A Study On Correlation Between HOX Gene And Hypospadias

Background : Hypospadias is a congenital defect of the penis resulting in incomplete development of the penile urethra. Hypospadias is one of the most common congenital malformation in human urogenital system .The incidence of hypospadias has an upward trend in recent years. Research findings confirmed that multiple genes were involved in the genesis of hypospadias. Study found HoxA13 mutations in some of patients with malformation syndrome who showed hypospadias. HoxA13-/- mutant mice show ectopic urethra orifice, markly shorter AGD and defect of the urogenital sinus.Objective: To investigate the role of HoxA13 in this anomaly, we compared the gene's mRNA/protein expression in normal versus hypospadic human/mice tissue using molecular localization techniques.Methods: The whole experiment concludes two parts: experiment in humans and in mice.⑴Studies in humans: 25 young males with hypospadias scheduled to undergo surgical repair were prospectively entered into this study. Excess prepucial tissue was obtained at the time of elective surgery for hypospadias ; no periurethral tissue was taken. 15 controls consisted of patients undergoing elective circumcision were chosen. The controls and hypospadias samples were strictly age-matched. The levels of HoxA13 mRNA and protein was investigated by real-time PCR and immunohistochemistry.⑵Studies in mice: Pregnant C57BL/6 mice were selected and randomly divided into two groups : one treated with Di(2-ethylhexyl)phthalate 500mg/kg/day; and a control group. During the mice conception periods from day 12 to 17, the pregnant mice exposure groups were gastric intubation with 500mg/kg/day of DEHP at 0.5 ml mixture per 100g body weight, respectively, the mice in control group were receiced same volume of corn oil. Fetal mice were harvested at GD19. The body weight and anogenital distance of male fetal mice were measured. And the incidences of hypospadic genitalia as well as the changes of the histopathology in each group were examined. Subsequently, the mRNA and protein levels of HoxA13 in genitalia were determined using RT-PCR and immunohistochemistry.Results:(1)Studies in humans: HoxA13 mRNA expressions in prepuce of hypospadias were reduced significantly than those in control [(9.4684±6.5494),(52.827±35.733),P<0.01]. HoxA13 protein expressed in epidermis and localized at cytoplasm. In tissue of hypospadias, the protein showed negative or weakly positive, but manifested strongly positive in the controls.(2)Studies in mice: The incidence of hypospadic genitalia were higher obviously than those in control group(incidence of hypospadic genitalia 75.5%, 0%, P<0.01; AGD:0.208±0.01, 0.181±0.12, P<0.01); The result of histopathology in genitalia: the procedure of development of the penile urethra involves the movement or growth of the urethral folds toward the midline fell behind. HoxA13 mRNA expressions in fetal mice genitalia of hypospadias were reduced obviously than those in control. HoxA13 protein also expressed in epidermis. In tissue of hypospadias, the protein showed weakly positive, but manifested strongly positive in the controls.Conclusion: HoxA13 mRNA/protein expressions in prepuce of hypospadias reduced significantly compared with those in control, this fact indicate that there is a relationship between disfunction of HoxA13 and genesis of hypospadias. DEHP is very toxic to the fetal mice including urogenital development and body weight, and can induce hypospadias in fetal male mice. HoxA13 mRNA/protein expressions in fetal mice genitalia of hypospadias were reduced obviously than those in control. It also cued that the relationship of HoxA13 and hypospadias was closely.