Fig. 1. Bmp7 is expressed in developing lacrimal gland. All preparations are stained with X-gal. (A,C,G,H) The dermis overlying the developing lacrimal gland has been removed. (D,E,I,K,L-M) Paraffin wax-embedded sections counterstained with nuclear Fast Red. (A) E13.0, Bmp7^lacZ/+ mouse. The region of mesenchyme through which the lacrimal gland will grow does not stain for Bmp7^lacZ expression (broken yellow lines). (B) Section through eye region of E13.5 Bmp7^lacZ/+ embryo showing Bmp7-positive presumptive eyelid mesenchyme (asterisks) and periorbital mesenchyme (arrow). The section plane shown does not correspond to the Bmp7^lacZ-negative region in A. (C) Whole-mount Bmp7^lacZ/+, P6 5.0-lacZ embryo at E14.5 showing epithelial bud extending into Bmp7^lacZ-positive mesenchyme (arrows). (D) Section through E14.5 Bmp7^lacZ/+ lacrimal gland showing lacrimal bud (lb) and mass of mesenchymal cells (mes). The epithelium of the lacrimal bud is negative for Bmp7^lacZ expression; the mesenchyme is positive (blue X-gal staining). (E) As in D, but at higher magnification to show X-gal-negative epithelium (ep) and positive mesenchyme (mes). (F) The eye region of E15.5 Bmp7^lacZ/+ embryo showing lacrimal bud (lb) extending into Bmp7^lacZ-expressing mesenchyme (arrows). (G) As in C but at E15.5. (H) Whole-mount Bmp7^lacZ/+ embryo at E17.0 when secondary branching is apparent. The highest levels of lacZ expression are observed in the condensing mesenchyme surrounding the tips of the epithelial buds (red arrows) and the lacrimal duct (ld). (I) Section through E17.5 Bmp7^lacZ/+ lacrimal gland showing Bmp7^lacZ expression throughout mesenchyme (surrounded by broken line) in some cells of the ductal (ld) and bud epithelium (ep) and in mesenchyme adjacent to epithelial bud tips (arrowheads). (J) Dissected whole-mount preparation of E17.5 Bmp7^lacZ lacrimal gland showing general low level Bmp7^lacZ expression in mesenchyme and higher levels adjacent to epithelial bud tips. (K) Higher magnification of the lacrimal duct shown in I to indicate Bmp7^lacZ-expressing epithelial and mesenchymal cells. (L) Higher magnification of extended epithelial region in Bmp7^lacZ lacrimal gland showing distribution of X-gal-positive cells. (M) Section through terminal Bmp7^lacZ/+ epithelial bud showing X-gal-positive condensing mesenchyme (arrowheads). (N) Whole-mount Bmp7^lacZ/+ lacrimal gland at E18.5. (O) E18.5 P6 5.0-lacZ lacrimal gland to show contrasting pattern of epithelial expression.