Recent progress in gene isolation and gene mapping: implications for agricultural biotechnology

Advances in gene technology are driving plant and animal improvement into a new era which may bring with it argument, economic change and some social chaos. Industry will change, as will the role of research in public sector institutions underpinning the industry

Novel Interactions of the Hormone Leptin Revealed by PET Imaging in Rodents and Rhesus Macaques

Leptin is a polypeptide hormone, secreted principally by adipose tissue, which functions as an afferent signal in a feedback loop to maintain body weight and energy homeostasis. In addition to its well documented effects on food intake and energy expenditure, leptin modulates the function of many other physiological systems in mammals, through actions in the central nervous system and periphery. Remarkably, despite extensive studies on leptin receptor expression, the physiological biodistribution of the hormone remains essentially unknown. In order to characterize the distribution leptin in mammals, we have developed methodologies to radiolabel the hormone and visualize its biodistribution using positron emission tomography (PET). Two complementary techniques were developed to label leptin using the positron emitting isotopes 68Ga and 18F. 68Ga labeling was accomplished by lysine-directed conjugation with the chelator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) followed by chelation of the isotope. 18F labeling was accomplished using a site-specific, two step labeling procedure in which an aminooxy moiety was introduced at the Cterminus of leptin using expressed protein ligation (EPL), which was subsequently derivitized with 18F-4-fluorobenzaldehyde in an aniline accelerated radiochemical oximation reaction. These probes were used for PET imaging in mice, rats, and in rhesus macaques. PET imaging in these organisms revealed that the hormone was rapidly taken up by the cortex of the kidney, bone marrow, and visceral organs. Uptake in the kidney was partially saturable with cold ligand, and was not mediated by leptin receptor (ObR). Subsequent analysis in with a kidney specific knockout of the multiligand endocytic transporter megalin revealed loss of leptin in the urine, which was confirmed using PET imaging. Thus, megalin is required for the uptake of leptin in the proximal convoluted tubule within the cortex of the kidney. Subsequent biodistribution experiments revealed that the hormone was taken up by the brain, spleen, liver, fat, and lungs in mice, and that this uptake was leptin receptor dependant. Furthermore, PET imaging in rhesus macaques revealed that leptin was absorbed by the bone marrow and liver. Thus, leptin may activate and modulate hematopoiesis by direct action on either hematopoietic precursors or the stromal support tissue. Thus, novel hysiologically significant interactions of the hormone leptin were revealed using PET

Emerging Roles of L-Type Voltage-Gated and Other Calcium Channels in T Lymphocytes

In T lymphocytes, calcium ion controls a variety of biological processes including development, survival, proliferation, and effector functions. These distinct and specific roles are regulated by different calcium signals, which are generated by various plasma membrane calcium channels. The repertoire of calcium-conducting proteins in T lymphocytes includes store-operated CRAC channels, transient receptor potential (TRP) channels, P2X channels, and L-type voltage-gated calcium (Cav1) channels. In this paper, we will focus mainly on the role of the Cav1 channels found expressed by T lymphocytes, where these channels appear to operate in a TCR stimulation-dependent and voltage-sensor independent manner. We will review their expression profile at various differentiation stages of CD4 and CD8 T lymphocytes. Then, we will present crucial genetic evidence in favor of a role of these Cav1 channels and related regulatory proteins in both CD4 and CD8 T cell functions such as proliferation, survival, cytokine production and cytolysis. Finally, we will provide evidence and speculate on how these voltage-gated channels might function in the T lymphocyte, a non-excitable cell

Innate recognition of non-self nucleic acids

A variety of innate immune system receptors recognize and respond to the nucleic acids of invading pathogens

A Nonpolymorphic Class I Gene in the Murine Major Histocompatibility Complex

DNA sequence analysis of a class I gene (QlO), which maps to the Qa2,3 locus in the C57BL/lO (H- 2b haplotype) mouse, reveals that it is almost identical to a cDNA clone (pH16) isolated from a SWR/J (H-2q haplotype) mouse liver cDNA library. Exon 5, in particular, has an unusual structure such that a polypeptide product is unlikely to be anchored in the cell membrane. Our findings suggest that the two sequences are derived from allelic class I genes, which are nonpolymorphic, in contrast to H-2K allelic sequences from the same mice, and they may encode liver-specific polypeptides of unknown function. Our previous studies indicate that the QlO gene is a potential donor gene for the generation of mutations at the H-2K locus by inter-gene transfer of genetic information. Thus the lack of polymorphism in class I genes at the QlO locus implies either that they are not recipients for such exchanges or that selective pressure prevents the accumulation of mutations in genes at this locus

The role of CTCF in regulating nuclear organization

The spatial organization of the genome is thought to play an important part in the coordination of gene regulation. New techniques have been used to identify specific long-range interactions between distal DNA sequences, revealing an ever-increasing complexity to nuclear organization. CCCTC-binding factor (CTCF) is a versatile zinc finger protein with diverse regulatory functions. New data now help define how CTCF mediates both long-range intrachromosomal and interchromosomal interactions, and highlight CTCF as an important factor in determining the three-dimensional structure of the genome