A simple method for the preparation of antibodies to the mitochondrial biotin-dependent carboxylases

Summary Heterologous antiserum to the 3 biotin-dependent carboxylases was prepared by selective removal of these enzymes from human liver on an avidin-sepharose column. A carboxylase-avidin-sepharose matrix was used as an antigen to produce anti-carboxylase antibodies. The resultant antisera can be used to purifiy the specific carboxylases, to prepare monoclonal antibodies to these enzymes or to study inherited carboxylase deficiencies and biotin-dependent intermediary metabolism.The authors thank Dr Emmanuel Shapira for his helpful suggestions and Patricia Tuck for her technical assistance. This work was supported by NIH research grants AM25675 and AM26127. Barry Wolf is a recipient of an NIH Research Career Development Award (AM00677) and is aided by a Basil O'Connor Starter Research Grant from the National Foundation—March of Dimes (5–263). This is paper No. 137 from the Department of Human Genetics — Medical College of Virginia.     

Eomesodermin is required for mouse trophoblast development and mesoderm formation

The earliest cell fate decision in the mammalian embryo separates the extra-embryonic trophoblast lineage, which forms the fetal portion of the placenta, from the embryonic cell lineages. The body plan of the embryo proper is established only later at gastrulation, when the pluripotent epiblast gives rise to the germ layers ectoderm, mesoderm and endoderm. Here we show that the T-box gene Eomesodermin performs essential functions in both trophoblast development and gastrulation. Mouse embryos lacking Eomesodermin arrest at the blastocyst stage. Mutant trophoectoderm does not differentiate into trophoblast, indicating that Eomesodermin may be required for the development of trophoblast stem cells. In the embryo proper, Eomesodermin is essential for mesoderm formation. Although the specification of the anterior-posterior axis and the initial response to mesoderm-inducing signals is intact in mutant epiblasts, the prospective mesodermal cells are not recruited into the primitive streak. Our results indicate that Eomesodermin defines a conserved molecular pathway controlling the morphogenetic movements of germ layer formation and has acquired a new function in mammals in the differentiation of trophoblast.     

Transfer of a functional human immune system to mice with severe combined immunodeficiency

The pressing need for a better experimental system for AIDS research has brought into sharp focus the shortcomings of available animal models and the practical and ethical limitations of studies of immune responses and viral pathogenesis in humans. Current studies of the human immune responses are limited to relatively restrictive in vivo experiments and several in vitro systems that, although useful, allow only short-term studies and support responses to a few antigens. Neither model is particularly amenable to studies of the pathogenesis of diseases of the immune system. We report here that injection of human peripheral blood leukocytes (PBL) can result in the stable long-term reconstitution of a functional human immune system in mice with severe combined immunodeficiency (SCID). Human PBL transplanted to SCID mice increase in number and survive for at least six months; reconstituted mice show spontaneous secretion of human immunoglobulin and a specific human antibody response is induced following immunization with tetanus toxoid. All of the major cell populations present in PBL are found in the lymphoid tissue and blood of SCID recipients, although the relative proportions of B cells, T-cell subsets and monocytes/macrophages in long-term recipients differ from those found in normal PBL and, in mice transplanted with 50 x 10(6) or more PBL from Epstein-Barr virus (EBV)-seropositive donors, EBV-positive B-cell lymphomas often develop. Our results suggest that xenogeneic transplantation of human lymphoid cells into SCID mice may provide a useful model for the study of normal human immune function, the response of the immune system to pathogenic agents and early events in lymphomagensis.     

A human colon cancer cell capable of initiating tumour growth in immunodeficient mice

Colon cancer is one of the best-understood neoplasms from a genetic perspective, yet it remains the second most common cause of cancer-related death, indicating that some of its cancer cells are not eradicated by current therapies. What has yet to be established is whether every colon cancer cell possesses the potential to initiate and sustain tumour growth, or whether the tumour is hierarchically organized so that only a subset of cells--cancer stem cells--possess such potential. Here we use renal capsule transplantation in immunodeficient NOD/SCID mice to identify a human colon cancer-initiating cell (CC-IC). Purification experiments established that all CC-ICs were CD133+; the CD133- cells that comprised the majority of the tumour were unable to initiate tumour growth. We calculated by limiting dilution analysis that there was one CC-IC in 5.7 x 10(4) unfractionated tumour cells, whereas there was one CC-IC in 262 CD133+ cells, representing >200-fold enrichment. CC-ICs within the CD133+ population were able to maintain themselves as well as differentiate and re-establish tumour heterogeneity upon serial transplantation. The identification of colon cancer stem cells that are distinct from the bulk tumour cells provides strong support for the hierarchical organization of human colon cancer, and their existence suggests that for therapeutic strategies to be effective, they must target the cancer stem cells.     

An integrated model of kimberlite ascent and eruption

Diatremes are carrot-shaped bodies forming the upper parts of very deep magmatic intrusions of kimberlite rock. These unusual, enigmatic and complex features are famous as the source of diamonds. Here we present a new model of kimberlite ascent and eruption, emphasizing the extremely unsteady nature of this process to resolve many of the seemingly contradictory characteristics of kimberlites and diatremes. Dyke initiation in a deep CO2-rich source region in the mantle leads to rapid propagation of the dyke tip, below which CO2 fluid collects, with a zone of magmatic foam beneath. When the tip breaks the surface of the ground, gas release causes a depressurization wave to travel into the magma. This wave implodes the dyke walls, fragments the magma, and creates a 'ringing' fluidization wave. Together, these processes form the diatreme. Catastrophic magma chilling seals the dyke. No precursor to the eruption is felt at the surface and the processes are complete in about an hour.