Rbt (rabo torcido), a new mouse skeletal mutation involved in anteroposterior patterning of the axial skeleton,maps close to the ts (tail-short) locus and distal to the sox9 locus on chromosome 11

Rbt (Rabo torcido) is a new semidominant mouse mutant with a variety of skeletal abnormalities. Heterozygous Rbt mutants display homeotic anteroposterior patterning problems along the axial skeleton that resemble Polycomb group and trithorax gene mutations. In addition, the Rbt mutant displays strong similarities to the phenotype observed in Ts (Tail-short), indicating also a homeotically transformed phenotype in these mice. We have mapped the Rbt locus to an interval of approximately 6 cM on mouse Chromosome (Chr) 11 between microsatellite markers D11Mit128 and D11Mit103. The Ts locus was mapped within a shorter interval of approximately 3 cM between D11Mit128 and D11Mit203. This indicates that Rbt and Ts may be allelic mutations. Sox9, the human homolog of which is responsible for the skeletal malformation syndrome campomelic dysplasia, was mapped proximal to D11Mit128. It is, therefore, unlikely that Ts and Rbt are mouse models for this human skeletal disorder. Received: 14 April 1996 / Accepted: 22 July 1996     

Exclusion of Sox9 as a candidate for the mouse mutant Tail-short

The Sry-related gene Sox9 has been proposed as the gene responsible for the mouse skeletal mutant Tail-short (Ts), on the basis of its expression in skeletogenic mesenchymal condensations in the mouse embryo and its chromosomal location in the region of Ts on distal Chromosome (Chr) 11. We present here detailed mapping of Ts locus relative to the Sox9, using an intersubspecific cross. Among 521 backcross progeny, 16 recombinants were detected between Sox9 and Ts, suggesting a separation of 3.5 ± 0.01 cM, and excluding Sox9 as a candidate for Ts. A further nine recombinants were detected between Ts and the polycomb-like gene M33, suggesting that these loci are separated by 1.8 ± 0.011 cM. Six microsatellite markers were co-localized to the Ts locus, providing reagents for positional cloning of Ts. Received: 13 December 1995 / Accepted: 3 March 1996     

Arg-7 mutant x wild-type crosses in Chlamydomonas reinhardi: Study of the enzyme produced in diploid strains

Summary The arg-7 locus is the structural gene for the argininosuccinate lyase (ASL). Interallelic complementation was previously found to occur between several mutants of the locus: this is indicative for the homomultimeric nature of ASL.Two complementing (arg-7-5 and arg-7-7) and two non-complementing (arg-7-1 and arg-7-6) mutants of the arg-7 locus were crossed to the pab-2 strain (which is wild-type for the arg-7 locus). In each cross, heterozygote phenotypically wild-type strains were isolated; their diploid pattern was demonstrated by various criteria: mating type, cell volume, nuclear size.The four heterozygotes were compared to the haploid wild-type and in some experiments, to the diploid strain arg-1xpab-2 homozygous for the arg-7 locus. No difference was found in growth rate and in the Michaelis constant values for ASL. The specific activity of the enzyme produced in the heterozygotes was about 50 percent of the activity found in haploid or diploid wild-type. The heat sensitivity of ASL was also investigated in the different strains: two (containing the complementing mutations arg-7-5 and arg-7-7) of the four heterozygotes produce ASL varieties different from the wild-type enzyme as far as the thermolability is concerned.These results suggest that hybrid ASL can be formed by interaction between the products of wild-type and mutant genes. A clear dominance of the wild-type allele is expected only when the mutant allele has no product of the gene: this could be the case for arg-7-1 and arg-7-6.     

Tss (Tail-short Shionogi), a new short tail mutation found in the BALB/cMs strain, maps quite closely to the Tail-short (Ts) locus on mouse chromosome 11.

A spontaneous morphological mutation characterized by a short and kinky tail (Tail-short Shionogi: Tss) was observed in a BALB/cMs mouse breeding colony. The inheritance mode of the Tss mutation is semi-dominant, and homozygotes (Tss/Tss) are probably embryonic lethal. The viability of the Tss/+ heterozygotes appear to be influenced by the mating partner: 47.1% of the (BALB/cMs-Tss/+ x C57BL/6J)F1 embryos were the mutant phenotype, whereas there were no (BALB/cMs-Tss/+ x A/J)F1 embryos with the mutant phenotype. The Tss locus was mapped by linkage analysis between microsatellite markers D11Mit128 and D11Mit256 on mouse Chromosome 11. These results suggest that the Tss mutation is a new allele on the Tail-short (Ts) locus.     

A High-Resolution Genetic Map of the Nervous Locus on Mouse Chromosome 8

The nervous (nr) mutant mouse displays two gross recessive traits: both an exaggeration of juvenile hyperactivity and a pronounced ataxia become apparent during the third and fourth postnatal weeks. Using an intersubspecific intercross, we have established a high-resolution map of a segment of mouse Chromosome 8 that places thenrlocus in a genomic segment defined byD8Rck1on the centromeric end andD8Mit3on the telomeric end. This map position places thenrlocus within the BALB/cGr congenic region of the C3HeB/FeJ-nrstrain, confirming the accuracy of our study. We used this map position to identify and evaluate three genes—ankyrin 1, cortexin, and farnesyltransferase—as candidates for thenrgene. These three genes were eliminated from consideration but allowed us to establish the conservation of synteny between the region containing thenrlocus and a segment of the short arm of human chromosome 8 (8p21–p11.2). Finally, the incomplete penetrance of thenrphenotype led us to perform a screen for modifier loci, and we present evidence that such a nervous modifier locus may exist on mouse Chromosome 5.     

The vestigial locus of Drosophila melanogaster is involved in resistance to inhibitors of dTMP synthesis

The vestigal (vg) gene encodes a nuclear protein which plays a major role in the formation of the wing of Drosophila. Resistance or sensitivity to aminopterin, an inhibitor of the dihydrofolate reductase enzyme in D. melanogaster, seems to be associated with a specific alteration in vg gene function. Wild-type and vg mutant strains selected for growth on increasing concentrations of aminopterin display changes in physiological and biochemical parameters such as viability on normal and aminopterin-containing media, duration of development, wing phenotype, dihydrofolate reductase activity, and cross-resistance to fluorodeoxyuridine (FUdR) and to methotrexate. Our results indicate that the mechanisms of resistance differ in the wild-type and mutant strains. The vg ^83b27 mutant, in which the major part of intron 2 of the vg gene is deleted, is associated with a high rate of resistance to FUdR, an inhibitor of thymidylate synthetase. Moreover, vg ^83b27/vg ^BGheterozygotes, which are wild type when grown on normal medium, display a strong vg phenotype when grown on aminopterin. Our results indicate a role for the vestigial locus in mediating resistance to inhibitors of dTMP synthesis.     

Allelic Negative Complementation at the Abruptex Locus of DROSOPHILA MELANOGASTER

The mutations of the Abruptex locus in Drosophila melanogaster fall into three categories. There are recessive lethal alleles and viable alleles. The latter can be divided into suppressors and nonsuppressors of Notch mutations. The recessive lethals are lethal in heterozygous combination with Notch. As a rule the recessive lethals are lethal also in heterozygous combination with the viable alleles. Heterozygous combinations of certain viable alleles are also lethal. In such heterozygotes, one heteroallele is a suppressor of Notch and the other is a nonsuppressor. Other heterozygous combinations of viable alleles are viable and have an Abruptex phenotype. The insertion of the wild allele of the Abruptex locus as an extra dose (carried by a duplication) into the chromosomal complement of the fly fully restores the viability of the otherwise lethal heterozygotes if two viable alleles are involved. The extra wild allele also restores the viability of heterozygotes in which a lethal and a suppressor allele are present. If, however, a lethal and a nonsuppressor are involved, the wild allele only partly restores the viability, and the effect of the wild allele is weakest if two lethal alleles are involved. It seems likely that of the viable alleles the suppressors of Notch are hypermorphic and the nonsuppressors are hypomorphic. The lethal alleles share properties of both types, and are possibly antimorphic mutations. It is suggested that the locus is responsible for a single function which, however, consists of two components. The hypermorphic mutations are defects of the one component and the hypomorphic mutations of the other. In heterozygotes their cumulative action leads to decreased viability. The lethal alleles are supposed to be defects of the function as a whole. The function controlled by the locus might be a regulative function.     

Effect of aPMR1 disruption on the processing of heterologous glycoproteins secreted in the yeastSaccharomyces cerevisiae

TheSaccharomyces cerevisiae PMR1 gene encodes a Ca²⁺-ATPase localized in the Golgi. We have investigated the effects ofPMR1 disruption inS. cerevisiae on the glycosylation and secretion of three heterologous glycoproteins, human α₁-antitrypsin (α₁-AT), human antithrombin III (ATHIII), andAspergillus niger glucose oxidase (GOD). Thepmr1 null mutant strain secreted larger amounts of ATHIII and GOD proteins per a unit cell mass than the wild type strain. Despite a lower growth rate of thepmr1 mutant, two-fold higher level of human ATHIII was detected in the culture supernatant from thepmr1 mutant compared to that of the wild-type strain. Thepmr1 mutant strain secreted α₁-AT and the GOD proteins mostly as core-glycosylated forms, in contrast to the hyperglycosylated proteins secreted in the wild-type strain. Furthermore, the core-glycosylated forms secreted in thepmr1 mutant migrated slightly faster on SDS-PAGE than those secreted in themnn9 deletion mutant and the wild type strains. Analysis of the recombinant GOD with anti-α1,3-mannose antibody revealed that GOD secreted in thepmr1 mutant did not have terminal α1,3-linked mannoses unlike those secreted in themnn9 mutant and the wild type strains. The present results indicate that thepmr1 mutant, with the super-secretion phenotype, is useful as a host system to produce recombinant glycoproteins lacking high-mannose outer chains.     

A High-Resolution Map in the Chromosomal Region Surrounding theLpsLocus

TheLpslocus on mouse chromosome 4 controls host responsiveness to lipopolysaccharide, a major component of the outer membrane of Gram-negative bacteria. The C3H/HeJ inbred mouse strain is characterized by a mutantLpsallele (Lps^d) that renders it hyporesponsive to LPS and naturally tolerant of its lethal effects. To identify theLpsgene by a positional cloning strategy, we have generated a high-resolution linkage map of the chromosomal region surrounding this locus. We have analyzed a total of 1604 backcross mice from a preexisting interspecific backcross panel of 259 (Mus spretus× C57BL/6J)F1 × C57BL/6J and two novel panels of 597 (DBA/2J × C3H/HeJ)F1 × C3H/HeJ and 748 (C57BL/6J × C3H/HeJ)F1 × C3H/HeJ segregating atLps.A total of 50 DNA markers have been mapped in a 11.8-cM span overlapping theLpslocus. This positions theLpslocus within a 1.1-cM interval, flanked proximally by a large cluster of markers, including three known genes (Cd30l, Hxb,andAmbp), and distally by two microsatellite markers (D4Mit7/D4Mit178). The localization of theLpslocus is several centimorgans proximal to that previously assigned.     

Chromosomal location of the gene encoding the murine acute-phase protein serum amyloid P-component (SAP)

A full-length cDNA clone, pmSAP3, encoding the serum P component (SAP), has been used to search for DNA fragment length variation among mouse strains previously analyzed for differences in endogenous SAP levels. Three alleles were found usingEcoRI-digested DNA. The finding of a single 5.4-kb fragment, alleled, in DNA from DBA/2J mice suggests the presence of a singleSap locus. Segregation of DNA fragment associated withSap ^b andSap ^d alleles was analyzed in three sets of recombinant inbred (RI) strains. The strain distribution pattern found for theSap alleles was identical to that of alleles ofLy-9 in 43 individual RI strains, suggesting tight linkage withLy-9 on mouse chromosome 1. In the BXD RI strains, the SDP of theSap locus, defined by the difference in the endogenous SAP level, is also identical to the SDP of the DNA fragments. We propose to redesignate theSap locus to include both the structural element defined by the DNA polymorphism and the regulatory element involved in the regulation of SAP synthesis. TheSap locus is the major genetic element contributing to the regulation of SAP production. Other genetic factors are also involved, as shown by the presence of nonparental phenotypes in the individual BXH RI strains. This study was performed through special Coordination Funds of the Science and Technology Agency of the Japanese Government and PHS Grant GM24464 to R.W.E.     

Genetic Characterization of the Chromosomal Rearrangements That Accompany the Transgene Insertion in theChakragatiMouse Mutant

We have previously reported that the circling phenotype of thechakragatimouse segregates with the transgene integration event as an autosomal recessive trait. It was unclear, however, whether the phenotype was linked to the transgene integration point nearD16Ros1or to a potential disruption atD16Ros2,10 cM away. We report here that animals recombinant betweenD16Ros1andD16Ros2,homozygous for the transgene insertion atD16Ros1,but wildtype forD16Ros2,do indeed show the phenotype. We conclude that any potential disruption at theD16Ros2locus is not responsible for the circling phenotype. We further show that recombination betweenD16Ros1andD16Ros2occurs at a greatly reduced level in thechakragatimouse compared to wildtype strains. Detailed genetic analysis of recombinants indicates that the proximal-most 4.5 cM shows no recombination in over 1400 meioses. We propose that this is due to an inversion in this region, and we genetically define the proposed distal inversion break point to a 1.3-cM region betweenD16Mit63andD16Mit169.     

Genetic characterization of the Dyscalc locus

Calcification occurs frequently in the development of atherosclerotic lesions, and studies in mice have indicated a genetic contribution. We now show that one genetic factor contributing to aortic calcification is the Dyscalc locus, previously shown to contribute to myocardial calcification. Thus, the Dyscalc locus, on proximal mouse Chromosome (Chr) 7, segregated with vascular calcification in a large cross between susceptible strain DBA/2J and resistant strain C57BL/6J. Further evidence was observed by analysis of recombinant inbred strains derived from various susceptible and resistant parental strains. Myocardial and vascular calcifications are importantly influenced by multiple modifier loci as well as the Dyscalc gene, making fine mapping of Dyscalc difficult. In order to allow more detailed genetic and biochemical characterization of Dyscalc, we have identified congenic strains containing the Dyscalc locus from resistant strain C57BL/10 on the background of susceptible strain C3H/DiSnA. The congenic strains exhibit little or no myocardial or vascular calcification, unlike the background HcB C3H strain, and the calcification segregated as a Mendelian factor, allowing finer mapping of Dyscalc.     

Thehigh growth(hg) Locus Maps to a Deletion in Mouse Chromosome 10

Thehigh growth(hg) locus in mice produces a 30–50% increase in weight gain of homozygous individuals. Here we report that the microsatellite markerD10Mit69is deleted in high growth mice. The deletion ofD10Mit69was uncovered in a screen of the high growth mouse and its progenitor strains for available markers in thehgregion. We demonstrate thathgandD10Mit69cosegregate in a cross of congenic strains C57BL/6J-hghg× C57BL/6J. These results suggest that deletion of a region aroundD10Mit69is responsible for the high growth effect. MarkerD10Mit69will be utilized as an entry point to physical cloning of thehg-containing segment. A dense map of markers aroundhgconstructed here should allow identification of markers in homologous regions in domestic animals and humans, which may be utilized to assess the role of thehglocus in these other species.     

Genetic study of a lethal necrosis to soybean mosaic virus in PI 507389 soybean

PI 507389 soybean [Glycine max (L.) Merr.], a large-seeded line from Japan, exhibits a rapid, lethal, necrotic response to strains G1, G2, G5, and G6 of soybean mosaic virus (SMV). Unlike the hypersensitive necrotic reaction, this stem-tip necrosis can be a serious threat to soybean production. To investigate the genetic basis of lethal necrosis (LN), PI 507389 was crossed with the susceptible (S) cv. Lee 68 and with resistant (R) lines PI 96983, cv. York, and cv. Marshall, which carry single dominant genes for SMV resistance at the Rsv1 locus. F(1) plants, F(2) populations, and F(2:3) lines were inoculated with G1 and G6 in the greenhouse or in the field. Results indicated that LN is controlled by a single gene allelic to Rsv1, and this allele in PI 507389 is recessive to R alleles in PI 96983, York, and Marshall. The LN allele is codominant with the allele for S, for the heterozygotes showed a mixed phenotype of both necrosis (N) and mosaic (M) symptoms (NM). The LN allele becomes recessive to the S allele as the mixed NM shifts to S at a later stage in response to more virulent strains. The gene symbol Rsv1-n is assigned for the allele conferring LN in PI 507389. Rsv1-n is the only allele at the Rsv1 locus conditioning N to G1 and no R to any other SMV strains, and thus a unique genotype for SMV strain differentiation. The phenotypic expression of heterozygotes and the dominance relationships among R, N, and S depend on the virulence of SMV strains, source of alleles, and developmental stage.     

A new allele of the lurcher gene, lurcher

A new neurological mouse mutation that arose spontaneously in a BALB/cByJ stock displays a semidominant pattern of inheritance. In the heterozygote, this mutation results in an early loss of Purkinje cells in the cerebellum, which is followed by the overt symptom of an ataxic gait first observed at postnatal day 13 (P13). A portion of animals homozygous for the mutation die within P0; the remaining homozygotes die by P25. The mutation maps to mouse Chromosome (Chr) 6 between markers D6Rck314 and D6Rck361, a chromosomal segment that contains the lurcher (Lc) locus. The Lc mutation is also semidominant and has a strikingly similar phenotype. A cross between a new mutant (Nm) heterozygote and an Lc heterozygote yields double heterozygotes, animals that carry both mutations, with a phenotype similar to that of both Nm and Lc homozygotes. The similarity in phenotype, the colocalization of the two loci on mouse Chr 6, and the positive result of the allelism test demonstrate that the new mutation is an allele of the Lc gene. Received: 4 April 1997 / Accepted: 21 April 1997     

Wingless mutation inDrosophila melanogaster

A temperature sensitive lethal allele of thewingless locus ofDrosophila melanogaster together with previously studied lethal and viable alleles in this locus, has been used to study some properties of this locus. These studies show the existence of two lethal phases for thewingless lesion; one during embryogenesis and another during pupation. By growing embryos with temperature sensitivewingless lesion at the permissive temperature and letting the larvae develop at non-permissive temperature, a large-scale cell death and subsequent regeneration were seen to occur in the mutant wing discs. This cell death followed by regeneration alters the normal developmental potential of the wing disc. Disc transplantation experiments show that these discs are incapable of differentiating into wing blade structures.     

Isolation of a new paramutagenic allele of thesulfurea locus in the tomato cultivar Moneymaker following in vitro culture

A new allele, SC148, of thesulfurea locus inLycopersicon esculentum was detected in a line derived after repeated selfing of plants that had been regenerated from tissue culture. Like the originalsulf mutant, SC148 displayed two mutant phenotypes: green-yellow speckled plants in which thesulf ^vag allele is present and pure yellow plants homozygous for thesulf ^tpura allele. Although the mutant alleles are recessive to wild-type, an unpredictable number of variegated and pura plants appeared in F₁ progenies that had been derived from crosses between SC148 and wild-type tomato plants. The presence of the wild-typesulf ⁺ allele in these variegated heterozygotes was demonstrated using a cytological marker that is linked tosulf. It is concluded that the mutantsulf allele of SC148, imposes its variegated expression state on the wild-typesulf ⁺ allele present insulf ⁺/sulf^vag heterozygotes. This behaviour, known as paramutation, has also been described for the originalsulf allele. The SC148 allele, however, seems to induce changes at an earlier stage in development. The analogy of this paramutagenic system to dominant position effect variegation inDrosophila is discussed.     

A 76-bp Deletion in the Mip Gene Causes Autosomal Dominant Cataract in Hfi Mice

Hfi is a dominant cataract mutation where heterozygotes show hydropic lens fibers and homozygotes show total lens opacity. The Hfi locus was mapped to the distal part of mouse chromosome 10 close to the major intrinsic protein (Mip), which is expressed only in cell membranes of lens fibers. Molecular analysis of Mip revealed a 76-bp deletion that resulted in exon 2 skipping in Mip mRNA. In Hfi/Hfi this deletion resulted in a complete absence of the wildtype Mip. In contrast, Hfi/+ animals had the same amount of wildtype Mip as +/+. Results from pulse–chase expression studies excluded hetero-oligomerization of wildtype and mutant Mip as a possible mechanism for cataract formation in the Hfi/+. We propose that the cataract phenotype in the Hfi heterozygote mutant is due to a detrimental gain of function by the mutant Mip resulting in either cytotoxicity or disruption in processing of other proteins important for the lens. Cataract formation in the Hfi/Hfi mouse is probably a combined result of both the complete loss of wildtype Mip and a gain of function of the mutant Mip.     

Golden: a novel coat color mutant in the wild mouse Mus caroli

We identified a spontaneous pigmentation mutant in the wild mouse species Mus caroli. Mutant mice exhibit a golden coat color on the agouti background, easily distinguishable from the darker wild type. The golden phenotype segregates as an autosomal recessive, showing no linkage to the sex-linked enzyme marker glucose-6-phosphate dehydrogenase. Obligate heterozygotes are phenotypically indistinguishable from the wild type. At birth, homozygotes have poorly pigmented eyes, which darken with age to become indistinguishable from the wild type. Pigmentation of the ears, tail, and footpads is reduced in intensity. Preliminary studies indicate that the phenotype may be due to an alteration in the shape and pigmentation of the eumelanosomes. The viability and fertility of both heterozygotes and homozygotes, as measured by litter size, sex ratio, or frequency of survival to weaning, appear to be normal for M. caroli. Spectrophotometric analysis of hair samples from the mouse variant at the putative golden locus (gdn) suggests that this mutant is not homologous to at least six independent pigment mutants previously identified in M. musculus.     

BALB/c-H-2 db : A newH-2 mutant in BALB/cKh that identifies a locus associated with theD region

A newH-2 mutant, BALB/c-H-2 ^db , is described. This mutant originated in BALB/c, is inbred, and is coisogenic with the parental BALB/cKh strain. The mutation is of the loss type since BALB/c-H- ^db rejects BALB/c, but not vice versa. Complementation studies have localized the mutation to theD region of theH-2 complex. A cross between BALB/c-H-2 ^db and B10.D2-H-2 ^da failed to complement for either BALB/c or B10.D2 skin grafts, indicating that these are two separate mutations at the same locus (Z2). Direct serological analysis and absorption studies revealed that, with one exception, theH-2 andIa specificities of BALB/c and BALB/c-H-2 ^db are identical. In particular,H-2.4, the H-2D^d private specificity, is quantitatively and qualitatively identical in the two strains. The exception is that of the specificities detected by antiserum D28b: (k×r)F₁ anti-h, which contains anti-H-2.27, 28, and 29. These specificities appear to be absent from theH-2 ^db mutant since they are not detected directly or by absorption. Other public specificities are present in normal amounts,e.g., the reaction with antisera to H-2.3, 8, 13, 35, and 36. The reaction with antiserum D28 (f×k)F₁ anti-s, which contains antibodies to H-2.28, 36, and 42, is the same in both strains. Antiserum made between the two strains (H-2 ^db anti-H-2 ^d ) reacts like an anti-H-2 serum, in that it reacts with both T and B cells by cytotoxicity, but is not a hemagglutinating antibody. The serum reacts as does the D28b serum in both strain distribution and in cross-absorption studies. We conclude that theH-2 ^db mutation occurred at a locus in theD region, resulting in the loss of the H-2.28 public serological specificity and of a histocompatibility antigen. Whether these are one and the same antigen is not yet known. The data, in view of other evidence, imply that the public and private specificities are coded for by separate genes.Abbreviations used in this paper are as follows CML cell-mediated lysis - MLR mixed lymphocyte reaction - GVHR graft-versus-host reaction - RFC rosette-forming cells - RAM-Ig rabbit anti-mouse IgG