Current Geonomics, Vol. 2, No. 2, 2001

The advent of genomics approaches to studying human disease have yielded a large number of genes and gene families that are involved in the process of bone formation and bone remodeling. The identification and characterization of these genes has provided significant insights into the pathogenesis of numerous human bone diseases. This review details current understanding of the role of many of these genes in bone development and disease. We review the current status of bone disease prevention/treatment modalities and describe how recent advances in our understanding of the molecules responsible for different aspects of osteoblast, osteoclast and chondrocyte function may provide novel biochemical markers and treatment strategies for bone disease

[Back to top] EXTraordinary Bones: Functional and Genetic Analysis of the

EXT Gene Family

Carol A. Wise

Far from serving as an inert skeletal scaffold, bone is a dynamic tissue that cycles through tightly coordinated cycles of developmental growth and regeneration. Bone growth, which determines the overall growth of vertebrates, is well-characterized histologically and increasingly understood at the molecular level. In recent years traditional positional cloning applied to diseases of simple Mendelian inheritance have revealed genes important in the proper formation of bone. Functional studies of these genes, aided considerably by insights provided by studies of homologous genes in animal models and other organisms, have led to significant advances in our understanding of the pathways of mammalian bone morphogenesis. One such disorder, hereditary multiple exostoses, is caused by members of the EXT tumor suppressor gene family. Progress in the molecular dissection of this disorder, with emphasis on important genomic techniques and strategies, is reviewed herein. We are now challenged to reconstruct the biochemical pathway of chondrogenesis/osteogenesis defined by the EXT genes as a step toward therapeutic control of bone growth and malignancy.

[Back to top] Sperm-Specific Factors Implicated in Oolemma Binding and/or Fusion

A. A. Redkar

In mammals, a key event in the process of fertilization occurs when a sperm binds to and fuses with the oocyte plasma membrane (oolemma). However, information regarding the genetic and molecular bases of this complex process of sperm-oolemma penetration (SOP) is limited. Research to elucidate the sperm factors involved in SOP has resulted in the identification of several important candidate molecules, most of which have been recognized using antibodies to sperm surface antigens (immunological approach). Of these, the best characterized are those belonging to the ADAM (A Disintegrin and A Metalloprotease) and CRISP (Cysteine-Rich Secretory Protein) gene families. ADAM family members - Fertilin a, Fertilin b and Cyritestin - are known to be involved in sperm binding to the oolemma. The CRISP family includes DE (also known as acidic epididymal glycoprotein [AEG], CRISP-1) which appears to play a role in sperm-egg fusion, without affecting sperm-oolemma binding. In addition to the immunological approach, studies on mouse t haplotypes have led to the identification of genetic loci important in the process of SOP. Mouse t haplotypes carry mutations that cause defects in several sperm functions. Recent studies have suggested that t haplotypes contain altered alleles of genes that encode sperm-oolemma binding and/or fusion proteins. The molecular identification of these various sperm-specific factors and the elucidation of their roles in SOP will increase our knowledge of the cellular basis of fertilization, and will help in designing therapeutic strategies for contraception and sperm dysfunction.

[Back to top] Protein Microarrays - A Tool for the Post-Genomic Era

Angelika Lueking , Zoltán Konthur, Holger Eickhoff, Konrad Büssow,

Hans Lehrach and Dolores J. Cahill

The human genome is sequenced and the challenges of understanding the function of the newly discovered genes have been addressed. For this purpose, high-throughput technologies have been developed that allow the monitoring of gene activity at the transcriptional level by analysis of complex expression patterns of a specific tissue. Differential gene expression can be most efficiently monitored by oligonucleotide or cDNA hybridization on DNA arrays. Recently, protein arrays are emerging to follow DNA chips as a tool to profile protein products encoded by globally or differentially expressed cDNA clones. Array technology was enabled by the development of devices that could array biological samples at high density with high precision onto immobilizing surfaces, ranging from the classic microtiter plate to new chip-sized supports. In addition, the introduction of automated technology to the protein level involves the simultaneous expression of a large number of cDNA clones in an appropriate vector and expression system, allowing the specific detection and purification of all the recombinant proteins. With the ordered arrangement of recombinantly expressed proteins, a direct link to the corresponding DNA sequence information is possible and consequently, clone libraries become amenable to be integrated in a database including all steps from DNA sequencing to functional assays of the translated gene product. Here, we review the generation and application of microarray technology as a highly parallel approach to obtain more information on the regulation of proteins, their biochemical function and potential interaction partners. Already, a large variety of assays based on antibody-antigen interaction exists and in addition, the medical relevance of protein arrays will be discussed. Also, further applications such as protein-DNA, protein-RNA and protein-substrate interactions will be presented, since initial studies on immobilized proteins were reported.

Proteomics is an emerging field to profile protein repertoires. Because there is no reliable correlation between gene activity monitored by genomic studies and cellular protein abundance, application of protein arrays will link both genomics and proteomics.

[Back to top] Identification of Defective CD36 as a Quantitative Trait Locus for Cardiovascular Risk Factor Clustering in the Spontaneously

Hypertensive Rat

M. Pravenec, V. Landa, V. Zídek and V. Kren

It was demonstrated that a gene or genes responsible for a whole spectrum of cardiovascular risk factors map to a limited segment of the centromeric region of rat chromosome 4. Recently, a spontaneous deletion in the gene for Cd36 that encodes a fatty acid transporter and is located directly at the peak of QTL linkages on chromosome 4 has been indirectly linked to the transmission of insulin resistance, defective fatty acid metabolism, and increased blood pressure. To directly test whether mutant Cd36 is a QTL that promotes clustering of multiple cardiovascular risk factors in the Spontaneously Hypertensive Rat (SHR), transgenic lines were derived that carry a wild type Cd36 transgene on the genetic background of the SHR strain harboring a deletion variant of Cd36. It was found that in SHR harboring the deletion variant of Cd36, transgenic expression of wild type Cd36 in modest amounts ameliorated defects in fatty acid metabolism, glucose tolerance, and insulin stimulated glucose uptake in muscle and fat tissue, however, exerted little or no effect on blood pressure. In conclusion, the current studies provided definitive evidence that mutant Cd36 is a QTL with major effects on fatty acid metabolism, insulin action, and glucose tolerance but have no effects on spontaneous hypertension in the SHR/NIH strains.

[Back to top] Cell Cycle Checkpoint Genes and Aneuploidy: A Short Review

William G. Kearns and Johnson M. Liu

Checkpoints regulate the normal progression of the cell cycle. Disturbance in the normal function of these checkpoints can induce genomic instability, which is associated with cancer initiation. One such form of instability, aneuploidy, can result from alterations of cell cycle checkpoints, and can induce large imbalances in gene copy number. These imbalances could, in turn, alter the expression of gene products involved in cancer development

[Back to top] Bioengineered Crops: The Commercial and Ethical Considerations

Susmita Sengupta, L.K. Sengupta and P.S. Bisen

Recombinant DNA technology has opened up a novel field for the agricultural biotechnologists to explore and design custom-made crops with specific trait(s). In addition to enhancing yield, transgenic plants are designed to have enhanced defense against pathogens, remove toxic compounds from the soil, to be tolerant to environmental stresses, to be live bioreactors to produce pharmaceuticals, to have improved nutritional features reflecting changes in protein, oil or vitamin content or to have woody species with lower generation time. But all plants with novel characters come with a price. The objective of the article is to evaluate the utility of the transgenic plants with respect to their novel features, the economic implications, seed security, agricultural sustainability and food safety. The gene mapping program of Arabidopsis and rice gives rise to the ethical question of the commercial patentability of the bioengineered plants. The impact of this science on agriculture that is being faced by the world with special reference to the developing countries of Asia is being discussed.

[Back to top] Impact of SINEs and LINEs on the Mammalian Genome

D. H. Kass

Several families of short and long interspersed DNA elements (SINEs and LINEs) inhabit mammalian genomes. Amplification of these elements (which can exceed one million copies) has occurred primarily by an RNA-mediated mechanism referred to as retroposition (or retrotransposition). When integrated into a gene, these elements may cause deleterious effects to the individual organism, as exemplified in various human disorders. Alternatively, several integration-recipient genes with altered function or expression are evolutionarily conserved within or among species. Experimental analyses further demonstrate effects of gene regulation by retroposed elements. Although most integrations apparently have no significant impact on the phenotype of various mammalian species, the accumulation of SINEs and LINEs provides a multitude of sites for homologous recombination and yields a considerable proportion of methylation sites in mammalian genomes. Specific and cumulative integrations may provide an integral component in the speciation process. This review examines the functional and regulatory impact of retroposon integrations on individual genes, the impact of accumulated integration events, and the evidence for the role of these elements in the evolution of species. Since these elements continue to integrate into mammalian genomes, it is important to further understand and evaluate their functional impact.