Functional hemizygosity of PAFAH1B3 due to a PAFAH1B3-CLK2 fusion gene in a female with mental retardation, ataxia and atrophy of the brain.

We report on the molecular characterization of a translocation t(1;19)(q21.3;q13.2) in a female with mental retardation, ataxia and atrophy of the brain. Sequence analysis of the breakpoints revealed an ALU:-repeat-mediated mechanism of recombination that led to truncation of two genes: the kinase CLK2 and PAFAH1B3, the gene product of which interacts with LIS1 as part of a heterotrimeric G protein complex PAF-AH1B. In addition, two reciprocal fusion genes are present. One expressed fusion gene encodes the first 136 amino acids of PAFAH1B3 followed by the complete CLK2 protein. Truncated PAFAH1B3 protein lost its potential to interact with LIS1 whereas CLK2 activity was conserved within the fusion protein. These data emphasize the importance of PAF-AH1B in brain development and functioning and demonstrate the first fusion gene apparently not associated with cancer.

Regulation of signal transducer, GP13O and the LIF receptor in acute inflammation in vivo.

Recently we examined the expression of the IL-6 receptor (gp80) in three different models of acute inflammation [Geisterfer et al., 1993, Cytokine 5:1]. To continue these studies, we examined the mRNA expression of signal transducing molecule, gp130, and the LIF-R as associated members of a receptor family. Rats were treated with either Freund's complete adjuvant (FA) via intraperitoneal injection, LPS via intravenous injection, or turpentine via subcutaneous injection. The levels of gp130 and LIF-R mRNA expression had a maximum 2-3-fold increase over a 24 h period. However, the time of the maximum increase differed depending on the treatment the rats received. FA treated rats had a maximum induction of gp130 mRNA levels of 2.2-fold (for the 7.5 kb transcript) and 1.3-fold (for the 9.0 kb transcript) at 12 h. LPS treated rats had a maximum increase at 3 h where message levels increased 2.5-fold (7.5 kb) and 1.2-fold (9.0 kb). Turpentine-injected rats showed little difference in gp130 mRNA levels at any time after injection compared to controls. Maximum LIF-R mRNA levels also differed depending on the type of treatment the rats received. FA-injected rats showed a 2.1-fold mRNA increase at 3 h, whereas LPS treated rats show a maximum 2.4-fold increase at 18 h. Turpentine-injected rats showed little increase in mRNA levels compared to controls. Injection of purified recombinant rat IL-6 (rIL-6) had little effect on LIF-R mRNA levels, but had a dramatic inducing effect on gp130 mRNA levels. Rats were also injected (i.p.) with Dexamethasone (Dex) and this had no effect on either gp130 or LIF-R mRNA level expression. These in vivo results indicated that IL-6 has a major role in the regulation of its own receptors, IL-6R (gp80), and gp130, and the onset of acute phase response. We found that the maximum IL-6R (gp80), gp130 and LIF-R mRNA levels peaked at different times depending on the type of acute inflammation induced in the rat. It seems that various combinations of cytokines and hormones are released depending on the type of acute inflammation, and these in turn regulate the expression of diverse receptors on the hepatocyte, resulting in different acute phase kinetics in the various models of inflammation.

IL-6 stimulates vitronectin gene expression in vivo.

We tested the hypothesis that vitronectin (Vn) is regulated as an acute phase reactant in response to inflammatory stimuli. In initial experiments, Vn levels were measured during the surgically induced acute phase response in humans. The plasma concentration of Vn increased approximately twofold following elective orthopedic surgery and remained elevated up to 5 days. To examine the mechanism(s) of increased Vn synthesis, hepatic Vn mRNA expression and serum levels were examined in three rat models of acute inflammation: LPS (i.v.), CFA (i.p.), or turpentine (s.c.) injection. The serum concentration of Vn increased approximately twofold 24 h following treatment with turpentine. The expression of Vn mRNA in the liver increased markedly as early as 3 h after treatment in these models and remained elevated up to 18 h. Northern blot analysis of RNA isolated from fractionated liver cells derived from rats treated with LPS indicated that Vn was mainly expressed in hepatocytes, but not in the endothelial or nonparenchymal cell fractions. To analyze the individual effects of raised corticosterone and IL-6 levels on the expression of hepatic Vn mRNA, rats were injected (i.p.) with either dexamethasone or purified recombinant rat IL-6. Vn mRNA expression was elevated within 1 h after IL-6 injection, whereas dexamethasone-injected rats showed unchanged Vn expression. Vn mRNA also was increased in rats chronically injected with IL-6. These results indicate that the Vn gene is up-regulated in acute and chronic inflammation, and this induction is primarily mediated by IL-6.

Cytokines oncostatin M and interleukin 1 regulate the expression of the IL-6 receptor (gp80, gp130).

The steady-state mRNA levels of the interleukin 6 receptor (IL-6R, gp80) and its signal transducing molecule, gp130, were examined in the rat hepatoma cell line, H-35, stimulated by cytokines IL-6, IL-1, oncostatin M (OSM) and/or Dexamethasone (Dex). In contrast to our previous findings in vivo [Geisterfer et al., 1993, Cytokine, 5:1] in vitro Dex seemed to be the major stimulator of IL-6R mRNA expression, whereas IL-6 seemed to have little effect on the expression of its own receptor mRNA levels. However, the presence of other cytokines influenced the Dex mediated stimulation of IL-6R expression. OSM stimulated IL-6R mRNA levels. At 6 h, cells stimulated with OSM showed a 2.1-fold increase in IL-6R mRNA expression. This stimulation was additive with the Dex-mediated stimulation of IL-6R mRNA levels. In contrast, IL-1 inhibited the Dex-mediated stimulation of IL-6R mRNA. At the same time, IL-1 stimulated the presence of a second smaller mRNA transcript. This mRNA species contained the extracellular domain but lacked both the transmembrane and cytoplasmic domains of the IL-6R, suggesting alternate splicing, possibly coding for a soluble form of gp80. Unlike the gp80 IL-6R molecule, the expression of the gp130 molecule normally expressed as two species of mRNA was not regulated to any major extent in vitro. IL-1 and OSM stimulated both mRNA bands (7.5 and 9.0 kb) approximately 2-fold, whereas IL-6 stimulated mainly the upper 9.0 kb mRNA band.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of IL-6 and the hepatic IL-6 receptor in acute inflammation in vivo.

The serum levels of interleukin 6 (IL-6) and the expression (mRNA) of the 80 kDa IL-6 receptor (IL-6R) were examined in three different models of acute inflammation. Rats were treated with either Freund's complete adjuvant (FA) via intraperitoneal injection, LPS via intravenous injection, or turpentine via subcutaneous injection. Using bio- and specific immunoassays, rat serum levels of IL-6, corticosterone, and acute phase proteins were quantified. LPS treatment induced the quickest and greatest serum IL-6 response (> 100 ng/ml within 3 h). In comparison, sera from turpentine and FA-treated rats contained much lower levels of IL-6 activity (< 10 ng/ml). Serum corticosterone levels increased by 3 h after injection in all three models, and equivalent raised serum levels of acute phase proteins were detected within 12-24 h. The expression of IL-6 receptor mRNA in hepatocytes increased markedly as early as 3 h after treatment and message levels began to decline by 6-12 h in all three models. To analyze the individual effects of raised corticosterone and IL-6 on the expression of hepatic IL-6R mRNA, rats were injected with either dexamethasone (Dex) or purified recombinant rat IL-6 (rIL-6) via intraperitoneal injection. Rats injected with rIL-6 showed highly induced IL-6R mRNA levels as early as 1 h after injection, and Dex-injected rats showed a significant but less dramatic rise in IL-6R message levels. Dex- or rIL-6-injected rats demonstrated a distinct profile of acute phase protein response different from that seen in the three experimental models. Regulation of IL-6R gene expression in the liver in vivo depends on a complex interaction between the hepatocyte and a combination of cytokines and other hormones.