Restriction fragment length polymorphism of C4 genes in mice with t chromosomes

Limits of the distal inversion in the t complex of the house mouse: evidence from linkage disequilibria

The suppression of crossing-over and the consequent linkage disequilibrium of genetic markers within the t complex of the house mouse is caused by two large and two short inversions. The inversions encompass a region that is some 15 centiMorgans (cM) long in the homologous wild-type chromosome. The limits of the proximal inversions are reasonably well-defined, those of the distal inversions much less so. We have recently obtained seven new DNA markers (D17Tu) which in wild-type chromosomes map into the region presumably involved in the distal inversions of the t chromosomes. To find out whether the corresponding loci do indeed reside within the inversions, we have determined their variability among 26 complete and 12 partial t haplotypes. In addition, we also tested the same collection of t haplotypes for their variability at five D17Leh, Hba-ps4, Pim-1, and Crya-1 loci. The results suggest that the distal end of the most distal inversion lies between the loci D17Leh467 and D17Tu26. The proximal end of the large distal inversion was mapped to the region between the D17Tu43 and Hba-ps4 loci, but this assignment is rather ambiguous. The loci Pim-1, Crya-1, and the H-2 complex, which have been mapped between the Hba-ps4 and Grr within the large distal inversion, behave as if they recombine from time to time with their wild-type homologs.

The D17Tu5 locus in the t complex: implications for the origin of t haplotypes and inbred strains

The mouse x Chinese hamster cell line R4 4-1 contains only one mouse chromosome, the bulk of which corresponds to Mus musculus chromosomes 17 and 18 (MMU17 and MMU18, respectively). A genomic library was prepared from the R4 4-1 DNA, and a mouse clone was isolated from the library, which-with the help of somatic cell hybrids-could be mapped to the MMU17. A locus defined by a 2.7-kb long Bam HI probe from this clone was designated D17Tu5 (Tu for Tübingen). The locus proved to be polymorphic among inbred strains and wild mice. By testing of recombinant inbred strains and partial t haplotypes, the D17Tu5 locus could be mapped to a position between the D17Leh66E and D17Rp17 loci within the t complex. Two alleles were found at this locus, D17Tu5a and D17Tu5b, defined by Taq I restriction fragment length polymorphism. Both alleles are present among inbred strains and wild mice of the species M. domesticus. All complete t haplotypes tested carry the D17Tu5a allele and all tested wild mice of the species M. musculus, with the exception of those bearing t haplotypes, carry the D17Tu5b allele. Additional alleles are found in some populations of wild mice and in other species of the genus Mus. The distribution of the two alleles among the inbred strains correlates well with their known or postulated genealogy. Their distribution between the two species of Mus and among the mice with T haplotypes suggests a relatively recent origin of the t haplotypes.

Three new t-haplotypes of Mus musculus reveal structural similarities to t-haplotypes of Mus domesticus

Three newt-haplotypes,tp 4,tp 12andtp 14, were isolated fromM. musculusmale mice captured in Central and East Bohemia, Czechoslovakia, about 400 km from the zone of hybridization betweenM. musculusandM. domesticusspecies. Complementation tests have shown that all three newt-haplotypes belong totw 73group. When compared with 5t-haplotypes fromM. domesticusthey displayed the same pattern ofBamHI restriction fragments withH-2class I genes, and they also shared thet-specific 5·2 kbTaqI fragment of the alpha globin pseudogene. However, they differed fromM. domesticus t-haplotypes at the D17Leh443 locus since they all displayed a 10·5 kbMspI fragment, labelled by the Tu443 probe, not found in wild type-chromosomes or inM. domesticus t-haplotypes. A hypothesis is proposed thatt-haplotypes inM. domesticusoriginated by a single successful introgression from a parental species during speciation.

Nucleotide sequence analysis of class II genes borne by mouse t chromosomes

Five class IIH-2genes borne bytchromosomes were partially sequenced:borne by thetTuw10chromosome of EDY589 (H-2w2);andborne by thetTuw8chromosome of CR0437 (H-2w57), as well asandborne by thetTuw7chromosome of CR0435 (H-2w37). These genes are representatives of the three major groups of alleles found associated withtchromosomes. The sequenced part consisted of almost the entire exon 2 and the entire exon 3 coding for the first and the second domain of the β polypeptide chains, respectively. The sequence was compared with the published sequences ofAβandEβalleles borne, by non-tchromosomes. The comparison revealed that thet-associated alleles are no more similar to one another than they are to the corresponding genes present on non-tchromosomes in laboratory mice. This divergence in the nucleotide sequence among the class II genes is interpreted as evidence that thetcomplex is very old.

A region flanking H-2K is duplicated to a distant site in most mouse t haplotypes

Mouse t haplotypes contain at least one inversion, which encompasses the major histocompatibility complex, relative to their wild-type counterparts. A DNA probe for a single copy sequence which flanks the H-2K region in inbred strains was found to have undergone further rearrangements in the t haplotypes. In most t haplotypes, this sequence is duplicated at a distant site, and the two regions show 1% recombination. The length of homology shared by the two sites is likely to be at least 10-15 kb. Three different alleles, as defined by restriction fragment length polymorphisms, were found for each of the two sites among different t haplotypes. These may reveal evolutionary relationships among these chromosomes.

Molecular cloning and sequence analysis of a haploid expressed gene encoding t complex polypeptide 1

The mouse t haplotypes show defects in spermatogenesis attributed to multiple loci on chromosome 17. We have cloned the gene for an abundant testicular germ cell protein, t complex polypeptide 1, which has a variant form in t haplotypes, TCP-1A. A cDNA clone, pB1.4, which hybridizes to a 19S mRNA that is abundant in haploid cells during mouse spermatogenesis, derives from the 3' end of the mRNA encoding TCP-1B. The Tcp-1 gene appears to be a member of a novel gene family and shows multiple changes between the predicted amino acid sequences of TCP-1B and TCP-1A. An additional Taq1 site is created by a T to C transition in the predicted open reading frame of the Tcp-1a gene. The resultant RFLP has allowed typing of the Tcp-1 gene cluster in 54 complete and partial t haplotype chromosomes. DNA sequence comparison of the Tcp-1 genes suggests that the t haplotype chromosome arose within the genus Mus more than one million years ago.

Cosegregation of the polymorphic C4 with the MHC in the frog, Xenopus laevis

Employing isoeletric focusing combined with enzyme-linked immunoelectrotransfer blot analysis, the fourth component of complement (C4) was analyzed in the two highly histocompatible, major histocompatibility complex homozygous groups (J and K) of Xenopus laevis. Each group had a characteristic C4 isoelectric focusing pattern, i.e., an isoelectric point range of 8.0-8.5 for J (C4jC4j) and 7.6-8.1 for K (C4kC4k). In (J X K)F1 frogs, C4 proteins were expressed in a codominant fashion (C4jC4k). In the backcrossed progeny B1 [J X (J X K)F1], those with C4jC4j rejected (J X K)F1 skins hyperacutely (less than 17 days), were high responders against (J X K)F1 cells, and nonstimulators to J cells in mixed lymphocyte reaction (MLR), but they did not suffer from the graft-versus-host reaction (GVHR), even after the injection of (J X K)F1 cell-stimulated J splenocytes. On the other hand, the B1 frogs with C4jC4k acutely or chronically (greater than 17 days) rejected (J X K)F1 skins, were low or nonresponders against (J X K)F1 cells and high stimulators to J cells in MLR, and they suffered from GVHR after the injection of prestimulated J splenocytes. These results argue for the notion that the genes equivalent to mammalian class III map to the MHC at the phylogenetic level of the anuran amphibian.

Male sterility of the mouse t-complex is due to homozygosity of the distorter genes

Evidence is presented that the male sterility produced by the mouse t-complex is due to interaction of at least three sterility factors. These factors are carried in the same partial haplotypes as the three distorter genes, Tcd-1, Tcd-2, and Tcd-3 and are suggested to be identical with them. When heterozygous, the distorter/sterility genes act on the wild-type form of the responder gene, rendering sperm carrying it nonfunctional, thus leading to high transmission of the t form of the responder. When homozygous, the harmful effects of the distorter genes are stronger and affect both forms of the responder, leading to sterility. If homozygous sterility is an inescapable part of ratio distortion, then the t-lethals confer a selective advantage in removing sterile males from the population. Thus, the relationship between the various properties of the t-complex can now be understood.