The important roles of microRNAs (miRNAs) in almost all aspects of genome regulation and organismal biology have become appreciated in the past decade, and methods to probe their functions have become routine in invertebrate models and in mammalian cell culture paradigms. However, functional studies of miRNAs in mammalian gametogenesis have lagged due to the physiological complexities of this process and the lack of suitable in vitro systems. Our project seeks to develop technologies to query the function and targets of virtually all conserved miRNAs that are expressed during mouse and human spermatogenesis. One strategy to identify the bona-fide gene targets of all conserved, male germ cell-expressed miRNAs involves the creation of a comprehensive and flexible set of combinatorial transgenic mice bearing miRNA arrays, followed by RNA-seq analysis of the transgenic lines to identify the in vivo targets of the miRNAs. The second strategy is to ablate miRNAs, then use RNA-seq to identify mRNAs or proteins that increase in abundance. Towards this end, we are using CRISPR-mediated mutagenesis to simultaneously knockout multiple miRNAs in mouse embryos. If successful, this would be readily scalable to all miRNAs of interest in the germline. Ultimately, the success of either strategy will allow us to deduce the roles of small RNAs in male fertility.
Recent Publications in the area of Reproduction include:
For more information on Dr. Schimenti's research, please see his lab website.
A new study from Andrew Grimson's lab, in collaboration with Paula Cohen's lab, has identified a key pathway required for maintenance of sex chromosome telomere integrity. Using conditional knockout mice for Dicer and Dgcr8, two key enzymes required for small RNA processing, Modzelewski et al (2015) show that loss of small RNAs during prophase I leads to telomere fusion events specifically involving the X and Y chromosomes. For further information, see the May edition of Journal of Cell Science
A recent publication by Dabaja et al (2015) has identified key cell:cell interactions that are necessary to establish normal profiles of one key microRNA, miR202-5p, in Sertoli cells. This is the first example of a germ cell regulatory interaction that is necessary for miR expression in neighboring somatic cells of the testis
The lab of Center member John Schimenti recently identified the DNA damage checkpoint pathway responsible for culling oocytes that fail to repair double stranded breaks (DSBs) that occur during meiosis or which arise in a female's oocyte pool (Bolcun-Filas et al, Science 343:533-536, 2014). Using combinations of mutants involved in recombination and DNA damage responses, they found that this pathway involves signaling of checkpoint kinase 2 (CHK2) to both p53 and p63. Disruption of this checkpoint pathway restored fertility to females that normally would be deficient of all oocytes due to defects in meiotic recombination or exposure to radiation. This discovery opens the way to using available CHK2 inhibitors to protect the oocytes of women undergoing cancer therapy that would normally cause infertility.