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BackgroundGonadal sex determination (GSD) in humans is a complex biological process that takes place in early stages of embryonic development when the bipotential gonadal primordium (BGP) differentiates towards testes or ovaries. This decision is directed by one of two distinct pathways embedded in a GSD network activated in a population of coelomic epithelial cells, the Sertoli progenitor cells (SPC) and the granulosa progenitor cells (GPC). In males, the pathway is activated when the Sex-Determining Region Y (SRY) gene starts to be expressed, whereas in females the WNT4/ β-catenin pathway promotes the differentiation of the GPCs towards ovaries. The interactions and dynamics of the elements that constitute the GSD network are poorly understood, thus our group is interested in inferring the general architecture of this network as well as modeling the dynamic behavior of a set of genes associated to this process under wild-type and mutant conditions.MethodsWe reconstructed the regulatory network of GSD with a set of genes directly associated with the process of differentiation from SPC and GPC towards Sertoli and granulosa cells, respectively. These genes are experimentally well-characterized and the effects of their deficiency have been clinically reported. We modeled this GSD network as a synchronous Boolean network model (BNM) and characterized its attractors under wild-type and mutant conditions.ResultsThree attractors with a clear biological meaning were found; one of them corresponding to the currently known gene expression pattern of Sertoli cells, the second correlating to the granulosa cells and, the third resembling a disgenetic gonad.ConclusionsThe BNM of GSD that we present summarizes the experimental data on the pathways for Sertoli and granulosa establishment and sheds light on the overall behavior of a population of cells that differentiate within the developing gonad. With this model we propose a set of regulatory interactions needed to activate either the SRY or the WNT4/ β-catenin pathway as well as their downstream targets, which are critical for further sex differentiation. In addition, we observed a pattern of altered regulatory interactions and their dynamics that lead to some disorders of sex development (DSD).Electronic supplementary materialThe online version of this article (doi:10.1186/s12976-015-0023-0) contains supplementary material, which is available to authorized users.

Cytogenetic studies have shown that 40-60% of patients with Ullrich-Turner syndrome (UTS) are 45,X, whereas the rest have structural aberrations of the X chromosome or mosaicism with a second cell line containing a structurally normal or abnormal X or Y chromosome. However, molecular analysis has demonstrated a higher proportion of mosaicism, and studies in different populations have shown an extremely variable frequency of Y mosaicism of 0-61%. We used Southern blot analysis and polymerase chain reaction (PCR) to detect the presence of Ycen, ZFY, SRY, and Yqh in 50 Mexican patients with UTS and different karyotypes to determine the origin of marker chromosomes and the presence of Y sequences. Our results indicated the origin of the marker chromosome in 1 patient and detected the presence of Y sequences in 4 45,X patients. Taken together, we found a 12% incidence of Y sequences in individuals with UTS. The amount of Y-derived material was variable, making the correlation between phenotype and molecular data difficult. Only 1 patient had a gonadoblastoma. We discuss the presence of Y chromosomes or Y sequences in patients with UTS and compare our frequency with that previously reported.

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We propose a Boolean network model of the FA/BRCA pathway, Checkpoint proteins and some alternative DNA repair pathways. To our knowledge, this is the largest network model incorporating a DNA repair pathway. Our model is able to simulate the ICL repair process mediated by the FA/BRCA pathway, the activation of Checkpoint proteins observed by recurrent DNA damage, as well as the repair of DNA double-strand breaks and DNA adducts. We generated a series of simulations for mutants, some of which have never been reported and thus constitute predictions about the function of the FA/BRCA pathway. Finally, our model suggests alternative DNA repair pathways that become active whenever the FA/BRCA pathway is defective.