In a new study conducted at the University of Hawaiʻi at Mānoa, researchers from the John A. Burns School of Medicine (JABSOM) have shown that the loss of a key male fertility gene leads to infertility and changes expression of hundreds of other important genes.
The study was led by Professor Dr. Monika Ward from the Department of Anatomy, Biochemistry & Physiology and the Yanagimachi Institute for Biogenesis Research (YIBR). The team has been investigating a zinc finger Y-encoded gene called Zfy. This gene, encoded on Y chromosome in both mice and humans, is considered a male fertility factor. In mice, Zfy is present as two copies, Zfy1 and Zfy2.
The researchers first used CRISPR-Cas9 to produce knockout mice specifically lacking Zfy1, Zfy2, and both Zfy1 and Zfy2 genes, the latter called Zfy DKO (Zfy double knockout). They observed that Zfy DKO males were completely infertile and had severely abnormal sperm. In the most severe cases, Zfy DKO males could not produce sperm at all. These findings were published in 2022, in Biology of Reproduction.
The team then applied assisted reproduction technologies (ART) to produce more infertile Zfy DKO males so that investigations of these mice can continue. They used intracytoplasmic sperm injection (ICSI) and round spermatid injection (ROSI) – techniques pioneered at the University of Hawaiʻi by the YIBR founder, Ryuzo Yanagimachi. In the new study, published on August 27 in Cell Death and Differentiation, the team shows the molecular consequences of Zfy loss.
The researchers demonstrated that without Zfy hundreds of genes become deregulated, expressed either too strongly or too weak. Among these genes are those responsible for sperm production, for DNA packaging and organization, and for cell death. The team linked deregulation of these genes to changes in testes and sperm. They found that sperm precursor cells in the testes were dying prematurely and sperm, if produced, had DNA that was not properly condensed and as such vulnerable to damage.
"This work really pushes forward our understanding of how this important Zfy gene works. We identified pathways and other genes that are affected and we can now study how exactly Zfy regulates them." said Dr. Ward.
"This study exemplifies a critical role undergraduate and graduate students play in research at the University of Hawaiʻi. The first author of the paper, and a person who performed most of the work, is a recently graduated PhD student in the Developmental and Reproductive Biology (DRB) graduate program, Hayden Holmlund. Hayden now continues his academic career as a post-doctoral fellow in California. Some of the experiments were performed by an undergraduate INBRE student, Benazir Yarbabaeva, who has just started as a MS student in DRB program to continue her explorations of Zfy DKO sperm", continued Dr. Ward.
"Finally, the study exemplifies the core mission of the YIBR." said Dr. Ward. The YIBR fosters collaboration in reproductive and developmental biology and beyond. "The new study was performed with contributions from colleagues from France and England"
The study represents a significant step forward in our understanding of how male fertility is regulated and opens the path for future explorations of Zfy regulatory role in sperm production. The fundamental knowledge obtained through basic research using mice as a model addresses a specific health need - management of male fertility/treatment of male infertility - and has translational implications.
The study details can be found in an article published in Cell Death and Differentiation, a leading peer-reviewed journal: https://rdcu.be/eCLBl
