The genetic map around the tail kinks (tk) locus on mouse Chromosome 9

Tail kinks (tk) is a classical mouse skeletal mutation, located on Chromosome (Chr) 9. As the first step for the positional cloning of the tk gene, we have established a genetic map of a region surrounding the tk locus by generating a backcross segregating for tk. From this backcross, 1004 progeny were analyzed for the coat-color phenotype of the proximally located dilute (d) gene and for the distally flanking microsatellite marker, D9Mit12. Fifty-six recombinants between d and tk and 75 recombinants between tk and D9Mit12 were identified, completing a panel of 130 recombinants including one double recombinant. This panel allowed us to map five microsatellite loci as well as d and Mod-1 with respect to tk. We show that one of the microsatellite markers mapped, D9Mit9, does not recombine at all with tk in our backcross. This indicates that the D9Mit9 locus will serve as a good starting point for a chromosomal walk to the tk gene.     

Assignment of a locus for mouse lung tumor susceptibility to proximal Chromosome 19

Previous studies have hypothesized that at least three genetic loci contribute to differences in pulmonary adenoma susceptibility between mouse strains A/J and C57BL/6J. One gene that may confer susceptibility to lung tumorigenesis is the Kras protooncogene. To identify other relevant loci involved in this polygenic trait, we determined tumor multiplicity in 56 randomly chosen N-ethyl-N-nitrosourea-treated (A/J×C57BL/6J) N1×C57BL/6 backcross (AB6N2) progeny and correlated it with genotypes at 77 microsatellite markers spanning the genome. A correlation of lung tumor multiplicity phenotypes with genotypes of microsatellite markers on distal Chromosome (Chr) 6 in the Kras region (Pas1) was confirmed, and a new region on Chr 19 (designated Pas3) was identified that also contributes to susceptibility. Linkage analysis on Chr 19 with 270 AB6N2 mice localized the region flanked by D19Mit42 and D19Mit19 that is most closely associated with lung tumor susceptibility. The Pas3 locus may be an enhancer of the susceptibility locus on Chr 6.     

Low resolution mapping around the flavivirus resistance locus (Flv) on mouse Chromosome 5

Although the phenomenon of innate resistance to flaviviruses in mice was recognized many years ago, it was only recently that the genetic locus (Flv) controlling this resistance was mapped to mouse Chromosome (Chr) 5. Here we report the fine mapping of the Flv locus, using 12 microsatellite markers which have recently been developed for mouse Chr 5. The new markers were genotyped in 325 backcross mice of both (C3H/HeJxC3H/ RV)F₁xC3H/HeJ and (BALB/cxC3H/RV)F₁xBALB/c backgrounds, relative to Flv. The composite genetic map that has been constructed identifies three novel microsatellite loci, D5Mit68, D5Mit159, and D5Mit242, tightly linked to the Flv locus. One of those loci, D5Mit159, showed no recombinations with Flv in any of the backcross mice analyzed, indicating tight linkage (<0.3 cM). The other two, D5Mit68 and D5Mit242, exhibited two and one recombinations with Flv (0.6 and 0.3 cM) respectively, defining the proximal and distal boundaries of a 0.9-cM segment around this locus. The proximal flanking marker, D5Mit68, maps to a segment on mouse Chr 5 homologous to human Chr 4. This, together with the previous data produced by our group, locates Flv to a region on mouse Chr 5 carrying segments that are conserved on either human Chr 4, 12, or 7, but present knowledge does not allow precise identification of the syntenic element.     

Chromosomal mapping of the peroneal muscular atrophy (pma) gene in the mouse.

We conducted chromosomal mapping of the pma gene that is a causative gene in the peroneal muscular atrophy mouse, which shows a club foot at birth and unusual gait due to a dropped foot in the adult. Linkage analyses using backcross progeny revealed a significant linkage between the pma gene and three microsatellite markers, D5Mit263 at 73 cM, D5Mit141 and D5Mit97 at 74 cM on Chr 5. The gene order was determined as follows: centromere-D5Mit263-[2.65 cM]-D5Mit141-[2.56 cM]-pma-[5.13 cM]-D5Mit97-telomere.     

High-resolution linkage map in the vicinity of the Lp locus

Looptail (Lp) is a mutation that profoundly affects neurulation in mouse and is characterized by craniorachischisis, an open neural tube extending from the midbrain to the tail in embryos homozygous for the mutation. Lp maps to the distal portion of mouse chromosome 1, and as part of a positional cloning approach, we have generated a high-resolution linkage map of the Lp chromosomal region. For this, we have carried out extensive segregation analysis in a total of 706 backcross mice informative for Lp and derived from two crosses, (Lp/ + X SJL/J)F1 X SJL/J and (Lp/ + X SWR/J)F1 X SWR/J. In addition, 269 mice from a (Mus spretus X C57BL/6J)F1 X C57BL/6J interspecific backcross were also used to order marker loci and calculate intergene distances for this region. With these mice, a total of 28 DNA markers corresponding to either cloned genes or anonymous markers of the SSLP or SSCP-types were mapped within a 5-cM interval overlapping the Lp region, with the following locus order and interlocus distances (in cM): centromere-D1Mit110 / Atp1β1 / Cd3ζ / Cd3η / D1Mit145 — D1Hun14 / D1Mit15 — D1Mit111 / D1Mit112 — D1Mit114 — D1Mit148 / D1Mit205/ D1Mit36 / D1Mit146 / D1Mit147 / D1Mit270 / D1Hun13 — Fcgr2 — Mpp — Apoa2/Fcer1γ - Lp - D1Mit149 / Spna1/Fcer1α-Eph1-Hlx1/D1Mit62. These studies have allowed the delineation of a maximum genetic interval for Lp of 0.5 cM, a size amenable to physical mapping techniques.     

A high-resolution map around the locus Om on mouse Chromosome 11

The locus Om (ovum mutant) identified in the mouse strain DDK affects the viability of (DDK |m~ non-DDK)F₁ preimplantation embryos. We previously located this locus on Chromosome (Chr) 11 close to Scya2 (Baldacci et al. Mamm. Genome 2, 100–105, 1992). Here we report a high-resolution map of the region around Om based on a large number of backcross individuals. The same region has been analyzed on the EUCIB backcross, and the two maps have been compared. The results define the proximal and distal boundaries for the Om mutation as Scya2 and D11Mit36 respectively. The distance between these two markers is about 2 cM. These data should facilitate the positional cloning and molecular characterization of Om. Received: 10 July 1995 / Accepted: 11 September 1995     

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     

A genetic map of mouse chromosome 1 near the Lsh-Ity-Bcg disease resistance locus

Isozyme and restriction fragment length polymorphism (RFLP) analyses of backcross progeny, recombinant inbred strains, and congenic strains of mice positioned eight genetic markers with respect to the Lsh-Ity-Bcg disease resistance locus. Allelic isoforms of Idh-1 and Pep-3 and RFLPs detected by Southern hybridization for Myl-1, Cryg, Vil, Achrg, bcl-2, and Ren-1,2, between BALB/cAnPt and DBA/2NPt mice, were utilized to examine the cosegregation of these markers with the Lsh-Ity-Bcg resistance phenotype in 103 backcross progeny. An additional 47 backcross progeny from a cross between C57BL/10ScSn and B10.L-Lshr/s mice were examined for the cosegregation of Myl-1 and Vil RFLPs with Lsh phenotypic differences. Similarly, BXD recombinant inbred strains were typed for RFLPs upon hybridization with Vil and Achrg. Recombination frequencies generated in the different test systems were statistically similar, and villin (Vil) was identified as the molecular marker closest (1.7 +/- 0.8 cM) to the Lsh-Ity-Bcg locus. Two other DNA sequences, nebulin (Neb) and an anonymous DNA fragment (D2S3), which map to a region of human chromosome 2q that is homologous to proximal mouse chromosome 1, were not closely linked to the Lsh-Ity-Bcg locus. This multipoint linkage analysis of chromosome 1 surrounding the Lsh-Ity-Bcg locus provides a basis for the eventual isolation of the disease gene.     

Synteny on mouse chromosome 5 of homologs for human DNA loci linked to the Huntington disease gene

Comparative mapping in man and mouse has revealed frequent conservation of chromosomal segments, offering a potential approach to human disease genes via their murine homologs. Using DNA markers near the Huntington disease gene on the short arm of chromosome 4, we defined a conserved linkage group on mouse chromosome 5. Linkage analyses using recombinant inbred strains, a standard outcross, and an interspecific backcross were used to assign homologs for five human loci, D4S43, D4S62, QDPR, D4S76, and D4S80, to chromosome 5 and to determine their relationships with previously mapped markers for this autosome. The relative order of the conserved loci was preserved in a linkage group that spanned 13% recombination in the interspecific backcross analysis. The most proximal of the conserved markers on the mouse map, D4S43h, showed no recombination with Emv-1, an endogenous ecotropic virus, in 84 outcross progeny and 19 recombinant inbred strains. Hx, a dominant mutation that causes deformities in limb development, maps approximately 2 cM proximal to Emv-1. Since the human D4S43 locus is less than 1 cM proximal to HD near the telomere of chromosome 4, the murine counterpart of the HD gene might lie between Hx and Emv-1 or D4S43h. Cloning of the region between these markers could generate new probes for conserved human sequences in the vicinity of the HD gene or possibly candidates for the murine counterpart of this human disease locus.     

The deafness locus (dn) maps to mouse Chromosome 19

The deafness mouse has profound sensorineural hearing loss with degeneration of hair cells soon after birth. The mode of inheritance is recessive, and there are no associated phenotypic anomalies. Thus, this mouse provides a model for recessive, nonsyndromic, prelingual deafness. We have mapped the gene causing deafness in the mouse to Chromosome (Chr) 19 by analysis of 230 intersubspecific backcross progeny. No recombinants were found with the microsatellite marker D19Mit14. The loci for two guanine nucleotide-binding proteins are tightly linked to this marker, and they are being investigated as possible candidate genes. The identification of the defective gene in the mouse will help to explain the mechanism that causes hair cell degeneration and is likely to identify a homologous gene for deafness in humans.     

A linkage map of mouse Chromosome 1 using an interspecific cross segregating for the gld autoimmunity mutation

An interspecific backross was used to define a high resolution linkage map of mouse Chromosome (Chr) 1 and to analyze the segregation of the generalized lymphoproliferative disease (gld) mutation. Mice homozygous for gld have multiple features of autoimmune disease. Analysis of up to 428 progeny from the backcross [(C3H/HeJ-gld x Mus spretus)F₁ x C3H/HeJ-gld] established a map that spans 77.6 cM and includes 56 markers distributed over 34 ordered genetic loci. The gld mutation was mapped to a less than 1 cM segment on distal mouse Chr 1 using 357 gld phenotype-positive backcross mice. A second backcross, between the laboratory strains C57BL/6J and SWR/J, was examined to compare recombination frequency between selected markers on mouse Chr 1. Significant differences in crossover frequency were demonstrated between the interspecific backcross and the inbred laboratory cross for the entire interval studied. Sex difference in meiotic crossover frequency was also significant in the laboratory mouse cross. Two linkage groups known to be conserved between segments of mouse Chr 1 and the long arm of human Chrs 1 and 2 where further defined and a new conserved linkage group was identified that includes markers of distal mouse Chr 1 and human Chr 1, bands q32 to q42.     

Rat mutations cvd and hob with cerebellar malformations map to chromosome 2.

In this paper, we executed genome mapping and comparative mapping analyses for cvd and hob, autosomal recessive mutations with cerebellar vermis defect and cerebellar dysplasia in the rat. For the linkage analysis, we produced three sets of backcross progeny, (ACI x CVD)F(1) and (F344 x CVD)F(1) females crossed to a cvd homozygous male rat, and (HOB x WKY)F(1) males crossed to hob homozygous female rats. Analysis of the segregation patterns of simple sequence length polymorphism (SSLP) markers scanning the whole rat genome allowed the mapping of these autosomal recessive mutations to rat Chromosome (Chr) 2. The most likely gene order is D2Mgh12 - D2Rat86 - D2Mit15 - D2Rat185 - cvd - D2Rat66 - D2Mgh13, and D2Mit18 - Fga -D2Mit14 - D2Rat16 - hob - D2Mgh13. Crossing test between a proven cvd heterozygous and a hob heterozygous rats demonstrated their allelism. Furthermore, comparative mapping indicated the cvd locus corresponds to mouse chromosome 3 and a strong candidate gene Unc5h3, a causative gene for the rostral cerebellar malformation mouse, was implicated.     

Genetic mapping of the whirler mutation

The whirler (wi) mutation on mouse Chromosome (Chr) 4 results in an autosomal recessive neuroepithelial deafness and vestibular dysfunction exhibited as a characteristic shaker-waltzer behavior (deafness, circling, and head-bobbing). We have constructed a genetic linkage map across the wi region in both an interspecific [(wi/wi× CAST/Ei)F₁×wi/wi] backcross (n = 817) and an intraspecific [(wi/wi× CBA/Ca)F₁×wi/wi)] backcross (n = 335). In the interspecific backcross, wi was found to be non-recombinant with Orm1, 0.12 cM distal of D4Mit87 and Ambp, and 0.12 cM proximal of CD301. In the intraspecific backcross, wi was found to be non-recombinant with Orm1 and D4Mit244, 0.3 cM distal of Mup1, and 0.6 cM proximal of Tnc. We also report a family from the interspecific backcross that shows evidence of multiple recombinations across the region of mouse Chr 4 around the wi locus. These rearrangements appear specific to both the region and the family. Received: 10 July 1998 / Accepted: 19 January 1999     

A high-resolution radiation hybrid map of the proximal portion of mouse chromosome 5

Radiation hybrid (RH) mapping of the mouse genome provides a useful tool in the integration of existing genetic and physical maps, as well as in the ongoing effort to generate a dense map of expressed sequence tags. To facilitate functional analysis of mouse Chromosome 5, we have constructed a high-resolution RH map spanning 75 cM of the chromosome. During the course of these studies, we have developed RHBase, an RH data management program that provides data storage and an interface to several RH mapping programs and databases. We have typed 95 markers on the T31 RH panel and generated an integrated map, pooling data from several sources. The integrated RH map ranges from the most proximal marker, D5Mit331 (Chromosome Committee offset, 3 cM), to D5Mit326, 74.5 cM distal on our genetic map (Chromosome Committee offset, 80 cM), and consists of 138 markers, including 89 simple sequence length polymorphic markers, 11 sequence-tagged sites generated from BAC end sequence, and 38 gene loci, and represents average coverage of approximately one locus per 0.5 cM with some regions more densely mapped. In addition to the RH mapping of markers and genes previously localized on mouse Chromosome 5, this RH map places the alpha-4 GABA(A) receptor subunit gene (Gabra4) in the central portion of the chromosome, in the vicinity of the cluster of three other GABA(A) receptor subunit genes (Gabrg1-Gabra2-Gabrb1). Our mapping effort has also defined a new cluster of four genes in the semaphorin gene family (Sema3a, Sema3c, Sema3d, and Sema3e) and the Wolfram syndrome gene (Wfs1) in this region of the chromosome.     

Mea2/Golga3 gene is disrupted in a line of transgenic mice with a reciprocal translocation between Chromosomes 5 and 19 and is responsible for a defective spermatogenesis in homozygotes

A line of transgenic mouse T604 transmitted a transgene to progeny together with a set of chromosomes with a reciprocal translocation. The transgene was integrated at a single site in the translocated chromosomes, as revealed by fluorescence in situ hybridization. The transgenic hemizygous males, also heterozygous for the translocation of chromosomes, showed apparently normal spermatogenesis, while the males homozygous for the transgene as well as for the translocated chromosomes showed a defect in spermatogenesis. Considering that the genetic rearrangement by either insertion of the transgene or the chromosome translocation in the T604 mouse line might have caused a recessive mutation in a gene indispensable for spermatogenesis, we have mapped the transgene integration site and the translocation breakpoints in mouse chromosomes. Linkage analysis with SSLP markers showed that the loci for the transgene and the translocation breakpoints were closely located to D5Mit24 on Chromosome (Chr) 5, and to a region between D19Mit19 and D19Jpk2 on Chr 19. Mea2 gene, mapped only 2 cM from D5Mit24 and known to show male-specific enhanced expression in the testis, was analyzed as a candidate for the gene disrupted in T604 transgenic mice. Southern blot analysis revealed that Mea2 gene was indeed disrupted in T604 mice, and Northern blot analysis of the testis RNA showed that the expression of Mea2 was annihilated in the testis of T604 transgenic homozygotes. Received: 8 July 1998 / Accepted: 23 September 1998     

A major determinant quantitative-trait locus responsible for atopic dermatitis-like skin lesions in NC/Nga mice is located on Chromosome 9

NC/Nga (NC) is a newly discovered model mouse for human atopic dermatitis, NC mice showing specific symptoms such as dermatitis and overproduction of IgE. To detect the loci responsible for the onset of dermatitis in the mice, backcross (N2) progeny between (NCxMSM/MS)F1 and NC were generated, where MSM/MS is an inbred strain from Japanese wild mice, Mus musculus molossinus. Linkage disequilibrium between dermatitis and various chromosome-specific microsatellite markers was then examined in the N2 segregants with severe dermatitis. The analysis revealed that the locus of the major determinant (designated here as derm1) was tightly linked to D9Mit163, D9Mit72, D9Mit143, D9Mit103, D9Mit207, and D9Mit209, because these markers showed the highest and most significant chi2 values. Since no recombination was observed among the markers in our linkage map, a radiation hybrid (RH) panel was applied to locate the derm1 locus more precisely. The markers were separated on the RH map, and their order was D9Mit163-D9Mit72-D9Mit143-D9Mit103-D9Mit207-D9Mit209 from the centromere. Several functional candidate genes are located near the locus derm1. These candidates are Thy1, Cd3d, Cd3e, Cd3g, Il10ra, 1118, and Csk, all of which could be involved in allergic responses through effects on T-cell function. Of these candidates, Csk is the strongest for NC dermatitis, since its map position was most tightly linked to the derm1 locus.     

A locus for eosinophilia in the MES rat is on Chromosome 19

Matsumoto Eosinophilia Shinshu (MES) is a rat strain that spontaneously develops eosinophilia and eosinophil-related inflammatory lesions in many organs. We performed chromosomal mapping of the gene for eosinophilia by breeding backcross progeny. The onset of eosinophilia appeared to be delayed in the progeny compared with that in MES, with the prevalence of eosinophilia in the backcross progeny at 12 weeks of age being 22.5%. Genetic linkage analysis with marker loci indicated the major locus for eosinophilia was located at the end of the q arm region of Chromosome 19 (between D19Rat8 and telomere). The locus was denoted eosinophilia 1 (eos1). These data will form the basis for identification of the eos1 gene using a reverse genetic approach, which will hopefully lead to elucidation of the mechanisms involved in eosinophilia and eosinophilopoiesis.     

Genetic mapping of the lurcher locus on mouse chromosome 6 using an intersubspecific backcross.

The lurcher (Lc) mutant mouse strain exhibits postnatal degeneration of cerebellar Purkinje cells. We have typed progeny from an intersubspecific, phenotypic backcross at seven loci to develop a genetic linkage map which spans approximately 35 cM surrounding and including the Lc locus on mouse chromosome 6. [(Mus musculus castaneus x B6CBA-Aw-J/A-Lc)F1 x B6CBA-Aw-J/A]N2 progeny were scored visually for the lurcher phenotype and molecularly, through restriction fragment length polymorphism analysis, for six cloned markers. Two candidate genes, Npy and Pcp-1, which map to mouse chromosome 6 and which are expressed in the cerebellum, are demonstrated to be distinct from Lc. Three genes are shown to be closely linked to the Lc locus, and the map order cen-Cpa-Npy-Cbl-1-Lc-Igk, Fabpl-Pcp-1 is determined. The molecular genetic linkage map presented here represents progress toward isolating a clone of the Lc gene.     

Localization of the mouse kidney disease (kd) gene to a YAC/BAC contig on Chromosome 10

Mice that are homozygous for the kidney disease (kd) gene on Chromosome (Chr) 10 spontaneously develop a progressive and fatal interstitial nephritis. The disease phenotype is similar to that of the human disease, juvenile nephronophthisis. Using a backcross and intercross breeding strategy and analysis of over 900 resultant progeny, this genetic locus has now been mapped to a minimal co-segregating region of approximately two megabases between D10Mit 193 and D10Mit 38. The location assigned to kd by this study is over 3 cM from the current Mouse Genome Database location. The entire interval has been cloned in yeast artificial chromosome (YAC) and bacterial artificial chromosome (BAC) clones. Recombinant analysis has permitted assignment of 13 Mit microsatellite markers to positions near or within the region. Two new markers have been identified by using single-strand conformation polymorphism (SSCP) analysis of sequenced BAC ends. Several BAC end sequences align with human BAC clones from Chr 6q21 that contain NR2E1, Snx3, and Ros1. Three murine genes, CD24a, fyn, and ColX reported to map in or near the kd region as defined by this study have been evaluated. Though not definitely excluded, they appear to be unlikely candidates. Received: 23 July 1999 / Accepted 23 June 2000