EXAMINING THE ROLE OF BMAL1, A NOVEL MATERNAL FACTOR IN PREIMPLANTATION DEVELOPMENT

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PROJECT SUMMARY Unexplained infertility accounts for 25% of infertility cases. One of the challenges in identifying factors related to infertility, particularly unexplained infertility is that there are no live births. A hallmark of genes essential in oogenesis and during preimplantation development is a failure to progress to the point a viable pregnancy can be recognized. As such, identifying genes essential to the these crucial stages is an important step in understating unexplained infertility. Prior research suggests that Bmal1-/- mice produce embryos which are largely lost before the blastocyst stage, even when implanted into pseudopregnant wildtype mice. Dr. Cassin’s preliminary data suggests that initial deficits occur much earlier as Bmal1-/- oocytes are largely observed to be abnormal, likely leading to the phenotype previously described. Further, preliminary work in this grant reveals that BMAL1 is expressed in developing follicles and throughout preimplantation development. BMAL1 has been shown to regulate many of the most essential regulatory functions in early development such as cap-dependent translation, and mRNA regulation, but the role of Bmal1 has not yet been investigated. This grant proposes the examination of Bmal1 during oogenesis and the maternal to zygotic transition (MZT). The overarching hypothesis of this grant is Bmal1 is an essential maternal factor during oogenesis, aids in the regulation of many essential early genes transcribed by the embryo, and regulates a cell-autonomous embryonic clock. Aim1 will address the expression and phenotype of Bmal1 activity during oogenesis. The guiding hypothesis for Aim1 is a primary deficit in oogenesis as a result of Bmal1 m-KO contributes to poor oocyte quality and defects in MZT progression. This Aim will be addressed through the use of embryo culture and immunohistochemical (IHC) techniques. The guiding hypothesis for Aim2 is BMAL1 is an essential factor for preimplantation through the regulation of both maternal mRNAs as well as early embryonic genome activation. As BMAL1 has many regulatory functions Aim2 combine rescue experiments with several -omics techniques to investigate the specific function that BMAL1 has in the MZT. Aim3 examines the regulation of the MZT by Bmal1. The guiding hypothesis of Aim3 is the cell- autonomous clock of the developing embryo is regulated through Bmal1. To address Aim3 live cell imaging of reporter mice will be used to observe movement of BMAL1 throughout the cell. This work specifically focuses on one gene, Bmal1. However, because Bmal1 is a gene involved in many regulatory pathways, this grant opens up a new area of research, the circadian genes in early development. Further, it identifies a novel potential factor in unexplained infertility, and identifies a new direction in the field of infertility. Dr. Cassin will be trained by her mentors in the fields of embryology and circadian biology. Together with training in presenting, scientific writing, and bioinformatics, Dr. Cassin will possess all the skills necessary to establish a successful, independent lab following the mentored phase of the grant.