Patients with familial Mediterranean fever suffer sporadic inflammatory attacks characterized by fever and intense pain (in joints, abdomen, or chest). Pyrin, the product of the MEFV locus, is a cytosolic protein whose function is unknown. Using pyrin as a "bait" to probe a yeast two-hybrid library made from neutrophil cDNA, we isolated apoptotic speck protein containing a caspase recruitment domain (CARD) (ASC), a proapoptotic protein that induces the formation of large cytosolic "specks" in transfected cells. We found that when HeLa cells are transfected with ASC, specks are formed. After co-transfection of cells with ASC plus wild type pyrin, an increase in speck-positive cells is found, and speck-positive cells show increased survival. Immunofluorescence studies show that pyrin co-localizes with ASC in specks. Speck localization requires exon 1 of pyrin, but exon 1 alone of pyrin does not result in an increase in the number of specks. Exon 1 of pyrin and exon 1 of ASC show 42% sequence similarity and resemble death domain-related structures in modeling studies. These findings link pyrin to apoptosis pathways and suggest that the modulation of cell survival may be a component of the pathophysiology of familial Mediterranean fever.

We compared the effects of mutations in transmembrane segments (TMs) TM1, TM5, and TM6 on the conduction and activation properties of the cystic fibrosis transmembrane conductance regulator (CFTR) to determine which functional property was most sensitive to mutations and, thereby, to develop a criterion for measuring the importance of a particular residue or TM for anion conduction or activation. Anion substitution studies provided strong evidence for the binding of permeant anions in the pore. Anion binding was highly sensitive to point mutations in TM5 and TM6. Permeability ratios, in contrast, were relatively unaffected by the same mutations, so that anion binding emerged as the conduction property most sensitive to structural changes in CFTR. The relative insensitivity of permeability ratios to CFTR mutations was in accord with the notion that anion-water interactions are important determinants of permeability selectivity. By the criterion of anion binding, TM5 and TM6 were judged to be likely to contribute to the structure of the anion-selective pore, whereas TM1 was judged to be less important. Mutations in TM5 and TM6 also dramatically reduced the sensitivity of CFTR to activation by 3-isobutyl 1-methyl xanthine (IBMX), as expected if these TMs are intimately involved in the physical process that opens and closes the channel.

Familial Mediterranean fever (FMF; MIM 249100) is an autosomal recessive disease characterized by recurrent attacks of fever with synovial, pleural or peritoneal inflammation. The disease is caused by mutations in the gene encoding the pyrin protein. Human population studies have revealed extremely high allele frequencies for several different pyrin mutations, leading to the conclusion that the mutant alleles confer a selective advantage. Here we examine the ret finger protein (rfp) domain (which contains most of the disease-causing mutations) of pyrin during primate evolution. Amino acids that cause human disease are often present as wild type in other species. This is true at positions 653 (a novel mutation), 680, 681, 726, 744 and 761. For several of these human mutations, the mutant represents the reappearance of an ancestral amino acid state. Examination of lineage-specific dN/dS ratios revealed a pattern consistent with the signature of episodic positive selection. Our data, together with previous human population studies, indicate that selective pressures may have caused functional evolution of pyrin in humans and other primates.

Objective. To investigate the expression of the familial Mediterranean fever (FMF) gene (MEFV) in human synovial fibroblasts.Methods. MEFV messenger RNA in synovial fibroblasts, chondrocytes, and peripheral blood leukocytes (PBLs) was analyzed by semiquantitative and real-time polymerase chain reaction and ribonuclease protection assay. The subcellular localization of pyrin, the MEFV product, was determined in transfected synovial fibroblasts and HeLa cells with plasmids encoding pyrin isoforms. Native pyrin was detected with an antipyrin antibody.Results. MEFV was expressed in synovial fibroblasts, but not in chondrocytes. Four alternatively spliced transcripts were identified: an extension of exon 8 (exon 8ext) resulting in a frameshift that predicts a truncated protein lacking exons 9 and 10, the addition of an exon (exon 4a) predicting a truncated protein at exon 5, the in-frame substitution of exon 2a for exon 2, and the previously described removal of exon 2 (exon 2⌬). Exon 8ext transcripts represented 27% of the total message population in synovial fibroblasts. All other alternatively spliced transcripts were rare. Consensus and alternatively spliced transcripts were induced by lipopolysaccharide in synovial fibroblasts and PBLs. In transfected cells, the proteins encoded by all highly expressed splice forms were cytoplasmic. In contrast, native pyrin was predominantly nuclear in synovial fibroblasts, neutrophils, and dendritic cells, but was cytoplasmic in monocytes.Conclusion. Several MEFV transcripts are expressed and inducible in synovial fibroblasts. A prominent isoform lacks the C-terminal domain that contains the majority of mutations found in patients with FMF. While recombinant forms of all major pyrin isoforms are cytoplasmic, native pyrin is nuclear in several cell types. Thus, mechanisms in addition to splicing patterns must control pyrin's subcellular distribution.

Summary The Hedgehog (Hh) pathway plays multiple patterning roles during development of the mammalian gastrointestinal tract, but its role in adult gut function has not been extensively examined. Here we show that chronic reduction in the combined epithelial Indian (Ihh) and Sonic (Shh) hedgehog signal leads to mislocalization of intestinal subepithelial myofibroblasts, loss of smooth muscle in villus cores and muscularis mucosa as well as crypt hyperplasia. In contrast, chronic over-expression of Ihh in the intestinal epithelium leads to progressive expansion of villus smooth muscle, but does not result in reduced epithelial proliferation. Together, these mouse models show that smooth muscle populations in the adult intestinal lamina propria are highly sensitive to the level of Hh ligand. We demonstrate further that Hh ligand drives smooth muscle differentiation in primary intestinal mesenchyme cultures and that cell-autonomous Hh signal transduction in C3H10T1/2 cells activates the smooth muscle master regulator myocardin (Myocd) and induces smooth muscle differentiation. The rapid kinetics of Myocd activation by Hh ligands as well as the presence of an unusual concentration of Gli sties in this gene suggest that regulation of Myocd by Hh might be direct. Thus, these data indicate that Hh is a critical regulator of adult intestinal smooth muscle homeostasis and suggest an important link between Hh signaling and Myocd activation. Moreover, the data support the idea that lowered Hh signals promote crypt expansion and increased epithelial cell proliferation, but indicate that chronically increased Hh ligand levels do not dampen crypt proliferation as previously proposed.

Familial Mediterranean fever (FMF) is an autoinflammatory disease caused by mutations in the MEFV locus, which encodes the protein pyrin. While it is known that pyrin is expressed in myeloid cells and several fibroblastic cell types, the exact function of pyrin in these cells and the mechanism underlying the pathological effect of pyrin mutations have yet to be revealed. Here, we document that in migrating human monocytes, pyrin protein is dramatically polarized at the leading edge, where it co-localizes with polymerizing actin. ASC (Apoptosis-associated Speck protein with CARD domain), a known pyrin-interacting protein and a critical component of the inflamma-some, is also located at the leading edge in migrating monocytes. Similarly, both pyrin and ASC concentrate in dynamically polymerizing actin-rich tails generated by Listeria monocytogenes. Pyrin's B-box and coiled-coil region is required for its association with Listeria tails. Pyrin also binds, with low affinity and via the same domains, to actin, VASP, and Arp3. Though disease-causing mutations in pyrin do not appear to alter its localization to the leading edge or to Listeria rocket tails, they could potentially have important functional consequences in the context of processes such as migration and cell synapse formation. The co-localization of pyrin and ASC together at such sites may provide an important link between cytoskeletal signaling and inflammasome function.

In the adult mouse, distinct morphological and transcriptional differences separate stomach from intestinal epithelium. Remarkably, the epithelial boundary between these two organs is literally one cell thick. This discrete junction is established suddenly and precisely at embryonic day (E) 16.5, by sharpening a previously diffuse intermediate zone. In the present study, we define the dynamic transcriptome of stomach, pylorus, and intestinal tissues between E14.5 and E16.5. We show that establishment of this boundary is concomitant with the induction of over a thousand genes in intestinal epithelium, and these gene products provide intestinal character. Hence, we call this process intestinalization. We identify specific transcription factors (Hnf4c, Creb3l3, and Tcfec) and examine signaling pathways (Hedgehog and Wnt) that may play a role in this process. Finally, we define a unique expression domain at the pylorus itself and detect novel pylorus-specific patterns for the transcription factor Gata3 and the secreted protein nephrocan. Developmental Dynamics 238:3205-3217,

Apoptosis-associated speck-like protein with CARD domain (ASC), an adaptor protein composed of caspase recruitment and pyrin domains, can efficiently self-associate to form a large spherical structure, called a speck. Although ASC aggregation is generally involved with both inflammatory processes and apoptosis, the detailed dynamics of speck formation have not been characterized. In this report, speck formation in HeLa cells transfected with ASC is examined by time-lapse live-imaging by confocal laser scanning microscopy. The results show that ASC aggregation is a very rapid and tightly regulated process. Prior to speck formation, soluble ASC aggregation is a low probability event, and the affinity of ASC subunits for one another is very low. Following a speck nucleation event, the affinity for further addition of ASC subunits increases dramatically, and aggregation is a highly energetically favorable reaction (Gibbs free energy approximately -40 kJ/mol). This leads to a rapid depletion of soluble ASC, making it highly unlikely that a second speck will form inside the same cell and assuring that speck formation is "all or none," with a well-defined end point. Comparison with kinetic models of the aggregation process indicates diffusion, instead of active transport, is the dominant process for speck growth. Though speck formation and aggresome formation share some properties, we show that the two processes are distinct.