DNA fingerprinting Dolly

Mechanisms and strategies to promote cardiac xenotransplantation

End stage heart failure is a terminal disease, and the only curative therapy is orthotopic heart transplantation. Due to limited organ availability, alternative strategies have received intense interest for treatment of patients with advanced heart failure. Recent studies using gene-edited porcine organs suggest that cardiac xenotransplantation may provide a future source of organs. In this review, we highlight the historical milestones for cardiac xenotransplantation and the gene editing strategies designed to overcome immunological barriers, which have culminated in a recent cardiac pig-to-human xenotransplant. We also discuss recent results of studies on the engineering of human-porcine chimeric organs that may provide an alternative and complementary strategy to overcome some of the major immunological barriers to producing a new source of transplantable organs.

New advances in cloning and their potential impact on genetic variation in livestock

Cloning has advanced through the recent demonstrations that it is feasible to produce, in principle and with significant effort, an unlimited number of individuals of identical genotype from differentiated cell lines that have been frozen and thawed. These advances have been based upon understanding the importance of interactions between the stage of the cell cycle of both the oocyte and donor cell for the success of the nuclear transfer. Whilst the impact of the biological advance is immense for biomedicai applications, the significance is less clear for livestock breeding. In our view the scientific issues for breeding programmes lie in whether clones can increase genetic progress without a cost to biodiversity. Biodiversity within a species may be categorized as: (i) betvjeen-breed variation; (ix) genetic variation among parents within breeds; (iii) genetic variation among individuals within a farm; and (iv) allelic variation within an individual. In the face of a rapid global decline in breed diversity, cloning, in particular cloning of adults, may be an important route to protect biodiversity since it may allow far more genetic variation to be made available for new breed development in the future than is practicable at present. For variation among parents, the judicious use of clones may give significantly faster rates of progress without increasing the rate of loss of genetic variation and furthermore can help improve traits associated with health and welfare which are at present less tractable than, say, milk yield. Local diversity within a farm may be greatly affected if cloning is utilized to disseminate genetic progress widely and more answers are required on the importance of genetic variation within any one locality either in buffering diseases or ameliorating other management problems. Experience from clonal forestry can provide some indications but now there are models capable of answering this question directly in livestock. Allelic variation within individuals per se is not generally advantageous but at loci where it is identified to he beneficial, the use of cloning may exploit it more widely.

Analysis of telomere length in Dolly, a sheep derived by nuclear transfer

We have used a (TTAGGG) oligonucleotide probe to demonstrate that ovine telomeres are composed of (TTAGGG) repeat arrays and to compare the terminal restriction fragment lengths of sheep derived by natural mating and nuclear transfer. Here we show that ovine somatic telomeres decrease in length with age, and that Dolly, derived by the transfer of 6-year-old adult somatic nucleus, exhibits diminished terminal restriction fragment lengths. The decrease is consistent with the age of the donor tissue and telomere erosion during in vitro culture. Nuclear transfer does not restore telomere lengths. Dolly otherwise appears physiologically and phenotypically normal for her breed and age. We further report on apparent telomere lengthening in sheep, occurring during the first year in naturally derived lambs.

The role of forensic dentist following mass disaster

This review article focuses on mass disaster situations that may arise from natural or manmade circumstances and the significant role of forensic dental personnel in human identification following such occurrences. The various forensic dental modalities of identification that include matching techniques, postmortem profiling, genetic fingerprinting, dental fossil assessment and dental biometrics with digital subtraction were considered.

The varying extent of use of forensic dental techniques and the resulting positive impact on human identification were considered. The importance of preparation by way of special training for forensic dental personnel, mock disaster rehearsal, and use of modern day technology was stressed. The need for international standardization of identification through the use of Interpol Disaster Victim Identification (DVI) for ms was further emphasized.

Recommendations for improved human identification in Nigerian situation include reform of the National Emergency Management Association (NEMA), incorporation of dental care in primary health care to facilitate proper ante mortem database of the populace and commencement of identification at site of disaster.

Rearranged genomes of bovine blood cells can allow the development of clones till late fetal stages; but rare unrearranged genomes have greater potential and lead to adulthood

Cloning via nuclear transfer is promising, but rather inefficient. Moreover, to date, relatively few data are available for a satisfactory phenotypic and genotypic characterization of the clones. Here, we analyze the genomes of clones derived from bovine peripheral blood mononucleated cells (PBMC), known to be composed mainly by lymphocytes. Their genomes are rearranged at either the immunoglobulin (Ig) or the T-cell-receptor (TCR) loci. The DNA of the single survivor and of four aborted fetuses were amplified by semi-quantitative PCR and sequenced. We found the expected rearrangements in DNA from lymphocytes, but neither in DNA from chondrocytes of the survivor, nor in DNA from brain cells of three of the aborted fetuses. This indicates that these four clones derived from somatic cells bearing unrearranged genomes and suggests that in a population of variably differentiated cells those harbouring unrearranged genomes are better donors. Brain cells of the fourth fetus present rearrangements at both loci. The sequences of these rearrangements differ from those obtained from PBMC because they appear unique, thus confirming the clonal origin of the fetus from a cell bearing a rearranged genome. To our knowledge, this is the first example in which both the placenta and the soma of a late fetus are coded for by the rearranged genome of a terminally differentiated cell, unambiguously identified through a specific genetic marker.

Application of reproductive biotechnology in animals: implications and potentials. Applications of reproductive cloning

The development of new methods of nuclear transfer in mammals is creating many new opportunities in research, medicine and agriculture. The method of cloning is repeatable and has been established in many laboratories worldwide. However, the present procedure is inefficient with fewer than 4% of embryos becoming viable offspring. A considerable improvement in efficiency is required before wide scale use for livestock improvement. The opportunity to introduce precise genetic changes to livestock is available for the first time through the use of gene targeting procedures in cultured cells that are used as nuclear donors. This has potential application in the production of organs for transplantation to humans, studies of human genetic disease and basic research in to the control of gene expression and function.

God's signature: DNA profiling, the new gold standard in forensic science

In the mid-1980s, when the first DNA profiling techniques were developed, the name DNA 'fingerprinting' was widely used. At the time, fingerprinting was a well-established forensic method, and it was rarely questioned in the courts. Fingerprint examiners were permitted to describe matching prints as evidence of individual identity, and they were not required to give probability estimates. Despite its nominal association with the older technique, DNA 'fingerprinting' went through a period of controversy, especially in the US courts. The association with fingerprinting was questioned, and experts were required to qualify their testimony with probability figures. Heated debate occurred in scientific publications and law courts about the statistical and population genetic assumptions that went into the probability calculations presented in court cases. However, by the late 1990s DNA profiling was so widely accepted that it became a basis for invidious comparison with all other forms of forensic evidence, including fingerprinting. In the past three years, the admissibility of fingerprint evidence has been challenged in several US federal and state courts. This article discusses the socio-legal and socio-technical issues that led to the inversion of credibility that characterized the intertwined history of the two techniques.

Animal cloning--the route to new genomics in agriculture and medicine

This paper reviews the origin and development of animal cloning in metazoans starting with primitive experiments performed during the late 1880's and early 1900's, followed by nuclear transplantation in amphibians in 1952, then extended to fish and insects in the 1960's, and finally to mammals in the 1980's. Emphasis is placed on the applications of mammalian cloning to agriculture, medicine, and the conservation of endangered species. In addition, the introduction of genes via random insertion or gene targeting into the genome of donor cells to be used for cloning has opened up another route for new genomics in agriculture and medicine. The production of transgenic clones starting in 1997 has indeed contributed a milestone to scientific research. Although cloning efficiency is still low, certain kinds of experiments are quite feasible, and we anticipate improvements in the future.

Review: Somatic Cell Nuclear Transfer in Mammals: Progress and Applications

Somatic nuclear transfer has been performed with frogs since the early 1960s, yet it has proved impossible to generate an adult frog using an adult cell as nuclear donor. After some initial skepticism, the birth of sheep, cows, goats, and mice using this technique with fetal or adult cell donors is now established fact. The success with adult mammalian cell donors extends the historic work in frogs by attesting to the totipotency of nuclei in at least some adult, differentiated cell types. Because the technique offers a developmental read out of the totality of genetic and molecular lifetime changes accumulated by the nucleus of a single somatic cell, basic research applications are seen in the fields of ageing, cancer, X chromosome inactivation, and imprinting. The prospect of a method for gene targeting in livestock holds particular promise for commercial applications; whilst for humans, the use of nuclear transfer to provide diverse populations of customized stem cells for therapeutic purposes presents a tantalizing future goal.

Should You Clone Your Dog? An Animal Rights Perspective on Somacloning

This paper uses the Missyplicity Project ‘s detailed Code of Bioethics as a starting point for discussion of animal rights perspectives on cloning. Although funded by a couple in order to clone their pet dog, the project has more important collateral goals and forms part of a general line of research that, if successful, promises enormous clinical benefits to humans.

A particular type of animal rights perspective is described and used to evaluate this project. This perspective accepts a ‘principle of axiological anthropocentrism’ (PAA), according to which only human beings have certain interests, or a kind of value, which is of pre-eminent moral significance. The best-known animal rights views (those of Singer and Regan) are shown to be consistent with the PAA. This perspective also denies that potential characteristics qualify their possessors for the same type of moral respect as actualized characteristics.

The balancing of potential benefits against risks to research subjects is discussed and it is concluded that, from the particular ethical perspective adopted in this paper, cloning research of this general type is not particularly problematic; and, given its stringent Code of Bioethics, only an abolitionist perspective could condemn the Missyplicity Project in particular.

Dolly, Polly and other 'ollys': likely impact of cloning technology on biomedical uses of livestock

The idea of generating transgenic livestock which secrete into their milk large quantities of proteins for therapeutic use, was pioneered in the late 1980s with the disclosure of the production of a number of transgenic sheep. One particular animal, a sheep called Tracy, produced milk where over 50% of the protein consisted of human alpha 1 anti-trypsin. Sheep-derived protein has now entered clinical trials for cystic fibrosis (UK, USA) and congenital emphysema (UK). There are many other examples where this technology is making inroads into more traditional ways of making biopharmaceuticals. However, although robust, this technology has several limitations, including an inability to allow targeted insertion/modification of the animal genome, long timelines to production flocks/herds, and the rather unpredictable expression levels seen when different transgenic founders are compared. We believe that there is now a technical solution to all of these problems. Dolly is a high profile example of a new technology comprising the generation of identical animals from cultured somatic cells. This work has many implications. In the commercial context, the real benefits of this advance will be seen when genetically engineered somatic cells are shown to be suitable nuclear donors, and particularly when the manipulations are targeted to pre-determined sites in the host cell genome. The first objective has now been achieved with the birth of Polly, a cloned sheep which contains the human gene encoding Factor IX, a protein involved in preventing haemophilia.

The presence of transcription factors in chicken albumin, yolk and blastoderm

Embryonic development is determined by preset intrinsic programs and extrinsic signals. To explore the possibility that transcription factors are present at the onset of development, preparations of yolk, albumin, and blastoderm from unfertilized and fertilized white Leghorn chicken eggs were screened by a panel of 16 transcription factor antibodies with Western blot techniques. Yolk was positive for 13 transcription factors, whereas blastoderm was positive for 10, and albumin was positive for 5. In yolk, several transcription factors, GATA-2, E2F-1, MyoD, and TFIID, were developmentally regulated. These results indicate that intracellular yolk and extracellular albumin contain transcription factors which presumably influence early chick embryonic development from prefertilization to the late blastoderm stage. Thus, the utility of preset maternal transcription factors within yolk and albumin complement maternally derived mRNA to determine the early development of the zygote.

Nuclear transfer in mammals: recent developments and future perspectives

A clone can be defined as a set of genetically identical animals. Small clones of two or occasionally up to four identical animals can be obtained by embryo splitting or blastomere separation. Embryo cloning by nuclear transfer involves the transfer of genetic material from a donor cell (karyoplast) to the cytoplasm of an oocyte or zygote from which the genetic material has been removed (cytoplast). In farm animals, metaphase II oocytes are most widely used as cytoplasts. There are now many factors known to influence the efficiency of embryo cloning by nuclear transfer. These include stage of development and cell cycle of donor cells, the choice of the recipient cell, the methods for activation of oocytes, the cell cycle coordination between donor cell and recipient cytoplast, and the method for fusion between nuclear donor and recipient cytoplast. Recent progress in cloning embryos and animals from cultured cells of embryonic, fetal, or adult origin offers a wide spectrum of potential applications of nuclear transfer, such as the unlimited multiplication of elite embryos or animals from selected matings and the potential for precise genetic modification of farm animals for gene farming or xenotransplantation.