Supp. Figure S1: Prx1-Cre is expressed in mesenchymal tissues. Prx1-Cre animals were
crossed to animals carrying the Rosa26-LSL-LacZ allele. Embryonic tissues were stained
with X-Gal to assess -galactosidase activity then sectioned and counterstained with
Nuclear Fast Red. Blue cells, indicating LacZ expression were observed in all mesenchymal
tissues tested and were not found in the same tissue dissected from animals that carried
the Rosa26-LSL-LacZ allele but did not carry the Prx1-Cre transgene.
Supp. Figure S2: Rb is deleted in the bone upon Prx1-Cre expression. Sections of
neonatal humerii were stained with an antibody against pRB. Staining was observed in
bone cells from Rbc/c animals that did not carry the Prx1-Cre transgene (arrowheads), but
not in bone cells from Rbc/c;Prx1-Cre animals (arrows). 3 embryos/genotype were
analyzed.
Supp. Figure S3: Mineralization and bone collar formation are normal in DKO
animals. Sections from non-decalcified e18.5 humerii were stained with Alizarin Red to
assess mineralization of the growth plate. Staining was equivalent in all genotypes. 3
embryos/genotype were analyzed.
Supp. Figure S4: Enchondromas are not proliferative. Growth plates were stained for
BrdU incorporation. There are no positive cells in either the control or DKO growth plates
(3 animals examined/genotype). Bar = 200µm
Supp. Figure S5: Growth Plate Abnormalities and Enchondroma Formation in 4-week
and 8-week-old DKO mice. Sections from 4wk old and 8wk old humerii were stained with
1
H&E (A and D, respectively). Growth plate abnormalities and the presence of
enchondromas was observed in the 8 week old DKOs but not control animals (three
animals/genotype/timepoint). Boxes represent regions magnified in lower panel. (B and
E) Growth plates were stained for BrdU incorporation (arrowheads indicate areas with
BrdU-positive cells), (C and F) collagen X expression (arrows indicate collagen X staining in
enchondromas). Bar = 200µm.
Supp. Figure S6: TKO growth plates appear similar to DKO growth plates at 4 and 8
weeks of age. Sections from 4wk old and 8wk old TKO humerii were stained with H&E (A
and D, respectively showed growth plate abnormalities (three
animals/genotype/timepoint). Boxes represent regions magnified in lower panel. (B and
E) Growth plates were stained for BrdU incorporation (arrowheads indicate areas with
BrdU positive cells), (C and F) collagen X expression. TKO-a: Rbc/c;p107-/-;E2f3a-/-;Prx1-Cre.
TKO-b: Rbc/c;p107-/-;E2f3b-/-;Prx1-Cre. Bar = 200µm.
2