mes Mice, that have a mutation in the C-terminus of Patched-1, have a block to mammary morphogenesis at puberty.

Expression of a conditional allele of ER伪 overcomes this defect.

Stimulation of primary mammary epithelial cells with Shh activates Erk1/2 but not Ptch1 expression.

Shh-dependent activation of Erk1/2 can be blocked by inhibition of c-src or ER伪.

These data have defined a novel Hh-signalling cascade involved in pubescent mammary gland morphogenesis.