Paediatrics (RCH) - Research Publications
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ItemCopy Number Variation in Patients with Disorders of Sex Development Due to 46,XY Gonadal Dysgenesis(PUBLIC LIBRARY SCIENCE, 2011-03-07)Disorders of sex development (DSD), ranging in severity from mild genital abnormalities to complete sex reversal, represent a major concern for patients and their families. DSD are often due to disruption of the genetic programs that regulate gonad development. Although some genes have been identified in these developmental pathways, the causative mutations have not been identified in more than 50% 46,XY DSD cases. We used the Affymetrix Genome-Wide Human SNP Array 6.0 to analyse copy number variation in 23 individuals with unexplained 46,XY DSD due to gonadal dysgenesis (GD). Here we describe three discrete changes in copy number that are the likely cause of the GD. Firstly, we identified a large duplication on the X chromosome that included DAX1 (NR0B1). Secondly, we identified a rearrangement that appears to affect a novel gonad-specific regulatory region in a known testis gene, SOX9. Surprisingly this patient lacked any signs of campomelic dysplasia, suggesting that the deletion affected expression of SOX9 only in the gonad. Functional analysis of potential SRY binding sites within this deleted region identified five putative enhancers, suggesting that sequences additional to the known SRY-binding TES enhancer influence human testis-specific SOX9 expression. Thirdly, we identified a small deletion immediately downstream of GATA4, supporting a role for GATA4 in gonad development in humans. These CNV analyses give new insights into the pathways involved in human gonad development and dysfunction, and suggest that rearrangements of non-coding sequences disturbing gene regulation may account for significant proportion of DSD cases.
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ItemDisorders of sex development: insights from targeted gene sequencing of a large international patient cohort(BIOMED CENTRAL LTD, 2016-11-29)BACKGROUND: Disorders of sex development (DSD) are congenital conditions in which chromosomal, gonadal, or phenotypic sex is atypical. Clinical management of DSD is often difficult and currently only 13% of patients receive an accurate clinical genetic diagnosis. To address this we have developed a massively parallel sequencing targeted DSD gene panel which allows us to sequence all 64 known diagnostic DSD genes and candidate genes simultaneously. RESULTS: We analyzed DNA from the largest reported international cohort of patients with DSD (278 patients with 46,XY DSD and 48 with 46,XX DSD). Our targeted gene panel compares favorably with other sequencing platforms. We found a total of 28 diagnostic genes that are implicated in DSD, highlighting the genetic spectrum of this disorder. Sequencing revealed 93 previously unreported DSD gene variants. Overall, we identified a likely genetic diagnosis in 43% of patients with 46,XY DSD. In patients with 46,XY disorders of androgen synthesis and action the genetic diagnosis rate reached 60%. Surprisingly, little difference in diagnostic rate was observed between singletons and trios. In many cases our findings are informative as to the likely cause of the DSD, which will facilitate clinical management. CONCLUSIONS: Our massively parallel sequencing targeted DSD gene panel represents an economical means of improving the genetic diagnostic capability for patients affected by DSD. Implementation of this panel in a large cohort of patients has expanded our understanding of the underlying genetic etiology of DSD. The inclusion of research candidate genes also provides an invaluable resource for future identification of novel genes.
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ItemFunctional characterization of novelNR5A1variants reveals multiple complex roles in disorders of sex development(WILEY-HINDAWI, 2018-01)Variants in the NR5A1 gene encoding SF1 have been described in a diverse spectrum of disorders of sex development (DSD). Recently, we reported the use of a targeted gene panel for DSD where we identified 15 individuals with a variant in NR5A1, nine of which are novel. Here, we examine the functional effect of these changes in relation to the patient phenotype. All novel variants tested had reduced trans-activational activity, while several had altered protein level, localization, or conformation. In addition, we found evidence of new roles for SF1 protein domains including a region within the ligand binding domain that appears to contribute to SF1 regulation of Müllerian development. There was little correlation between the severity of the phenotype and the nature of the NR5A1 variant. We report two familial cases of NR5A1 deficiency with evidence of variable expressivity; we also report on individuals with oligogenic inheritance. Finally, we found that the nature of the NR5A1 variant does not inform patient outcomes (including pubertal androgenization and malignancy risk). This study adds nine novel pathogenic NR5A1 variants to the pool of diagnostic variants. It highlights a greater need for understanding the complexity of SF1 function and the additional factors that contribute.
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ItemFertility in Turner syndrome(WILEY, 2013-11)There is increasing interest in fertility and use of assisted reproductive technologies for women with Turner syndrome (TS). Current parenting options include adoption, surrogacy, and spontaneous and assisted reproduction. For women with TS, specific risks of pregnancy include higher than usual rates of spontaneous abortion, foetal anomaly, maternal morbidity and mortality. Heterologous fertility assistance using oocytes from related or unrelated donors is an established technique for women with TS. Homologous fertility preservation includes cryopreservation of the patient's own gametes prior to the progressive ovarian atresia known to occur: preserving either mature oocytes or ovarian tissue containing primordial follicles. Mature oocyte cryopreservation requires ovarian stimulation and can be performed only in postpubertal individuals, when few women with TS have viable oocytes. Ovarian tissue cryopreservation, however, can be performed in younger girls prior to ovarian atresia - over 30 pregnancies have resulted using this technique, however, none in women with TS. We recommend consideration of homologous fertility preservation techniques in children only within specialized centres, with informed consent using protocols approved by a research or clinical ethics board. It is essential that further research is performed to improve maternal and foetal outcomes for women with TS.
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ItemAn X-traordinary stroke(ELSEVIER SCIENCE INC, 2011-04-09)