Increased Indoleamine 2,3-Dioxygenase Levels at the Onset of Sjögren's Syndrome in SATB1-Conditional Knockout Mice.

Sjögren's syndrome (SS) is a chronic autoimmune disease characterized by dysfunction of salivary and lacrimal glands, resulting in xerostomia (dry mouth) and keratoconjunctivitis sicca (dry eyes). Autoantibodies, such as anti-SSA and anti-SSB antibodies, are hallmarks and important diagnostic factors for SS. In our previous study, we demonstrated that SS-like xerostomia was observed in SATB1 conditional knockout (SATB1cKO) mice, in which the floxed SATB1 gene was specifically deleted in hematopoietic cells as early as 4 weeks of age. In these mice, autoantibodies were not detected until 8 weeks of age in SATB1cKO mice, although exocrine gland function reached its lowest at this age. Therefore, other markers may be necessary for the diagnosis of SS in the early phase. Here, we found that mRNA expression of the interferonγ (IFN-γ) gene and the IFN-responsive indoleamine 2,3-dioxygenase (IDO) gene is upregulated in the salivary glands of SATB1cKO mice after 3 and 4 weeks of age, respectively. We detected l-kynurenine (l-KYN), an intermediate of l-tryptophan (l-Trp) metabolism mediated by IDO, in the serum of SATB1cKO mice after 4 weeks of age. In addition, the upregulation of IDO expression was significantly suppressed by the administration of IFN-γ neutralizing antibodies in SATB1cKO mice. These results suggest that the induction of IFN-dependent IDO expression is an initial event that occurs immediately after the onset of SS in SATB1cKO mice. These results also imply that serum l-KYN could be used as a marker for SS diagnosis in the early phases of the disease before autoantibodies are detectable.

Scaffold attachment factor B: distribution and interaction with ERα in the rat brain.

Scaffold attachment factor (SAFB) 1 and its homologue SAFB2 are multifunctional proteins that are involved in various cellular mechanisms, including chromatin organization and transcriptional regulation, and are also corepressors of estrogen receptor alpha (ERα). Both SAFBs are expressed at high levels in the brain. However, the distributions of SAFB1 and SAFB2 have yet to be characterized in detail and it is unclear whether both proteins interact with ERα in the brain. In this study, we investigated the expression and distribution of both SAFBs and their interaction with ERα in adult male rat brain. Immunohistochemical staining showed that SAFB1 and SAFB2 have a similar distribution pattern and are widely expressed throughout the brain. Double-fluorescence immunohistochemical and immunocytochemical analyses in primary cultures showed that the two SAFB proteins are localized in nuclei of neurons, astrocytes, and oligodendrocytes. Of note, SAFB2 was also found in cytoplasmic regions in these cell lineages. Both SAFB proteins were also expressed in ERα-positive cells in the medial preoptic area (MPOA) and arcuate and ventromedial hypothalamic nuclei. Co-immunoprecipitation experiments revealed that both SAFB proteins from the MPOA reciprocally interact with endogenous ERα. These results indicate that, in addition to a role in basal cellular function in the brain, the SAFB proteins may serve as ERα corepressors in hormone-sensitive regions.

Long noncoding RNA DRAIC acts as a microRNA-122 sponge to facilitate nasopharyngeal carcinoma cell proliferation, migration and invasion via regulating SATB1.

Increasing evidences have revealed that long noncoding RNAs (lncRNAs) are frequently involved in various cancers. However, the expression and function of lncRNA DRAIC in nasopharyngeal carcinoma (NPC) remain unknown. In this study, we found that DRAIC was significantly increased in NPC tissues. Increased expression of DRAIC was positively correlated with advanced clinical stages of NPC patients. Functional assays revealed that ectopic expression of DRAIC enhances NPC cell growth, migration and invasion. DRAIC knockdown represses NPC cell growth, migration and invasion. Mechanistically, we identified two miR-122 binding sites on DRAIC. RNA pull-down, RNA immunoprecipitation, and dual-luciferase reporter assays confirmed the binding of DRAIC to miR-122. Via binding of miR-122, DRAIC upregulated the expression of miR-122 target SATB1, which was abolished by the mutation of miR-122 binding sites on SATB1. Moreover, the oncogenic roles of DRAIC on NPC were reversed by the mutation of miR-122 binding sites on SATB1, simultaneous overexpression of miR-122, or depletion of SATB1. In addition, the expression of SATB1 was also increased and positively associated with that of DRAIC in NPC tissues. In conclusion, these findings revealed the important roles of DRAIC-miR-122-SATB1 axis in NPC and suggested that DRAIC may be a potential therapeutic target for NPC.

Variable SATB1 Levels Regulate Hematopoietic Stem Cell Heterogeneity with Distinct Lineage Fate.

Hematopoietic stem cells (HSCs) comprise a heterogeneous population exhibiting self-renewal and differentiation capabilities; however, the mechanisms involved in maintaining this heterogeneity remain unclear. Here, we show that SATB1 is involved in regulating HSC heterogeneity. Results in conditional Satb1-knockout mice revealed that SATB1 was important for the self-renewal and lymphopoiesis of adult HSCs. Additionally, HSCs from Satb1/Tomato-knockin reporter mice were classified based on SATB1/Tomato intensity, with transplantation experiments revealing stronger differentiation toward the lymphocytic lineage along with high SATB1 levels, whereas SATB1- HSCs followed the myeloid lineage in agreement with genome-wide transcription and cell culture studies. Importantly, SATB1- and SATB1+ HSC populations were interconvertible upon transplantation, with SATB1+ HSCs showing higher reconstituting and lymphopoietic potentials in primary recipients relative to SATB1- HSCs, whereas both HSCs exhibited equally efficient reconstituted lympho-hematopoiesis in secondary recipients. These results suggest that SATB1 levels regulate the maintenance of HSC multipotency, with variations contributing to HSC heterogeneity.

SATB1 Conditional Knockout Results in Sjögren's Syndrome in Mice.

Sjögren's syndrome (SS) is an autoimmune disease in which exocrine tissues are affected by cellular and humoral immunity. As a result, the salivary and lacrimal glands of patients with SS are damaged, leading to xerostomia (dry mouth) and keratoconjunctivitis sicca (dry eyes). Because experimental approaches to investigate SS pathogenesis in human patients are limited, development of a mouse model is indispensable for understanding the disease. In this study, we show that special AT-rich sequence binding protein-1 conditional knockout (SATB1cKO) mice, in which the SATB1 gene is specifically deleted from hematopoietic cells, develop SS by 4 wk of age, soon after weaning. Female mice presented an earlier onset of the disease than males, suggesting that female SATB1cKO mice are more susceptible to SS. T cell-dominant immune cell infiltration was observed in the salivary glands of 4 wk old SATB1cKO mice, and the frequency of B cells gradually increased as the mice aged. Consistently, levels of anti-SSA and anti-SSB Abs were increased around 8 wk of age, after salivary production reached its lowest level in SATB1cKO mice. These results suggest that SATB1cKO mice can be a novel SS model, in which the progression and characteristics of the disease resemble those of human SS.

Specific behavioural phenotype and secondary cognitive decline as a result of an 8.6 Mb deletion of 2q32.2q33.1.

Chromosomal abnormalities involving 2q32q33 deletions are very rare and present with a specific phenotype. This case report describes a 37-year-old female patient with 2q32q33 microdeletion syndrome presenting with the characteristic features, but with the addition of secondary cognitive decline. Molecular karyotyping was performed on the patient and her parents. It revealed an 8.6 megabase deletion with the proximal breakpoint in the chromosome band 2q32.2 and the distal breakpoint in 2q33.1. The deletion encompassed 22 known genes, including theGLS,MYO1B,TMEFF2,PGAP1andSATB2genes. The observed deletion was confirmed using a paralogue ratio test. This case report provides further evidence that theSATB2gene, together withGLS,MYO1B,TMEFF2and possiblyPGAP1,is a crucial gene in 2q32q33 microdeletion syndrome. TheSATB2gene seems to be crucial for the behavioural problems noted in our case, but deletion of theGLS,MYO1BandTMEFF2genes presumably contributed to the more complex behavioural characteristics observed. Our patient is also, to our knowledge, the only patient with 2q32q33 microdeletion syndrome with secondary cognitive decline.

SATB1 Plays a Critical Role in Establishment of Immune Tolerance.

Special AT-rich sequence binding protein 1 (SATB1) is a genome organizer that is expressed by T cells. T cell development is severely impaired in SATB1 null mice; however, because SATB1 null mice die by 3 wk of age, the roles of SATB1 in T cell development have not been well clarified. In this study, we generated and analyzed SATB1 conditional knockout (cKO) mice, in which the SATB1 gene was deleted from all hematopoietic cells. T cell numbers were reduced in these mice, mainly because of a deficiency in positive selection at the CD4(+)CD8(+) double-positive stage during T cell development in the thymus. We also found that SATB1 cKO mice developed autoimmune diseases within 16 wk after birth. In SATB1 cKO mice, the numbers of Foxp3(+) regulatory T (Treg) cells were significantly reduced at 2 wk of age compared with wild-type littermates. Although the numbers gradually increased upon aging, Treg cells in SATB1 cKO mice were still less than those in wild-type littermates at adulthood. Suppressive functions of Treg cells, which play a major role in establishment of peripheral tolerance, were also affected in the absence of SATB1. In addition, negative selection during T cell development in the thymus was severely impaired in SATB1 deficient mice. These results suggest that SATB1 plays an essential role in establishment of immune tolerance.

Satb2-independent acquisition of the cholinergic sudomotor phenotype in rodents.

Expression of Satb2 (Special AT-rich sequence-binding protein-2) elicits expression of the vesicular acetylcholine transporter (VAChT) and choline acetyltransferase (ChAT) in cultured rat sympathetic neurons exposed to soluble differentiation factors. Here, we determined whether or not Satb2 plays a similar role in cholinergic differentiation in vivo, by comparing the postnatal profile of Satb2 expression in the rodent stellate ganglion to that of VAChT and ChAT. Throughout postnatal development, VAChT and ChAT were found to be co-expressed in a numerically stable subpopulation of rat stellate ganglion neurons. Nerve fibers innervating rat forepaw sweat glands on P1 were VAChT immunoreactive, while ChAT was detectable at this target only after P5. The postnatal abundance of VAChT transcripts in the stellate ganglion was at maximum already on P1, whereas ChAT mRNA levels increased from low levels on P1 to reach maximum levels between P5 and P21. Satb2 mRNA was detected in cholinergic neurons in the stellate ganglion beginning with P8, thus coincident with the onset of unequivocal detection of ChAT immunoreactivity in forepaw sweat gland endings. Satb2 knockout mice exhibited no change in the P1 cholinergic VAChT/ChAT co-phenotype in stellate ganglion neurons. Thus, cholinergic phenotype maturation involves first, early target (sweat-gland)-independent expression and trafficking of VAChT, and later, potentially target- and Satb2-dependent elevation of ChAT mRNA and protein transport into sweat gland endings. In rat sudomotor neurons that, unlike mouse sudomotor neurons, co-express calcitonin gene-related peptide (CGRP), Satb2 may also be related to the establishment of species-specific neuropeptide co-phenotypes during postnatal development.

Protooncogene Ski cooperates with the chromatin-remodeling factor Satb2 in specifying callosal neurons.

First insights into the molecular programs orchestrating the progression from neural stem cells to cortical projection neurons are emerging. Loss of the transcriptional regulator Ski has been linked to the human 1p36 deletion syndrome, which includes central nervous system defects. Here, we report critical roles for Ski in the maintenance of the neural stem cell pool and the specification of callosal neurons. Ski-deficient callosal neurons lose their identity and ectopically express the transcription factor Ctip2. The misspecified callosal neurons largely fail to form the corpus callosum and instead redirect their axons toward subcortical targets. We identify the chromatin-remodeling factor Satb2 as a partner of Ski, and show that both proteins are required for transcriptional repression of Ctip2 in callosal neurons. We propose a model in which Satb2 recruits Ski to the Ctip2 locus, and Ski attracts histone deacetylases, thereby enabling the formation of a functional nucleosome remodeling and deacetylase repressor complex. Our findings establish a central role for Ski-Satb2 interactions in regulating transcriptional mechanisms of callosal neuron specification.

SATB1 reprogrammes gene expression to promote breast tumour growth and metastasis.

Mechanisms underlying global changes in gene expression during tumour progression are poorly understood. SATB1 is a genome organizer that tethers multiple genomic loci and recruits chromatin-remodelling enzymes to regulate chromatin structure and gene expression. Here we show that SATB1 is expressed by aggressive breast cancer cells and its expression level has high prognostic significance (P < 0.0001), independent of lymph-node status. RNA-interference-mediated knockdown of SATB1 in highly aggressive (MDA-MB-231) cancer cells altered the expression of >1,000 genes, reversing tumorigenesis by restoring breast-like acinar polarity and inhibiting tumour growth and metastasis in vivo. Conversely, ectopic SATB1 expression in non-aggressive (SKBR3) cells led to gene expression patterns consistent with aggressive-tumour phenotypes, acquiring metastatic activity in vivo. SATB1 delineates specific epigenetic modifications at target gene loci, directly upregulating metastasis-associated genes while downregulating tumour-suppressor genes. SATB1 reprogrammes chromatin organization and the transcription profiles of breast tumours to promote growth and metastasis; this is a new mechanism of tumour progression.

Tissue-specific nuclear architecture and gene expression regulated by SATB1.

Eukaryotic chromosomes are packaged in nuclei by many orders of folding. Little is known about how higher-order chromatin packaging might affect gene expression. SATB1 is a cell-type specific nuclear protein that recruits chromatin-remodeling factors and regulates numerous genes during thymocyte differentiation. Here we show that in thymocyte nuclei, SATB1 has a cage-like 'network' distribution circumscribing heterochromatin and selectively tethers specialized DNA sequences onto its network. This was shown by fluorescence in situ hybridization on wild-type and Satb1-null thymocytes using in vivo SATB1-bound sequences as probes. Many gene loci, including that of Myc and a brain-specific gene, are anchored by the SATB1 network at specific genomic sites, and this phenomenon is precisely correlated with proper regulation of distant genes. Histone-modification analyses across a gene-enriched genomic region of 70 kb showed that acetylation of histone H3 at Lys9 and Lys14 peaks at the SATB1-binding site and extends over a region of roughly 10 kb covering genes regulated by SATB1. By contrast, in Satb1-null thymocytes, this site is marked by methylation at H3 Lys9. We propose SATB1 as a new type of gene regulator with a novel nuclear architecture, providing sites for tissue-specific organization of DNA sequences and regulating region-specific histone modification.