The consequence of PRELP overexpression on skin.

PRELP is a member of the small leucine-rich repeat proteoglycan family that is abundantly expressed in many cartilages compared to other connective tissues. To study the consequence of PRELP overexpression in tissues where it is normally expressed at low abundance, transgenic mice were generated in which the human PRELP transgene was placed under control of the CMV promoter. A connective tissue phenotype was observed in the skin, where the organization of collagen fibrils in the dermis was perturbed and the thickness of the hypodermal fat layer was diminished.

The A-type lamins: nuclear structural proteins as a focus for muscular dystrophy and cardiovascular diseases.

Mutations in the lamin A (LMNA) gene are associated with the tissue-specific diseases Emery-Dreifuss muscular dystrophy (EDMD), limb girdle muscular dystrophy (LGMD-1B), dilated cardiomyopathy with conduction system disease (DCM-CD), and Dunnigan's familial partial lipodystrophy (FPLD). Lamins A and C, the products of the LMNA gene, are nuclear intermediate filament proteins and are the major structural components of the lamina network that underlies and supports the nuclear envelope. Nuclear fragility and mislocalization of the nuclear envelope protein emerin are two defects induced by a lack of the A-type lamins. These observations reveal that organization and structural integrity of the nucleus are critical factors in the origins of certain dystrophic and cardiovascular diseases.

Evaluation of the role of lipoprotein metabolism genes in systemic cationic liposome-mediated gene transfer in vivo.

Germ line gene disruption and gene insertion are often used to study the function of selected genes in vivo. We used selected knockout and transgenic mouse models to attempt to identify lipoprotein-related genes and gene products that regulate the process of intravenous cationic liposome-DNA complex (CLDC)-based gene delivery. Several observations suggested that proteins involved in lipoprotein metabolism might be important in influencing the delivery and/or expression of CLDC. First, in vitro transfection of either K562 or CHO cells by CLDCs was enhanced by the presence of a functional low-density lipoprotein receptor (LDLR). Second, pretreatment of mice with 4-aminopyrazolopyrimidine (4APP), an agent that alters lipoprotein profiles in mice, significantly decreased expression of luciferase (luc) after intravenous injection of CLDC-luc complexes in mice. Therefore, we tested mouse model systems either deficient for, or overexpressing, selected genes involved in lipoprotein metabolism, for their potential to regulate intravenous, CLDC-based gene delivery. Although homozygous knockout mutation in the apoE gene caused a significant decrease in gene expression in many tissues of apoE-deficient mice, mice with homozygous deletion of both the apoE and LDLR genes showed wild-type levels of gene transfer efficiency. Thus, a secondary event, produced by homozygous deletion of apoE, but compensated for by the concomitant deletion of LDLR, and/or effects resulting from strain-related, genetic background differences, appeared to play a significant role in mediating intravenous, CLDC-based gene delivery. Secondary alterations resulting from germ line knockouts, as well as epigenetic effects produced by strain differences, may limit the ability to assign specific, gene transfer-related functions to the deleted gene.

The nuclear envelope in muscular dystrophy and cardiovascular diseases.

Considerable interest has been focused on the nuclear envelope in recent years following the realization that several human diseases are linked to defects in genes encoding nuclear envelope specific proteins, most notably A-type lamins and emerin. These disorders, described as laminopathies or nuclear envelopathies, include both X-linked and autosomal dominant forms of Emery-Dreifuss muscular dystrophy, dilated cardiomyopathy with conduction system defects, limb girdle muscular dystrophy 1B with atrioventricular conduction disturbances, and Dunnigan-type familial partial lipodystrophy. Certain of these diseases are associated with nuclear structural abnormalities that can be seen in a variety of cells and tissues. These observations clearly demonstrate that A-type lamins in particular play a central role, not only in the maintenance of nuclear envelope integrity but also in the large-scale organization of nuclear architecture. What is not obvious, however, is why defects in nuclear envelope proteins that are found in most adult cell types should give rise to pathologies associated predominantly with skeletal and cardiac muscle and adipocytes. The recognition of these various disorders now raises the novel possibility that the nuclear envelope may have functions that go beyond housekeeping and which impact upon cell-type specific nuclear processes.

Molecular characterization of mutant alleles of the DNA repair/basal transcription factor haywire/ERCC3 in Drosophila.

The haywire gene of Drosophila encodes a putative helicase essential for transcription and nucleotide excision repair. A haywire allele encoding a dominant acting poison product, lethal alleles, and viable but UV-sensitive alleles isolated as revertants of the dominant acting poison allele were molecularly characterized. Sequence analysis of lethal haywire alleles revealed the importance of the nucleotide-binding domain, suggesting an essential role for ATPase activity. The viable haync2 allele, which encodes a poison product, has a single amino acid change in conserved helicase domain VI. This mutation results in accumulation of a 68-kD polypeptide that is much more abundant than the wild-type haywire protein.

Proteoglycans mediate cationic liposome-DNA complex-based gene delivery in vitro and in vivo.

The factors controlling cationic liposome-DNA complex (CLDC)-based gene transfer in cells and in animals are poorly understood. We found that cell surface heparin/heparan sulfate-bearing proteoglycans mediate CLDC-based gene transfer and expression both in cultured cells and following intravenous gene delivery into animals. CLDC did not transfect Raji cells, which lack proteoglycans, but did efficiently transfect Raji cells stably transfected with the proteoglycan, syndecan-1. Fucoidan, heparin, or dextran sulfate, all of which are highly anionic polysaccharides, each blocked CLDC-mediated transfection both in cultured cells and following intravenous injection into mice, but had no effect on transfection by either recombinant adenovirus infection or electroporation. Intravenous pretreatment of mice with heparinases, which specifically cleave heparan sulfate molecules from cell surface proteoglycans, blocked intravenous, CLDC-mediated transfection in mice, confirming that proteoglycans mediate CLDC gene delivery in vivo. Modulation of proteoglycan expression may prove useful in controlling the efficiency of, as well as targeting the sites of, CLDC-based gene transfer in animals.

The DUG gene of Drosophila melanogaster encodes a structural and functional homolog of the S. cerevisiae SUG1 predicted ATPase associated with the 26S proteasome.

The DUG gene of Drosophila encodes a putative ATPase that is a structural and functional homolog of the yeast SUG1 product. When introduced into S. cerevisiae, the Drosophila DUG gene rescued the lethality associated with a SUG1 mutant. Anti-DUG antibodies recognized a protein that migrated in high molecular weight complexes, along with components of the 26S proteasome, and also immunoprecipitated components of the 26S proteasome from embryonic extracts. Proteins recognized by the affinity-purified antibody raised against DUG were localized in either a punctate cytoplasmic distribution or in the nucleus, depending on the cell type, consistent with the subcellular localization of the 26S proteasome in various cell types.

Factors influencing the efficiency of cationic liposome-mediated intravenous gene delivery.

We have characterized the relationships between the design of cationic liposomes as a gene transfer vehicle, their resulting biodistribution and processing in animals, and the level and sites of gene expression they produce. By redesigning conventional cationic liposomes, incorporating cholesterol (chol) as the neutral lipid and preparing them as multilamellar vesicles (MLV), we increased the efficiency of cationic liposome:DNA complex (CLDC)-mediated gene delivery. Expression of the luciferase gene increased up to 1,740-fold and of the human granulocyte-colony stimulating factor (hG-CSF) gene up to 569-fold due to prolonged circulation time of injected CLDC, and increased uptake and retention in tissues. The level of gene expression per microgram of DNA taken up per tissue was 1,000-fold higher in lung than in liver, indicating that in addition to issues of delivery and retention of injected DNA, tissue-specific host factors also play a central role in determining the efficiency of expression. Vascular endothelial cells, monocytes, and macrophages are the cell types most commonly transfected by intravenous injection of CLDC.

A Drosophila model for xeroderma pigmentosum and Cockayne's syndrome: haywire encodes the fly homolog of ERCC3, a human excision repair gene.

The haywire gene of Drosophila encodes a protein with 66% identity to the product of the human ERCC3 gene, associated with xeroderma pigmentosum B (XP-B) and Cockayne's syndrome (CS). XP is a human autosomal recessive disease characterized by extreme sensitivity to ultraviolet irradiation and marked susceptibility to skin cancer. In addition, XP and CS patients often exhibit a variety of defects, ranging from central nervous system disorders to hypogonadism. Phenotypes of haywire mutants mimic some of the effects of XP. Many haywire alleles are recessive lethal, viable alleles cause ultraviolet sensitivity, and files expressing marginal levels of haywire display motor defects and reduced life span. Progeny of females carrying a maternal effect allele show central nervous system defects.