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L M Silver

Publications and source records attributed to L M Silver.

At least 109 records · Page 6Linked to original sources
PubMed1986

Genetic analysis of the proximal portion of the mouse t complex: evidence for a second inversion within t haplotypes.

Genomic sequences derived from the mouse t complex by a microdissection cloning technique have been used as tools to obtain high resolution genetic maps of the wild-type and t haplotype forms of the most proximal portion of chromosome 17. Genetic mapping was performed through a recombinant inbred strain analysis and an analysis of partial t haplotypes. The accumulated data demonstrate the existence of a large inversion of genetic material, encompassing the loci of T and qk, within the proximal portion of t haplotypes. This newly described proximal inversion and the previously described distal inversion provide an explanation for the suppression of recombination observed along the length of t haplotype DNA in heterozygous mice.

Animals↗
PubMed1986

Nonhomologous pairing in mice heterozygous for a t haplotype can produce recombinant chromosomes with duplications and deletions.

We have investigated the structure and properties of a chromosomal product recovered from a rare recombination event between a t haplotype and a wild-type form of mouse chromosome 17. Our embryological and molecular studies indicate that this chromosome (twLub2) is characterized by both a deletion and duplication of adjacent genetic material. The deletion appears to be responsible for a dominant lethal maternal effect and a recessive embryonic lethality. The duplication provides an explanation for the twLub2 suppression of the dominant T locus phenotype. A reanalysis of previously described results with another chromosome 17 variant called TtOrl indicates a structure for this chromosome that is reciprocal to that observed for twLub2. We have postulated the existence of an inversion over the proximal portion of all complete t haplotypes in order to explain the generation of the partial t haplotypes twLub2 and TtOrl. This proximal inversion and the previously described distal inversion are sufficient to account for all of the recombination properties that are characteristic of complete t haplotypes. The structures determined for twLub2 and TtOrl indicate that rare recombination can occur between nonequivalent genomic sequences within the inverted proximal t region when wild-type and t chromosomes are paired in a linear, nonhomologous configuration.

Alleles↗
PubMed1986

Genetic analysis of a mouse t complex locus that is homologous to a kidney cDNA clone.

A mouse kidney cDNA clone, pMK174, identifies restriction fragment length polymorphisms (RFLPs) that map to two unlinked loci. One, designated D17Rp17, has been mapped near quaking, (qk), on chromosome 17 using three sets of recombinant inbred (RI) strains. A study of several t haplotypes resulted in the identification of t-specific alleles of D17Rp17 that map to the proximal half of the t complex. Neither t-specific nor wild-type D17Rp17 alleles are present in chromosomes carrying either the T Orleans (TtOrl) or the T hairpin tail (Thp) deletions. Comparison with other molecular markers indicates that pMK174 identifies a new proximal t complex locus, Rp17. The second locus identified by pMK174, termed D4Rp18, is tentatively assigned to chromosome 4 by mouse-Chinese hamster somatic cell hybrid analysis.

Alleles↗
PubMed1985

Molecular probes define different regions of the mouse t complex.

Four genomic clones obtained from microdissected fragments of the proximal portion of mouse chromosome 17 have been used to identify a series of t-haplotype-specific restriction fragments. Their specificity is defined by presence in eight complete t haplotypes and absence from 18 inbred strains of wild-type mice. Partial t haplotypes contain subsets of the t-specific fragments, and each can be classified according to the t-specific fragments it contains. This is the first molecular evidence that independent partial t haplotypes contain different lengths of t haplotype DNA. Recombination studies indicate that partial t haplotypes suppress recombination in proportion to the extent of t haplotype DNA they contain. Molecular analysis of partial t haplotypes shows that the t-specific fragments map to and thus define different regions of the t complex. Certain regions of t haplotype DNA defined by t-specific restriction fragments can be correlated with loci involved in the control of transmission ratio distortion.

Alleles↗
PubMed1984

An alpha globin pseudogene is located within the mouse t complex.

Restriction fragment length polymorphisms have been identified in the alpha-globin pseudogene carried on chromosome 17. Different inbred strains of mice carry one of two forms of the sequence, whereas all complete t haplotypes carry a third form. With the use of partial t haplotypes, the alpha-psi 4 sequence has been mapped to the distal end of the t complex. This sequence appears to be closely linked to the tufted locus in the t complex.

Animals↗
PubMed1984

Transmission ratio distortion of mouse t haplotypes is not a consequence of wild-type sperm degeneration.

A mouse t-complex-specific DNA probe was used to determine the ratio of t-carrying and (+)-carrying sperm in epididymal, vas deferens, and postejaculatory sperm cell populations from heterozygous (+/t) mice with transmission ratios of greater than 95%. No detectable degeneration of (+)-carrying sperm was observed. In this respect, mouse t haplotypes differ from Drosophila melanogaster SD chromosomes. High transmission of t haplotypes must be a consequence of differential transport and/or differential sperm function during the fertilization process itself.

Alleles↗
PubMed1984

The differential expression of the actins and tubulins during spermatogenesis in the mouse.

Following intratesticular injection of [35S]methionine, the multiple isoforms of actin and tubulin from highly purified mouse testicular meiotic and post-meiotic cells have been analysed by high resolution two-dimensional gel electrophoresis. In pachytene spermatocytes both beta and gamma actin are synthesized, gamma actin being made in a significantly greater amount. The relative proportion of synthesis of beta and gamma actin changes during spermiogenesis, beta actin increasing and gamma actin decreasing in round spermatids, elongating spermatids, and residual bodies. Both alpha and beta tubulin are synthesized in approximately equal proportion in pachytene spermatocytes. In addition to the tubulin isoforms synthesized during meiosis, at least one new form of both alpha and beta tubulin first appears in post-meiotic (haploid) cells. In elongating spermatids and residual bodies, the synthesis of alpha tubulin is drastically reduced.

Actins↗
PubMed1984

Molecular clones of the mouse t complex derived from microdissected metaphase chromosomes.

Fragments of the proximal half of mouse chromosome 17 including the t-complex region were microdissected from metaphase spreads. DNA was isolated from a pool of such fragments, and was cloned on microscale. Individual clones were used to probe genomic digests of DNA from a pair of Chinese hamster cell lines with or without mouse chromosome 17, and livers of congenic inbred lines of mice carrying wild-type and/or t-haplotype forms of chromosome 17. The data obtained indicate that 95% of the low copy number microclone inserts recognize DNA sequences present on mouse chromosome 17. It has been possible to use one-third of these clones to identify restriction-fragment-length polymorphisms between wild-type and t-haplotype DNA on a congenic background. These results demonstrate that these clones have been derived from the t-complex or regions closely linked to it. Clones of this type should provide starting points for a molecular analysis of this region of the mouse genome.

Animals↗
PubMed1984

Characterization of a recombinant mouse T haplotype that expresses a dominant lethal maternal effect.

The twLub2 chromosome was generated by rare recombination between a complete t haplotype and a wild-type form of mouse chromosome 17. This recombinant chromosome expresses a dominant lethal effect in all embryos that inherit the mutant chromosome from their mothers. The phenotype of this maternal effect is indistinguishable from that expressed by the previously described Thp deletion chromosome. It appears likely that the crossing over event that gave rise to twLub2 was unequal and resulted in the alteration or deletion of a gene (which is named the T-associated maternal effect locus, Tme) that must be inherited from the mother in order for normal development to proceed through late stages of gestation. The results presented here allow a mapping of the Tme locus between the quaking and tufted loci which are 3 cM apart within the proximal region of chromosome 17.

Animals↗
PubMed1983

TOr1 is a novel, variant form of mouse chromosome 17 with a deletion in a partial t haplotype.

Moutier discovered, in a mouse from a noninbred Swiss/Orleans laboratory stock, a spontaneous dominant mutation which mapped to the T locus, and which was named TOr1. Genetic analyses indicated that TOr1 was not a simple mutation at one locus, but rather a deletion over a 3-centimorgan region of chromosome 17 that included both T and quaking (qk). Further experiments reported by Erickson et al., and a more comprehensive study by Hammerberg, have demonstrated that TOr1 is associated with recessive genetic properties affecting sperm function, characteristic of the proximal region of complete t haplotypes. These results were interpreted as evidence for the location of proximal t haplotype 'sperm factors' within the region deleted by TOr1. We now provide conclusive biochemical and genetic evidence that the 'TOr1 haplotype' is inseparably associated with a chromosomal region derived from a naturally occurring mouse t haplotype. Hence, it is likely that the t haplotype properties of TOr1 are a consequence not of the deletion itself, but of closely linked mutant t haplotype genes.

Animals↗
PubMed1983

A diversified set of testicular cell proteins specified by genes within the mouse t complex.

We have conducted a comparative high-resolution, two-dimensional gel analysis of testicular cell proteins synthesized by inbred mice congenic for a series of t haplotypes on the 129/SvJ background. At least nine t haplotype-specific proteins can be identified within the 1000 most prominent proteins observed. Apparent allelic wild-type forms of six of these t complex proteins (TCPs) have also been identified, and evidence from cell-free translation experiments indicates that all of these are coded for directly by genes within the t complex. Eight of the mutant t-haplotype-specific proteins are expressed in an identical form by testicular cells carrying any one of the complete t haplotypes analyzed. The ninth protein is polymorphic among different t haplotypes, as well as among different inbred strains of mice. Partial t haplotypes were used to map the genes specifying the expression of each TCP protein to a subregion of the t complex. The accumulated data suggest a subset of TCP proteins that are most likely to be involved in t haplotype effects on germ cell differentiation and fertility.

Animals↗