| First Author | Sweet HO | Year | 1991 |
| Journal | Mouse Genome | Volume | 89 |
| Pages | 574-5 | Mgi Jnum | J:14314 |
| Mgi Id | MGI:62485 | Citation | Sweet HO, et al. (1991) Juvenile depilation (jd): a new hair loss mutation in the mouse. Mouse Genome 89:574-5 |
| abstractText | Full text of Mouse Genome contribution: Juvenile depilation (jd): a new hair loss mutation in the mouse. Hope O. Sweet, Roderick T. Bronson, Muriel T. Davisson; The Jackson Laboratory, Bar Harbor, ME 04609 USA. Introduction We describe a new autosomal recessive mutation that causes dorsal hair loss in weaning age homozygotes and a rough unkempt looking coat in adult homozygotes. The jd mutation has been mapped to mouse Chromosome 13 near muted. Materials and Methods The jd mutation arose in The Jackson Laboratory's Animal Resources C3H/HeJ colony in 1984. Genetic mapping crosses are described in the Results. To define the hair defect samples of hair from 3-4 jd/jd and +/jd littermate controls of both sexes at 26-28 days and 6 months of age were collected on sticky tape, placed on glass slides, and examined for hair type. To look for pathologic lesions in the skin hematoxylin and eosin stained paraffin sections of skin from two jd/jd and two jd/+ 21 day old mice and from two jd/jd and two jd/+ 26 day old mice were prepared. Results Phenotype: Some homozygotes (jd/jd) can be identified at 11 days of age when hair starts to thin around the eyes, top of head, and nape of neck. Vibrissae are normal. Weaning age (21-25 days) jd/jd mice are easier to identify. The dorsum changes from skin with sparse hair to skin devoid of hair. A very fine stubble of hair with an occasional longer bristle can be seen with the aid of a dissecting scope. Hair remains on the snout, around the legs and tail and on the belly. Hair on the dorsum begins to regrow at 28 days, concurrent with the second normal hair growth cycle. Thereafter, the dorsum is never devoid of hair during successive hair cycles, although the adult coat appears unkempt and becomes thinner with age. Hair loss is more noticeable among aging jd/jd females than males. Hairtypes: Four types of hair are present in the normal mouse coat; guard hairs, awls, auchenes and zigzags. Guard hairs, awls and auchenes comprise the over hairs, zigzag hairs comprise the undercoat. The majority of hair types observed in the coat of both juvenile and adult jd/jd homozygotes were awls and auchenes. Guard hairs were thin and few in number. Very few zigzag hairs were found, and those observed had no medulla. Numerous short broken pieces of fine septate hair observed in dorsal hair samples from 26-28 day old homozygous jd/jd mice could not be classified. These short segments of hair were not found in dorsal hair samples from adult homozygotes. Histology: Longitudinal and cross sections of skin from 21 and 26 day old jd/jd and +/jd mutant and control mice were similar. At 21 days, the hair follicles were in the atrophic catagenic stage in both. At 26 days of age, both had numerous follicles in the hyperplastic stage of development. Genetics: Linkage was found between jd and pearl (pe) on Chr 13. Crosses and results are listed below. The estimates of recombination values were calculated using Finney's(1) tables. The combined RE from crosses 1-4 for jd - pe is 16.55 +/- 1.84. Mating: 1. jd+/+pe x jd +/+ pe; Phenotype of Progeny: ++: 164; jd+: 70; +pe: 60; jd pe: 1; Total: 295; RE+/-SE: 16.31 +/- 5.54. Mating: 2. jd +/+ pe x jd pe/jd pe; Phenotype of Progeny: ++: 9; jd+: 56; +pe: 33; jd pe: 12; Total: 110; RE+/-SE: 19.09 +/- 3.75. Mating: 3. jd pe/+ + x jd pe/+ +; Phenotype of Progeny: ++: 180; jd+: 12; +pe: 25; jd pe: 28; Total: 245; RE+/-SE: 18.75 +/- 2.89. Mating: 4. jd pe/+ + x jd pe/jd pe; Phenotype of Progeny: ++: 26; jd+: 4; +pe: 3; jd pe: 34; Total: 67; RE+/-SE: 10.45 +/- 3.74. Cross 3 was a three point intercross with muted (mu) in repulsion to jd and pe. No recombinants between mu and jd were detected in 245 F2 progeny, giving a maximum estimated recombination frequency (95% upper confidence level) between mu and jd of 22% and suggesting jd was close to mu and proximal to pe. (We have omitted mu from the table to simplify presentation of the jd - pe data.) To confirm the position of jd a three point cross using a Robertsonian chromosome Rb(11.13)4Bnr was made: Rb + +/+ jd pe x + jd pe/+ jd pe. The data from this cross (shown below) gives the recombination percentages shown and the order cen - jd - pe. Phenotype of Progeny Rb+ +: 37; + jd pe: 47; Rb jd pe: 10; + + +: 19; Rb + pe: 17; +jd+: 17; Rb jd +: 1; + + pe: 1; Total: 149. Rb - jd: 31/149 = 20.81 +/- 3.33 jd - pe: 36/149 = 24.16 +/- 3.51 Rb - pe: 63/149 = 42.28 +/- 4.05 Because jd maps near the hair loss mutation furless (fs)(2), we tested jd for allelism with fs. Eight normal progeny were obtained from a mating between a homozygous jd/jd female and a homozygous fs/fs male, proving that jd is not a remutation to furless. Discussion: We describe a new hair loss mutation in the mouse that affects the first hair growth cycle and causes permanent failure of zigzag hair growth. We hypothesize the locus causes a defect in hair follicle development. Guard hairs are produced from follicles initiated in the 14-17 day embryo, awls and auchenes are produced by follicles initiated at 17-19 days, and zigzags are produced from hair follicles initiated after birth(3). Despite the striking loss of hair beginning at 21 days of age in jd/jd mice, there were no differences histologically between mutants and controls at that time or later after hair regrowth had begun. We hypothesize that the mutation affects the intrafollicular environment such that the first growth of hairs of all 4 types is brittle resulting in their loss during the first catagenic stage. Thereafter the mutant hair coat recovers with the exception of the zigzag hairs. Developmental studies to test this hypothesis would require a closely linked marker detectable before birth to differentiate mutants from controls when hair follicles are developing. We plan to store the mutation as frozen embryos only. References 1. Finney, D.J. 1949. The estimation of the frequency of recombination. J. Genet. 49:159-176. 2. Green, E.L. 1954. The genetics of a new hair deficiency, furless, in the house mouse. J. Hered. 45:115-118. 3. Slee, J. 1962. Developmental morphology of the skin and hair follicles in normal and "ragged" mice. J. Embryol. Exp. Morphol. 10:507-529. Acknowledgements We thank Melanie Amicone for discovering jd and Belinda Harris for chromosome preparations. This work was supported by NSF grant BSR84-18828, NCI Cancer Core Grant CA34196, and a gift from the E.N. Dana Charitable Trust. The National Institutes of Health is not responsible for the contents of this publication nor do they necessarily represent the official views of that agency. The Jackson Laboratory is fully accredited by the American Association for Accreditation of Laboratory Animal Care. |
