Antibody:	anti-Nrg1a (Ab-3)
Detection system:	Biotinylated secondary antibody/[Strept]avidin coupled to horseradish peroxidase
Assay notes:	Fixative was either: 4% paraformaldehyde, formalin, or Carnoy's fixative.

Structure	Level	Pattern	Image	Note
TS19: mammary placode	Weak		6e
TS19: surface ectoderm	Weak	Regionally restricted	6e	Expression is in the epithelium adjacent to the placode.
TS19: trunk mesenchyme	Weak	Regionally restricted	6e	Expression is in the mesenchyme flanking the placode.

Structure	Level	Pattern	Image	Note
TS20: mammary bud	Present		6g
TS20: epidermis	Present	Regionally restricted	6g	Expression is in the epithelium adjacent to the mammary bud.
TS20: trunk mesenchyme	Present	Regionally restricted	6g	Expression is in the mesenchyme flanking the mammary bud.

Structure	Level	Pattern	Image	Note
TS21: mammary gland primordium epithelium	Weak		6i
TS21: epidermis	Weak	Regionally restricted	6i	Expression is in the epithelium adjacent to the mammary bud.
TS21: dermis	Weak	Regionally restricted	6i	Expression is in the dermal mesenchyme.

Structure	Level	Pattern	Image	Note
TS22: trunk mesenchyme	Weak	Regionally restricted	6k	Expression is throughout most of the mesenchyme with the exception of the mammary mesenchyme surrounding the mammary bud
TS22: mammary gland primordium epithelium	Weak		6k
TS22: epidermis	Weak	Regionally restricted	6k	Expression is in the epithelium adjacent to the mammary bud.

Structure	Level	Pattern	Image	Note
TS20: mammary bud	Present		S2_Nrg1