Time-line of normal cloacal partitioning in the mouse (A), and arrest in cloacal septation in <i>Bmp7</i> null embryo (C compare to B).

Abstract

<p>(A) Domains of <i>Bmp7</i> expression in the urorectal mesenchyme (URM), urethral plate (up), and genital ectoderm (ge) are shown in blue. Cloacal endoderm is in green. At E10, the ventral part of the cloaca (cl) extends rostrally to give rise to the embryonic urogenital sinus and the primordium of the bladder (bl). At E12, <i>Bmp7</i> expression appears in the dorsal genital mesenchyme (gm). At E14, <i>Bmp7</i> expression in the URM shifts to the ventral portion of the genital tubercle (dashed arrow). (B, C) Histological sagittal sections of normal <i>Bmp7^lacZ/+</i> (B) and <i>Bmp7^lacZ/lacZ</i> null embryos (C) stained with X-gal. Heterozygous embryo (B) shows normal position of the rectum (r) and anus (an). In <i>Bmp7^lacZ/lacZ</i> null embryo (C), a hypoplastic rectum and urethra (ur) open into a common cloacal orifice covered by the cloacal membrane (clm). Scale bars: 100 µm.</p