Variations in the mitochondrial cytochrome c oxidase subunit I gene indicate northward expanding populations of Culicoides imicola in Spain

Culicoides imicola is the main vector for bluetongue (BT) and African horse sickness (AHS) viruses in the Mediterranean basin and in southern Europe. In this study, we analysed partial mitochondrial cytochrome c oxidase subunit I (COI) gene to characterize and confirm population expansion of Culicoides imicola across Spain. The data were analysed at two hierarchical levels to test the relationship between C. imicola haplotypes in Spain (n = 215 from 58 different locations) and worldwide (n = 277). We found nineteen different haplotypes within the Spanish population, including 11 new haplotypes. No matrilineal subdivision was found within the Spanish population, while western and eastern Mediterranean C. imicola populations were very structured. These findings were further supported by median networks and mismatch haplotype distributions. Median networks demonstrated that the haplotypes we observed in the western Mediterranean region were closely related with one another, creating a clear star-like phylogeny separated only by a single mutation from eastern haplotypes. The two, genetically distinct, sources of C. imicola in the Mediterranean basin, thus, were confirmed. This type of star-like population structure centred around the most frequent haplotype is best explained by rapid expansion. Furthermore, the proposed northern expansion was also supported by the statistically negative Tajima's D and Fu's Fs values, as well as predicted mismatch distributions of sudden and spatially expanding populations. Our results thus indicated that C. imicola population expansion was a rapid and recent phenomenon.

Reliability of sex determination in ovine embryos using amelogenin gene (AMEL)

Sex specific sequence variability of the amelogenin gene has been used for sex determination in the family of Bovidae. In our study, suitability and reliability of the amelogenin gene for ovine sex determination in embryos was studied. The specificity of the method was previously demonstrated by testing 579 blood samples from several Spanish sheep breeds (161 males and 198 females). No amplification failures and very high agreement between genotypic and phenotypic sex was found (578/579), in contrast to humans, where errors in sex determination has been reported because of mutations in AMELX or AMELY genes. However, one female animal showed a male genotypic sex, being the most plausible explanation that a recombination event has happened during the meiosis. In our study only 0.17% (1/579) of the samples tested has been misdiagnosed using the amelogenin gene. Finally, 1-10 cells from each of 67 compact morulae were aspirated through the zona pellucida, and genotyped for sex determination. The efficiency in sex determination was 95 and 98% when more than two and more than three cells were sampled, respectively. The total time required for the genetic test, was less than 4h. These results confirm that the amelogenin gene can be used for rapid sex determination in ovine embryos, with a high efficiency and accuracy (100%) when three or more cells are sampled, allowing transferring sexed fresh embryos in MOET programmes. To our knowledge, this was the first time that sex determination using the amelogenin gene was performed in ovine embryos.