Fig. 8. Development of follicular cysts and matricomas, mesenchymal BMP signaling, and paw phenotype in 5-month-old K14-Cre-ER^T2; Bmpr1a^cl/cl Bmpr1a mutant mice. (A-F) Histology of dorsal skin from uninduced (A,B,D-F) and tamoxifen-treated (C) mutants. Abnormal hair follicles are shown in A,D; follicular cysts in B,C; and proliferations of undifferentiated matrix-like cells, histologically similar to human matricomas, in E,F. (G-I) Anti-BrdU immunofluorescence of dorsal skin from uninduced mutants. (J-U) Immunofluorescence of dorsal skin from uninduced mutants with antibodies to the proteins indicated (red). (V) Anti-phospho-SMAD immunofluorescence of abnormal hair follicles showing nuclear phospho-SMAD in dermal cells (arrow). A dashed white line indicates the dermal-epithelial boundary. (W,X) Sagittal sections of the nail region from uninduced control K14-Cre-ER^T2; Bmpr1a^cl/+ mouse (W) and uninduced K14-Cre-ER^T2; Bmpr1a^cl/cl mutant (X), showing expanded mesenchyme in the mutant. Arrow indicates a calcifying osteoid.