Antibody:	Nrg4 (L-16) antibody
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: trunk mesenchyme	Present	Regionally restricted	9g	Expression is in the mesenchyme adjacent to the mammary placode and diffusely throughout the dermal mesenchyme.
TS19: mammary placode	Weak	Regionally restricted	9g
TS19: surface ectoderm	Weak	Regionally restricted	9g

Structure	Level	Pattern	Image	Note
TS20: trunk mesenchyme	Present	Regionally restricted	9h	Expression is in the mesenchyme surrounding the mammary bud.
TS20: epidermis	Weak	Regionally restricted	9h
TS20: mammary placode	Absent		9h

Structure	Level	Pattern	Image	Note
TS21: mammary mesenchyme	Present		9i
TS21: connective tissue	Present	Regionally restricted	9i	Expression is at the site of the future fat pads.
TS21: epidermis	Weak	Regionally restricted	9i	Expression is in the surface epithelium adjacent to the mammary bud.
TS21: mammary gland primordium epithelium	Absent		9i

Structure	Level	Pattern	Image	Note
TS22: mammary mesenchyme	Moderate		9j
TS22: connective tissue	Present	Regionally restricted	9j	Expression is at the site of the future fat pads.
TS22: epidermis	Moderate	Regionally restricted	9j
TS22: mammary gland primordium epithelium	Absent		9j

Structure	Level	Pattern	Image	Note
TS20: mammary bud	Present		S2_Nrg4