A gene-based SNP linkage map for pacific white shrimp, Litopenaeus vannamei

Pacific white shrimp (Litopenaeus vannamei) are of particular economic importance to the global shrimp aquaculture industry. However, limited genomics information is available for the penaeid species. We utilized the limited public information available, mainly single nucleotide polymorphisms (SNPs) and expressed sequence tags, to discover markers for the construction of the first SNP genetic map for Pacific white shrimp. In total, 1344 putative SNPs were discovered, and out of 825 SNPs genotyped, 418 SNP markers from 347 contigs were mapped onto 45 sex-averaged linkage groups, with approximate coverage of 2071 and 2130 cm for the female and male maps, respectively. The average-squared correlation coefficient (r(2)), a measure of linkage disequilibrium, for markers located more than 50 cm apart on the same linkage group, was 0.15. Levels of r(2) increased with decreasing inter-marker distance from approximately 80 cm, and increased more rapidly from approximately 30 cm. A QTL for shrimp gender was mapped on linkage group 13. Comparative mapping to model organisms, Daphnia pulex and Drosophila melanogaster, revealed extensive rearrangement of genome architecture for L. vannamei, and that L. vannamei was more related to Daphnia pulex. This SNP genetic map lays the foundation for future shrimp genomics studies, especially the identification of genetic markers or regions for economically important traits.

An outbreak of plague including cases with probable pneumonic infection, Ecuador, 1998

During February and March of 1998, 12 sudden deaths were reported among residents of a high-Andean community in Ecuador. All 12 fatalities were members of the same extended family and some had apparent exposure to sick guinea-pigs. Following an initial investigation by public health officials, an additional death was reported in a nearby community in April, also associated with exposure to sick guinea-pigs. Blood samples from humans, dogs, and a rodent were tested for antibody to the F1 antigen of Yersinia pestis by passive haemagglutination assay. Tissue from rodents was subjected to direct fluorescent antibody staining using fluorescein-labelled monoclonal antibody to Y. pestis F1 antigen. Formalin-fixed specimens from the 2 autopsies were evaluated using a 2-step alkaline phosphatase immunoassay with a monoclonal antibody to Y. pestis F1 antigen, and tissues that had not been embedded in paraffin were tested for the presence of DNA encoding the F1 structural antigen by polymerase chain reaction. Serological evaluation of close contacts of the fatalities revealed positive titres to F1 antigen of Y. pestis, the aetiological agent of plague, in 3 contacts from the first community and 1 from the second. Immunohistochemical staining of tissues collected from 2 of the fatalities provided evidence that both had pneumonic plague. Five of 14 dogs found in the communities were seropositive for plague antibody, providing evidence of a recent epizootic plague in the area.

[Polymorphism of the gene of vitamin D receptor and bone mineral density in postmenopausal women]

BACKGROUND

Conflicting results have been reported on the association between restriction fragment length polymorphism at the vitamin D receptor (VDR) gene locus and bone mineral density (BMD). Population differences in environmental factors, such as calcium intake and calcidiol levels which have strong influence in BMD, may alter this association.

PATIENTS AND METHODS

We analyzed the Bsml RFLP at the eight introm of the VDR gene in a population sample (n = 204) of postmenopausal Spanish women aged 50-65 years being seen clinically and studied calcium intake (dietetic questionnaire) and biochemical parameters (PTH and calcidiol). In parallel bone densitometry were measured in lumbar spine and proximal femur.

RESULTS

We identified low BMD of the proximal femur in the BB group. This effect was not observed at other body locations. The calcium intake was lees than 500 mg/day in 60% of the studied population as calcidiol levels were lower than 10 ng/l in 36% of it. The total group population with normal calcium intake (> 1,000 mg/day) showed higher BMD (proximal femur and spine) than the group with low calcium intake, this variation not being observed in group BB alleles. Interestingly, we observed significant differences in BMD proximal femur between genotype groups BB versus Bb + bb when calcidiol levels were < 10 ng/l. Moreover, within the BB subgroup, those subjects with normal calcidiol levels have higher proximal femur BMD compared with those with low calcidiol levels.

CONCLUSIONS

Our results indicate an effect of the VDR genotype on BMD proximal femur which is clearly influenced by calcium intake and calcidiol serum levels.