The organizational-activational hypothesis as the foundation for a unified theory of sexual differentiation of all mammalian tissues

Clinical and therapeutic aspects of Klinefelter's syndrome: sexual function

Klinefelter's syndrome (KS) is the most common sex chromosomal aberration among men, with estimated prevalence of about 1 in 500 newborn males. The classical phenotype of KS is widely recognized, but many affected subjects present only very mild signs. While the association between KS and infertility has been well documented, few studies have investigated sexual function in the KS patients. In the present paper we reviewed studies addressed to emotional processing and sexual function in KS. We searched the following databases Medline, Pubmed, Embase, for Klinefelter's syndrome, sexuality. We focus on the peculiar contribution of genetic and hormonal background, which characterizes sexual dysfunction in KS. Abnormal structure and function of the emotional brain circuits have been described in KS. These alterations were less pronounced when the patients underwent to testosterone replacement therapy suggesting that they were mediated by testosterone deficiency. Accordingly, clinical studies indicate that sexual dysfunctions, eventually present in KS, are not specifically associated with the syndrome but are related to the underlying hypogonadism. In conclusion, androgen deficiency more than chromosomal abnormality is the major pathogenic factor of sexual dysfunction in KS.

Somatic sex reprogramming of adult ovaries to testes by FOXL2 ablation

In mammals, the transcription factor SRY, encoded by the Y chromosome, is normally responsible for triggering the indifferent gonads to develop as testes rather than ovaries. However, testis differentiation can occur in its absence. Here we demonstrate in the mouse that a single factor, the forkhead transcriptional regulator FOXL2, is required to prevent transdifferentiation of an adult ovary to a testis. Inducible deletion of Foxl2 in adult ovarian follicles leads to immediate upregulation of testis-specific genes including the critical SRY target gene Sox9. Concordantly, reprogramming of granulosa and theca cell lineages into Sertoli-like and Leydig-like cell lineages occurs with testosterone levels comparable to those of normal XY male littermates. Our results show that maintenance of the ovarian phenotype is an active process throughout life. They might also have important medical implications for the understanding and treatment of some disorders of sexual development in children and premature menopause in women.