These mice carry the spontaneous mutation patchwork (pwk) characterized by hairs that are either totally white or totally pigmented due to the presence of or absence of melanotyes in the hair follicles.Read More +
Homozygous patchwork mice have hairs that are either totally white or totally pigmented, but no diluted coloration of the hair. On a nonagouti background this produces a salt-and-pepper appearance from white hairs juxtaposed with black hairs. This occurs throughout the coat and does not vary by anatomic region. The absence of pigment in the white hairs is due to an absence of melanocytes in the hair follicles of the white hairs; functioning melanocytes are present in the hair follicles of the black hairs. The absence of melanotyes in the follicles of the white hairs results from premature death of melanoblasts during development. TUNEL staining indicates that this melanoblast death is apoptotic and begins around embryonic day 18.5. This suggests that patchwork melanoblasts can survive and function if enough survive, but fail to survive when adequately reduced in number. Analysis of aggregation chimeras between patchwork and albino donors revealed gray hairs at the boundaries between the white and black hairs indicating that the albino melanoblasts could enhance the survival of patchwork melanoblasts. Thus, the patchwork defect is not strictly melanoblast autonomous. (Aubin-Houzelstein et al., 1998.)
pwk is a spontaneous mutation that was identified in an outbred stock referred to as Pm stock. Pm stock was homozygous for at and segregating for Tyrp1b, Tyrc, Ednrbs, Foxq1sa, p, Myo5ad, and Fgf5go. pwk was backcrossed 4 times via backcross-intercross from this Pm stock onto C57BL/6. Then, in 1993 Dr. Karen Moore sent N4F1 males homozygous for pwk to Dr. Eva Eicher at The Jackson Laboratory. pwk was then backcrossed onto the C57BL/6JEi background, and in 1996 C57BL/6J females were bred with N9F2 B6Ei.Cg-pwk homozygotes to generate embryos for cryopreservation.