Recent studies indicate that CTLA-4 interaction with B7 ligands transduces an inhibitory signal to T lymphocytes. Mice homozygous for a null mutation in CTLA-4 have provided the most dramatic example of the functional importance of CTLA-4 in vivo. These animals develop a fatal lymphoproliferative disorder and were reported to have an increase in CD4 ؉ and CD8؉ thymocytes and CD4 ؊ CD8؊ thymocytes, and a decrease in CD4 ؉ CD8 ؉ thymocytes. Based on these observations, it was proposed that CTLA-4 is necessary for normal thymocyte development. In this study, CTLA-4-deficient mice carrying an insertional mutation into exon 3 of the ctla-4 gene were generated. Although these mice display a lymphoproliferative disorder similar to previous reports, there was no alteration in the thymocyte profiles when the parathymic lymph nodes were excluded from the thymi. Further, thymocyte development was normal throughout ontogeny and in neonates, and there was no increase in thymocyte production. Finally, T cell antigen receptor signaling, as assessed by proximal and distal events, was not altered in thymocytes from CTLA-4 ؊/؊ animals. Collectively, these results clearly demonstrate that the abnormal T cell expansion in the CTLA-4-deficient mice is not due to altered thymocyte development and suggest that the apparent altered thymic phenotype previously described was due to the inclusion of parathymic lymph nodes and, in visibly ill animals, to the infiltration of the thymus by activated peripheral T cells. Thus it appears that CTLA-4 is primarily involved in the regulation of peripheral T cell activation.

We studied the cellular function of Nell-1, a craniosynostosis-related gene, in craniofacial development. Nell-1 modulates calvarial osteoblast differentiation and apoptosis pathways. Nell-1 overexpression disrupts these pathways resulting in craniofacial anomalies such as premature suture closure.Introduction: Craniosynostosis (CS), one of the most common congenital craniofacial deformities, is the premature closure of cranial sutures. Previously, we reported NELL-1 as a novel molecule overexpressed during premature cranial suture closure in patients with CS. Nell-1 overexpression induced calvarial overgrowth and resulted in premature suture closure in a rodent model. On a cellular level, Nell-1 is suggested to promote osteoblast differentiation. Materials and Methods: Different levels of Nell-1 were introduced into osteoblastic cells by viral infection and recombinant protein. Apoptosis and gene expression assays were performed. Mice overexpressing Nell-1 were examined for apoptosis. Results: In this report, we further showed that overexpression of Nell-1 induced apoptosis along with modulation of apoptosis-related genes. The induction of apoptosis by Nell-1 was observed only in osteoblastic cells and not in NIH3T3 or primary fibroblasts. The CS mouse model overexpressing Nell-1 showed increased levels of apoptosis in the calvaria. Conclusion:We show that Nell-1 expression modulates calvarial osteoblast differentiation and apoptosis pathways. Nell-1 overexpression disrupts these pathways resulting in craniofacial anomalies such as premature suture closure.

We studied the transcriptional regulation of NELL-1, a craniosynostosis-related gene. We identitifed three OSE2 elements in the NELL-1 promoter that are directly bound and transactivated by Runx2. Forced expression of Runx2 induces NELL-1 expression in rat calvarial cells. Introduction:We previously reported the upregulation of NELL-1 in human craniosynostosis and the overexpression of Nell-1 in transgenic animals that induced premature suture closure associated with increased osteoblast differentiation. To study the transcriptional regulation of NELL-1, we analyzed the 5Ј flanking region of the human NELL-1 gene. We identified three osteoblast specific binding elements 2 (OSE2) sites (A, B, and C) within 2.2 kb upstream of the transcription start site and further studied the functionality of these sites. Materials and Methods: An area of 2.2 kb and a truncated 325 bp, which lacked the three OSE sites, were cloned into a luciferase reporter gene, and co-transfected with Runx2 expression plasmid. The three OSE2 sites were individually mutated and co-transfected with Runx2 expression plasmid into Saos2 cells. Gel shifts and supershifts with Runx2 antibodies were used to determine specific binding to OSE2 sites. CHIP assays were used to study in vivo binding of Runx2 to the Nell-1 promoter. Runx2 expression plasmid was transfected into wildtype and Runx2 −/− calvarial cells. Nell-1, osteocalcin, and Runx2 expression levels were measured using RT-PCR. Results: Addition of Runx2 dose-dependently increased the luciferase activity in the human NELL-1 promoter-luciferase p2213. The p325 truncated NELL-1 construct showed significantly lower basal level of activity. Nuclear extract from Saos2 cells formed complexes with site A, B, and C probes and were supershifted with Runx2 antibody. Mutation of sites A, B, and C significantly decreased basal promoter activity. Furthermore, mutation of sites B and C had a blunted response to Runx2, whereas mutation of site A had a lesser effect. Runx2 bound to NELL-1 promoter in vivo. Transfection of Runx2 in rat osteoblasts upregulated Nell-1 and Ocn expression, and in Runx2 null calvarial cells, both Nell-1 and Ocn expression were rescued. Conclusions: Runx2 directly binds to the OSE2 elements and transactivates the human NELL-1 promoter. These results suggest that Nell-1 is likely a downstream target of Runx2. These findings may also extend our understanding of the molecular mechanisms governing the pathogenesis of craniosynostosis.

The first structure-activity study involving the 1,2-dithiin class of compounds (1,2-dithiacyclohexadienes) is herein reported. A series of 3,6-disubstituted 1,2-dithiins was synthesized from dithiins 1d and 1e and evaluated as antifungal agents. A new and versatile synthesis of dithiins 1d and 1e is reported which is amenable to scale-up at the kilogram level. The novelty of the process derives from the use of beta-mercaptopropionitrile as the thiophile, relying on a beta-elimination strategy and subsequent oxidation to create the 1,2-dithiin ring. Optimal geometries of dithiins 1d, 18i, and 45 and model dithiin 61 were determined by molecular mechanics and Hartree-Fock molecular orbital calculations. Two possible mechanisms of action are presented for the 1,2-dithiin class of compounds to explain their observed antifungal activities against Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus.

Irlbacholine and a series of related analogues were synthesized and their antifungal activities against Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus were assessed. The natural bisphosphocholine, irlbacholine, was the most potent compound, its 22-carbon chain length appearing to be optimal.