Involvement of Insulin-Like Factor 3 (Insl3) in Diethylstilbestrol-Induced Cryptorchidism

Abstract

Recently, it has been shown that targeted inactivation of the Insl3 gene in male mice results in cryptorchidism. The Insl3 gene encodes insulin-like factor 3 (Insl3), which is expressed in fetal Leydig cells. The testicular factor Insl3 appears to play an important role in the transabdominal phase of testis descent, which involves development of the gubernaculum. Other studies have demonstrated that in utero exposure to diethylstilbestrol (DES), a synthetic estrogen, can lead to cryptorchidism both in humans and in animal models. The present study was undertaken to investigate whether prenatal DES-exposure might interfere with testicular Insl3 mRNA expression. Furthermore, the effect of DES on steroidogenic factor 1 (SF-1) mRNA expression level was determined, since it has been shown that SF-1 plays an essential role in transcriptional activation of the Insl3 gene promoter. Timed pregnant mice were treated with DES (100 microg/kg body weight) or vehicle alone on days E9 (gestational day 9) through E17. Control and DES-exposed mouse fetuses were collected at E16, E17 and E18, when transabdominal testis descent is taking place. Lack of gubernaculum development in DES-exposed animals was confirmed by histological analyses at E17. Expression of Insl3 and SF-1 mRNAs was studied in testes of control and DES-exposed fetuses at E16 and E18 by RNase protection assay. Prenatal DES-exposure resulted in a three-fold decrease in Insl3 mRNA expression level (P<0.005), at both E16 and E18. In contrast, DES treatment had no effect on the expression of SF-1 mRNA. These results support our hypothesis that DES may interfere with gubernaculum development by altering Insl3 mRNA expression, providing a possible mechanism by which DES may cause cryptorchidism.

Maternal hormone levels among populations at high and low risk of testicular germ cell cancer

“…Insl3 is responsible for the transabdominal phase of testicular descent during first trimester through virilisation and outgrowth of the embryonic gubernaculum (Nef and Parada, 1999). Exposure to maternal oestrogens, including 17a-and b-estradiol, as well as diethylstilbestrol, downregulates Insl3 expression in embryonic Leydig cells (Emmen et al, 2000;Nef et al, 2000). On the other hand, based on the finding that oestrogens negatively regulate Leydig cell development via inhibition of replication of Leydig-cell precursor cells in adult and prepubertal rats, it is suggested that this regulatory mechanism may also control the number of Leydig cells in fetal life in humans (Sharpe and Skakkebaek, 1993).…”

Genetic analysis of the INSL3 gene in patients with maldescent of the testis

“…Recent evidence shows that murine INSL3 expression is substantially reduced by diethylstilbestrol (DES), a drug associated with a higher incidence of cryptorchidism and other genital anomalies following human intra-uterine exposure (25,26). It will be interesting to determine whether this is part of the mechanism of action, of other environmental endocrine disruptors.…”

Analysis of Single Nucleotide Polymorphisms in the 3' Region of the Estrogen Receptor 1 Gene in Normal and Cryptorchid Miniature Dachshunds and Chihuahuas

“…ERα has been shown to be a major contributor to estrogen-mediated cryptorchidism in ERα knockout mice [20]. Deleterious effects of estrogens and environmental estrogenic substances on CO have been also reported [21][22][23][24][25], and these previous findings highlight the importance of ESR1 in this scenario.Association of SNPs in canine ESR1 with CO has yet to be reported. In the present study, we analyzed SNPs and estimated haplotypes at the 3' end of the ESR1 in normal dogs and in different phenotypes of cryptorchid dogs (Miniature Dachshunds and Chihuahuas) to examine the presence of any associations of CO with the SNPs and haplotypes in the canine ESR1.…”