Fig. 2. In situ hybridization analyses comparing the expression of the human BRCA2 transgene and endogenous mouse Brca2. (A-D) Sagittal sections of a E9.5 transgenic embryo. (E-H) Sections of the testis of a 3-week-old transgenic male. (I-L) Sections of the ovary of 3-week-old transgenic female. (M-P) Sections of the ovary of a 10-week-old transgenic female. (A,E,I M) Bright-field pictures of Hematoxylin and Eosin stained sections adjacent to those used in the in situ hybridization studies; (D,H,L,P) respective sections hybridized with human BRCA2 sense probe as negative control. (B) Mouse Brca2 expression is detected in the E9.5 embryo in the brain in the neuroepithelium of the ventricular region and the neural tube (first branchial arches). (C) The BRCA2 transgene is expressed at reduced levels compared with the endogenous gene but the spatial expression pattern is identical to that of the endogenous gene. (F) Brca2 expression is detected using antisense probe in the spermatocytes present in the seminiferous tubules. (G) The human BRCA2 transgene expression is found at a level just above background. (J) In the ovary of a 3-week-old female, the mouse Brca2 gene is found to be highly expressed in follicles at various stages of maturation. (K) No specific signal is observed in the follicles by human BRCA2 antisense probe. (N) Brca2 expression is detected in the follicles in granulosa cells and oocytes (arrow) of 10-week-old ovary. (O) Expression of the human transgene is not detected in the ovary. A, antral follicle; ba, branchial arch; CL, corpus lutea, GC, granulosa cells; ne, neuralepithelium; nt, neural tube; O, oocyte; Pa, preantral follicle; Pr, primary follicle; Sp, spermatocytes; vl, ventricular layer. Scale bars: 100 µm.