title: Anatomical studies of the mouse genital tubercle.
abstract: BACKGROUND
  To study the etiology of hypospadias, we propose the use of a mouse model, the embryonic mouse genital tubercle. In this study, we define the development of the mouse genital tubercle with special emphasis on urethral formation demonstrating anatomical similarities to human development.
  
  
  METHODS
  Serial sections of genital tubercles from embryonic male and female mice ages 14 to 21 days gestation from timed pregnant animals, newborn and adult mice were immunohistochemical stained with antibodies to E-cadherin, cytokeratins 7, 10, and 14. Patency of the urethral was assessed by india ink injection via the bladder. Urethral lumen morphology was determined by the creation of plastic resin cast. Surface morphology of the genital tubercle was defined by scanning electron microscopy.
  
  
  RESULTS
  India Ink injection into the bladder showed that the urethral lumen was patent from 14 days gestation. Plastic resin casts revealed that the male urethra was characterized by a S shaped curve, the presence of the bulbar urethral gland and a longer length than age matched females. The ontogeny of the genital tubercle development revealed two epithelial edges that subsequently touched and fused into the completed urethra. During development cytokeratin immunohistochemical staining demonstrated that the epithelial cells of the urethral lumen are of bladder origin and the surface cells of skin origin.
  
  
  CONCLUSIONS
  The functional and developmental anatomy of the mouse genital tubercle provides a useful model to study normal and abnormal human urethral development.
authors.affiliation: Department of Urology, University of California, San Francisco, CA 94143-0738, USA. lbaskin@urol.ucsf.edu
authors.forename: Laurence S
authors.initials: LS
authors.lastname: Baskin
authors.forename: Wenhui
authors.initials: W
authors.lastname: Liu
authors.forename: Jacob
authors.initials: J
authors.lastname: Bastacky
authors.forename: Selcuk
authors.initials: S
authors.lastname: Yucel
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D015820:Cadherins / Q000032:analysis; D005314:Embryonic and Fetal Development; D005260:Female; D005865:Gestational Age; D006801:Humans; D007021:Hypospadias / Q000196:embryology; D007231:Infant, Newborn; D007633:Keratins / Q000032:analysis; D008297:Male; D051379:Mice; D008855:Microscopy, Electron, Scanning; D023421:Models, Animal; D014521:Urethra / Q000033:anatomy & histology* / Q000196:embryology / Q000648:ultrastructure; D001743:Urinary Bladder / Q000033:anatomy & histology* / Q000196:embryology
chemical_list: D015820:Cadherins; D007633:Keratins