Genome-wide linkage analysis replicates susceptibility locus for fasting plasma triglycerides: NHLBI Family Heart Study

Recent reports implicate chromosomal regions linked to inter-individual variation in plasma triglycerides. We conducted genome-wide scans to replicate these linkages and/or identify other loci influencing plasma triglycerides in the NHLBI Family Heart Study (FHS). Data were obtained for 501 three-generational families. Genotyping was done by the Utah Molecular Genetics Laboratory and NHLBI Mammalian Genotyping Service; markers from both were placed on one genetic map. Analysis was done using multipoint variance components linkage. Fasting plasma triglycerides were log-transformed and age-, sex-, and field center-adjusted; suggestive linkage evidence was found on chromosome 8 (LOD=2.80 at 89 cM, marker D8S1141). Further adjustment for waist girth, BMI, diabetes, hypertension, and lipid-lowering drugs suggested linkage regions on chromosomes 6 (LOD=2.29 at 79 cM, marker D6S295) and 15 (LOD=1.85 at 43 cM, marker D15S659). Since HDL is correlated with triglycerides and because it was linked to this region on chromosome 15 in FHS, we created a composite triglyceride–HDL phenotype. The combined phenotype LOD score was 3.0 at the same marker on chromosome 15. Chromosome 15 likely harbors a susceptibility locus with an influence on triglycerides and HDL. Regions on chromosomes 6 and 8 may also contain loci contributing to inter-individual variation in plasma triglycerides.     

O-glycan sialylation and the structure of the stalk-like region of the T cell co-receptor CD8

Studies of mucins suggest that the structural effects of O-glycans are restricted to steric interactions between peptide-linked GalNAc residues and adjacent polypeptide residues. It has been proposed, however, that differential O-glycan sialylation alters the structure of the stalk-like region of the T cell co-receptor, CD8, and that this, in turn, modulates ligand binding (Daniels, M. A., Devine, L., Miller, J. D., Moser, J. M., Lukacher, A. E., Altman, J. D., Kavathas, P., Hogquist, K. A., and Jameson, S. C. (2001) Immunity 15, 1051-1061; Moody, A. M., Chui, D., Reche, P. A., Priatel, J. J., Marth, J. D., and Reinherz, E. L. (2001) Cell 107, 501-512). We characterize the glycosylation of soluble, chimeric forms of the alphaalpha- and alphabeta-isoforms of murine CD8 containing the O-glycosylated stalk of rat CD8alphaalpha, and we show that the stalk O-glycans are differentially sialylated in CHO K1 versus Lec3.2.8.1 cells (82 versus approximately 6%, respectively). Sedimentation analysis indicates that the Perrin functions, Pexp, which reflect overall molecular shape, are very similar (1.61 versus 1.54), whereas the sedimentation coefficients (s) of the CHO K1- and Lec3.2.8.1-derived proteins differ considerably (3.73 versus 3.13 S). The hydrodynamic properties of molecular models also strongly imply that the sialylated and non-sialylated forms of the chimera have parallel, equally highly extended stalks ( approximately 2.6 A/residue). Our analysis indicates that, as in the case of mucins, the overall structure of O-glycosylated stalk-like peptides is sialylation-independent and that the functional effects of differential CD8 O-glycan sialylation need careful interpretation.     

Characterization and localization of short-specific polygalacturonase in distylous Turnera subulata (Turneraceae)

We describe for distylous Turnera subulata a polygalacturonase specific to short-styled plants that is localized to the style transmitting tissue (the tissue through which pollen tubes grow). The polygalacturonase gene is linked to and may be upregulated by the S allele of the distyly locus. Because of its tissue-specific location, the polygalacturonase may be involved in the self-incompatibility response, acting in a complementary or antagonistic manner, or possibly in signalling downstream events. A pollen-specific polygalacturonase was also identified and may be a member of a small multigene family of pollen polygalacturonases. The role, if any, played by the pollen polygalacturonase in distyly, is presently unknown.     

ACTN3 genotype is associated with human elite athletic performance

There is increasing evidence for strong genetic influences on athletic performance and for an evolutionary "trade-off" between performance traits for speed and endurance activities. We have recently demonstrated that the skeletal-muscle actin-binding protein alpha-actinin-3 is absent in 18% of healthy white individuals because of homozygosity for a common stop-codon polymorphism in the ACTN3 gene, R577X. alpha-Actinin-3 is specifically expressed in fast-twitch myofibers responsible for generating force at high velocity. The absence of a disease phenotype secondary to alpha-actinin-3 deficiency is likely due to compensation by the homologous protein, alpha-actinin-2. However, the high degree of evolutionary conservation of ACTN3 suggests function(s) independent of ACTN2. Here, we demonstrate highly significant associations between ACTN3 genotype and athletic performance. Both male and female elite sprint athletes have significantly higher frequencies of the 577R allele than do controls. This suggests that the presence of alpha-actinin-3 has a beneficial effect on the function of skeletal muscle in generating forceful contractions at high velocity, and provides an evolutionary advantage because of increased sprint performance. There is also a genotype effect in female sprint and endurance athletes, with higher than expected numbers of 577RX heterozygotes among sprint athletes and lower than expected numbers among endurance athletes. The lack of a similar effect in males suggests that the ACTN3 genotype affects athletic performance differently in males and females. The differential effects in sprint and endurance athletes suggests that the R577X polymorphism may have been maintained in the human population by balancing natural selection.     

ePAD,an oocyte and early embryo-abundant peptidylarginine deiminase-like protein that localizes to egg cytoplasmic sheets

Selected for its high relative abundance, a protein spot of MW approximately 75 kDa, pI 5.5 was cored from a Coomassie-stained two-dimensional gel of proteins from 2850 zona-free metaphase II mouse eggs and analyzed by tandem mass spectrometry (TMS), and novel microsequences were identified that indicated a previously uncharacterized egg protein. A 2.4-kb cDNA was then amplified from a mouse ovarian adapter-ligated cDNA library by RACE-PCR, and a unique 2043-bp open reading frame was defined encoding a 681-amino-acid protein. Comparison of the deduced amino acid sequence with the nonredundant database demonstrated that the protein was approximately 40% identical to the calcium-dependent peptidylarginine deiminase (PAD) enzyme family. Northern blotting, RT-PCR, and in situ hybridization analyses indicated that the protein was abundantly expressed in the ovary, weakly expressed in the testis, and absent from other tissues. Based on the homology with PADs and its oocyte-abundant expression pattern, the protein was designated ePAD, for egg and embryo-abundant peptidylarginine deiminase-like protein. Anti-recombinant ePAD monospecific antibodies localized the molecule to the cytoplasm of oocytes in primordial, primary, secondary, and Graafian follicles in ovarian sections, while no other ovarian cell type was stained. ePAD was also expressed in the immature oocyte, mature egg, and through the blastocyst stage of embryonic development, where expression levels began to decrease. Immunoelectron microscopy localized ePAD to egg cytoplasmic sheets, a unique keratin-containing intermediate filament structure found only in mammalian eggs and in early embryos, and known to undergo reorganization at critical stages of development. Previous reports that PAD-mediated deimination of epithelial cell keratin results in cytoskeletal remodeling suggest a possible role for ePAD in cytoskeletal reorganization in the egg and early embryo.     

Fluorescent labeling of endothelial cells allows in vivo,continuous characterization of the vascular development of Xenopus laevis

Appropriate blood supply and vascular development are necessary in development and in cancer, heart disease, and diabetes. Here, we report the use of DiI-labeled acetylated low-density lipoprotein (DiI-Ac-LDL) to label endothelial cells and characterize the vasculature of live Xenopus embryos. The atlas we have created provides a detailed map of normal vascular development against which perturbations of normal patterning can be compared. By following the development of the intersomitic vessels in real-time, we show that, while rostrocaudal gradient of maturing intersomitic vessels occurs, it is not absolute. In addition, the comparative study of the ontogeny of nerve bundles from the spinal cord of transgenic Xenopus embryos expressing green fluorescent protein in the nervous system and blood vessels demonstrates a strong anatomical correlation in neurovascular development. These studies provide the basis for understanding how the vascular system forms and assumes its complicated stereotypical pattern in normal development and in disease.