Because cloned dogs are genetically identical, variations among these animals can be a useful tool to elucidate mechanisms underlying phenotypic differences. To estimate the influence of genetic factors on phenotypic variation, changes in concentration patterns of growth hormone (GH), insulin like growth factor-1 (IGF-1), and IGF binding protein 3 (IGFBP-3) were compared among cloned and age-matched control dogs. In addition, the concentrations of GH and IGF-1 following administration of growth hormone releasing hormone (GHRH) and somatostatin (SRIF) were measured in both groups. In comparing hormone profiles, the control dogs had larger standard deviations from the means for GH, IGF-1, and IGFBP-3 than the clones. Also, the mean concentration of IGFBP-3 in clones was significantly lower than in the controls between 7 to 12 months of age, whereas the IGFBP-3 changes in clones and controls followed the same pattern. GHRH induced increased serum growth hormone concentration both in clones and controls. However, the concentration of IGF-1 was lower in clones than in controls, and larger standard variations were noted in the control group. In conclusion, the measured traits were more homogeneous in cloned animals than in controls, so cloned animals could be valuable for assessing effects of genotype and environment interactions.
[Show abstract][Hide abstract] ABSTRACT: Over the world, canine species, including the gray wolf, have been gradually endangered or extinct. Many efforts have been made to recover and conserve these canids. The aim of this study was to produce the endangered gray wolf with somatic cell nuclear transfer (SCNT) for conservation. Adult ear fibroblasts from a female gray wolf (Canis lupus) were isolated and cultured in vitro as donor cells. Because of limitations in obtaining gray wolf matured oocytes, in vivo matured canine oocytes obtained by flushing the oviducts from the isthmus to the infundibulum were used. After removing the cumulus cells, the oocyte was enucleated, microinjected, fused with a donor cell, and activated. The reconstructed cloned wolf embryos were transferred into the oviducts of the naturally synchronized surrogate mothers. Two pregnancies were detected by ultrasonography at 23 days of gestation in recipient dogs. In each surrogate dog, two fetal sacs were confirmed by early pregnancy diagnosis at 23 days, but only two cloned wolves were delivered. The first cloned wolf was delivered by cesarean section on October 18, 2005, 60 days after embryo transfer. The second cloned wolf was delivered on October 26, 2005, at 61 days postembryo transfer. Microsatellite analysis was performed with genomic DNA from the donor wolf, the two cloned wolves, and the two surrogate female recipients to confirm the genetic identity of the cloned wolves. Analysis of 19 microsatellite loci confirmed that the cloned wolves were genetically identical to the donor wolf. In conclusion, we demonstrated live birth of two cloned gray wolves by nuclear transfer of wolf somatic cells into enucleated canine oocyte, indicating that SCNT is a practical approach for conserving endangered canids.
[Show abstract][Hide abstract] ABSTRACT: Cloning using somatic cells offers many potential applications in biomedicine and basic research. The objective of this study was to test whether clones from the same genotype can be used as models to study the genetic influences of behavior. Specifically, several aspects of the behavior of four prepubertal heifers cloned from somatic cells of a 13-year-old Holstein cow along with age-matched control heifers were compared to determine whether juvenile clones from an aged adult behave similarly to their age-matched controls, and whether clones with identical genetic makeup exhibit any behavioral trends. Behavioral observations or behavior challenge tests were conducted to compare the following traits: vocalization, play behavior, movement frequencies, grooming, curiosity, and companion preference, as well as dominance and aggressiveness. From play behavior, movements and vocalization, we observed that these four juvenile clones of an aged genetic donor did not show behavioral indications of aging and were similar to their counterparts of comparable chronological age except that they tended to play less than controls. Behavioral trends were also observed in the clones that indicated that they exhibited higher levels of curiosity, more grooming activities and were more aggressive and dominant than controls. Furthermore, these four clones preferred each other or the donor as companions, which may indicate genetic kin recognition.
[Show abstract][Hide abstract] ABSTRACT: Twin studies have been a valuable source of information about the genetic basis of complex traits. To maximize the potential of twin studies, large, worldwide registers of data on twins and their relatives have been established. Here, we provide an overview of the current resources for twin research. These can be used to obtain insights into the genetic epidemiology of complex traits and diseases, to study the interaction of genotype with sex, age and lifestyle factors, and to study the causes of co-morbidity between traits and diseases. Because of their design, these registers offer unique opportunities for selected sampling for quantitative trait loci linkage and association studies.
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