Abstract: The invention provides a method and materials for monitoring and isolating differentially expressed genes. In accordance with the method of the invention, differently labeled populations of DNAs from sources to be compared are competitively hybridized with reference DNA cloned on solid phase supports, e.g. microparticles, to provide a differential expression library which, in the preferred embodiment, may be manipulated by fluorescence-activated cell sorting (FACS). Monitoring the relative signal intensity of the different fluorescent labels on the microparticles permits quantitative analysis of expression levels relative to the reference DNA. The invention also provides a method for identifying and isolating rare genes. Populations of microparticles having relative signal intensities of interest can be isolated by FACS and the attached DNAs identified by sequencing, such as with massively parallel signature sequencing (MPSS), or with conventional DNA sequencing protocols.

Abstract: The invention provides a method and materials for monitoring and isolating differentially expressed genes. In accordance with the method of the invention, differently labeled populations of DNAs from sources to be compared are competitively hybridized with reference DNA cloned on solid phase supports, e.g. microparticles, to provide a differential expression library which, in the preferred embodiment, may be manipulated by fluorescence-activated cell sorting (FACS). Monitoring the relative signal intensity of the different fluoresent labels on the microparticles permits quantitative analysis of expression levels relative to the reference DNA. Populations of microparticles having relative signal intensities of interest can be isolated by FACS and the attached DNAs identified by sequencing, such as with massively parallel signature sequencing (MPSS), or with conventional DNA sequencing protocols.

Abstract: An improvement in adaptor-based sequence analysis is provided that addresses the problems created by self-ligation of target polynucleotides that have complementary ends. The improvement includes preparation of target polynucleotides with dephosphorylated 5′ strands and the use of adaptors having a 3′ blocking group. In a preferred embodiment, adaptors are ligated to target polynucleotides by a single strand, 3′ blocking groups are removed, the adjacent 5′ hydroxyl of the target polynucleotide is phosphorylated, and the ligation of the adaptor is completed by treatment with a ligase.

Abstract: Homologous recombination is employed to inactivate genes, particularly genes associated with MHC antigens. Particularly, the .beta..sub.2- microglobulin gene is inactivated for reducing or eliminating the expression of functional Class I MHC antigens. The resulting cells may be used as allogeneic donor cells. Methods for homologous recombination in non-transformed mammalian somatic cells are also described.

Abstract: The invention provides a method of nucleic acid sequence analysis based on the ligation of one or more sets of encoded adaptors to the terminus of a target polynucleotide. Encoded adaptors whose protruding strands form perfectly matched duplexes with the complementary protruding strands of the target polynucleotide are ligated, and the identity of the nucleotides in the protruding strands is determined by an oligonucleotide tag carried by the encoded adaptor. Such determination, or "decoding" is carried out by specifically hybridizing a labeled tag complement to its corresponding tag on the ligated adaptor.

Abstract: An improvement in adaptor-based sequence analysis is provided that addresses the problems created by self-ligation of target polynucleotides that have complementary ends. The improvement includes preparation of target polynucleotides with dephosphorylated 5' strands and the use of adaptors having a 3' blocking group. In a preferred embodiment, adaptors are ligated to target polynucleotides by a single strand, 3' blocking groups are removed, the adjacent 5' hydroxyl of the target polynucleotide is phosphorylated, and the ligation of the adaptor is completed by treatment with a ligase.

Abstract: The invention provides a method of nucleic acid sequence analysis based on repeated cycles of ligation to and cleavage of probes at the terminus of a target polynucleotide. At each such cycle one or more terminal nucleotides are identified and one or more nucleotides are removed from the end of the target polynucleotide, such that further cycles of ligation and cleavage can take place. At each cycle the target sequence is shortened by one or more nucleotides until the nucleotide sequence of the target polynucleotide is determined. The method obviates electrophoretic separation of similarly sized DNA fragments and eliminates the difficulties associated with the detection and analysis of spatially overlapping bands of DNA fragments in a gel, or like medium. The invention further obviates the need to generate DNA fragments from long single stranded templates with a DNA polymerase.

Abstract: Novel regimens are provided for administering foreign genetically modified allogeneic cells to a host by combining the administration of the cells with a reduced regimen of an immunosuppressive agent. Particularly, cells having a reduced level of Class I MHC antigens may be employed in a variety of cellular therapy situations, where foreign cells are engrafted to treat diseased states.

Abstract: Homologous recombination is employed to inactivate genes, particularly genes associated with MHC antigens. Particularly, each of the .beta..sub.2- microglobulin gene and the IFN-.gamma.R gene is inactivated for reducing or eliminating the expression of functional MHC antigens. The resulting cells may be used as universal donor cells. In addition, embryonic stem cells may be modified by homologous recombination for use in producing chimeric or transgenic mammalian hosts, which may be used as source of universal donor organs, or as models for drug and transplantation therapies. Methods for homologous recombination in non-transformed mammalian somatic cells are also described.