| First Author | Lane PW | Year | 1995 |
| Journal | Mouse Genome | Volume | 93 |
| Issue | 1 | Pages | 158-160 |
| Mgi Jnum | J:24235 | Mgi Id | MGI:71984 |
| Citation | Lane PW, et al. (1995) Tippy (tip) a lethal mutation on Chromosome 9 in the mouse. Mouse Genome 93(1):158-160 |
| abstractText | Full text of Mouse Genome contribution: TIPPY (tip) A LETHAL MUTATION ON CHROMOSOME 9 IN THE MOUSE Priscilla W. Lane1 and Roderick T. Bronson2. 1 The Jackson Laboratory, 600 Main Street, Bar Harbor, Maine, 04609; 2 Tufts University School of Veterinary Medicine, Department of Pathology, 203 Harrison Avenue, Boston, Massachusetts, 02146. Introduction During the process of determining the order of loci on mouse Chromosome (Chr) 3 in 1977 (4), a new mutation arose in the osteopetrotic (op) and droopy-ear-H (deH) linkage cross. Because of the unusual behavior of this mutant it was called tippy with the symbol tip (3). In this report we show that tippy is located on Chr 9 between fur deficient (fd) and scant hair (sch) and very close to, but not allelic with, ducky (du). We also describe the effects of this lethal mutation. Materials And Methods The effects of the fully penetrant recessive mutations used in this study, short ear (se), scant hair (sch), dilute (d), fur deficient (fd) and ducky (du), are visible before weaning. For a description of each see Green (2). All mice were classified for these genes between 15 and 20 days of age. Each cross used to locate tip on Chr 9 is given a number and referred to by this number in the text and Tables. Information regarding the mating type is also given in the text or the Tables. All recombination estimates and the combined estimate were made using Finney's score's (1). Tissues for pathological study were prepared from 14 tip/tip mice and 12 littermate controls. All mice were perfused intracardially with Bouin's fixative. Spines, legs and heads with brain and spinal cord were demineralized in Bouin's solution and sliced with bone and nervous tissue in situ. Multiple histological sections of spine and legs were prepared from all mice and stained with luxol fast blue plus cresylecht violet (LFB-CV). Brains from two tip/tip mice were serially sectioned. Hind brains with inner ears from another two tippy mice were also serially sectioned. Alternate ribbons of serial sections were stained with H&E and LFB-CV. Whole inner ears were dissected from two affected and two control mice, cleared in alcohol and methyl salicylate and examined with a dissecting microscope. Histologic sections from somatic organs from two tippy mice were also prepared. Genetics The original parents of the first tippy mutant were the offspring of a op/+ female x a deH/deH male in the Mouse Mutant Resource of The Jackson Laboratory. This pair of Fl parents produced four litters, a total of 23 mice, of which five were affected and died prior to 20 days of age. Because of the early lethality of this mutant even on a heterogeneous background, it has been maintained by continuous backcrosses to the hybrid, C57BL/6J x C3HeBFeJLe-a/a Fl (hereafter referred to as B6C3Fe-a/a Fl) to provide vigorous breeding stock and improve survival time for the affected offspring. Linkage tests were made with various autosomal marker genes throughout the genome until a loose linkage was found with se. Data from all tests on Chr 9 are given in Tables I and II. The single factor segregations for se in cross 1 and for sch in cross 2 are normal but there is a significant deficiency of tip homozygotes in both cross 1 and cross 2 (X2 tip = 4.15 P < .02, 16.43 P < .01) and a significant deficiency of sch and tip homozygotes in cross 3 (X2 sch = 10.67 P < .01, X2 tip = 12.52 P < .01) in which the two mutations are in coupling phase. There is, as expected, an excess of d and fd homozygotes in cross 4 and a deficiency of tip/tip mice (X2 tip = 15.02 P < .01). With all three mutant genes in coupling phase in cross 5 there is a deficiency of d and fd and tip homozygotes (X2 d = 4.83 P < .02 X2 fd = 8.77 P < .01, X2 tip = 9.53 P < .01). These deficiencies are all probably due to the low viability of tippy homozygotes. The repulsion intercross se +/+ tip x se +/+ tip (Table I cross 1) shows a recombination estimate of 30.1 +/- 5.0% between se and tip. To determine a proximal or distal position for tip on Chr 9, crosses were first made with the distal marker gene, sch (Table I crosses 2 & 3). The repulsion and coupling crosses combined give a recombination estimate of 11.80 +/- 1.8% between sch and tip, thus placing tip distal to se. A three point cross (Table II cross 4) with the dilute fur deficient stock, in which d and fd were maintained in coupling phase was then made (d fd +/+ + tip x d fd +/+ + tip). No recombinants between d and tip or between fd and tip were recovered from cross 4 so 11 F2 d fd ?/d fd + mice were test mated to tip/+ mates to determine if any carried tip, indicating that a single crossover had occurred. One female was found of the genotype d fd tip/d fd +. This female was then mated to B6C3Fe-a/a F1 male to provide the three gene coupling chromosome. Six pairs of mice were carriers of all 3 genes and the data from this 3 point coupling cross (Table II cross 5) show the order and distance (cM) to be d - 8 - fd - 10 - tip. The recombination values in cross 5 for d - df are 8.3 +/- 1.6%, for fd - tip 10.4 +/- 1.8%, and for d - tip 17.9 +/- 2.5%. These data placed tippy very close to the neurological mutation ducky (du). Allele tests using heterozygous ducky (du/+) males mated to heterozygous tippy (tip/+) females produced 37 normal offspring and no abnormal offspring indicating that du and tip are not allelic. Table I. Results of linkage tests with se, sch, and tip. Cross: 1.; Matings: se +/+ tip x se +/+ tip; F2 Progeny: ++; # of Mice: 176; se +; # of Mice: 79; + tip; # of Mice: 58; se tip; # of Mice: 6. Total: 319. Recombination +/- SE: 30.1 +/- 5.0. Cross: 1.; Matings: se +/+ tip x se +/+ tip; F2 Progeny: ++; # of Mice: 176; se +; # of Mice: 79; + tip; # of Mice: 58; se tip; # of Mice: 6. Total: 319. Recombination +/- SE: 30.1 +/- 5.0. Cross: 2.; Matings: tip +/+ sch x tip +/+ sch; F2 Progeny: ++; # of Mice: 165; sch +; # of Mice: 88; + tip; # of Mice: 43; sch tip; # of Mice: 1. Total: 297. Recombination +/- SE: 13.3 +/- 5.7. Cross: 3.; Matings: tip sch/+ + x tip sch/+ +; F2 Progeny: ++; # of Mice: 227; sch +; # of Mice: 15; + tip; # of Mice: 13; sch tip; # of Mice: 33. Total: 288. Recombination +/- SE: 11.7 +/- 1.9. Crosses 2 + 3 combined: Recombination +/- SE: 11.8 +/- 1.8. *m = marker (se or sch) Table II. Three-point linkage cross data with tip, d and fd. Cross: 4: Matings: d fd +/+ + tip x d fd +/+ + tip; F2 Progeny: d fd +; # Cross 4: 54; # Cross 5: 12; + + tip; # Cross 4: 27; # Cross 5: 14; + fd +; # Cross 4: 15; # Cross 5: 3; d + tip; # Cross 4: 0; # Cross 5: 0. Cross: 5: Matings: d fd tip/+ + + x d fd tip/+ + +; F2 Progeny: d fd tip; # Cross 4: 0; # Cross 5: 38; + + +; # Cross 4: 95; # Cross 5: 241; d + +; # Cross 4: 13; # Cross 5: 15; + fd tip; # Cross 4: 0; # Cross 5: 6. Total: # Cross 4: 204; # Cross 5: 329. Cross 5 Recombination +/- SE: d Ð fd; 8.3 +/- 1.6; d Ð tip: 17.9 +/- 2.5; fd Ð tip: 10.4 +/-1.8 Description Homozygous tippy mice are distinguishable from their normal litter mates by 12-14 days of age by their small size and hyperactivity. Their gait is uncoordinated and they fall over frequently, both backwards and sideways. They show no tremor but they exhibit sudden bursts of activity by bouncing around the pen. They hear and may be supersensitive to sound for a sudden noise tends to stimulate the hyperactivity. The tip/tip mouse can stand up for only short periods and is constantly trying to stay upright. It stretches forward and backward and sometimes uses the side of the pen for support. Only one affected mouse has ever lived beyond weaning age (28 days). This one affected female survived in a pen alone with her mother until she was 14 months old. During this time powdered mouse food was regularly placed in the pen for her, but the mutant remained small and scrawny and never weighed over 5g. As she aged the behavior did not become noticeably more severe. In attempting to walk she would take a few wobbly steps then shrink back to a sitting position on her haunches with hind legs extended forward or fall over to one side. However, movement could also be fast and jumpy. The disorder never really progressed beyond the level it had reached at weaning age. Although the homozygous tippy mouse behaves in some ways like mutants with cerebellar or vestibular abnormalities, no lesions were observed in the cerebellum, nor vestibular nuclei, eighth cranial nerve or inner ears. Otoconia were present. Even though the effects of the mutation are very severe, resulting in death of the affected mouse we have not been able to find lesions in any tissue that would explain the neurological abnormality or death. Acknowledgement This work was supported by NSF Grant BIR8915728 and Cancer Core Grant CA34196. References 1. Finney D.J. J Genet 49:159-176 (1976). 2. Green M.C. Catalogue of mutant genes and polymorphic loci, pp. 12-403. In: Genetic Variants and Strains of the Laboratory Mouse, Lyon M.F. and Searle A.G. (eds.), 2nd Edition: New York: Oxford University Press (1989). 3. Lane P.W. Mouse News Lett 71:31 (1984). 4. Lane P.W. and Eicher E.M. J Hered 70:239-244 (1979). |
