Testicular Descent Lab Report

The molecular basis of testicular descent is demonstrated in pioneering experiment on dog puppies, which stated that abnormal gubernaculum development has occurred following unilateral and bilateral castration (Wensing, 1973c). afterwards, a low molecular weight factor extracted from porcine testicular tissue was shown to stimulate gubernacular mesenchymal cells during the transabdominal phase of testicular descent. This proliferative response was not mediated by androgens (Fentener van Vlissingen et al., 1988; 1989; Heyns et al., 1990; 1986; Visser and Heyns, 1995). This elusive low-molecular-weight factor likely resembles the insulin-like peptide hormone INSL3 which is structurally closely related to relaxin (Adham et al., 1993; Pusch and

In the INSL3 knockout, the testes are abdominal, but only loosely connected in the peritoneal cavity (Nef and Parada, 1999; Zimmermann et al., 1999). The reason for this is that these mice express androgens, and therefore the involution of the CSL occurs as in the wild type. Only the gubernaculum fails to develop. In the tfm mouse, which lacks a functional androgen receptor, INSL3/RLF would be expressed normally. Therefore the gubernaculum would develop as in the wildtype, retaining the testis in the inguinal region. However, the lack of an androgenic effect caused by the mutation means that the CSL does not involute, but remains developed, causing the testis to be held in the peritoneal cavity as if on a taut bowstring (Adham et al., 2000). If the tfm mouse is crossed with the INSL3 knockout mouse, then the testes in the male progeny adopt an ovarian location: the CSL is well developed, and the gubernaculum, in the absence of INSL3/RLF, involutes (Adham et al., 2000). Two recent studies have used transgenics to induce expression of INS3/RLF in fetal female mice (Adham et al., 2002; Koskimies et al., 2003). Of particular interest here, besides the movement of the ovary to an inguinal location, is the observation that there is also an increased incidence of inguinal hernia in the female mice, suggesting that INSL3/RLF may also play a role in the passage of the testes from the abdominal cavity through the body wall into the