Life science
Medical & healthcare, Drug development, Livestock industry

Development of infertility model mice and search for target factors for thedevelopment of infertility treatment and contraceptive drugs
Genome Information Research Center, Department of Experimental Genome Research, Research Institute for Microbial Diseases
Professor Masahito Ikawa
Researchmap https://researchmap.jp/read0054910?lang=en

Life science

Abstract
In our laboratory, we are conducting research to investigate thecauses of male infertility and to develop male contraceptive drugs.
Specifically, we use the latest genome editing technology to generate gene-knockout (KO) mice that target genes are expressed
specifically in the testis, and analyze their phenotypes. When maleinfertility is observed, we elucidate the molecular mechanism andinvestigate the relationship with human infertility in cooperation
with clinical researchers. In addition, for critical factors that control
spermatogenesis and sperm function, we are working with Prof.
Martin Matzuk at Baylor College of Medicine in the U.S. to develop
non-hormonal male contraceptives by screening DNA-encoded
small molecules.

▍ Background & Results
In mammals, it is said that there are more than 23,000 protein-coding genes, but there are about 1,000 genes that arespecifically or abundantly expressed in the testis. We generated
KO mice using the CRISPR/Cas9 genome editing method andconducted mating tests. As a result, we showed that 93 of the 321
testis-specific genes are essential for male fertility. For example, in2015, we showed that sperm-specific calcineurin is essential for
sperm motility, and that its inhibitors can induce temporary maleinfertility; in 2020, we showed that NELL2 factor produced in thetestis go through the luminal space of the male reproductive tracts
and regulates the differentiation of neighboring tissue (epididymis,responsible for sperm maturation). In combination with GWAS analysis of male infertility patients and KO mice studies, we elucidated
the DNA8 is indispensable for sperm flagella formation and malefertility. In addition, we found that deficiency of ARMC12 causes
defective formation of the sperm mitochondrial sheath, and that
IZUMO1, FIMP, SOF1, TMEM95, SPACA6, and DCST1/2 are essential factors for sperm-egg fusion. Currently, we are collaboratingwith Professor Matzuk Martin at Baylor College of Medicine in theU.S. to develop male contraceptives through screening of DNA-encoding small molecules that bind to these essential factors.

▍ Significance of the research and Future perspective
Family planning requires the cooperation of men as well as women, but currently, the only contraceptives on the market are targeted at women. In addition, about one in six couples suffers frominfertility, while about 40% of pregnancies are said to be unintended. Through safe and secure control of reproduction, we hope tolead to a society that provides gender equality, health and welfare
to all people. In addition, the application of this technology to theefficient breeding of livestock animals is expected to contribute toa hunger-free society and to the conservation of rare animals.

P a t e n t
Kiyozumi, D et al. NELL2-mediated lumicrine signaling through OVCH2 is required for male fertility. Science. 2020 Jun 5; 368(6495): 1132-1135. doi:
10.1126/science. aay5134
Shimada, K et al. ARMC12 regulates spatiotemporal mitochondrial dynamics during spermiogenesis and is required for male fertility. PNAS. 2021; 118(6):Tr e a t i s ee2018355118. doi: 10.1073/pnas.2018355118
Miyata, H et al. SPATA33 localizes calcineurin to the mitochondria and regulates sperm motility in mice. PNAS. 2021; 118(35): e2106673118. doi: 10.1073/
pnas.2106673118
UR
L https://egr.biken.osaka-u.ac.jp/
K e y w o r d genome editing, reproductive medicine, family planning