Gene targeting of Desrt, a novel ARID class DNA-binding protein, causes growth retardation and abnormal development of reproductive organs.

We have cloned and characterized a novel murine DNA-binding protein Desrt, with a motif characteristic of the ARID (A-T rich interaction domain) family of transcription factors. The Desrt gene encodes an 83-kD protein that is shown to bind DNA and is widely expressed in adult tissues. To examine the in vivo function of Desrt, we have generated mice with a targeted mutation in the ARID domain of Desrt. Homozygous mutants have reduced viability, pronounced growth retardation, and a high incidence of abnormalities of the female and male reproductive organs including cryptorchidism. This may thus serve as a model to dissect the mechanisms involved in the development of the reproductive tract including testicular descent. Gene-targeted mice also display a reduction in the thickness of the zona reticularis of the adrenal gland and transient aberrations of the T and B cell compartments of primary lymphoid organs. These data show that this novel DNA-binding protein, Desrt, has a nonredundant function during growth and in the development of the reproductive system.

Desrt, an AT-rich interaction domain family transcription factor gene, is an early marker for nephrogenic mesoderm and is expressed dynamically during mouse limb development.

Desrt is a mouse gene of the AT-rich interaction domain family of transcription factors. Here we describe the temporal and spatial pattern of expression of Desrt during mouse organogenesis. Desrt expression is first detected in the intermediate plate mesoderm, providing an early embryonic marker for this tissue, and subsequently in the nephrogenic cords of the urogenital ridges. A highly dynamic expression pattern is observed in the developing limb, implicating Desrt in limb patterning. Desrt is also detected in the myotome of the somites, the oro-naso-pharyngeal ectoderm and underlying mesenchyme, otic vesicles, the gut and its derivatives, and transiently in the liver.

Carotid artery intima-medial thickness is increased in chronic renal failure.

1. Chronic renal failure (CRF) is associated with rapidly progressive atherosclerotic vascular disease. In the present study, carotid arterial intima-medial thickness (IMT) was assessed in a large cohort of patients with CRF and matched controls and related to risk factors. 2. A total of 159 subjects with CRF (serum creatinine > or =0.40 mmol/L) aged > 50 years (mean (+/-SD) 63.8+/-7.7 years) and 159 healthy controls matched for age, sex and smoking status were studied. 3. The IMT was determined using B-mode ultrasound measurements of the far wall of both common carotid arteries and presented as the mean IMT. Fasting plasma homocysteine (tHcy) was measured in the CRF group. 4. Intima-medial thickness was significantly greater in CRF patients than controls (0.89+/-0.17 vs 0.73+/-0.13 mm, respectively) after matching for age, sex and smoking status. Heart rate and pulse pressure were also significantly increased. The tHcy was increased two-fold in the CRF group (27.7+/-11.3 micromol/L; normal < 13.0 micromol/L) and did not correlate with carotid IMT. 5. Compared with controls after adjusting for traditional risk factors, patients with CRF exhibit significantly increased IMT.

Novel endogenous type D retroviral particles expressed at high levels in a SCID mouse thymic lymphoma.

A xenograft model of the human disease Langerhans cell histiocytosis (LCH) was investigated with severe combined immunodeficiency (SCID) mice. Transplantation of human LCH biopsy material into SCID mice resulted in the generation of mouse tumors resembling lymphomas. A thymoma cell line (ThyE1M6) was generated from one of these mice and found to display significant levels of Mg2+-dependent reverse transcriptase activity. Electron microscopy revealed particles with type D retroviral morphology budding from ThyE1M6 cells at a high frequency, whereas control cultures were negative. Reverse transcription-PCR of virion RNA with degenerate primers for conserved regions of various mouse, human, and primate retroviruses amplified novel sequences related to primate type D retroviruses, murine intracisternal A particles, Jaagsiekte sheep retrovirus, and murine long interspersed nuclear elements but not other retroviral classes. We demonstrate that these sequences represent a novel group of endogenous retroviruses expressed at low levels in mice but expressed at high levels in the ThyE1M6 cell line. Furthermore, we propose that the activation of endogenous retroviral elements may be associated with a high incidence of thymomas in SCID mice.

High-level expression of a mitochondrial enzyme, ornithine transcarbamylase from rat liver, in a baculovirus expression system.

The mitochondrial enzyme, ornithine transcarbamylase (OTC) from rat liver was expressed in Spodoptera frugiperda (Sf) insect cells using a baculovirus vector. When insect cells were infected with recombinant Autographica californica nuclear polyhedrosis virus (AcNPV) containing a cDNA encoding the precursor form of OTC (pOTC) inserted into the polyhedrin gene, they expressed catalytically active enzyme at levels of approximately 2.5 micrograms/10(6) cells. About 25% of the active enzyme was a novel, partially processed product of pOTC containing four extra amino acids at the amino terminus of OTC. The most abundant protein found in mitochondria from infected insect cells was the normal processing intermediate iOTC, which contains 8 extra amino acids at the amino terminus of OTC. Whereas this species, present at 20 micrograms/10(6) cells, was not active and did not bind the transition-state analog inhibitor of OTC, delta-PALO, the novel processing product did bind and was affinity-purified, along with mature OTC, on a PALO-affinity column. The OTC expressed in insect cells was located in the same compartment of the mitochondrion as in rat liver. The incomplete processing occurred in vitro in both noninfected and infected insect cells. The high level of expression of iOTC using the baculoviral expression system provides a means of overproducing an obligatory intermediate in the mitochondrial import process.

Complementation of the Aspergillus nidulans arg B1 mutation by ornithine transcarbamylase cDNA from rat liver.

An Aspergillus nidulans strain which is deficient in ornithine transcarbamylase due to the arg B1 mutation was transformed with a plasmid containing the ornithine transcarbamylase cDNA from rat liver under the control of the amd S promoter. Stable transformants were obtained by selection on arginine free medium indicating complementation of the arg B mutation. Proof of expression of the rat enzyme in transformants was obtained by immunoprecipitation of all ornithine transcarbamylase activity from cell extracts with antibodies specific for the rat enzyme. The presence of catalytically active rat ornithine transcarbamylase in the transformants indicated that it is capable of being imported into mitochondria in A. nidulans, proteolytically processed and assembled into its homotrimeric form. In vitro uptake experiments using isolated A. nidulans mitochondria demonstrate that processing of the precursor of rat ornithine transcarbamylase occurs in two temporally separated steps as it does in rat liver mitochondria suggesting evolutionary conservation of the processing machinery. Up to 560 ng of active rat enzyme was produced per gm wet weight mycelia. Use of beta-D-alanine, an inducer of amd S, as sole N-source resulted in increased levels of active rat ornithine transcarbamylase relative to uninduced cultures.