IL-15 prolongs CD154 expression on human CD4 T cells via STAT5 binding to the CD154 transcriptional promoter

Activation-induced CD154 expression on CD4 T cells is prolonged in systemic lupus erythematosus, but the mechanism(s) for its dysregulation are unknown. The studies reported herein demonstrate that interleukin-15 (IL-15) is capable of prolonging CD154 expression on phytohemagglutinin (PHA)-activated CD4 T cells. As IL-15 signals through signal transducer and activator of transcription 5 (STAT5), predicted STAT5 binding sites in the human CD154 transcriptional promoter were identified, and STAT5 binding to the proximal CD154 promoter in vitro and in vivo following primary CD4 T-cell activation was demonstrated. Moreover, overexpression of wild-type STAT5 in primary human CD4 T cells augmented CD154 transcription, whereas overexpression of a dominant-negative (DN) STAT5 protein inhibited CD154 transcription. Mutation of the most proximal STAT5 binding site in the CD154 promoter resulted in diminished DNA binding and reduced CD154 transcriptional activity. Interestingly, STAT5-specific small interfering RNA inhibited CD154 surface expression at 48 but not 24 h after T-cell activation. Thus, these findings provide some of the first evidence to support a possible mechanistic link to explain how the overexpression of IL-15 observed in lupus patients may be involved in the prolonged expression of CD154 that has also been observed on lupus CD4 T cells.

Jagged1 (JAG1) mutation detection in an Australian Alagille syndrome population

Alagille syndrome (AGS) is an autosomal dominant disorder characterized by abnormal development of the liver, heart, skeleton, eye, and face. Mutations in the Jagged1 gene (JAG1) have been found to result in the AGS phenotype and both protein truncating mutations and missense mutations have been identified. Using single stranded conformational polymorphism analysis we have screened 22 AGS affected individuals from 19 families for mutations within Jagged1. Twelve distinct Jagged1 mutations were identified in 15 (68.2%) of the 22 AGS cases, seven of which are novel. The mutations include three small deletions (25%), two small insertions (16.6%), three missense mutations (25%), two nonsense mutations (16.6%), and two splice-site mutations (16.6%). These mutations are spread across the entire coding sequence of the gene and most are localized to highly conserved motifs of the protein predicted to be important for Jagged1 function. One-half of the mutations found in this study are located between exons 9 and 12, a region constituting only 12% of the coding sequence. A splice-donor site mutation in intron 11 was shown to cause aberrant splicing of Jagged1 mRNA, consequently terminating translation prematurely in exon 12. The results of this study are consistent with the proposal that either haploinsufficiency for wild type Jagged1 and/or dominant negative effects produced by mutated Jagged1 are responsible for the AGS phenotype.

Homozygous deletion of the death receptor DR4 gene in a nasopharyngeal cancer cell line is associated with TRAIL resistance

The family of tumor necrosis factor related apoptosis inducing ligand (TRAIL) receptors, including the pro-apoptotic DR4 and p53-regulated KILLER/DR5, as well as the decoys TRID and TRUNDD, are all located on human chromosome 8p21-22. This region of the genome is frequently altered in head and neck cancer. We previously reported that KILLER/DR5 can be mutationally inactivated in head and neck cancer. Here, we report that the FaDu nasopharyngeal cancer cell line contains an abnormal chromosome 8p21-22 region. In addition, there appears to be a homozygous deletion involving DR4 but not KILLER/DR5 in FaDu cells. The homozygous loss within the DR4 gene encompasses its death domain, which is required for apoptotic signaling. The deletion of DR4 in FaDu cells is associated with resistance to the cytotoxic effects of TRAIL. Re-introduction of wild-type DR4 leads to apoptosis and restores TRAIL sensitivity of FaDu cells. These observations suggest that the death inducing DR4 receptor gene may be a rare target for inactivation in human cancer and that DR4 loss may contribute to resistance to TRAIL therapy.

Unique forms of human and mouse nuclear receptor corepressor SMRT

Nuclear hormone receptors have been shown to repress transcription in the absence of ligand. This repression is mediated by a corepressor complex that contains the Sin3A protein and histone deacetylases (HDAC1 and 2). Studies by several groups demonstrate that this complex is recruited to nuclear receptors through the highly related corepressors SMRT (silencing mediator of retinoid acid and thyroid hormone receptor) and N-CoR (nuclear receptor corepressor). We describe here the cloning, characterization, and chromosomal mapping of forms of human and mouse SMRT that includes a 1,000-aa extension, which reveals striking homology to the amino terminus of N-CoR. Structure and function studies of wild-type and natural splicing variants suggest the presence of 3-4 amino terminal domains that repress in a cooperative as well as mechanistically distinct fashion.

The gene encoding human nuclear protein tyrosine phosphatase, PRL-1. Cloning, chromosomal localization, and identification of an intron enhancer

Expression of the rat PRL-1 gene, which encodes a unique nuclear protein tyrosine phosphatase, is positively associated with cellular growth during liver development, regeneration, and oncogenesis but with differentiation in intestine and other tissues. Here, we analyzed the structure of the human PRL-1 gene and localized it to chromosome 6 within band q12. Human, rat, and mouse PRL-1 are 100% conserved at the amino acid level and 55% identical to a newly identified Caenorhabditis elegans PRL-1. The presence of two promoter activities, P1 and P2, in the human PRL-1 gene were identified by primer extension and RNase protection assays. A functional TATA box was identified in promoter P1 upstream of the non-coding first exon. A non-canonical internal promoter, P2, was found in the first intron that results in PRL-1 transcripts beginning 8 base pairs downstream of the 5'-end of exon 2 and causes no alteration in the encoded protein. The first 200-base pair region of either promoter P1 or P2 conferred high basal transcriptional activity. An enhancer that bound a developmentally regulated factor, PRL-1 intron enhancer complex (PIEC), was localized to the first intron of the human PRL-1 gene. The presence of PIEC correlated with the ability of the intron enhancer to confer transcriptional activation in HepG2 and F9 cells. The intron enhancer contributed significantly to PRL-1 promoter activity in HepG2 cells which contain PIEC but not to NIH 3T3 cells which do not.

Spectrum and frequency of jagged1 (JAG1) mutations in Alagille syndrome patients and their families

Alagille syndrome (AGS) is a dominantly inherited disorder characterized by liver disease in combination with heart, skeletal, ocular, facial, renal, and pancreatic abnormalities. We have recently demonstrated that Jagged1 (JAG1) is the AGS gene. JAG1 encodes a ligand in the Notch intercellular signaling pathway. AGS is the first developmental disorder to be associated with this pathway and the first human disorder caused by a Notch ligand. We have screened 54 AGS probands and family members to determine the frequency of mutations in JAG1. Three patients (6%) had deletions of the entire gene. Of the remaining 51 patients, 35 (69%) had mutations within JAG1, identified by SSCP analysis. Of the 35 identified intragenic mutations, all were unique, with the exceptions of a 5-bp deletion in exon 16, seen in two unrelated patients, and a C insertion at base 1618 in exon 9, also seen in two unrelated patients. The 35 intragenic mutations included 9 nonsense mutations (26%); 2 missense mutations (6%); 11 small deletions (31%), 8 small insertions (23%), and 1 complex rearrangement (3%), all leading to frameshifts; and 4 splice-site mutations (11%). The mutations are spread across the coding sequence of the gene within the evolutionarily conserved motifs of the JAG1 protein. There is no phenotypic difference between patients with deletions of the entire JAG1 gene and those with intragenic mutations, which suggests that one mechanism involved in AGS is haploinsufficiency. The two missense mutations occur at the same amino acid residue. The mechanism by which these missense mutations lead to the disease is not yet understood; however, they suggest that mechanisms other than haploinsufficiency may result in the AGS phenotype.

Cloning, human chromosomal assignment, and adipose and hepatic expression of the CL-6/INSIG1 gene

Rat CL-6 is the most highly insulin-induced gene in a liver cell line and is expressed in proliferating liver during regeneration and development. CL-6 is now denoted INSIG1 (insulin-induced gene 1). Human INSIG1 was isolated and found to be 80% identical to the rat gene within the translated region. It was located on human chromosome 7 within band q36. The human INSIG1 promoter conferred a high level of expression in both liver and fibroblast cell lines. INSIG1 expression was upregulated at the transcriptional level in rat regenerating liver and induced in a model of murine adipocyte differentiation, suggesting that INSIG1 may play a role in growth and differentiation of tissues involved in metabolic control.

Mutations in the human Jagged1 gene are responsible for Alagille syndrome

Alagille syndrome (AGS) is an autosomal-dominant disorder characterized by intrahepatic cholestasis and abnormalities of heart, eye and vertebrae, as well as a characteristic facial appearance. Identification of rare AGS patients with cytogenetic deletions has allowed mapping of the gene of 20p12. We have generated a cloned contig of the critical region and used fluorescent in situ hybridization on cells from patients with submicroscopic deletions to narrow the candidate region to only 250 kb. Within this region we identified JAG1, the human homologue of rat Jagged1, which encodes a ligand for the Notch receptor. Cell-cell Jagged/Notch interactions are known to be critical for determination of cell fates in early development, making this an attractive candidate gene for a developmental disorder in humans. Determining the complete exon-intron structure of JAG1 allowed detailed mutational analysis of DNA samples from non-deletion AGS patients, revealing three frame-shift mutations, two splice donor mutations and one mutation abolishing RNA expression from the altered allele. We conclude that AGS is caused by haploinsufficiency of JAG1.

Alagille syndrome is caused by mutations in human Jagged1, which encodes a ligand for Notch1

Alagille syndrome is an autosomal dominant disorder characterized by abnormal development of liver, heart, skeleton, eye, face and, less frequently, kidney. Analyses of many patients with cytogenetic deletions or rearrangements have mapped the gene to chromosome 20p12, although deletions are found in a relatively small proportion of patients (< 7%). We have mapped the human Jagged1 gene (JAG1), encoding a ligand for the developmentally important Notch transmembrane receptor, to the Alagille syndrome critical region within 20p12. The Notch intercellular signalling pathway has been shown to mediate cell fate decisions during development in invertebrates and vertebrates. We demonstrate four distinct coding mutations in JAG1 from four Alagille syndrome families, providing evidence that it is the causal gene for Alagille syndrome. All four mutations lie within conserved regions of the gene and cause translational frameshifts, resulting in gross alterations of the protein product Patients with cytogenetically detectable deletions including JAG1 have Alagille syndrome, supporting the hypothesis that haploinsufficiency for this gene is one of the mechanisms causing the Alagille syndrome phenotype.

Deletions of 20p12 in Alagille syndrome: frequency and molecular characterization

Alagille syndrome is an autosomal dominant disorder comprising cholestasis (associated with intrahepatic bile duct paucity), characteristic facial appearance, and cardiac, ocular and skeletal defects. Multiple patients have been reported with deletions or translocation involving 20p11.23-p12, providing evidence for the localization of the disease gene to this region. Fifty-six Alagille syndrome patients have been studied by cytogenetic and/or molecular analysis to determine the frequency of detectable abnormalities of 20p12. Two of fifty-six patients studied by cytogenetic analysis had abnormalities: an interstitial deletion in one patient and a translocation in another. Of forty-five patients studied by molecular analysis, three were found to have deletions of 20p, including the two patients identified with cytogenetic abnormalities. Molecular and molecular cytogenetic (FISH) analysis of the translocation (46,XX,t(2;20)(q21.3p12)) demonstrated a deletion at the translocation breakpoint. The deletions identified in the three patients are overlapping, contributing to the delineation of an Alagille syndrome critical region within 20p12. This region lies between markers D20S41 and D20S162. The frequency of detectable cytogenetic abnormalities of 20p12 in this group of Alagille patients is 2/56 (3.6%), and the frequency of molecular deletions is 3/45 (6.7%). This is considerably lower than the frequency of deletions observed in contiguous gene deletion syndromes suggesting that Alagille syndrome may be caused by the alteration of a single gene.

Cloning and characterization of two vertebrate homologs of the Drosophila eyes absent gene

The Drosophila eyes absent (eya) gene plays an essential role in the events that lead to proper development of the fly eye and embryo. Here we report the analysis of two human and two mouse homologs of the fly eya gene. Sequence comparison reveals a large domain of approximately 270 amino acids in the carboxyl terminus of the predicted mammalian proteins that shows 53% identity between the fly sequence and all of the vertebrate homologs. This Eya-homology domain is of novel sequence, with no previously identified motifs. RNA hybridization studies indicate that the mouse genes are expressed during embryogenesis and in select tissues of the adult. Both mouse Eya genes are expressed in the eye, suggesting that these genes may function in eye development in vertebrates as eya does in the fly. The mouse Eya2 gene maps to chromosome 2 in the region syntenic with human chromosome 20q13, and the mouse Eya2 gene maps to chromosome 4 in the region syntenic with human chromosome 1p36. Our findings support the notion that several families of genes (Pax-6/eyeless, Six-3/sine oculis, and Eya) play related and critical roles in the eye for both files and vertebrates.

Identification, characterization, and chromosomal localization of the human homolog (hES) of ES/130

The chicken extracellular matrix glycoprotein ES/ 130 is necessary for epithelial--mesenchymal transformation in the developing heart and is also expressed in noncardiac chicken tissues such as limb and notochord. We have identified hES, the human homolog of chicken ES/130. Fluorescence in situ hybridization analysis (FISH) localizes hES to human chromosome 20p11.2-p12. FISH analyses of individuals with 20p12 deletions and affected by Alagille syndrome exclude hES as a candidate gene for this disorder. Reverse transcriptase-polymerase chain reaction studies reveal that hES is expressed in both fetal and adult human tissues and that hES expression in the left ventricle is increased in the failing adult heart. Further studies will evaluate how hES mutations may relate to congenital human cardiac and skeletal anomalies as well as cardiac remodeling in the adult.

Herbivory in Asymbiotic Soft Corals

A zooxanthellae-free soft coral from the Red Sea feeds almost exclusively on phytoplankton, a mode of nutrition so far unknown for corals. Herbivory was also found in three other azooxanthellate soft corals. In tropical oligotrophic waters, phytoplankton biomass density may be an order of magnitude higher than that of zooplankton. Use of this resource allows these azooxanthellate cnidarians to be highly productive in flow-exposed oligotrophic reef waters.

Cytologically balanced t(2;20) in a two-generation family with alagille syndrome: cytogenetic and molecular studies

Alagille syndrome is a clinically defined, dominantly inherited disorder affecting the liver, heart, face, eye, and vertebrae. Alagille syndrome has previously been localized to the short arm of chromosome 20, on the basis of reports of a small number of patients with chromosomal deletions of 20p. We undertook a cytogenetic study of patients with Alagille syndrome and identified a family in which a cytologically balanced translocation between chromosomes 2 and 20, 46,XX/XY, t(2;20)(q21.3;p12), is segregating concordantly with the disease. The breakpoint on chromosome 20p in this t(2;20) is consistent with the shortest region of overlap demonstrated in the reported deletion patients. This is the first report of a translocation associated with 20p and Alagille syndrome, and this rearrangement confirms the location of the Alagille disease gene at 20p12. We have established a somatic cell hybrid from a lymphoblastoid cell line from one of the affected individuals that contains the derivative chromosome 20 (20qter-->p12::2q21.3-->qter) but not the derivative chromosome 2, the normal chromosome 2, or the normal chromosome 20. Southern blot and PCR analysis of probes and sequences from 20p have been studied to define the location of the translocation breakpoint. Our results show that the breakpoint lies distal to D20S61 and D20S56 within band 20p12.

Flow Velocity Induces a Switch From Active to Passive Suspension Feeding in the Porcelain Crab Petrolisthes leptocheles (Heller)

A flow-induced switch in suspension-feeding behavior of the porcelain crab Petrolisthes leptocheles was investigated in a laboratory flow tank. Crabs were exposed to two types of experimental water flow to stimulate them to switch from active to passive suspension feeding. In the first experiment, feeding crabs were exposed to a unidirectional accelerating water current, and they switched from active to passive suspension feeding at a mean water velocity of 3.49 cm s-1. In the second experiment, crabs were exposed to flow that was fixed at a constant velocity for at least 10 min, and their feeding behavior in this steady flow was observed. This procedure was repeated, using a range of constant-velocity flows that were successively adjusted to increased velocity levels. Crabs exposed to these different constant-velocity flows fed exclusively actively at flows below 1.5 cm s-1 and exclusively passively at those above 4.5 cm s-1. Switches from active to passive feeding occurred throughout the range of constant-velocity flows from 1.5 to 4.5 cm s-1. Changes in feeding activity rate induced by an increase in water velocity were measured. The mean activity rate of active feeding (1.05 Hz) was 3.4 times higher than that of passive feeding (0.31 Hz). The porcelain crab's ability to switch feeding modes in response to increased water velocity probably enhances energetic feeding efficiency in two ways. First, the passive feeding activity rate is lower than the active one and should reduce energetic expenditure. Additionally, the flux of suspended food increases with water flow velocity, so passive feeders are likely to catch more food per unit time than active feeders do. The ability to switch feeding modes is quite similar to that already described for balanomorph barnacles and appears to represent convergent evolution of flexible feeding behavior in response to variable water flow environment.