetic basis of the primary feather from multiple phenotypes, and offered valuable insights into the genetic basis for the growth and development of duck feathers and feather color pattern.

A novel variant of the SOX10 gene associated with Waardenburg syndrome type IV

BACKGROUND

Waardenburg syndrome (WS) is a rare genetic disorder characterized by varying degrees of sensorineural hearing loss and accumulated pigmentation in the skin, hair and iris. The syndrome is classified into four types (WS1, WS2, WS3, and WS4), each with different clinical phenotypes and underlying genetic causes. The aim of this study was to identify the pathogenic variant in a Chinese family with Waardenburg syndrome type IV.

METHODS

The patient and his parents underwent a thorough medical examination. We applied whole exome sequencing to identify the causal variant on the patient and other family members.

RESULTS

The patient presented with iris pigmentary abnormality, congenital megacolon and sensorineural hearing loss. The clinical diagnosis of the patient was WS4. The whole exome sequencing (WES) revealed a novel variant (c.452_456dup) in the SOX10 gene, which could be responsible for the observed pathogenic of WS4 in this patient. Our analysis suggests that this variant produces a truncated protein that contributes to the development of the disease. The genetic test confirmed the diagnosis of WS4 in the patient from the studied pedigree.

CONCLUSIONS

This present study demonstrated that genetic test based on WES, an effective alternative to regular clinical examinations, helps diagnose WS4. The newly identified SOX10 gene variant can expand the understanding of WS4.

Coordinated microRNA/mRNA Expression Profiles Reveal Unique Skin Color Regulatory Mechanisms in Chinese Giant Salamander (Andrias davidianus)

The Chinese giant salamander (Andrias davidianus) has been increasingly popular in the aquaculture market in China in recent years. In the breeding process of Andrias davidianus, we found that some albino individuals were extremely rare and could not be inherited stably, which severely limits their commercialization in the aquaculture market. In this study, we performed transcriptome and small RNA (sRNA) sequencing analyses in the skin samples of wild-type (WT) and albino (AL) Andrias davidianus. In total, among 5517 differentially expressed genes (DEGs), 2911 DEGs were down-regulated in AL, including almost all the key genes involved in melanin formation. A total of 25 miRNAs were differentially expressed in AL compared to WT, of which 17 were up-regulated. Through the integrated analysis, no intersection was found between the target genes of the differentially expressed miRNAs and the key genes for melanin formation. Gene Ontology (GO) and KEGG pathway analyses on DEGs showed that these genes involved multiple processes relevant to melanin synthesis and the key signal pathway MAPK. Interestingly, the transcription factors SOX10 and PAX3 and the Wnt signaling pathway that play a key role in other species were not included, while the other two transcription factors in the SOX family, SOX21 and SOX7, were included. After analyzing the key genes for melanin formation, it was interesting to note an alternative splicing form of the MITF in WT and a critical mutation of the SLC24A5 gene in AL, which might be the main reason for the skin color change of Andrias davidianus. The results contributed to understanding the molecular mechanism of skin pigmentation in Andrias davidianus and accelerating the acquisition process of individuals with specific body colors by genetic means.

Candidate pigmentation genes related to feather color variation in an indigenous chicken breed revealed by whole genome data

Chicken plumage color is an inheritable phenotype that was naturally and artificially selected for during domestication. The Baicheng You chicken is an indigenous Chinese chicken breed presenting three main feather colors, lavender, black, and yellow plumages. To explore the genetic mechanisms underlying the pigmentation in Baicheng You chickens, we re-sequenced the whole genome of Baicheng You chicken with the three plumage colors. By analyzing the divergent regions of the genome among the chickens with different feather colors, we identified some candidate genomic regions associated with the feather colors in Baicheng You chickens. We found that EGR1, MLPH, RAB17, SOX5, and GRM5 genes were the potential genes for black, lavender, and yellow feathers. MLPH, GRM5, and SOX5 genes have been found to be related to plumage colors in birds. Our results showed that EGR1 is a most plausible candidate gene for black plumage, RAB17, MLPH, and SOX5 for lavender plumage, and GRM5 for yellow plumage in Baicheng You chicken.

Genetic insights, disease mechanisms, and biological therapeutics for Waardenburg syndrome

Waardenburg syndrome (WS), also known as auditory-pigmentary syndrome, is the most common cause of syndromic hearing loss (HL), which accounts for approximately 2-5% of all patients with congenital hearing loss. WS is classified into four subtypes depending on the clinical phenotypes. Currently, pathogenic mutations of PAX3, MITF, SOX10, EDN3, EDNRB or SNAI2 are associated with different subtypes of WS. Although supportive techniques like hearing aids, cochlear implants, or other assistive listening devices can alleviate the HL symptom, there is no cure for WS to date. Recently major progress has been achieved in preclinical studies of genetic HL in animal models, including gene delivery and stem cell replacement therapies. This review focuses on the current understandings of pathogenic mechanisms and potential biological therapeutic approaches for HL in WS, providing strategies and directions for implementing WS biological therapies, as well as possible problems to be faced, in the future.

PRAME Immunocytochemistry for the Diagnosis of Melanoma Metastases in Cytological Samples

(1) Background: Fine-needle aspiration cytology is often used for the pre-operative diagnosis of melanoma metastases. The diagnosis may not be confidently established based on morphology alone, and immunocytochemistry is mandatory. The choice of the most advantageous immunocytochemical antibodies is critical, as the sample may be scant, and the presence of pigmented histiocytes may be confounding. However, the diagnostic performance of melanocytic markers in this setting is poorly investigated. Moreover, PRAME (preferentially expressed antigen in melanoma) recently emerged as a novel marker for the diagnosis of melanoma. The current work aimed to evaluate the sensitivity and specificity of PRAME for the diagnosis of melanoma metastases in cytological samples, compared to other melanocytic markers. (2) Methods: PRAME, S100, Melan-A, HMB45 and SOX10 were tested on cell block sections of 48 cases of melanoma metastases diagnosed from cytological samples, and 20 cases of reactive lymphadenopathy. (3) Results: S100 and SOX10 showed the highest sensitivity (100%), while the sensitivity of PRAME was 85.4%. PRAME, Melan-A, SOX10 and HMB45 showed a specificity of 100%, while the specificity of S100 was lower (85%), as it marked some histiocytes. (4) Conclusion: PRAME immunocytochemistry is highly specific for the diagnosis of melanoma metastasis from a cytological sample, but is less sensitive compared with other melanocytic markers.

SoxD transcription factor deficiency in Schwann cells delays myelination in the developing peripheral nervous system

The three SoxD proteins, Sox5, Sox6 and Sox13, represent closely related transcription factors with important roles during development. In the developing nervous system, SoxD proteins have so far been primarily studied in oligodendroglial cells and in interneurons of brain and spinal cord. In oligodendroglial cells, Sox5 and Sox6 jointly maintain the precursor state, interfere with terminal differentiation, and thereby ensure the proper timing of myelination in the central nervous system. Here we studied the role of SoxD proteins in Schwann cells, the functional counterpart of oligodendrocytes in the peripheral nervous system. We show that Schwann cells express Sox5 and Sox13 but not Sox6. Expression was transient and ceased with the onset of terminal differentiation. In mice with early Schwann cell-specific deletion of both Sox5 and Sox13, embryonic Schwann cell development was not substantially affected and progressed normally into the promyelinating stage. However, there was a mild and transient delay in the myelination of the peripheral nervous system of these mice. We therefore conclude that SoxD proteins—in stark contrast to their action in oligodendrocytes—promote differentiation and myelination in Schwann cells.

Identification of a novel Sox5 transcript in mouse testis

The transcription factor SOX5 is present in two distinct isoforms in both human and mouse, L-SOX5 and S-SOX5 (long and short isoforms of SOX5). Here, we identified and characterized a novel transcript of Sox5 (S-Sox5 variant) in mouse testis. eCLIP-based amplification of cDNA ends were performed to identify the potential Sox5 mRNA variant. This novel transcript shares a high similarity with the previously reported S-Sox5 in nucleotide sequence, but with a unique stretch of 5'UTR and an additional exon 9. Semi-quantitative PCR analysis revealed both S-Sox5 variant and S-Sox5 express specifically in mouse testis. Both transcripts increase significantly in mouse testis at postnatal day 21, when round spermatids appear. We further made a series of truncated Sox5 constructs and tagged them with eGFP in HeLa cells. In vitro transfection assay identified the N-terminus and the DNA-binding HMG domain are required for the nuclear localization of SOX5. Our results provides a basis for the future study to investigate the biological function of SOX5 in spermatogenesis.

Comparative analysis of hypothalamus transcriptome between laying hens with different egg-laying rates

Egg-laying performance is one of the most important economic traits in the poultry industry. Commercial layers can lay one egg almost every day during their peak-laying period. However, many Chinese indigenous chicken breeds show a relatively low egg-laying rate, even during their peak-laying period. To understand what makes the difference in egg production, we compared the hypothalamus transcriptome profiles of Lushi blue-shelled-egg chickens (LBS), a Chinese indigenous breed with low egg-laying rate and Rhode Island Red chickens (RIR), a commercial layer with relatively high egg-laying rate using RNA-seq. A total of 753 differentially expressed genes (DEGs) were obtained. Of these DEGs, 38 genes were enriched in 2 Gene Ontology (GO) terms, namely reproduction term and the reproductive process term, and 6 KEGG pathways, namely Wnt signaling pathway, Oocyte meiosis, GnRH signaling pathway, Thyroid hormone signaling pathway, Thyroid hormone synthesis and MAPK signaling pathway, which have been long known to be involved in egg production regulation. To further determine the core genes from the 38 DEGs, protein-protein interaction (PPI) network, co-expression network and transcriptional regulatory network analyses were carried out. After integrated analysis and experimental validation, 4 core genes including RAC1, MRE11A, MAP7 and SOX5 were identified as the potential core genes that are responsible for the laying-rate difference between the 2 breeds. These findings paved the way for future investigating the mechanism of egg-laying regulation and enriched the chicken reproductive regulation theory.

Sorting Sox: Diverse Roles for Sox Transcription Factors During Neural Crest and Craniofacial Development

Sox transcription factors play many diverse roles during development, including regulating stem cell states, directing differentiation, and influencing the local chromatin landscape. Of the twenty vertebrate Sox factors, several play critical roles in the development the neural crest, a key vertebrate innovation, and the subsequent formation of neural crest-derived structures, including the craniofacial complex. Herein, we review the specific roles for individual Sox factors during neural crest cell formation and discuss how some factors may have been essential for the evolution of the neural crest. Additionally, we describe how Sox factors direct neural crest cell differentiation into diverse lineages such as melanocytes, glia, and cartilage and detail their involvement in the development of specific craniofacial structures. Finally, we highlight several SOXopathies associated with craniofacial phenotypes.

SOX5 Regulates Cell Proliferation, Apoptosis, Migration and Invasion in KSHV-Infected Cells

Kaposi's sarcoma (KS) originates from vascular endothelial cells, with KS-associated herpesvirus (KSHV) as the etiological agent. SRY-box transcription factor 5 (SOX5) plays different roles in various types of cancer, although its role in KS remains poorly understood. In this study, we identified the role of SOX5 in KS tissues and KSHV-infected cells and elucidated the molecular mechanism. Thirty-two KS patients were enrolled in this study. Measurement of SOX5 mRNA and protein levels in human KS tissues and adjacent control tissues revealed lower levels in KS tissues, with KS patients having higher SOX5 level in the early stages of the disease compared to the later stages. And SOX5 mRNA and protein was also lower in KSHV-infected cells (iSLK-219 and iSLK-BAC) than normal cells (iSLK-Puro). Additionally, SOX5 overexpression inhibited cell proliferation and promoted apoptosis and decreased KSHV-infected cell migration and invasion. Moreover, we found that SOX5 overexpression suppressed the epithelial-to-mesenchymal transition of KSHV-infected cells. These results suggest SOX5 is a suppressor factor during KS development and a potential target for KS treatment.

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.

Serum levels of miRNA-21-5p in vitiligo patients and effects of miRNA-21-5p on SOX5, beta-catenin, CDK2 and MITF protein expression in normal human melanocytes

BACKGROUND

Epigenetics of vitiligo was evaluated in few studies. In particular, the role of miR-21, a microRNA involved in various processes, including melanogenesis, was never investigated.

OBJECTIVE

Evaluation of serum levels of miR-21-5p in vitiligo patients and miR-21-5p effects on melanogenesis.

METHODS

We measured serum levels of miR-21-5p in 40 patients affected by nonsegmental vitiligo and 40 sex- and age-matched healthy controls. Next, normal human melanocytes were transfected with miR-21-5p to study the effects of this microRNA, which targeted some proteins involved in melanogenesis pathway like SOX5, beta-catenin, cyclin-dependent kinase 2 (CDK2), and MITF.

RESULTS

The expression of miR-21-5p in vitiligo patients was 3.6-4454.4 fold (mean 990.4 ± 1397.9) higher than in controls. The relative expression of miR-21-5p was directly and significantly correlated with disease severity, defined by VASI (Vitiligo Area and Severity Index) score (Rho = 0.89, p = 10^-7), but not other individual or clinical characteristics. In the second part of the study, a significant reduction of SOX5, beta-catenin and CDK2 protein expression and increase of MITF protein expression was observed in cultured melanocytes after 24 h trasfection with miR-21-5p.

CONCLUSION

According to literature, miR-21-5p upregulation and consequent SOX5 downregulation should upregulate melanogenesis, while vitiligo is characterized by skin depigmentation. Our results suggest that current knowledge of the pathogenesis of vitiligo is probably incomplete. Clinical manifestations could result from an altered balance between metabolic pathways with contrasting effects. In this view, miR-21-5p upregulation might be a tentative compensation mechanism. Further studies appear necessary to confirm and better understand our results and their importance.

High expression levels and localization of Sox5 in dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a disease that can lead to heart expansion and severe heart failure, but the specific pathogenesis remains unclear. Sox5 is a member of the Sox family with a key role in cardiac function. However, the role of Sox5 in DCM remains unclear. In the present study, wild-type mice were intraperitoneally injected with doxorubicin (Dox) to induce DCM, and heart specimens from human patients with DCM were used to investigate the preliminary role of Sox5 in DCM. The present study demonstrated that, compared with control human hearts, the hearts of patients with DCM exhibited high expression levels of Sox5 and activation of the wnt/β-catenin pathway. This result was consistent with Dox-induced DCM in mice. Furthermore, in Dox-treated mice, apoptosis was activated during the development of DCM. Inflammation and collagen deposition also increased in DCM mice. The results of the present study indicate that Sox5 may be associated with the development of DCM. Sox5 may be a novel potential factor that regulates DCM.

Genome-wide assessment of DNA methylation in mouse oocytes reveals effects associated with in vitro growth, superovulation, and sexual maturity

Background

In vitro follicle culture (IFC), as applied in the mouse system, allows the growth and maturation of a large number of immature preantral follicles to become mature and competent oocytes. In the human oncofertility clinic, there is increasing interest in developing this technique as an alternative to ovarian cortical tissue transplantation and to preserve the fertility of prepubertal cancer patients. However, the effect of IFC and hormonal stimulation on DNA methylation in the oocyte is not fully known, and there is legitimate concern over epigenetic abnormalities that could be induced by procedures applied during assisted reproductive technology (ART).

Results

In this study, we present the first genome-wide analysis of DNA methylation in MII oocytes obtained after natural ovulation, after IFC and after superovulation. We also performed a comparison between prepubertal and adult hormonally stimulated oocytes. Globally, the distinctive methylation landscape of oocytes, comprising alternating hyper- and hypomethylated domains, is preserved irrespective of the procedure. The conservation of methylation extends to the germline differential methylated regions (DMRs) of imprinted genes, necessary for their monoallelic expression in the embryo. However, we do detect specific, consistent, and coherent differences in DNA methylation in IFC oocytes, and between oocytes obtained after superovulation from prepubertal compared with sexually mature females. Several methylation differences span entire transcription units. Among these, we found alterations in Tcf4, Sox5, Zfp521, and other genes related to nervous system development.

Conclusions

Our observations show that IFC is associated with altered methylation at specific set of loci. DNA methylation of superovulated prepubertal oocytes differs from that of superovulated adult oocytes, whereas oocytes from superovulated adult females differ very little from naturally ovulated oocytes. Importantly, we show that regions other than imprinted gDMRs are susceptible to methylation changes associated with superovulation, IFC, and/or sexual immaturity in mouse oocytes. Our results provide an important reference for the use of in vitro growth and maturation of oocytes, particularly from prepubertal females, in assisted reproductive treatments or fertility preservation.

MEK inhibition remodels the active chromatin landscape and induces SOX10 genomic recruitment in BRAF(V600E) mutant melanoma cells

Background

The MAPK/ERK signaling pathway is an essential regulator of numerous cell processes that are crucial for normal development as well as cancer progression. While much is known regarding MAPK/ERK signal conveyance from the cell membrane to the nucleus, the transcriptional and epigenetic mechanisms that govern gene expression downstream of MAPK signaling are not fully elucidated.

Results

This study employed an integrated epigenome analysis approach to interrogate the effects of MAPK/ERK pathway inhibition on the global transcriptome, the active chromatin landscape, and protein–DNA interactions in 501mel melanoma cells. Treatment of these cells with the small-molecule MEK inhibitor AZD6244 induces hyperpigmentation, widespread gene expression changes including alteration of genes linked to pigmentation, and extensive epigenomic reprogramming of transcriptionally distinct regulatory regions associated with the active chromatin mark H3K27ac. Regulatory regions with differentially acetylated H3K27ac regions following AZD6244 treatment are enriched in transcription factor binding motifs of ETV/ETS and ATF family members as well as the lineage-determining factors MITF and SOX10. H3K27ac-dense enhancer clusters known as super-enhancers show similar transcription factor motif enrichment, and furthermore, these super-enhancers are associated with genes encoding MITF, SOX10, and ETV/ETS proteins. Along with genome-wide resetting of the active enhancer landscape, MEK inhibition also results in widespread SOX10 recruitment throughout the genome, including increased SOX10 binding density at H3K27ac-marked enhancers. Importantly, these MEK inhibitor-responsive enhancers marked by H3K27ac and occupied by SOX10 are located near melanocyte lineage-specific and pigmentation genes and overlap numerous human SNPs associated with pigmentation and melanoma phenotypes, highlighting the variants located within these regions for prioritization in future studies.

Conclusions

These results reveal the epigenetic reprogramming underlying the re-activation of melanocyte pigmentation and developmental transcriptional programs in 501mel cells in response to MEK inhibition and suggest extensive involvement of a MEK-SOX10 axis in the regulation of these processes. The dynamic chromatin changes identified here provide a rich genomic resource for further analyses of the molecular mechanisms governing the MAPK pathway in pigmentation- and melanocyte-associated diseases.

Electronic supplementary material

The online version of this article (10.1186/s13072-019-0297-2) contains supplementary material, which is available to authorized users.

SOXopathies: Growing Family of Developmental Disorders Due to SOX Mutations

The SRY-related (SOX) transcription factor family pivotally contributes to determining cell fate and identity in many lineages. Since the original discovery that SRY deletions cause sex reversal, mutations in half of the 20 human SOX genes have been associated with rare congenital disorders, henceforward called SOXopathies. Mutations are generally de novo, heterozygous, and inactivating, revealing gene haploinsufficiency, but other types, including duplications, have been reported too. Missense variants primarily target the HMG domain, the SOX hallmark that mediates DNA binding and bending, nuclear trafficking, and protein-protein interactions. We here review key clinical and molecular features of SOXopathies and discuss the prospect that the disease family likely involves more SOX genes and larger clinical and genetic spectrums than currently appreciated.

Sox13 is a novel early marker for hair follicle development

Sox13, a group D member of the Sry-related high-mobility group box (Sox) transcription factor family, is expressed in various tissues including the hair follicle. However, its spatiotemporal expression patterns in the hair follicle and its role in hair development remain to be elucidated. To address these questions, we generated Sox13-LacZ-knock-in mice (Sox13^LacZ/+), in which the LacZ reporter gene was inserted in-frame into exon 2, which contains the translation initiation codon. X-gal staining in Sox13^LacZ/+ embryos revealed that Sox13 is initially expressed in the epithelial portion of the placode, and subsequently in the hair germ and the hair peg during early hair follicle development. In postnatal catagen and anagen, Sox13 was detected in the epithelial sheath, whereas in telogen, Sox13 was localized in the bulge region, where hair follicle stem cells reside. Immunohistochemistry with an anti-β-galactosidase antibody and anti-hair keratin antibodies that specifically mark the different layers of the hair follicle revealed that Sox13 was predominantly expressed in the outer root sheath in anagen. However, the integumentary structures of Sox13^LacZ/LacZ mice were grossly and histologically indistinguishable from those of wild type mice. These results suggest that although Sox13 is dispensable for epidermal and adnexal development, Sox13 is a useful marker for early hair follicle development.

Specification and formation of the neural crest: Perspectives on lineage segregation

The neural crest is a fascinating embryonic population unique to vertebrates that is endowed with remarkable differentiation capacity. Thought to originate from ectodermal tissue, neural crest cells generate neurons and glia of the peripheral nervous system, and melanocytes throughout the body. However, the neural crest also generates many ectomesenchymal derivatives in the cranial region, including cell types considered to be of mesodermal origin such as cartilage, bone, and adipose tissue. These ectomesenchymal derivatives play a critical role in the formation of the vertebrate head, and are thought to be a key attribute at the center of vertebrate evolution and diversity. Further, aberrant neural crest cell development and differentiation is the root cause of many human pathologies, including cancers, rare syndromes, and birth malformations. In this review, we discuss the current findings of neural crest cell ontogeny, and consider tissue, cell, and molecular contributions toward neural crest formation. We further provide current perspectives into the molecular network involved during the segregation of the neural crest lineage.

A transition from SoxB1 to SoxE transcription factors is essential for progression from pluripotent blastula cells to neural crest cells

The neural crest is a stem cell population unique to vertebrate embryos that gives rise to derivatives from multiple embryonic germ layers. The molecular underpinnings of potency that govern neural crest potential are highly conserved with that of pluripotent blastula stem cells, suggesting that neural crest cells may have evolved through retention of aspects of the pluripotency gene regulatory network (GRN). A striking difference in the regulatory factors utilized in pluripotent blastula cells and neural crest cells is the deployment of different sub-families of Sox transcription factors; SoxB1 factors play central roles in the pluripotency of naïve blastula and ES cells, whereas neural crest cells require SoxE function. Here we explore the shared and distinct activities of these factors to shed light on the role that this molecular hand-off of Sox factor activity plays in the genesis of neural crest and the lineages derived from it. Our findings provide evidence that SoxB1 and SoxE factors have both overlapping and distinct activities in regulating pluripotency and lineage restriction in the embryo. We hypothesize that SoxE factors may transiently replace SoxB1 factors to control pluripotency in neural crest cells, and then poise these cells to contribute to glial, chondrogenic and melanocyte lineages at stages when SoxB1 factors promote neuronal progenitor formation.

Xenopus SOX5 enhances myogenic transcription indirectly through transrepression

In anamniotes, somite compartimentalization in the lateral somitic domain leads simultaneously to myotome and dermomyotome formation. In the myotome, Xenopus Sox5 is co-expressed with Myod1 in the course of myogenic differentiation. Here, we studied the function of Sox5 using a Myod1-induced myogenic transcription assay in pluripotent cells of animal caps. We found that Sox5 enhances myogenic transcription of muscle markers Des, Actc1, Ckm and MyhE3. The use of chimeric transactivating or transrepressive Sox5 proteins indicates that Sox5 acts as a transrepressor and indirectly stimulates myogenic transcription except for the slow muscle-specific genes Myh7L, Myh7S, Myl2 and Tnnc1. We showed that this role is shared by Sox6, which is structurally similar to Sox5, both belonging to the SoxD subfamily of transcription factors. Moreover, Sox5 can antagonize the inhibitory function of Meox2 on myogenic differentiation. Meox2 which is a dermomyotome marker, represses myogenic transcription in Myod-induced myogenic transcription assay and in Nodal5-induced mesoderm from animal cap assay. The inhibitory function of Meox2 and the pro-myogenic function of Sox5 were confirmed during Xenopus normal development by the use of translation-blocking oligomorpholinos and dexamethasone inducible chimeric Sox5 and Meox2 proteins. We have therefore identified a new function for SoxD proteins in muscle cells, which can indirectly enhance myogenic transcription through transrepression, in addition to the previously identified function as a direct repressor of slow muscle-specific genes.

The role of sex-determining region Y-box 6 in melanogenesis in alpaca melanocytes

BACKGROUND

Sex-determining region Y-box (SOX) proteins function as transcriptional regulators. The derivation of melanocytes from nerve crest cells has been reported to depend on SOX proteins, including SOX10 and SOX5. Whether SOX6 is expressed and has a functional role in melanocytes is unknown.

OBJECTIVE

We aimed to study the effect of transcription factor SOX6 on melanogenesis in alpaca melanocytes.

METHODS

We verified the role of SOX6 in melanogenesis by overexpressing and inhibiting SOX6 in melanocytes. Co-immunoprecipitation (co-IP) experiments were performed to further explore the function of SOX6 in melanogenesis and its mechanism of melanin production. We found that SOX6 interacted with cyclin-dependent kinase （CDK5）, β-catenin, and Cyclin D1.

RESULTS

Bioinformatics analysis suggested that SOX6 has a phosphorylation site for CDK5, which regulates melanogenesis, suggesting that SOX6 might play a role in melanogenesis. Co-IP experiments indicated that SOX6 interacted with CDK5, β-catenin, and Cyclin D1. Quantitative real-time polymerase chain reaction and western blot analyses of SOX6-overexpressing melanocytes revealed increased mRNA and protein expression of Cyclin D1, CDK5, microphthalmia transcription factor (MITF), tyrosinase (TYR), tyrosine related protein-1 (TYRP1), and dopachrome-tautomerase (DCT), whereas β-catenin levels decreased in SOX6-overexpressing melanocytes. The opposite results were observed upon SOX6 knockdown. The melanin content was significantly increased or decreased, respectively, by SOX6 overexpression or knockdown.

CONCLUSION

Our results suggest that SOX6 might enhance melanogenesis by binding with β-catenin to increase Cyclin D1 and MITF expression.

Comparative microRNA-seq Analysis Depicts Candidate miRNAs Involved in Skin Color Differentiation in Red Tilapia

Differentiation and variation in body color has been a growing limitation to the commercial value of red tilapia. Limited microRNA (miRNA) information is available on skin color differentiation and variation in fish so far. In this study, a high-throughput Illumina sequencing of sRNAs was conducted on three color varieties of red tilapia and 81,394,491 raw reads were generated. A total of 158 differentially expressed miRNAs (|log₂(fold change)| ≥ 1 and q-value ≤ 0.001) were identified. Target prediction and functional analysis of color-related miRNAs showed that a variety of putative target genes—including slc7a11, mc1r and asip—played potential roles in pigmentation. Moreover; the miRNA-mRNA regulatory network was illustrated to elucidate the pigmentation differentiation, in which miR-138-5p and miR-722 were predicted to play important roles in regulating the pigmentation process. These results advance our understanding of the molecular mechanisms of skin pigmentation differentiation in red tilapia.

Distinct interactions of Sox5 and Sox10 in fate specification of pigment cells in medaka and zebrafish

Mechanisms generating diverse cell types from multipotent progenitors are fundamental for normal development. Pigment cells are derived from multipotent neural crest cells and their diversity in teleosts provides an excellent model for studying mechanisms controlling fate specification of distinct cell types. Zebrafish have three types of pigment cells (melanocytes, iridophores and xanthophores) while medaka have four (three shared with zebrafish, plus leucophores), raising questions about how conserved mechanisms of fate specification of each pigment cell type are in these fish. We have previously shown that the Sry-related transcription factor Sox10 is crucial for fate specification of pigment cells in zebrafish, and that Sox5 promotes xanthophores and represses leucophores in a shared xanthophore/leucophore progenitor in medaka. Employing TILLING, TALEN and CRISPR/Cas9 technologies, we generated medaka and zebrafish sox5 and sox10 mutants and conducted comparative analyses of their compound mutant phenotypes. We show that specification of all pigment cells, except leucophores, is dependent on Sox10. Loss of Sox5 in Sox10-defective fish partially rescued the formation of all pigment cells in zebrafish, and melanocytes and iridophores in medaka, suggesting that Sox5 represses Sox10-dependent formation of these pigment cells, similar to their interaction in mammalian melanocyte specification. In contrast, in medaka, loss of Sox10 acts cooperatively with Sox5, enhancing both xanthophore reduction and leucophore increase in sox5 mutants. Misexpression of Sox5 in the xanthophore/leucophore progenitors increased xanthophores and reduced leucophores in medaka. Thus, the mode of Sox5 function in xanthophore specification differs between medaka (promoting) and zebrafish (repressing), which is also the case in adult fish. Our findings reveal surprising diversity in even the mode of the interactions between Sox5 and Sox10 governing specification of pigment cell types in medaka and zebrafish, and suggest that this is related to the evolution of a fourth pigment cell type.

How individual cell fates become specified from multipotent progenitors is a fundamental question in developmental and stem cell biology. Body pigment cells derive from a multipotent progenitor, but while in zebrafish there are three types of pigment cells (melanocytes, iridophores and xanthophores), in medaka these progenitors form four (as zebrafish, plus leucophores). Here, we address whether mechanisms generating each cell-type are conserved between the two species. We focus on two key regulatory proteins, Sox5 and Sox10, which we previously showed were involved in pigment cell development in medaka and zebrafish, respectively. We compare experimentally how the two proteins interact in regulating development of each of the pigment cell lineages in these fish. We show that development of all pigment cells, except leucophores, is dependent on Sox10, and that Sox5 modulates Sox10 activity antagonistically in all pigment cells in zebrafish, and melanocytes and iridophores in medaka. Surprisingly, in medaka, Sox5 acts co-operatively with Sox10 to promote xanthophore fate and to repress leucophore fate. Our findings reveal surprising diversity how Sox5 and Sox10 interact to govern pigment cell development in medaka and zebrafish, and suggest that this likely relates to the evolution of the novel leucophore pigment cell type in medaka.

BRG1 interacts with SOX10 to establish the melanocyte lineage and to promote differentiation

Mutations in SOX10 cause neurocristopathies which display varying degrees of hypopigmentation. Using a sensitized mutagenesis screen, we identified Smarca4 as a modifier gene that exacerbates the phenotypic severity of Sox10 haplo-insufficient mice. Conditional deletion of Smarca4 in SOX10 expressing cells resulted in reduced numbers of cranial and ventral trunk melanoblasts. To define the requirement for the Smarca4 -encoded BRG1 subunit of the SWI/SNF chromatin remodeling complex, we employed in vitro models of melanocyte differentiation in which induction of melanocyte-specific gene expression is closely linked to chromatin alterations. We found that BRG1 was required for expression of Dct, Tyrp1 and Tyr, genes that are regulated by SOX10 and MITF and for chromatin remodeling at distal and proximal regulatory sites. SOX10 was found to physically interact with BRG1 in differentiating melanocytes and binding of SOX10 to the Tyrp1 distal enhancer temporally coincided with recruitment of BRG1. Our data show that SOX10 cooperates with MITF to facilitate BRG1 binding to distal enhancers of melanocyte-specific genes. Thus, BRG1 is a SOX10 co-activator, required to establish the melanocyte lineage and promote expression of genes important for melanocyte function.

The long noncoding RNA SPRIGHTLY acts as an intranuclear organizing hub for pre-mRNA molecules

Molecular mechanisms by which long noncoding RNA (lncRNA) molecules may influence cancerous condition are poorly understood. The aberrant expression of SPRIGHTLY lncRNA, encoded within the drosophila gene homolog Sprouty-4 intron, is correlated with a variety of cancers, including human melanomas. We demonstrate by SHAPE-seq and dChIRP that SPRIGHTLY RNA secondary structure has a core pseudoknotted domain. This lncRNA interacts with the intronic regions of six pre-mRNAs: SOX5, SMYD3, SND1, MEOX2, DCTN6, and RASAL2, all of which have cancer-related functions. Hemizygous knockout of SPRIGHTLY by CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 in melanoma cells significantly decreases SPRIGHTLY lncRNA levels, simultaneously decreases the levels of its interacting pre-mRNA molecules, and decreases anchorage-independent growth rate of cells and the rate of in vivo tumor growth in mouse xenografts. These results provide the first demonstration of an lncRNA's three-dimensional coordinating role in facilitating cancer-related gene expression in human melanomas.

Candidate Loci are Revealed by an Initial Genome-wide Association Study of Juvenile Osteochondritis Dissecans

BACKGROUND

Osteochondritis dissecans (OCD) is a condition that oftentimes causes significant knee pain in pediatric patient populations. If left untreated, OCD significantly increases the risk of developing degenerative osteoarthritis along with its associated consequences and costs. Although a genetic component has been suggested to play a role in this disorder, few studies have been carried out in order to determine the underlying genetic etiology of this relatively common complex trait. The goal of our study was to perform an initial genome-wide association study (GWAS) to uncover candidate loci associated with the pathogenesis of OCD.

METHODS

Blood samples were acquired from 2 cohorts, aged 0 to 18 years old, consisting of 209 OCD cases and 1855 population-matched controls. Agencourt Genfind DNA isolation technology was used to isolate high-quality DNA from each sample. Genotype data was then generated utilizing the Illumina Infinium BeadChip array to examine single-nucleotide polymorphisms (SNPs).

RESULTS

In an initial GWAS analysis of our cohort, where a SNP was excluded if the Hardy-Weinberg Equilibrium test P<0.0001, the minor allele frequency<5%, and the genotyping call rate<90%, we obtained our first results for OCD. Although there was no SNP strictly reaching the threshold for genome-wide significance at this early stage, multiple SNPs (35) at several loci revealed evidence of suggestive association with OCD (P<5.0×10).

CONCLUSIONS

The results from our preliminary study are encouraging. Herein we not only discuss the relevance and applicability of GWAS in studying a genetic basis for OCD, but have also identified top signals that may suggest loci involved in coordinated expression as well as a transcription factor involved in development that may be highly relevant to this trait.

CLINICAL RELEVANCE

If genetic predispositions for OCD are detected early enough in life, attempts at activity modification, counseling, and orthopaedic monitoring may successfully reduce progression of this condition, which may lead to progressive osteoarthritis in the third to fourth decade in at-risk patients.

SoxD Transcription Factors: Multifaceted Players of Neural Development

SoxD transcription factor subfamily includes three members, Sox5, Sox6, and Sox13. Like other Sox genes, they contain the High-Mobility-Group (HMG) box as the DNA binding domain but in addition feature the subgroup-specific leucine zipper motif. SoxD genes are expressed in diverse cell types in multiple organs during embryogenesis and in adulthood. Among the cells expressing them are those present in the developing nervous system including neural stem (or progenitor) cells as well as differentiating neurons and oligodendrocytes. SoxD transcription factors do not contain distinct activator or repressor domain, and they are believed to function in modulation of other transcription factors in promoter-specific manners. This brief review article will attempt to summarize the latest studies on the function of SoxD genes in embryogenesis with a particular emphasis on the regulation of neural development.

MicroRNA-21a-5p Functions on the Regulation of Melanogenesis by Targeting Sox5 in Mouse Skin Melanocytes

MicroRNAs (miRNAs) play an important role in regulating almost all biological processes. miRNAs bind to the 3′ untranslated region (UTR) of mRNAs by sequence matching. In a previous study, we demonstrated that miR-21 was differently expressed in alpaca skin with different hair color. However, the molecular and cellular mechanisms for miR-21 to regulate the coat color are not yet completely understood. In this study, we transfected miR-21a-5p into mouse melanocytes and demonstrated its function on melanogenesis of miR-21a-5p by targeting Sox5, which inhibits melanogenesis in mouse melanocytes. The results suggested that miR-21a-5p targeted Sox5 gene based on the binding site in 3′ UTR of Sox5 and overexpression of miR-21a-5p significantly down-regulated Sox5 mRNA and protein expression. Meanwhile, mRNA and protein expression of microphthalmia transcription factor (MITF) and Tyrosinase (TYR) were up-regulated, which subsequently make the melanin production in melanocytes increased. The results suggest that miR-21a-5p regulates melanogenesis via MITF by targeting Sox5.

SOX5 is involved in balanced MITF regulation in human melanoma cells

Background

Melanoma is a cancer with rising incidence and new therapeutics are needed. For this, it is necessary to understand the molecular mechanisms of melanoma development and progression. Melanoma differs from other cancers by its ability to produce the pigment melanin via melanogenesis; this biosynthesis is essentially regulated by microphthalmia-associated transcription factor (MITF). MITF regulates various processes such as cell cycling and differentiation. MITF shows an ambivalent role, since high levels inhibit cell proliferation and low levels promote invasion. Hence, well-balanced MITF homeostasis is important for the progression and spread of melanoma. Therefore, it is difficult to use MITF itself for targeted therapy, but elucidating its complex regulation may lead to a promising melanoma-cell specific therapy.

Method

We systematically analyzed the regulation of MITF with a novel established transcription factor based gene regulatory network model. Starting from comparative transcriptomics analysis using data from cells originating from nine different tumors and a melanoma cell dataset, we predicted the transcriptional regulators of MITF employing ChIP binding information from a comprehensive set of databases. The most striking regulators were experimentally validated by functional assays and an MITF-promoter reporter assay. Finally, we analyzed the impact of the expression of the identified regulators on clinically relevant parameters of melanoma, i.e. the thickness of primary tumors and patient overall survival.

Results

Our model predictions identified SOX10 and SOX5 as regulators of MITF. We experimentally confirmed the role of the already well-known regulator SOX10. Additionally, we found that SOX5 knockdown led to MITF up-regulation in melanoma cells, while double knockdown with SOX10 showed a rescue effect; both effects were validated by reporter assays. Regarding clinical samples, SOX5 expression was distinctively up-regulated in metastatic compared to primary melanoma. In contrast, survival analysis of melanoma patients with predominantly metastatic disease revealed that low SOX5 levels were associated with a poor prognosis.

Conclusion

MITF regulation by SOX5 has been shown only in murine cells, but not yet in human melanoma cells. SOX5 has a strong inhibitory effect on MITF expression and seems to have a decisive clinical impact on melanoma during tumor progression.

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-016-0170-0) contains supplementary material, which is available to authorized users.

Sox13 functionally complements the related Sox5 and Sox6 as important developmental modulators in mouse spinal cord oligodendrocytes

The role of transcription factor Sox13, which together with Sox5 and Sox6 belongs to the SoxD family, is only poorly characterized in central nervous system development. Therefore, we analysed whether Sox13 expression and function overlaps with or differs from that of its close relatives Sox5 and Sox6. In the developing mouse spinal cord, we found Sox13 predominantly expressed in neuroepithelial precursors, oligodendroglial and astroglial cells. The substantially overlapping expression with Sox5 and Sox6 in oligodendroglial cells prompted us to study potential roles during specification, lineage progression and differentiation of oligodendrocytes. In contrast to Sox5 and Sox6, Sox13 expression continues after differentiation and even increases in myelinating oligodendrocytes. Sox13 deletion did not interfere with oligodendroglial development, which was normal in Sox13-deficient mice. However, the premature differentiation of oligodendrocyte precursors triggered by loss of Sox6 was slightly more prominent in Sox6/Sox13 double-deficient mice. Sox13 can bind to the same sites in myelin gene promoters as Sox5 and Sox6 in vitro. Reporter gene assays furthermore reveal a similar antagonizing effect on Sox10-dependent transactivation of myelin gene promoters as previously shown for Sox5 and Sox6. This argues that Sox13 is functionally redundant with the other SoxD proteins and complements Sox5 and Sox6 in their role as important modulators of oligodendrocyte development. The transcription factor Sox13 is co-expressed with the related Sox5 and Sox6 in cells of the oligodendroglial lineage. By itself, it has little impact on oligodendrocyte development but supports Sox5 and Sox6 during the process as a functionally redundant transcription factor.

Genomic analysis reveals distinct mechanisms and functional classes of SOX10-regulated genes in melanocytes

SOX10 is required for melanocyte development and maintenance, and has been linked to melanoma initiation and progression. However, the molecular mechanisms by which SOX10 guides the appropriate gene expression programs necessary to promote the melanocyte lineage are not fully understood. Here we employ genetic and epigenomic analysis approaches to uncover novel genomic targets and previously unappreciated molecular roles of SOX10 in melanocytes. Through global analysis of SOX10-binding sites and epigenetic characteristics of chromatin states, we uncover an extensive catalog of SOX10 targets genome-wide. Our findings reveal that SOX10 predominantly engages 'open' chromatin regions and binds to distal regulatory elements, including novel and previously known melanocyte enhancers. Integrated chromatin occupancy and transcriptome analysis suggest a role for SOX10 in both transcriptional activation and repression to regulate functionally distinct classes of genes. We demonstrate that distinct epigenetic signatures and cis-regulatory sequence motifs predicted to bind putative co-regulatory transcription factors define SOX10-activated and SOX10-repressed target genes. Collectively, these findings uncover a central role of SOX10 as a global regulator of gene expression in the melanocyte lineage by targeting diverse regulatory pathways.

The transcription factors SOX9 and SOX5/SOX6 cooperate genome-wide through super-enhancers to drive chondrogenesis

SOX9 is a transcriptional activator required for chondrogenesis, and SOX5 and SOX6 are closely related DNA-binding proteins that critically enhance its function. We use here genome-wide approaches to gain novel insights into the full spectrum of the target genes and modes of action of this chondrogenic trio. Using the RCS cell line as a faithful model for proliferating/early prehypertrophic growth plate chondrocytes, we uncover that SOX6 and SOX9 bind thousands of genomic sites, frequently and most efficiently near each other. SOX9 recognizes pairs of inverted SOX motifs, whereas SOX6 favors pairs of tandem SOX motifs. The SOX proteins primarily target enhancers. While binding to a small fraction of typical enhancers, they bind multiple sites on almost all super-enhancers (SEs) present in RCS cells. These SEs are predominantly linked to cartilage-specific genes. The SOX proteins effectively work together to activate these SEs and are required for in vivo expression of their associated genes. These genes encode key regulatory factors, including the SOX trio proteins, and all essential cartilage extracellular matrix components. Chst11, Fgfr3, Runx2 and Runx3 are among many other newly identified SOX trio targets. SOX9 and SOX5/SOX6 thus cooperate genome-wide, primarily through SEs, to implement the growth plate chondrocyte differentiation program.

Antagonistic cross-regulation between Sox9 and Sox10 controls an anti-tumorigenic program in melanoma

Melanoma is the most fatal skin cancer, but the etiology of this devastating disease is still poorly understood. Recently, the transcription factor Sox10 has been shown to promote both melanoma initiation and progression. Reducing SOX10 expression levels in human melanoma cells and in a genetic melanoma mouse model, efficiently abolishes tumorigenesis by inducing cell cycle exit and apoptosis. Here, we show that this anti-tumorigenic effect functionally involves SOX9, a factor related to SOX10 and upregulated in melanoma cells upon loss of SOX10. Unlike SOX10, SOX9 is not required for normal melanocyte stem cell function, the formation of hyperplastic lesions, and melanoma initiation. To the contrary, SOX9 overexpression results in cell cycle arrest, apoptosis, and a gene expression profile shared by melanoma cells with reduced SOX10 expression. Moreover, SOX9 binds to the SOX10 promoter and induces downregulation of SOX10 expression, revealing a feedback loop reinforcing the SOX10 low/SOX9 high ant,m/ii-tumorigenic program. Finally, SOX9 is required in vitro and in vivo for the anti-tumorigenic effect achieved by reducing SOX10 expression. Thus, SOX10 and SOX9 are functionally antagonistic regulators of melanoma development.

For the development of future cancer therapies it is imperative to understand the molecular processes underlying tumor initiation and expansion. Many key factors involved in these processes have been identified based on cell culture and transplantation experiments, but their relevance for tumor formation and disease progression in the living organism is often unclear. Therefore, genetically modified mice spontaneously developing tumors present indispensable models for cancer research. Here, we address this issue by studying the formation of melanoma, the most fatal skin tumor in industrialized countries. To this end, we use a transgenic mouse model to elucidate cellular and molecular mechanisms regulating congenital nevus and melanoma initiation. We show that a transcription factor called SOX10 promotes melanoma formation by repressing an anti-tumorigenic program involving the activity of a related factor, SOX9. When SOX10 is inactivated, SOX9 becomes upregulated and induces cell cycle arrest and death in melanoma cells. Furthermore, upon experimental elevation of SOX9 levels, SOX10 activity is suppressed, revealing an antagonistic relationship between SOX9 and SOX10 in melanoma initiation. Knowledge of how an anti-tumorigenic program can be stimulated by modulating the activities of these key factors might help to design novel therapeutic strategies.

Sox5 controls dorsal progenitor and interneuron specification in the spinal cord

The basic organization of somatosensory circuits in the spinal cord is already setup during the initial patterning of the dorsal neural tube. Extrinsic signals, such as Wnt and TGF-β pathways, activate combinatorial codes of transcription factors that are responsible for generating a pattern of discrete domains of dorsal progenitors (dp). These progenitors will give rise to distinct dorsal interneurons (dI). The Wnt/ βcatenin signaling pathway controls specification of dp/dI1-3 progenitors and interneurons. According to the current model in the field, Wnt/βcatenin activity seems to act in a graded fashion in the spinal cord, as different relative levels determine the identity of adjacent progenitors. However, it is not clear how this activity gradient is controlled and how the identities of dI1-3 are differentially regulated by Wnt signalling. We have determined that two SoxD transcription factors, Sox5 and Sox6, are expressed in restricted domains of dorsal progenitors in the neural tube. Using gain- and loss-of function approaches in chicken embryos, we have established that Sox5 controls cell fate specification of dp2 and dp3 progenitors and, as a result, controls the correct number of the corresponding dorsal interneurons (dI2 and dI3). Furthermore, Sox5 exerts its function by restricting dorsally Wnt signaling activity via direct transcriptional induction of the negative Wnt pathway regulator Axin2. By that way, Sox5 acts as a Wnt pathway modulator that contributes to sharpen the dorsal gradient of Wnt/βcatenin activity to control the distinction of two functionally distinct types of interneurons, dI2 and dI3 involved in the somatosensory relay.

Sox5 Is a DNA-binding cofactor for BMP R-Smads that directs target specificity during patterning of the early ectoderm

The SoxD factor, Sox5, is expressed in ectodermal cells at times and places where BMP signaling is active, including the cells of the animal hemisphere at blastula stages and the neural plate border and neural crest at neurula stages. Sox5 is required for proper ectoderm development, and deficient embryos display patterning defects characteristic of perturbations of BMP signaling, including loss of neural crest and epidermis and expansion of the neural plate. We show that Sox5 is essential for activation of BMP target genes in embryos and explants, that it physically interacts with BMP R-Smads, and that it is essential for recruitment of Smad1/4 to BMP regulatory elements. Our findings identify Sox5 as the long-sought DNA-binding partner for BMP R-Smads essential to plasticity and pattern in the early ectoderm.

Sox2 acts as a rheostat of epithelial to mesenchymal transition during neural crest development

Precise control of self-renewal and differentiation of progenitor cells into the cranial neural crest (CNC) pool ensures proper head development, guided by signaling pathways such as BMPs, FGFs, Shh and Notch. Here, we show that murine Sox2 plays an essential role in controlling progenitor cell behavior during craniofacial development. A “Conditional by Inversion” Sox2 allele (Sox2^COIN) has been employed to generate an epiblast ablation of Sox2 function (Sox2^EpINV). Sox2^EpINV/+(H) haploinsufficient and conditional (Sox2^EpINV/mosaic) mutant embryos proceed beyond gastrulation and die around E11. These mutant embryos exhibit severe anterior malformations, with hydrocephaly and frontonasal truncations, which could be attributed to the deregulation of CNC progenitor cells during their epithelial to mesenchymal transition. This irregularity results in an exacerbated and aberrant migration of Sox10⁺ NCC in the branchial arches and frontonasal process of the Sox2 mutant embryos. These results suggest a novel role for Sox2 as a regulator of the epithelial to mesenchymal transitions (EMT) that are important for the cell flow in the developing head.

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.

From CNS stem cells to neurons and glia: Sox for everyone

Neuroepithelial precursor cells of the vertebrate central nervous system either self-renew or differentiate into neurons, oligodendrocytes or astrocytes under the influence of a gene regulatory network that consists in transcription factors, epigenetic modifiers and microRNAs. Sox transcription factors are central to this regulatory network, especially members of the SoxB, SoxC, SoxD, SoxE and SoxF groups. These Sox proteins are widely expressed in neuroepithelial precursor cells and in newly specified, differentiating and mature neurons, oligodendrocytes and astrocytes and influence their identity, survival and development. They exert their effect predominantly at the transcriptional level but also have substantial impact on expression at the epigenetic and posttranscriptional levels with some Sox proteins acting as pioneer factors, recruiting chromatin-modifying and -remodelling complexes or influencing microRNA expression. They interact with a large variety of other transcription factors and influence the expression of regulatory molecules and effector genes in a cell-type-specific and temporally controlled manner. As versatile regulators with context-dependent functions, they are not only indispensable for central nervous system development but might also be instrumental for the development of reprogramming and cell conversion strategies for replacement therapies and for assisted regeneration after injury or degeneration-induced cell loss in the central nervous system.

The nerve growth factor receptor CD271 is crucial to maintain tumorigenicity and stem-like properties of melanoma cells

Background

Large-scale genomic analyses of patient cohorts have revealed extensive heterogeneity between individual tumors, contributing to treatment failure and drug resistance. In malignant melanoma, heterogeneity is thought to arise as a consequence of the differentiation of melanoma-initiating cells that are defined by cell-surface markers like CD271 or CD133.

Results

Here we confirmed that the nerve growth factor receptor (CD271) is a crucial determinant of tumorigenicity, stem-like properties, heterogeneity and plasticity in melanoma cells. Stable shRNA mediated knock-down of CD271 in patient-derived melanoma cells abrogated their tumor-initiating and colony-forming capacity. A genome-wide expression profiling and gene-set enrichment analysis revealed novel connections of CD271 with melanoma-associated genes like CD133 and points to a neural crest stem cell (NCSC) signature lost upon CD271 knock-down. In a meta-analysis we have determined a shared set of 271 differentially regulated genes, linking CD271 to SOX10, a marker that specifies the neural crest. To dissect the connection of CD271 and CD133 we have analyzed 10 patient-derived melanoma-cell strains for cell-surface expression of both markers compared to established cell lines MeWo and A375. We found CD271⁺ cells in the majority of cell strains analyzed as well as in a set of 16 different patient-derived melanoma metastases. Strikingly, only 2/12 cell strains harbored a CD133⁺ sub-set that in addition comprised a fraction of cells of a CD271⁺/CD133⁺ phenotype. Those cells were found in the label-retaining fraction and in vitro deduced from CD271⁺ but not CD271 knock-down cells.

Conclusions

Our present study provides a deeper insight into the regulation of melanoma cell properties and points CD271 out as a regulator of several melanoma-associated genes. Further, our data strongly suggest that CD271 is a crucial determinant of stem-like properties of melanoma cells like colony-formation and tumorigenicity.

Sox5 functions as a fate switch in medaka pigment cell development

Mechanisms generating diverse cell types from multipotent progenitors are crucial for normal development. Neural crest cells (NCCs) are multipotent stem cells that give rise to numerous cell-types, including pigment cells. Medaka has four types of NCC-derived pigment cells (xanthophores, leucophores, melanophores and iridophores), making medaka pigment cell development an excellent model for studying the mechanisms controlling specification of distinct cell types from a multipotent progenitor. Medaka many leucophores-3 (ml-3) mutant embryos exhibit a unique phenotype characterized by excessive formation of leucophores and absence of xanthophores. We show that ml-3 encodes sox5, which is expressed in premigratory NCCs and differentiating xanthophores. Cell transplantation studies reveal a cell-autonomous role of sox5 in the xanthophore lineage. pax7a is expressed in NCCs and required for both xanthophore and leucophore lineages; we demonstrate that Sox5 functions downstream of Pax7a. We propose a model in which multipotent NCCs first give rise to pax7a-positive partially fate-restricted intermediate progenitors for xanthophores and leucophores; some of these progenitors then express sox5, and as a result of Sox5 action develop into xanthophores. Our results provide the first demonstration that Sox5 can function as a molecular switch driving specification of a specific cell-fate (xanthophore) from a partially-restricted, but still multipotent, progenitor (the shared xanthophore-leucophore progenitor).

How individual cell fates are specified from multipotent progenitor cells is a fundamental question in developmental and stem cell biology. Accumulating evidence indicates that stem cells develop into each of their final, diverse cell-types after progression through one or more partially-restricted intermediates, but the molecular mechanisms underlying final fate choice are largely unknown. Neural crest cells (NCCs) give rise to diverse cell-types including multiple pigment cells and thus are a favored model for understanding the mechanism of fate specification. We have investigated how a specific fate choice is made from partially-restricted pigment cell progenitors in medaka. We show that Sry-related transcription factor Sox5 is required for fate determination between yellow xanthophore and white leucophore, and its loss causes excessive formation of leucophores and absence of xanthophores. We demonstrate that Sox5 functions cell-autonomously in the xanthophore lineage in medaka. Furthermore, pax7a is expressed in the partially-restricted progenitor cells shared with xanthophore and leucophore lineages, and Sox5 acts in some of these cells to promote xanthophore lineage. Our work reveals the role of Sox5 as a molecular switch determining xanthophore versus leucophore fate choice from the shared progenitor, and identifies an important mechanism regulating pigment cell fate choice from NCCs.

Expression and function of a novel isoform of Sox5 in malignant B cells

Using a mouse model with the tumor suppressor TRAF3 deleted from B cells, we identified Sox5 as a gene strikingly up-regulated in B lymphomas. Sox5 proteins were not detected in normal or premalignant TRAF3(-/-) B cells even after treatment with B cell stimuli. The Sox5 expressed in TRAF3(-/-) B lymphomas represents a novel isoform of Sox5, and was localized in the nucleus of malignant B cells. Overexpression of Sox5 inhibited cell cycle progression, and up-regulated the protein levels of p27 and β-catenin in human multiple myeloma cells. Together, our findings indicate that Sox5 regulates the proliferation of malignant B cells.

Pleiotropic function of SRY-related HMG box transcription factor 4 in regulation of tumorigenesis

In addition to their critical roles in embryonic development, cell fate decision, and differentiation, members of Sox (Sry-related high-mobility group box) family of transcription factors including Sox4 have been implicated in various cancers. Multiple studies have revealed an increased expression along with specific oncogenic function of Sox4 in tumors, while others observed a reduced expression of Sox4 in different types of malignancies and suppression of tumor initiation or progression by this protein. More interestingly, the prognostic value of Sox4 is debated due to obvious differences between various reports as well as inconsistencies within specific studies. This review summarizes our current understanding of Sox4 expression pattern and its transcription-dependent, as well as transcription-independent, functions in tumor initiation or progression and its correlation with patient survival. We also discuss the existing discrepancies between different reports and their possible explanations.