Isolation of differentially expressed genes in human heart tissues

AAV9-Tspyl2 gene therapy retards bleomycin-induced pulmonary fibrosis by modulating downstream TGF-β signaling in mice

Idiopathic pulmonary fibrosis (IPF) is a devastating fibrotic lung disease characterized by scarring and destruction of the lung architecture, with limited treatment options. Targeted gene therapy to restore cell division autoantigen-1 (CDA1) expression may be a potential treatment approach to delay the progression of pulmonary fibrosis (PF). Here, we focused on CDA1, which was significantly decreased in human IPF, in a mouse model of bleomycin (BLM)-induced PF, and in transforming growth factor (TGF-β)-challenged lung fibroblasts. In vitro, CDA1 overexpression by lentivirus infection in human embryonic lung fibroblasts (HFL1 cells) inhibited the production of pro-fibrotic and pro-inflammatory cytokines, lung fibroblast-to-myofibroblast transition, and extracellular matrix protein expression induced by exogenous TGF-β1 treatment, whereas CDA1 knockdown with small interfering RNA promoted this effect. CDA1 overexpression also inhibited cell proliferation and migration. In a mouse model of BLM-induced PF, we provided novel evidence that the intratracheal delivery of adeno-associated virus serotype 9 carrying the mouse Tspyl2 gene reduced lung tissue inflammation and fibrosis. Mechanistically, CDA1, as a transcription regulator, could repress the TGF-β signal transduction in vivo and in vitro. In conclusion, our results show that Tspyl2 gene therapy plays an antifibrotic role by inhibiting the lung fibroblast-to-myofibroblast transition and downstream TGF-β/Smad3 signaling transduction in BLM-induced PF in mice, suggesting that CDA1 is an appropriate and promising therapeutic target for PF.

The Role of Cell Division Autoantigen 1 (CDA1) in Renal Fibrosis of Diabetic Nephropathy

The common kidney disease diabetic nephropathy (DN) accounts for significant morbidity and mortality in patients with diabetes, and its effective diagnosis in incipient stages is still lacking. Renal fibrosis is the main pathological feature of DN. Cell division autoantigen 1 (CDA1), a phosphorylated protein encoded by TSPYL2 on the X chromosome, plays a fibrogenic role by modulating the transforming growth factor-β (TGF-β) signaling, but the exact mechanism remains unclear. TGF-β signaling has been recognized as the key factor in promoting the development and progression of DN. At present, strict control of blood sugar and blood pressure can significantly lower the development and progression of DN in the early stages, and many studies have shown that blocking TGF-β signaling can delay the progress of DN. However, TGF-β is a multifunctional cytokine. Its direct intervention may result in increased side effects. Therefore, the targeted intervention of CDA1 not only can block the TGF-β signaling pathway but also can reduce these side effects. In this article, we review the main physiological roles of CDA1, with particular attention to its effect and potential mechanism in the renal fibrosis of DN.

Tspyl2 Loss-of-Function Causes Neurodevelopmental Brain and Behavior Abnormalities in Mice

Testis specific protein, Y-encoded-like 2 (TSPYL2) regulates the expression of genes encoding glutamate receptors. Glutamate pathology is implicated in neurodevelopmental conditions such as autism spectrum disorder, attention deficit hyperactivity disorder (ADHD) and schizophrenia. In line with this, a microduplication incorporating the TSPYL2 locus has been reported in people with ADHD. However, the role of Tspyl2 remains unclear. Therefore here we used a Tspyl2 loss-of-function mouse model to directly examine how this gene impacts upon behavior and brain anatomy. We hypothesized that Tspyl2 knockout (KO) would precipitate a phenotype relevant to neurodevelopmental conditions. In line with this prediction, we found that Tspyl2 KO mice were marginally more active, had significantly impaired prepulse inhibition, and were significantly more 'sensitive' to the dopamine agonist amphetamine. In addition, the lateral ventricles were significantly smaller in KO mice. These findings suggest that disrupting Tspyl2 gene expression leads to behavioral and brain morphological alterations that mirror a number of neurodevelopmental psychiatric traits.

p600/UBR4 in the central nervous system

A decade ago, the large 600 kDa mammalian protein p600 (also known as UBR4) was discovered as a multifunctional protein with roles in anoikis, viral transformation and protein degradation. Recently, p600 has emerged as a critical protein in the mammalian brain with roles in neurogenesis, neuronal migration, neuronal signaling and survival. How p600 integrates these apparently unrelated functions to maintain tissue homeostasis and murine survival remains unclear. The common molecular basis underlying many of the actions of p600 suggests, however, certain conservation and transposition of these functions across systems. In this review, we summarize the central nervous system functions of p600 and propose new perspectives on its biological complexity in neuronal physiology and neurological diseases.

The nucleosome assembly protein TSPYL2 regulates the expression of NMDA receptor subunits GluN2A and GluN2B

TSPYL2 is an X-linked gene encoding a nucleosome assembly protein. TSPYL2 interacts with calmodulin-associated serine/threonine kinase, which is implicated in X-linked mental retardation. As nucleosome assembly and chromatin remodeling are important in transcriptional regulation and neuronal function, we addressed the importance of TSPYL2 through analyzing Tspyl2 loss-of-function mice. We detected down-regulation of N-methyl-D-aspartate receptor subunits 2A and 2B (GluN2A and GluN2B) in the mutant hippocampus. Evidence from luciferase reporter assays and chromatin immunoprecipitation supported that TSPYL2 regulated the expression of Grin2a and Grin2b, the genes encoding GluN2A and GluN2B. We also detected an interaction between TSPYL2 and CBP, indicating that TSPYL2 may activate gene expression through binding CBP. In terms of functional outcome, Tspyl2 loss-of-function impaired long-term potentiation at hippocampal Schaffer collateral-CA1 synapses. Moreover, mutant mice showed a deficit in fear learning and memory. We conclude that TSPYL2 contributes to cognitive variability through regulating the expression of Grin2a and Grin2b.

p600 Plays Essential Roles in Fetal Development

p600 is a multifunctional protein implicated in cytoskeletal organization, integrin-mediated survival signaling, calcium-calmodulin signaling and the N-end rule pathway of ubiquitin-proteasome-mediated proteolysis. While push, the Drosophila counterpart of p600, is dispensable for development up to adult stage, the role of p600 has not been studied during mouse development. Here we generated p600 knockout mice to investigate the in vivo functions of p600. Interestingly, we found that homozygous deletion of p600 results in lethality between embryonic days 11.5 and 13.5 with severe defects in both embryo and placenta. Since p600 is required for placental development, we performed conditional disruption of p600, which deletes selectively p600 in the embryo but not in the placenta. The conditional mutant embryos survive longer than knockout embryos but ultimately die before embryonic day 14.5. The mutant embryos display severe cardiac problems characterized by ventricular septal defects and thin ventricular walls. These anomalies are associated with reduced activation of FAK and decreased expression of MEF2, which is regulated by FAK and plays a crucial role in cardiac development. Moreover, we observed pleiotropic defects in the liver and brain. In sum, our study sheds light on the essential roles of p600 in fetal development.

Report of interstitial 22q13.1q13.2 microduplication in two siblings with distinctive dysmorphic features, heart defect and mental retardation

We present two siblings (a boy and a girl) with a submicroscopic 4 Mb duplication at 22q13.1q13.2. Both children manifested infantile hypotonia and delayed motor milestones, congenital heart defect, growth deficiency, and strikingly similar and distinctive craniofacial dysmorphism including brachycephaly, blepharophimosis, short broad-based nose and wide mouth with thin upper lip. The boy had also a submucous cleft palate. Both had fair skin and hair compared with their parents. Both had moderate mental retardation associated with a short attention span. A 4-Mb interstitial duplication at 22q13.1q13.2 was detected by whole genome microarray comparative genomic hybridisation (array CGH) in both children. The duplication was confirmed by fluorescence in situ hybridisation (FISH) analysis. Their parents had normal array CGH results. FISH analysis revealed that the father was a carrier of a balanced interchromosomal submicroscopic insertion of 22q13 into chromosome 11q23, explaining the unbalanced aberration detected in both children. This report narrows down the critical region at 22q13.1q13.2, which is associated with mental retardation, pre- and post-natal growth retardation, hippocampal malformation, psychiatric symptoms such as short attention span and facial dysmorphism including hypertelorism, epicanthal folds and low set/abnormal ears.

TSPYL2 is important for G1 checkpoint maintenance upon DNA damage

Nucleosome assembly proteins play important roles in chromatin remodeling, which determines gene expression, cell proliferation and terminal differentiation. Testis specific protein, Y-encoded-like 2 (TSPYL2) is a nucleosome assembly protein expressed in neuronal precursors and mature neurons. Previous studies have shown that TSPYL2 binds cyclin B and inhibits cell proliferation in cultured cells suggesting a role in cell cycle regulation. To investigate the physiological significance of TSPYL2 in the control of cell cycle, we generated mice with targeted disruption of Tspyl2. These mutant mice appear grossly normal, have normal life span and do not exhibit increased tumor incidence. To define the role of TSPYL2 in DNA repair, checkpoint arrest and apoptosis, primary embryonic fibroblasts and thymocytes from Tspyl2 deficient mice were isolated and examined under unperturbed and stressed conditions. We show that mutant fibroblasts are impaired in G1 arrest under the situation of DNA damage induced by gamma irradiation. This is mainly attributed to the defective activation of p21 transcription despite proper p53 protein accumulation, suggesting that TSPYL2 is additionally required for p21 induction. TSPYL2 serves a biological role in maintaining the G1 checkpoint under stress condition.

Subcellular localization of SUN2 is regulated by lamin A and Rab5

SUN2 is an inner nuclear membrane protein with a conserved Sad1/UNC-84 homology SUN-domain at the C-terminus. Intriguingly, SUN2 has also been reported to interact with Rab5, which localizes in early endosomes. To clarify the dual subcellular localization of SUN2, we investigated its localization in lamin A/C deficient cells rescued with lamin A or lamin C isoform, and in HeLa cells transfected with Rab5 or its mutants. We found that expression of lamin A but not lamin C partly restored the nuclear envelope localization of SUN2. SUN2 was redistributed to endosomes upon overexpression of Rab5, but remained on the nuclear envelope when the SUN domain was deleted. To explore the physiological function of SUN2 in vesicle trafficking and endocytosis, we demonstrated the colocalization of endogenous SUN2 and Rab5. Moreover, overexpression of SUN2 stimulated the uptake of transferrin while suppression of SUN2 expression attenuated the process. These findings support a role of SUN2 in endocytosis.

Role of Cell Division Autoantigen 1 (CDA1) in Cell Proliferation and Fibrosis

Cell Division Autoantigen 1 (CDA1) was discovered following screening a human expression library with serum from a patient with Discoid Lupus Erythematosus. CDA1, encoded by TSPYL2 on the X chromosome, shares anti-proliferative, pro‑fibrotic properties with TGF-β. It inhibits cell growth through p53, pERK1/2, p21‑mediated pathways, is implicated in tumorigenesis, the DNA damage response. Its pro-fibrotic property is mediated through cross-talk with TGF-β that results in upregulation of extracellular matrix proteins. The latter properties have identified a key role for CDA1 in diabetes associated atherosclerosis. These dual properties place CDA1 as an attractive molecular target for treating tumors, vascular fibrosis including atherosclerosis, other vascular disorders associated with enhanced TGF-β action, tissue scarring.

Lamin A/C-mediated neuromuscular junction defects in Emery-Dreifuss muscular dystrophy

The LMNA gene encodes lamins A and C, two intermediate filament-type proteins that are important determinants of interphase nuclear architecture. Mutations in LMNA lead to a wide spectrum of human diseases including autosomal dominant Emery-Dreifuss muscular dystrophy (AD-EDMD), which affects skeletal and cardiac muscle. The cellular mechanisms by which mutations in LMNA cause disease have been elusive. Here, we demonstrate that defects in neuromuscular junctions (NMJs) are part of the disease mechanism in AD-EDMD. Two AD-EDMD mouse models show innervation defects including misexpression of electrical activity–dependent genes and altered epigenetic chromatin modifications. Synaptic nuclei are not properly recruited to the NMJ because of mislocalization of nuclear envelope components. AD-EDMD patients with LMNA mutations show the same cellular defects as the AD-EDMD mouse models. These results suggest that lamin A/C–mediated NMJ defects contribute to the AD-EDMD disease phenotype and provide insights into the cellular and molecular mechanisms for the muscle-specific phenotype of AD-EDMD.

Antiproliferative autoantigen CDA1 transcriptionally up-regulates p21(Waf1/Cip1) by activating p53 and MEK/ERK1/2 MAPK pathways

We previously reported that overexpression of cell division autoantigen 1 (CDA1) in HeLa cells arrests cell growth and inhibits DNA synthesis at S-phase. Here we show that CDA1-induced arrest of cell growth is accompanied by increases in protein and mRNA levels of the cyclin-dependent kinase (Cdk) inhibitor protein, p21(Waf1/Cip1) (p21). Both p21 induction and cell growth arrest are reversed when CDA1 expression is inhibited. CDA1 also increases p53 protein, but not its mRNA, in a time- and dose-dependent manner. MDM2, a ubiquitin ligase regulating p53 degradation, is inactivated by CDA1, suggesting that p53 protein accumulation is due to decreased protein degradation. Knockdown of p53, using siRNA targeting two sites of p53 mRNA, abrogates transcriptional induction of p21 by CDA1. Deletion of the p53 responsive element in the distal region of p21 promoter attenuates promoter activity in response to CDA1. DNA damage caused by camptothecin treatment increases mRNA and protein levels of CDA1, accompanied by induction of p53. The DNA damage-induced p53 induction is markedly attenuated by CDA1 knockdown. CDA1 induces phosphorylation of ERK1/2(p44/42), an activity blocked by PD98059 and U0126, inhibitors of the upstream kinase MEK1/2. The MEK inhibitors also block induction of p21 mRNA and abrogate p21 promoter activity stimulated by CDA1. Cell cycle kinases, Cdk1, -2, -4, and -6 are inhibited by CDA1 overexpression. We conclude that CDA1 induces p53- and MEK/ERK1/2 MAPK-dependent expression of p21 by acting through the p53 responsive element in the p21 promoter and that this contributes to its antiproliferative activity.

Identification of differentially expressed genes in human heart with ventricular septal defect using suppression subtractive hybridization

Ventricular septal defect (VSD) accounts for the largest number of birth congenital heart defects in human, but the genetic programs that control ventricular septation are poorly understood. To identify differentially expressed genes between ventricular septal defect and normal ventricular septum myocardium, we have undertaken suppression subtractive hybridization (SSH) and generated reciprocal cDNA collections of representative mRNAs specific to human heart with ventricular septal defect versus normal control. Following SSH, 1378 clones were sequenced and found to derive from 551 different genes. These predominately expressed genes included genes involved in energy metabolism, cell cycle and growth, cytoskeleton and cell adhesion, LIM protein, zinc finger protein, and development. It is anticipated that further study of genes identified will provide insights into their specific roles in the etiology of VSD, even in cardiac development, aging, and disease.

The nuclear membrane proteome: extending the envelope

The marriage of proteomics with cell biology has produced extensive inventories of the proteins that inhabit several subcellular organelles. Recent proteomic analysis has identified many new putative transmembrane proteins in the nuclear envelope, and transcriptome profiling suggests that the nuclear-membrane proteome exhibits some significant variations among different tissues. Cell-type-specific differences in the composition of protein sub-complexes of the nuclear envelope, particularly those containing the disease-associated protein lamin A, could yield distinctive functions and, thus, explain the tissue specificity of a diverse group of nuclear-envelope-linked disorders in humans. Considered together, these recent results suggest an unexpected functional complexity at the nuclear envelope.

Topology of genes and nontranscribed sequences in human interphase nuclei

Knowledge about the functional impact of the topological organization of DNA sequences within interphase chromosome territories is still sparse. Of the few analyzed single copy genomic DNA sequences, the majority had been found to localize preferentially at the chromosome periphery or to loop out from chromosome territories. By means of dual-color fluorescence in situ hybridization (FISH), immunolabeling, confocal microscopy, and three-dimensional (3D) image analysis, we analyzed the intraterritorial and nuclear localization of 10 genomic fragments of different sequence classes in four different human cell types. The localization of three muscle-specific genes FLNA, NEB, and TTN, the oncogene BCL2, the tumor suppressor gene MADH4, and five putatively nontranscribed genomic sequences was predominantly in the periphery of the respective chromosome territories, independent from transcriptional status and from GC content. In interphase nuclei, the noncoding sequences were only rarely found associated with heterochromatic sites marked by the satellite III DNA D1Z1 or clusters of mammalian heterochromatin proteins (HP1alpha, HP1beta, HP1gamma). However, the nontranscribed sequences were found predominantly at the nuclear periphery or at the nucleoli, whereas genes tended to localize on chromosome surfaces exposed to the nuclear interior.

Sun2 Is a Novel Mammalian Inner Nuclear Membrane Protein

Sun protein (Sun1 and Sun2) cDNAs were previously cloned based on the homology of their C-terminal regions (SUN (Sad1 and UNC) domain) with the Caenorhabditis elegans protein UNC-84 whose mutation disrupts nuclear migration/positioning. In this study, we raised an anti-Sun2 serum and identified Sun2 in mammalian cells. In HeLa cells, Sun2 displays a nuclear rim-like pattern typical for a nuclear envelope protein. The Sun2 antibody signal co-localizes with nuclear pore and INM markers signals. The rim-like pattern was also observed with the recombinant full-length Sun2 protein fused to either EGFP or V5 epitopes. In addition, we found that a recombinant truncated form of Sun2, extending from amino acids 26 to 339, is sufficient to specify the nuclear envelope localization. Biochemical analyses show that Sun2 is an 85-kDa protein that is partially insoluble in detergent with high salt concentration and in chaotropic agents. Furthermore, Sun2 is enriched in purified HeLa cell nuclei. Electron microscopy analysis shows that Sun2 localizes in the nuclear envelope with a sub-population present in small clusters. Additionally, we show that the SUN domain of Sun2 is localized to the periplasmic space between the inner and the outer nuclear membranes. From our data, we conclude that Sun2 is a new mammalian inner nuclear membrane protein. Because the SUN domain is conserved from fission yeast to mammals, we suggest that Sun2 belongs to a new class of nuclear envelope proteins with potential relevance to nuclear membrane function in the context of the involvement of its components in an increasing spectrum of human diseases.