Abstract. nonmuscle filamin) is a ubiquitous dimeric actin cross-linking phosphoprotein of peripheral cytoplasm, where it promotes orthogonal branching of actin filaments and links actin filaments to membrane glycoproteins. The complete nucleotide sequence of human endothelial cell ABP cDNA predicts a polypeptide subunit chain of 2,647 amino acids, corresponding to 280 kD, also the mass derived from physical measurements of the native protein. The actin-binding domain is near the amino-terminus of the subunit where the amino acid sequence is similar to other actin filament binding proteins, including t~-actinin,/3-spectrin, dystrophin, and Dictyostelium abp-120. The remaining 90% of the sequence comprises 24 repeats, each ~96 residues long, predicted to have stretches of/3-sheet secondary structure interspersed with turns. The first 15 repeats may have substantial intrachain hydrophobic interactions and overlap in a staggered fashion to yield a backbone with mechanical resilience. Sequence insertions immediately before repeats 16 and 24 predict two hinges in the molecule near points where rotaryshadowed molecules appear to swivel in electron micrographs. Both putative hinge regions are susceptible to cleavage by proteases and the second also contains the site that binds the platelet glycoprotein Ib/IX complex. Phosphorylation consensus sequences are also located in the hinges or near them. Degeneracy within every even-numbered repeat between 16 and 24 and the insertion before repeat 24 may convert interactions within chains to interactions between chains to account for dimer formation within a domain of 7 kD at the carboxy-terminus. The structure of ABP dimers resembles a leaf spring. Interchain interactions hold the leaves firmly together at one end, whereas intrachain hydrophobic bonds reinforce the arms of the spring where the leaves diverge, making it sufficiently stiff to promote high-angle branching of actin illaments. The large size of the leaves, their interruption by two hinges and flexible actin-binding site, facilitate cross-linking of widely dispersed actin filaments.N ONMUSCLE cells achieve a wide variety of shapes by arranging peripheral linear actin filaments in different ways. Actin-modulating proteins are responsible for this versatility by adjusting actin filament length and by defining the organization of actin filaments and their binding to other cellular components (54, 56). Actin-binding protein (ABE also called nonmuscle filamin) ~ was among the first such proteins discovered (25,55,62) and has a broad phylogenetic distribution (3,4,34,47,49,51,59,60,63). ABP from most cell types examined promotes high-angle

Tle1 (transducin-like enhancer of split 1) is a corepressor that interacts with a variety of DNA-binding transcription factors and has been implicated in many cellular functions; however, physiological studies are limited. Tle1-deficient (Tle1 Δ/Δ ) mice, although grossly normal at birth, exhibit skin defects, lung hypoplasia, severe runting, poor body condition, and early mortality. Tle1 Δ/Δ mice display a chronic inflammatory phenotype with increased expression of inflammatory cytokines and chemokines in the skin, lung, and intestine and increased circulatory IL-6 and G-CSF, along with a hematopoietic shift toward granulocyte macrophage progenitor and myeloid cells. Tle1 Δ/Δ macrophages produce increased inflammatory cytokines in response to Toll-like receptor (TLR) agonists and lipopolysaccharides (LPS), and Tle1 Δ/Δ mice display an enhanced inflammatory response to ear skin 12-O-tetradecanoylphorbol-13-acetate treatment. Loss of Tle1 not only results in increased phosphorylation and activation of proinflammatory NF-κB but also results in decreased Hes1 (hairy and enhancer of split-1), a negative regulator of inflammation in macrophages. Furthermore, Tle1 Δ/Δ mice exhibit accelerated growth of B6-F10 melanoma xenografts. Our work provides the first in vivo evidence, to our knowledge, that TLE1 is a major counterregulator of inflammation with potential roles in a variety of inflammatory diseases and in cancer progression.T ransducin-like enhancer of split 1 (TLE1) belongs to a family of corepressor proteins called transducin-like enhancer of split, or TLEs. Groucho, the TLE homolog in Drosophila, has crucial roles in neurogenesis, segmentation, and sex determination (1). These corepressors do not bind directly to DNA but rather interact with many different classes of transcription factors and help create a repressor complex (1, 2).Vertebrates express five different TLEs (TLE1-4, AES), although the distinct functions of each of the TLEs has not been well determined. TLE1, the most studied among the Groucho family proteins in mammalian systems, is widely expressed in different tissues and cell types and has been implicated in neuronal differentiation (3, 4) and pancreatic beta cell development (5). TLE1 has tumor suppressor activity (6-8) as well as oncogenic functions in cancer (9, 10). TLE1 associates with many important transcription factors integral for cell proliferation and differentiation, including Runx2 to block rRNA expression (11), HES1 to suppresses MASH2 expression (12), and TCF/LEF proteins to block Wnt target gene activation (13). TLE1 also represses NF-κB activity (14,15). Involvement in these diverse cellular functions and diseases was studied primarily in vitro or using in vivo overexpression systems. The major physiological function of TLE1, however, remains poorly understood.A few recent studies suggest TLE1 might regulate immune function. For example, a single noncoding nucleotide polymorphism within the TLE1 locus was associated with inflammatory bowel diseases (16), and in human monocytes,...

Hematopoiesis is a complex process that relies on various cell types, signaling pathways, transcription factors and a specific niche. The integration of these various components is of critical importance to normal blood development, as deregulation of these may lead to bone marrow failure or malignancy. Tle4, a transcriptional corepressor, acts as a tumor suppressor gene in a subset of acute myeloid leukemia, yet little is known about its function in normal and malignant hematopoiesis or in mammalian development. We report here that Tle4 knockout mice are runted and die at around four weeks with defects in bone development and BM aplasia. By two weeks of age, Tle4 knockout mice exhibit leukocytopenia, B cell lymphopenia, and significant reductions in hematopoietic stem and progenitor cells. Tle4 deficient hematopoietic stem cells are intrinsically defective in B lymphopoiesis and exhaust upon stress, such as serial transplantation. In the absence of Tle4 there is a profound decrease in bone mineralization. In addition, Tle4 knockout stromal cells are defective at maintaining wild-type hematopoietic stem cell function in vitro. In summary, we illustrate a novel and essential role for Tle4 in the extrinsic and intrinsic regulation of hematopoiesis and in bone development.

Beyond being one the most widely used psychoactive drugs in the world, cannabis has been identified as an environmental risk factor for psychosis. Though the relationship between cannabis use and psychiatric disorders remains controversial, consistent association between early adolescent cannabis use and the subsequent risk of psychosis suggested adolescence may be a particularly vulnerable period. Previous findings on gene by environment interactions indicated that cannabis use may only increase the risk for psychosis in the subjects who have a specific genetic vulnerability. The type 1 cannabinoid receptor (CB1), encoded by the CNR1 gene, is a key component of the endocannabinoid system. As the primary endocannabinoid receptor in the brain, CB1 is the main molecular target of the endocannabinoid ligand, as well as tetrahydrocannabinol (THC), the principal psychoactive ingredient of cannabis. In this study, we have examined mRNA expression and DNA methylation of CNR1 in human prefrontal cortex (PFC), hippocampus, and caudate samples. The expression of CNR1 is higher in fetal PFC and hippocampus, then drops down dramatically after birth. The lifespan trajectory of CNR1 expression in the DLPFC differentially correlated with age by allelic variation at rs4680, a functional polymorphism in the COMT gene. Compared with COMT methionine158 carriers, Caucasian carriers of the COMT valine158 allele have a stronger negative correlation between the expression of CNR1 in DLPFC and age. In contrast, the methylation level of cg02498983, which is negatively correlated with the expression of CNR1 in PFC, showed the strongest positive correlation with age in PFC of Caucasian carriers of COMT valine158. Additionally, we have observed decreased mRNA expression of CNR1 in the DLPFC of patients with schizophrenia. Further analysis revealed a positive eQTL SNP, rs806368, which predicted the expression of a novel transcript of CNR1 in human DLPFC, hippocampus and caudate. This SNP has been associated with addiction and other psychiatric disorders. THC or ethanol are each significantly associated with dysregulated expression of CNR1 in the PFC of patients with affective disorder, and the expression of CNR1 is significantly upregulated in the PFC of schizophrenia patients who completed suicide. Our results support previous studies that have implicated the endocannabinoid system in the pathology of schizophrenia and provided additional insight into the mechanism of increasing risk for schizophrenia in the adolescent cannabis users.