The Waved-1 (wa1) Mutation, Chromosome 6
JAX® NOTES Issue 459, Fall 1994
John P. Sundberg, D.V.M., Ph.D.1, Richard S. Smith, M.D.1, and Margaret E. Hogan, Ph.D.2
1The Jackson Laboratory Pathology Program and 2Electron Microscopy Laboratory
History
The waved-1 (wa1) mouse mutation was discovered in a mixed mouse colony in 1930 by Evlyn Bondat the Institute of Animal Genetics in Edinburgh, Scotland (Crew, 1933). A single male with curled pelage hairs was identified in a litter of 6. A normal brother and sister from this litter were interbred,yielding five litters; 20 offspring were normal and 5 had curly hair. A number of remutations have subsequently been identified (Taylor and Ivey, 1987).
The waved-1 mouse mutation is recessive and has been mapped to mouse Chromosome 6 (Fig. 1; Green,1989; Maltais, et al., 1993). It is currently maintainedon the ABP/Le inbred strain.
Gross Lesions
Affected pups can be identified at birth or shortly thereafter by the presence of short "hooked"or "corkscrew" shaped vibrissae. Littermate controls have long, straight vibrissae. Mutants (wa1/wa1) are usually smaller and weaker than littermate control (wa1/+, +/+) mice. The curly hair is progressively more evident until 7-8 weeks of age, when the waved vibrissae and pelage hairs have been replaced by more normal appearing hair. Adults can still be identified since dorsal pelage hairs incline toward the midline rather than caudally, as in controls (Crew, 1933). Most adult wa1/wa1 mice can be identified by having a short coat, curved guard hairs, and irregular hair direction affecting the back, shoulder, and thigh areas (Fig. 2; Keeler, 1935). Corneal opacity was observed in some homozygotes of wa1 (Fig. 3) and all homozygotes of wa1, another mutant allele at wa1 (Taylor and Ivey, 1987). The gene has no adverse effect on viability (Gruneberg, 1952).
Microscopic Lesions
All hair types are affected and develop a variety of curves along the length ofthe hair shaft (David, 1937; T rigg, 1972) Fig. 4, 5). By light microscopy the midshaft region of zigzag hairs become locally septulate (Trigg, 1972; Luetteke et al. 1993). Scanning electron microscopic studies of adult wa1/wa1 hairs revealed that the shafts emerge from the skin with a round profile and normal cuticular pattern (Fig. 6). The midshaft develops a deep longitudinal groove, which is normal, however, the walls of the groove are asymmetrical, which may cause the abnormal curvature (Fig. 7). The hair follicles in wa1/wa1 neonatal mouse skin are curved abnormally compared to controls (David, 1937; Trigg, 1972) which is due to an abnormality of the inner root sheath (Trigg, 1972). In the TGF knockout model (allele of wa1) TGF expression was restricted lengthwise in the follicle into zones of differentiation and keratinization above the hair bulb (Luetteke et al. 1993) which may correspond negatively tothe regions where the hair develops abnormally. The epidermis in these mice, both spontaneous and induced mutations, appears to be normal (Mann, et al. 1993).
Corneal opacity may be evident in wa1/wa1 mice and knockout mutations at this locus (Tgfa). The ocular lesions may be the end result of corneal ulcer formation with subsequent perforation with associated shrinkage of the globe. Histologically there is corneal edema, neovascularization, infiltration of the substantiapropria with neutrophils and hyperplasia of the external epithelium (Bennett and Gresham, 1956; Mann, et al., 1993; Luetteke et al., 1993). In one of the knockout mutations other ocular lesions included hypoplasia ofthe orbicularis muscle and Meibomian glands, micropthalmia, anterior segment dysgenesis,absence of the lens, and retinal dysplasia (Luetteke et al. 1993). The ocular lesions varied in severity and numbers of animals affected in all of these studies. The pathogenesis of the corneal lesions has been attributed to failure of prenatal fusion of the eyelids in wa1/wa1 mice (Bennett and Gresham, 1956). More detailed studies are in progress to determine the pathogenesis of ocular lesions in this mutation.
Immunological and Biochemical Abnormalities
Guard hairs from wa1/wa1 mice have been described as "frizzled" (Keeler, 1935). The cause of the abnormal shape of these hairs has been ascribed to the fact that most hairfollicles are curved (David, 1937). The torsion was attributed to either unequal cell division during hair development or abnormal keratinization of hairs resulting in the hairs having difficulty piercing the epidermis (David, 1937).
The transforming growth factor alpha (Tgfa) gene was recently mapped near the wa1 gene on mouse Chromosome 6 (Fowler, et al. 1993; Green, 1989). Two independent groups created null mutations of the Tgfa gene which were phenotypically indistinguishable from wa1/wa1 mice. Both groups crossed their null mutations with wa1/wa1 mice and obtained affected offspring, indicating that the null mutants and wa1 were allelic. Furthermore, TGF levels were reduced in wa1/wa1 mice, similar to the null mutations, indicating that this is the biochemical defect in the wa1 mutation (Mann et al., 1993; Luetteke et al., 1993).
Analogous Human Disease
In the original description of the waved-1 mouse mutation, Crew described that the hair in these mice "...looked exactly as though the animals had been to the hairdresser and had had a permanent wave treatment" (Crew, 1933). No analogous human disease has been compared to the waved-1 mouse mutation.
Analogous Animal Disease
A rat mutation known as curly coat is dominant and has a wavy hair coat, similar to waved-1, that becomes progressively worse with age (Crew, 1933). Two or more rex mutations in rats also have wavy hair coats (Keeler, 1935).
Domestic rabbits are known to have at least three genetically distinct, phenotypically indistinguishable mutations known as rex that have waved hair (Keeler, 1935).
Several mouse mutations have curly pelage hairs and/or vibrissae. These include curly whiskers (cw, Chr 9), frizzy (fr, Chr 7), fuzzy (fz, Chr 1), 3 alleles at the rex gene (Re; opossum, Re
Two null mutations of the Tgfa gene were created independently. Both are virtually identical to waved-1 and have been shown to be alleles in breeding studies (Mann et al.,1993; Luetteke et al., 1993).
Premature opening of eyelids in newborn mice is a feature of some alleles of waved-1 and the recessive mouse mutation called eyelids open at birth (eo). These two genes may be linked or this feature may be a pleotrophic effect of wa1 (Bennett and Gresham, 1956).
Common Uses of the Waved 1 Mutation
The ABP/Le inbred strain, which carries wa1, has been used for linkage testing because it carries multiple visible genetic markers including wa1 (Carter, 1951; Staats, 1985).
This mutation is currently being used to investigate the functions of TGF now that the molecular defect has been identified (Mann et al., 1993; Luetteke et al., 1993). The biological roles of TGF and related growth factors such as epidermal growth factor (EGF) and their common receptor, epidermal growth factor receptor (EGFR), can now be investigated when panels of mouse mutations with known or presumed abnormalities are used. Other mutations with abnormalities of EGF and/or EGFR include waved-2 (wa2), crinkled (cr), downless (dl), sleek (Dl
Availability
The waved-1 mutation is maintained by The Jackson Laboratory Genetic Resource as ABP/Le a/a b/b bt/bt p/p se/se wa1/wa1. This strain is preserved in The Jackson Laboratory Frozen Embryo Repository and DNA extracts are available from the Mouse DNA Resource at The Jackson Laboratory (Lane et al., 1992).
Figure 1. Partial map of mouse Chromosome 6 shows the location ofthe waved-1 locus (*wa1). Columns from left to right are the homologous regions from the human chromosome map, distance from the centromere incentimorgans, and mouse gene symbol or microsatelite probe locations (Maltais et al., 1994).
Figure 2. Three month old wa1/wa1 male mouse demonstrating wavy pelage hairs.
Figure 3. Corneal opacity (arrow) is evident in the mouse illustrated in figure 1.
Figure 4. Slight waviness of plucked hairs is evident by light microscopy (50 X).
Figure 5. Waviness is evident in all hair types by scanning electron microscopy (30 X).
Figure 6. The cuticle of a guard hair is normal near the bulb region of the shaft (SEM, 300 X).
Figure 7. Asymmetry of the sides of the groove in the midshaft of a guard hair may be the cause of waving in wa1/wa1 hair (SEM, 300 X).
References
Bennett JH, Gresham GA. A gene for eyelids open at birth in the house mouse. Nature 178:272-273, 1956.
Carter TC. Wavy-coated mice: phenotypic interactions and linkage tests between Rex and (a) waved-1, (b) waved-2. J Genet 50:268-276, 1951.
Crew F AE. Waved: an autosomal recessive coat form character in the mouse. J Genet 27:95-96, 1933.
David L T. Die gegenseitige Beeinflussung der Erbfactoren fur Haarlosigkeit und W elligkeit bei der Hausmaus (Mus musculus). Rev Suisse de Zoologie 44:397-400, 1937.
Fowler KJ, Mann GB, Dunn AR. Linkage of the murine transforming growth factor gene with lgk, Ly-2, and Fabp1 on Chromosome 6. Genomics 16:782-784, 1993.
Green MC. Catalog of mutant genes and polymorphic loci. In: Genetic Variants and Strains of the Laboratory Mouse. 2nd ed. Lyon MF, Searle AG, ed., Oxford Univ. Press, Oxford, pp. 12-403, 1989.
Gruneberg H. The Genetics of the Mouse. Martinus Nijhoff, The Hague, pp. 87-89, 1952.
Keeler CE. A second rexoid coat character in the house mouse. J Hered 26:189-191, 1935.
Lane PW, Mobraaten, LE, Neleski LA. Lists of mutations and mutant stocks of the mouse maintained at The Jackson Laboratory. The Jackson Laboratory, 1992.
Luetteke NC, Qiu TH, Peiffer RL, Oliver P, Smithies O, Lee DC. TGF deficiency results in hair follicle and eye abnormalities in targeted and waved-1 mice. Cell 73:263-278, 1993.
Maltais LJ, Hillyard AL, Doolittle DP, Davisson MT, Guidi JN, Roderick TH. GBASE, the genomic database of the mouse. Maintained at The Jackson Laboratory, 1994.
Mann GB, Fowler KJ, Gabriel A, Nice EC, W illiams RL, Dunn AR. Mice with a null mutation of the TGF gene have abnormal skin architecture, wavy hair, and curly whiskers and often develop corneal inflammation. Cell 73:249-261, 1993.
Staats J. Standardized nomenclature for inbred strains of mice: eighth listing. Cancer Res45:945-977, 1985.
Sundberg JP. Mouse Mutations with Skin and Hair Abnormalities: Animal Models and Biomedical Tools. CRC Press, Boca Raton, 1994.
Sundberg JP, Hogan ME. The waved-2 (wa2) mutation, Chromosome 11. Jax Notes in press, 1994.
Taylor BA, Ivey JM. New allele of waved-1 with open eyes at birth. Mouse News Lett. 77:129, 1987.
Trigg MJ. Hair growth in mouse mutants affecting coat texture. J Zool Lond 168:165-198, 1972.
