The lupus family registry and repository

The Lupus Family Registry and Repository (LFRR) was established with the goal of assembling and distributing materials and data from families with one or more living members diagnosed with SLE, in order to address SLE genetics. In the present article, we describe the problems and solutions of the registry design and biometric data gathering; the protocols implemented to guarantee data quality and protection of participant privacy and consent; and the establishment of a local and international network of collaborators. At the same time, we illustrate how the LFRR has enabled progress in lupus genetics research, answering old scientific questions while laying out new challenges in the elucidation of the biologic mechanisms that underlie disease pathogenesis. Trained staff ascertain SLE cases, unaffected family members and population-based controls, proceeding in compliance with the relevant laws and standards; participant consent and privacy are central to the LFRR's effort. Data, DNA, serum, plasma, peripheral blood and transformed B-cell lines are collected and stored, and subject to strict quality control and safety measures. Coded data and materials derived from the registry are available for approved scientific users. The LFRR has contributed to the discovery of most of the 37 genetic associations now known to contribute to lupus through 104 publications. The LFRR contains 2618 lupus cases from 1954 pedigrees that are being studied by 76 approved users and their collaborators. The registry includes difficult to obtain populations, such as multiplex pedigrees, minority patients and affected males, and constitutes the largest collection of lupus pedigrees in the world. The LFRR is a useful resource for the discovery and characterization of genetic associations in SLE.

European population substructure is associated with mucocutaneous manifestations and autoantibody production in systemic lupus erythematosus

OBJECTIVE

To determine whether genetic substructure in European-derived populations is associated with specific manifestations of systemic lupus erythematosus (SLE), including mucocutaneous phenotypes, autoantibody production, and renal disease.

METHODS

SLE patients of European descent (n=1,754) from 8 case collections were genotyped for >1,400 ancestry informative markers that define a north-south gradient of European substructure. Using the Structure program, each SLE patient was characterized in terms of percent Northern (versus percent Southern) European ancestry based on these genetic markers. Nonparametric methods, including tests for trend, were used to identify associations between Northern European ancestry and specific SLE manifestations.

RESULTS

In multivariate analyses, increasing levels of Northern European ancestry were significantly associated with photosensitivity (Ptrend=0.0021, odds ratio for highest quartile of Northern European ancestry versus lowest quartile [ORhigh-low] 1.64, 95% confidence interval [95% CI] 1.13-2.35) and discoid rash (Ptrend=0.014, ORhigh-low 1.93, 95% CI 0.98-3.83). In contrast, increasing levels of Northern European ancestry had a protective effect against the production of anticardiolipin autoantibodies (Ptrend=1.6x10(-4), ORhigh-low 0.46, 95% CI 0.30-0.69) and anti-double-stranded DNA autoantibodies (Ptrend=0.017, ORhigh-low 0.67, 95% CI 0.46-0.96).

CONCLUSION

This study demonstrates that specific SLE manifestations vary according to Northern versus Southern European ancestry. Thus, genetic ancestry may contribute to the clinical heterogeneity and variation in disease outcomes among SLE patients of European descent. Moreover, these results suggest that genetic studies of SLE subphenotypes will need to carefully address issues of population substructure based on genetic ancestry.

Ferrets. Examination and preventive medicine

As ferrets are anatomically and physiologically similar to dogs and cats, the basic elements of ferret examination, disease processes, and preventive health are familiar to small-animal practitioners. Like other domestic carnivores, ferrets are tolerant of handling and medical procedures, especially compared with rabbits, rodents, and most nondomestic mammals. These characteristics make ferrets amenable to many of the highly specialized diagnostic and therapeutic techniques that are now available in small-animal practice. Veterinarians who wish to add ferrets to their practices should be familiar with the ferret literature, but they should not forget to draw from the wealth of knowledge in canine and feline medicine when managing unusual or difficult ferret cases.

Hydroxyl radical production and lung injury in the rat following silica or titanium dioxide instillation in vivo

The hydroxyl radical (.OH) is a highly reactive oxygen free radical that has been implicated as a cause of lung injury following exposure to silica and silicates. Despite evidence that silica generates .OH in vitro, there has been no previous demonstration of in vivo production of .OH after exposure to nonfibrous mineral oxide dusts. We tested the hypothesis that instillation of silica into rat lungs is associated with greater .OH production and acute lung inflammation in vivo relative to the instillation of a less toxic nonsilicate particle, titanium dioxide. The production of .OH in the lungs following dust instillation was measured using sodium salicylate as an .OH trap. Seven days after dust exposure, the rats were given intraperitoneal salicylate, the lungs isolated, and salicylate hydroxylation products (2,3- and 2,5-dihydroxybenzoic acid), reflecting .OH, were measured. There was significantly more 2,3-dihydroxybenzoic acid in silica-exposed lungs compared with lungs instilled with titanium dioxide. In addition, the instillation of silica into rat lungs in vivo was associated with a greater acute inflammatory response. We conclude that following in vivo exposure, silica stimulates greater .OH production relative to the less toxic particle, titanium dioxide. These differences in .OH generation correspond to disparities in acute lung inflammation.

Hydroxyl radicals are formed in the rat lung after asbestos instillation in vivo

The hydroxyl radical (.OH) has been implicated as a cause of lung injury following asbestos exposure. However, despite in vitro evidence associating asbestos with .OH production, there has been no demonstration of such generation in vivo. We tested the hypothesis that .OH is formed in the lungs of rats exposed to asbestos in vivo by using salicylate as a free radical trap. Asbestos was instilled intratracheally, and control rats were sham-exposed. Six to seven days after exposure, the rats were given salicylate, the lungs were isolated, and salicylate hydroxylation products (2,3- and 2,5-dihydroxybenzoic acid), reflecting .OH production, were measured. There was significantly more 2,3-dihydroxybenzoic acid in asbestos-exposed lungs compared with control lungs (2.32 +/- 0.360 nmol/lung versus 0.292 +/- 0.125, respectively, P < 0.001) and 2,5-dihydroxybenzoic acid (9.69 +/- 1.65 nmol/lung versus 2.63 +/- 0.274, respectively, P < 0.001). To demonstrate that the dihydroxybenzoic acid was actually formed in the lungs, the lungs from asbestos-exposed and control rats were isolated and perfused with either salicylate or 2,3-dihydroxybenzoic acid. In the lungs perfused with salicylate, 2,3- and 2,5-dihydroxybenzoic acids were detectable only in asbestos-exposed lungs. In the isolated lungs perfused with 2,3-dihydroxybenzoic acid, there was no significant difference in 2,3-dihydroxybenzoic acid between asbestos-exposed and control lungs. We conclude that asbestos stimulates .OH production in lungs in vivo.

Unidirectional dominance of cytoplasmic inheritance in two genetic crosses of Plasmodium falciparum

Malarial parasites have two highly conserved cytoplasmic DNA molecules: a 6-kb tandemly arrayed DNA that has characteristics of a mitochondrial genome, and a 35-kb circular DNA that encodes functions commonly found in chloroplasts. We examined the inheritance pattern of these elements in two genetic crosses of Plasmodium falciparum clones. Parent-specific oligonucleotide probes and single-strand conformation polymorphism analysis identified single nucleotide changes that distinguished the parental 6- and 35-kb DNA molecules in the progeny. In all 16 independent recombinant progeny of a cross between a Central American clone, HB3, and a Southeast Asian clone, Dd2, the 6- and 35-kb DNAs were inherited from the Dd2 parent. In all nine independent recombinant progeny of a cross between clone HB3 and a likely African clone, 3D7, the 6-kb DNA was inherited from the 3D7 parent. Inheritance of cytoplasmic genomes of the Dd2 and 3D7 parents was, therefore, dominant over that of the HB3 parent. Cytoplasmic DNA molecules were found almost exclusively in the female gametes of malarial parasites; hence, clone HB3 did not appear to have served as a maternal parent for the progeny of two crosses. Defective differentiation into male gametes by clone Dd2 is likely to be a reason for the cytoplasmic inheritance pattern seen in the HB3 x Dd2 cross. However, incompetence of male or female gametes is unlikely to explain the uniparental dominance in recombinant progeny of the HB3 x 3D7 cross, since both parents readily self-fertilized and completed the malaria life cycle on their own. Instead, the data suggest unidirectional parental incompatibility in cross-fertilization of these malarial parasites, where a usually cosexual parental clone can participate only as a male or as a female. Such an incompatibility may be speculated as indicating an early phase of reproductive isolation of P. falciparum clones from different geographical regions.

Structural features of Plasmodium cytochrome b that may underlie susceptibility to 8-aminoquinolines and hydroxynaphthoquinones

Appropriate functioning of mitochondria is critical for survival and growth of erythrocytic stages of malarial parasites, making it an attractive target for antimalarial drugs which may take advantage of unique features of parasite mitochondrial metabolism. We have sequenced the presumptive mitochondrial DNA, the 6-kb element, of Plasmodium falciparum, permitting an analysis of the predicted structure of parasite electron transport proteins. Although the overall structures of the 3 polypeptides, cytochrome c oxidase subunit 1, cytochrome c oxidase subunit 3, and cytochrome b (cyt b), were similar to those from other species, some striking differences were observed, especially for the cyt b. Analysis of the cyt b structure showed that the critical quinone binding sites of the protein are quite divergent from those of other species. Comparative analysis suggests that these changes are the likely cause for the resistance of parasite cytochrome bc1 complex to antimycin and related inhibitors. We suggest that the same features are responsible for increased affinity of the parasite cyt b for antimalarial compounds of class 8-aminoquinolines and hydroxynaphthoquinones, explaining the therapeutic value of these drugs.

Immunocytochemical characterization of the high-affinity thiazide diuretic receptor in rabbit renal cortex

Thiazide diuretics increase urinary NaCl excretion primarily by inhibiting Na and Cl transport across the apical membrane of cells in the renal distal tubule. Although these diuretics bind to a membrane protein that couples transport of Na and Cl directly, the molecular nature of this transporter and its localization in the mammalian kidney remain controversial. The present experiments were designed to develop monoclonal antibodies to the high-affinity thiazide diuretic receptor to investigate its molecular characteristics and its cellular and subcellular localization in rabbit kidney. Mice were immunized with high-affinity thiazide diuretic receptors that had been partially purified from rabbit kidney cortex. Resulting hybridomas were screened for the ability to immunoprecipitate thiazide diuretic receptors that were labeled with the thiazide-like diuretic [3H]metolazone. A single hybridoma (MAb JM5) produced antibodies capable of immunoprecipitating up to 80% of the labeled thiazide receptors from solubilized renal cortical membranes. MAb JM5 reacted with a 125-kDa protein on Western blots of solubilized renal cortical apical membranes. It stained the apical membrane of cells in the distal convoluted and connecting tubule but did not stain proximal tubules, glomeruli, or interstitial structures. Less intense staining of apical membranes of principal cells in the collecting tubule and a subpopulation of cells in the thick ascending limb were also present. These results indicate that the high-affinity thiazide diuretic receptor comprises a 125-kDa protein that localizes to the apical membrane of cells in the renal distal tubule.

Solubilization and partial purification of the thiazide diuretic receptor from rabbit renal cortex

This study was designed to solubilize, characterize and begin to purify the thiazide-sensitive Na/Cl transporter from mammalian kidney. Metolazone, a thiazide-like diuretic drug, binds to receptors in rat renal cortex closely related to the thiazide-sensitive Na/Cl transport pathway of the renal distal tubule. In the current study, [3H]metolazone bound to receptors in rabbit renal cortical microsomes. The portion of [3H]metolazone binding that was inhibited by hydrochlorothiazide reflected binding to a high-affinity class of receptor. The affinity (Kd 2.0 +/- 0.1 nM) and number (Bmax = 0.9 +/- 0.4 pmol/mg protein) of high-affinity receptors in rabbit renal cortical membranes were similar to values reported previously for rat. When proximal and distal tubule fragments were separated by Percoll gradient centrifugation, receptors were restricted to the fraction that contained distal tubules. When compared with cortical homogenates, receptor density was enriched 12-fold by magnesium precipitation and differential centrifugation. The zwitterionic detergent CHAPS solubilized 25-35% of the receptors (at 6 mM). Chloride inhibited and Na stimulated binding of [3H]metolazone to solubilized high-affinity receptors. The receptors could be purified significantly by hydroxyapatite chromatography and size exclusion high performance liquid chromatography (HPLC). The combination of magnesium precipitation and differential centrifugation, hydroxyapatite chromatography, and size exclusion HPLC resulted in a 213-fold enrichment of receptors, compared to renal cortical homogenate. The current results indicate that thiazide receptors from rabbit kidney share characteristics with receptors from rat, and that rabbit receptors can be solubilized in CHAPS and purified significantly by hydroxyapatite chromatography and size exclusion HPLC.

Complex transcription from the extrachromosomal DNA encoding mitochondrial functions of Plasmodium yoelii

All tested members of genus Plasmodium contain tandemly arrayed, transcribed, extrachromosomal DNA with a unit length of 6.0 kb. This DNA contains two open reading frames with potential to encode cytochrome c oxidase subunit I (cox1) and cytochrome b (cob) as well as fragments of rRNA genes scattered on both strands. At least 10 discrete RNA molecules transcribed during erythrocytic stages of a rodent malarial parasite, Plasmodium yoelii, were recognized by the 6.0-kb DNA probes. The RNA molecules of 1.4 and 1.1 kb were identified as encoding cox1 and cob, respectively. Primer extension and RNA sequencing were used to locate and characterize 5' ends of these two RNAs, showing that an identical 12-nucleotide sequence, 5'-TATTTTT TGTTT-3', was present at these positions. This sequence may act as a promoter or as an RNA processing signal. A stem-loop structure signifying a possible transcription termination was present at the end of the cox1 open reading frame. At least six discrete RNA molecules of less than 250 nucleotides were recognized by different fractions of the 6.0-kb DNA. The largest of these, 200 nucleotides, was also characterized by primer extension and RNA sequencing. This molecule had a high homology to portions of the large-subunit rRNA domains IV and V. Other, small RNA molecules were recognized by regions of the 6.0-kb DNA that had homology to the highly conserved peptidyltransferase domain of large-subunit rRNA. These results show that the unusual compactly organized mitochondrionlike DNA of malarial parasites is transcribed in a complex pattern.