A 2025 Crick PhD project with Robin Lovell-Badge.
Project background and descriptionSex determination and gonadal development are fundamental processes, for which critical genes have been identified in mice and humans; the latter from studying individuals with disorders of sex development (DSDs). However, they are rapidly evolving processes where the same gene may have distinct relative importance in the two species. Studying embryological processes in humans is challenging, especially with DSDs that are not apparent until after birth, therefore knowledge of mechanisms, including gene and cell interactions, largely comes from studying mice and several other model organisms. The recent development of methods to obtain gonadal cell types in vitro beginning with pluripotent stem cells (PSCs: embryonic stem cells, ESCs, or induced pluripotent stem cells, iPSCs) permit the study of mechanisms in a human context, and, in theory, any mammal from which iPSCs can be derived.
Together with colleagues at the Pasteur Institute, my lab developed such methods with both mouse and human PSCs, where the outcome was dependent on the presence or absence of the Y-linked testis determining gene, SRY, with respect to developing testis-specific Sertoli cells or ovarian granulosa cells, the two arising from common progenitors that become supporting cells for differentiating sperm or eggs. The system was also used to explore one DSD with iPSCs from an XY female, revealing supporting cells with intermediate gene expression and behaviour.
This PhD project will capitalise on these methods, further refined by our collaborators, to explore gonadal cellular phenotypes and gene regulatory networks (GRNs) associated with genes of interest, especially where loss-of-function mutations are associated with species-specific differences in phenotypic outcome. One example is Foxl2, where homozygous null mutations in XX mice do not cause sex reversal, but later ovarian failure, whereas conditional mutation postnatally leads to transdifferentiation of granulosa cells to Sertoli-like cells and to structures resembling testis tubules. In contrast, in null mutant goats and chickens, a more primary sex reversal is seen with XX testis development. Homozygous human FOXL2 mutations have not been identified, but heterozygotes show premature ovarian insufficiency. SOX9 and DMRT1, genes involved in testis development also show different sensitivities to loss-of-function mutations between mouse and human.
The project will have three main aims. First, after using genome editing methods in XX and XY iPSCs, to explore the function of at least two of the genes mentioned above during in vitro gonadal differentiation, comparing phenotypes in human cells with those in mice. Second, to use 'omics' techniques, such as RNAseq, to examine the gene regulatory networks (GRNs) and protein-protein interactions in the human system, comparing these with existing data in mice. This should contribute to understanding of the evolution of such GRNs. Third, to ask if the in vitro systems are sufficiently robust to permit screens for genes or small molecules that interfere with or enhance cell fate decisions relevant to gonad development, to reveal novel causes of DSDs and, ultimately, better ways to manage them clinically.
Candidate BackgroundCandidates should have a degree in a relevant biological subject and some research experience, which could be as part of an MSc or MRES, or from working in a lab. I am particularly interested in receiving applications from those with good theoretical knowledge of genetics and/or developmental biology and molecular biology, with some practical experience of the latter. Experience of cell culture, imaging, and bioinformatics would all be useful, but are not essential. Training is available in these and other relevant techniques. The successful candidate will need to work with others in the lab and with various core facilities in order to profit from their expertise and help, but I also value and encourage independence.
References1. Migale, R., Neumann, M. and Lovell-Badge, R. (2021) Long-range regulation of key sex determination genes.
In vitro cellular reprogramming to model gonad development and its disorders.
Somatic sex reprogramming of adult ovaries to testes by FOXL2 ablation.
FOXL2 interaction with different binding partners regulates the dynamics of ovarian development.
Sex reversal following deletion of a single distal enhancer of Sox9.
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