Targeted mutation of the DNA methyltransferase gene results in embryonic lethality.

The invention relates to transgenic non-human animals capable of producing heterologous antibodies and methods for producing human sequence antibodies which bind to human antigens with substantial affinity.

Transgenic non-human animals capable of producing heterologous antibodies

RAG-1-deficient mice have no mature B and T lymphocytes

Targeted disruption of the c-src proto-oncogene leads to osteopetrosis in mice

Visualizing an Olfactory Sensory Map

Cloning and expression of the mouse pgk-1 gene and the nucleotide sequence of its promoter.

In both humans and mice, two genes encode phosphoglycerate kinase, a key enzyme in the glycolytic pathway. The pgk-1 gene is expressed in all somatic cells, is located on the X chromosome, and contains 10 introns. The pgk-2 gene is expressed only in sperm cells, is located on an autosome, and has no introns. The nucleotide sequence of the pgk-2 gene suggests that it arose from pgk-1 more than 100 million years ago by RNA-mediated gene duplication. The pgk-2 gene may, then, be a transcribed retroposon. Thus, gene duplication by retroposition may have been used as a mechanism for evolutionary diversification.

The testis-specific phosphoglycerate kinase gene pgk-2 is a recruited retroposon

The mouse X-linked Pgk-1 gene encodes phosphoglycerate kinase. When transfected into human cells, the Pgk-1b allele causes the appearance of mouse PGK-1b enzyme activity. We describe here cloning of mouse Pgk-1a, an allele of Pgk-1 which encodes an enzyme, PGK-1a, with distinct electrophoretic mobility. We constructed recombinants between the DNA encoding Pgk-1b and Pgk-1a and transfected these constructs into human cells to assess the electrophoretic characteristics of each recombinant. In this way the charge variation between the two proteins was localized to exons 4 or 5. Sequencing of these exons revealed a single base-pair difference between the two alleles at codon 155, which predicts the amino acids lysine and threonine in PGK-1b and PGK-1a, respectively. A number of other DNA sequence polymorphisms exist between Pgk-1b and Pgk-1a including part of an L1 repeated element unique to Pgk-1a.

Polymorphisms in the coding and noncoding regions of murine Pgk-1 alleles.

The mammalian genome contains two genes encodingphosphoglycerate kinase; the pgk-1gene is X-linked and is expressed in all cells except sperm, while the pgk-2gene is expressed exclusively in sperm cells. The mouse genome contains no pseudogenes derived from pgk-2.On the other hand, the genomes of Balb/c and C3H/He strain mice contain six other regions with sequences homologous to those of pgk-1cDNA. These pgk-related sequences are likely derived from the pgk-1gene by retroposition because all are located on autosomal chromosomes and because none appear to be interrupted by introns. Two of the presumed pseudogenes contain sequences homologous to all regions of the pgk-1cDNA while the other four genomic regions were truncated at the 5′, 3′, or both ends. One of the truncated pseudogenes was sequenced. Its pgk-related sequence was not flanked by direct repeats, suggesting that loss of the 5′ and/or 3′ ends of this retrogene may have occurred following its integration into the genome. Our evidence suggests that pgk-1-derived retroposons arose initially more than 100 million years ago and have continued to arise until so recently that some are unique to different mouse strains.

The family of mouse phosphoglycerate kinase genes and pseudogenes.

The extent of methylation of DNA sequences upstream and within the two X-linked genes,Pgk-1 andHprt, was analyzed in male and female somatic cells and in female embryonal carcinoma cells carrying either two active X chromosomes (Xa) or one active and one inactive X chromosome (Xi). Sites upstream and within the first intron of bothPgk-1 andHprt were heavily methylated on the Xi in somatic cells and in embryonal carcinoma cells with an Xi. Reactivation of this Xi was accompanied by extensive demethylation of these sites. In female embryonal carcinoma cells with two active X chromosomes, one X inactivates during differentiation in culture; however, methylation did not occur during differentiation, consistent with the idea that DNA methylation does not play a role in the initiation of X inactivation but may be involved in maintaining inactivation of those genes on the Xi.

Chaker N. Adra

Papers

Cloning and expression of the mouse pgk-1 gene and the nucleotide sequence of its promoter.

The testis-specific phosphoglycerate kinase gene pgk-2 is a recruited retroposon

Polymorphisms in the coding and noncoding regions of murine Pgk-1 alleles.

The family of mouse phosphoglycerate kinase genes and pseudogenes.

DNA methylation of two X chromosome genes in female somatic and embryonal carcinoma cells.