These mice carry the spontaneous jb mutation and are characterized by juvenile hair loss. in which the hair follicle follows irregular pathways to the surface and mutants generally become dystrophic when about 23 days of age.Read More +
jb/jbfemales breed but tend to have small litters. Only some breeding jb/jbfemales develop overgrown incisors with a tendency to break, resulting in undernourishment and inability to nurse. An occasional jb/jbmouse of either sex will convulse upon handling. Genetic background impacts the expression of the jbmutation. jb "is expressed on strains C57BL/6J, ABP/Le, and MEV/1Ty and C.B-17-Prkdcscid/Prkdcscid, but seldom expressed on C3HeB/FeJ, A/J, and CAST/Ei, and only partially expressed on the C57BL/6J x C3HeB/FeJLe-a/a hybrid (Lane et al., 1998). This strain does NOT show the seizure phenotype seen in 001510.
jb/jbhomozygotes are identifiable by phenotype between 15 and 21 days of age preweaning hair loss. Heterozygotes are distinguishable from wild type littermates only by test crossing.
jb occurred spontaneously in 1984 in The Mouse Mutant Stock Center (MMSC) at The Jackson Laboratory in B6C3Fe-a/a-hyh, a stock then maintained by crossing to (C57BL/6J x C3FeLe.B6-a/a)F1 mice. The hyh mutation was being transferred from C57BL/10 onto the B6C3Fe a/a background. hyh arose spontaneously on the C57BL/10J background, was sibling mated by progeny tested heterozygote x heterozygote for 11 generations, and was then maintained by outcrossing to (C57BL/6J x C3FeLe.B6-a/a)F1 mice at every other generation (through outcross-intercross breeding). At N3 of this outcross the jb mutation arose. Microsatellite marker testing has shown that the jb mutation arose on the C3HeB/FeJLe-a/a derived DNA. jb was initially identified in a male that had loss of hair at an early age. This male was bred to a normal sibling and then four affected pairs of progeny were mated, and all of the offspring exhibited the hair loss phenotype. 001510, STOCK a/a jb, a homozygous inbred jb/jb strain was generated beginning with these four pairs (Lane et al. 1998). A backcross was done from the homozygous STOCK a/a jb colony, 001510, at F15 onto C57BL/6J resulting in 001959, B6.Cg-jb. (The nclf mutation was discovered in 1991 in STOCK a/a jb from which the present 002648, STOCK a/a +jb/+ nclf/nclf , was bred. The F8 frozen stock of 001510 have the nclf mutation, but this mutation has been bred out of the 001510 that remains on the shelf)
When maintaining a live colony, homozygous mice may be bred together.
When using the juvenile bare mouse strain in a publication, please cite the originating article(s) and include JAX stock #001959 in your Materials and Methods section.