Molecular mapping of murine I region recombinants. III. Crossing over at two discrete sites within the beta 1-beta 2 intron of the E beta gene

The murine MHC provides a unique genetic system for studying meiotic recombination. A large number of murine H-2 recombinants cross over within a stretch of the E beta gene referred to as the E beta hot spot. The crossing over of eight such recombinants, derived from the s and k haplotypes, was studied at the nucleotide level. A 3-kb stretch of DNA, 3' to the beta 1 exon of the E beta gene, was sequenced after amplification of the genomic DNA from B10.S (one of the parental strains) by polymerase chain reaction. A number of sequence variations were identified with respect to B10.A (the other parental strain). Examination of these sequence variations by RFLP, simple sequence length polymorphism, as well as direct sequencing after polymerase chain reaction-amplification of genomic DNA from the recombinants led to unambiguous identification of the cross-over sites. Although all eight recombinants crossed over within the beta 1-beta 2 intron, two discrete nonoverlapping sites were involved. Five of the recombinants B10.BASR1, B10.ASR1, B10.ASR12, B10.HTT, and B10.S(9R) crossed over within a maximum of 395 bp of DNA 3' to the beta 1 exon. The remaining three recombinants B10.ASR7, B10.ASR11, and B10.S(8R) crossed over within 950 bp of DNA, adjacent to the cross-over site noted above. Each of these stretches of DNA was completely identical in the two parental haplotypes precluding further dissection of the cross-over sites. These cross-over sites are within those reported for the b and k recombination.     

Molecular cloning of mouse beta 2-glycoprotein I and mapping of the gene to chromosome 11.

beta 2-Glycoprotein I (beta 2 GPI), a plasma protein that binds to anionic phospholipids, is composed of five repeating units called a short consensus repeat (SCR), which is found mostly in the regulatory proteins of the complement system. Recently the human beta 2 GPI gene has been assigned to chromosome 17, not to chromosome 1 where most of the genes of the SCR-containing proteins are clustered. In this report, we have isolated a full-length cDNA clone of mouse beta 2 GPI and determined the chromosomal localization of the gene. The amino acid sequence deduced from the nucleotide sequence of mouse beta 2 GPI revealed 76.1% identity with that of human beta 2 GPI. A genetic mapping by in situ hybridization and linkage analysis using 50 backcross mice has shown that the mouse beta 2 GPI gene (designated B2gp1) is located on the terminal portion of the D region of chromosome 11, closely linked to Gfap, and is 18 cM distal to Acrb, extending a conserved linkage group between mouse chromosome 11 and human chromosome 17. On the basis of these results, the evolutionary relationships among the SCR-containing proteins are discussed.     

Extended nucleotide sequence of the switch region of the murine gene encoding immunoglobulin E

The nucleotide sequence of the switch region (S epsilon) of the gene encoding murine IgE was determined from a germline DNA clone. The sequence extends 1.7 kb 5' to the previously published S epsilon sequence. Another 33 repeat units were located by comparison to the S epsilon consensus sequence. Therefore, the complete S epsilon repetitive sequence consists of 53 repeat units contained in a region about 2.5 kb long.     

Molecular mapping of class II polymorphisms in the human major histocompatibility complex. I. DR beta

We have studied 27 cell lines homozygous by consanguinity for the major histocompatibility complex to establish the restriction fragment length polymorphism (RFLP) patterns seen with six different restriction enzymes (Bam HI, Bg1 II, Eco RI, Hinc II, Hind III, Pvu II) and DR beta chain probes. The probes used were a full-length cDNA DR beta probe and a probe specific for the 3' untranslated region. The RFLP obtained represent the first standard patterns for the individual haplotypes DR1 through 7 and DR9 as defined by genetically homozygous lines. The patterns obtained reflect the DR specificities closely, as well as the DRw52 and DRw53 specificities. These latter specificities are associated with the most prominent patterns of RFLP. Bands are present which are unique for the haplotypes DR1, DR2, DR4, DR7, DRw52, and DRw53, and could be used for typing these haplotypes in heterozygotes. Subtypes can be identified for all of the haplotypes except DR1. These subtypes indicate that there is an extensive amount of polymorphism in the DR subregion that has not been identified serologically.     

Chromosome mapping of the murine syndecan gene.

The chromosomal localization of the murine syndecan gene was determined by analysis of DNA from a panel of mouse-hamster cell hybrids containing various mouse chromosomes, detection of immunoreactive syndecan in culture medium of these cells, and linkage analysis of a mouse interspecific backcross. Southern analysis of the mouse-hamster cell hybrid DNA shows two distinct hybridizing sequences, one on mouse Chromosome 12 and the other on the X chromosome. Localization of the syndecan gene to mouse Chromosome 12 was determined by detection of immunoreactive syndecan in the culture medium of cell hybrids containing mouse Chromosome 12. Hybrids containing other mouse chromosomes were negative. Linkage analysis by Southern hybridization of DNA from a mouse interspecific backcross using a syndecan-specific probe localized the syndecan gene locus, Synd, to the proximal end of Chromosome 12, tightly linked to the Pomc-1 and Nmyc loci. The syndecan gene is likely on human Chromosome 2 because this region shows conservation of synteny between mouse and human chromosomes.     

Mitotic crossing over in chromosome I disomics of Aspergillus nidulans

Summary The frequency and pattern of homologous recombination in chromsome I disomics of Aspergillus nidulans is presented. Approximately 6% of randomly selected haploid breakdown sectors are recombinant. Most of these arise from double exchange events, one of which is located in the centromere region, the other distal on the left arm. Other marked regions are rarely involved in a recombination event. Reciprocal genotypes arise in approximately equal frequencies indicating that exchange results in reciprocally recombined non-sister chromatids at the four strand stage of mitosis. Possible theories for the extreme localisation of exchange events are discussed.     

Metaphase I bound arms and crossing over frequency in rye

Using a Giemsa C-banding procedure it has been possible to identify at meiosis three chromosome pairs of a local Spanish rye cultivar. Two of these chromosomes (3 and 5) were heterozygous for an interstitial C-band in the long arm and the other (chromosome 7) was heterozygous for a telomeric C-band, also in the long arm. From the frequency of being bound at metaphase I and the frequency of recombined chromatids at anaphase I in the arms considered, estimates of actual chiasma frequencies have been derived. The results have been compared with those obtained in a Fl between two inbred lines. It is concluded that: (i) Although the frequency of bound arms analyzed was similar in all cases, the chiasma frequency was higher in the cultivar than in the Fl plants. Cultivar plants showed a variation in chiasma frequency for the bivalent arms studied which was correlated with the frequency of bound arms per cell, indicating that the estimation for chiasma frequency by means of bound arm frequency has an error that increases with increasing number of bound arms per cell, (ii) Evidence of chiasma terminalization has not been found, (iii) It is suggested that the different rye chromosomes have different chiasma localization patterns, which, in turn, are related with the chiasma frequency.     

Molecular cloning of the murine PHEX gene promoter

We report the novel cloning of the murine PHEX promoter, the gene that is mutated in X-linked hypophosphatemic rickets (XLH). Four promoter/reporter gene constructs, -133/+104, -542/+104, -1061/+104, and -2866/+104, showed significant luciferase activity (4.9-13.2-fold over background) when transfected into rat osteogenic sarcoma (UMR-106) cells.     

Mapping dystrophin gene recombinants in Greek DMD/BMD families: low recombination frequencies in the STR region

A systematic study of 42 Greek DMD/BMD families using 14 polymorphic markers that span the dystrophin gene was performed in order to assess the position and frequency of recombinants in the Greek population and to test whether hot spots of recombination and deletions coincide when exclusively studying DMD/BMD families. We report a low percentage of recombination between markers STR44 and STR50; otherwise, the distribution of recombination events in other parts of the gene is largely in agreement with previously published data on Centre d'Etude du Polymorphisme Humaine families. We therefore propose that recombination frequencies and the correlation between recombination and deletion hot spots should be evaluated on DMD/BMD families exclusively.     

Cycloheximide induces expression of the human interferon beta 1 gene in mouse cells transformed by bovine papillomavirus-interferon beta 1 recombinants.

Mouse cells transformed by a bovine papillomavirus recombinant vector containing the human interferon (IFN) beta 1 (IFN-beta 1) gene could be induced to produce human as well as mouse IFNs. The optimal conditions for induction of human IFN and of its mRNA in these transformants resembled those needed for mouse IFN: high concentrations of DEAE-dextran and low concentrations of polyriboinosinic acid-polyribocytidylic acid. Superinduction by inhibitors of protein synthesis which strongly stimulate IFN-beta 1 induction in human cells had only a small effect on human IFN induction in bovine papillomavirus IFN-beta 1-transformed mouse cells. In contrast, cycloheximide without double-stranded RNA could induce significant levels of human IFN in the bovine papillomavirus IFN-beta 1 mouse transformants. After cycloheximide treatment, these cells contained IFN-beta 1 mRNA whose 5' ends originated in the authentic start site of the human IFN-beta 1 gene, as shown by S1 nuclease mapping. The transferred human gene, propagated extrachromosomally in the mouse cells, was, therefore, inducible under conditions different from those in human cells. The results also confirmed that the inhibitor of protein synthesis, cycloheximide, can induce expression of a human IFN gene.