A novel transcriptional factor Nkapl is a germ cell-specific suppressor of Notch signaling and is indispensable for spermatogenesis

Hidenobu Okuda; Hiroshi Kiuchi; Tetsuya Takao; Yasushi Miyagawa; Akira Tsujimura; Norio Nonomura; Haruhiko Miyata; Masaru Okabe; Masahito Ikawa; Yoshitaka Kawakami; Naoki Goshima; Morimasa Wada; Hiromitsu Tanaka

doi:10.1371/journal.pone.0124293

A novel transcriptional factor Nkapl is a germ cell-specific suppressor of Notch signaling and is indispensable for spermatogenesis

PLoS One. 2015 Apr 14;10(4):e0124293. doi: 10.1371/journal.pone.0124293. eCollection 2015.

Authors

Affiliations

¹ Department of Urology, Osaka University Graduate School of Medicine, Osaka, Japan.
² Department of Urology, Juntendo University Hospital, Tokyo, Japan.
³ Animal Resource Center for Infectious Diseases, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan.
⁴ National Institute of Advanced Industrial Science and Technology, Tokyo, Japan.
⁵ Molecular Biology Division, Faculty of Pharmaceutical Sciences, Nagasaki International University, Nagasaki, Japan.

Abstract

Spermatogenesis is an elaborately regulated system dedicated to the continuous production of spermatozoa via the genesis of spermatogonia. In this process, a variety of genes are expressed that are relevant to the differentiation of germ cells at each stage. Although Notch signaling plays a critical role in germ cell development in Drosophila and Caenorhabditis elegans, its function and importance for spermatogenesis in mammals is controversial. We report that Nkapl is a novel germ cell-specific transcriptional suppressor in Notch signaling. It is also associated with several molecules of the Notch corepressor complex such as CIR, HDAC3, and CSL. It was expressed robustly in spermatogonia and early spermatocytes after the age of 3 weeks. Nkapl-deleted mice showed complete arrest at the level of pachytene spermatocytes. In addition, apoptosis was observed in this cell type. Overexpression of NKAPL in germline stem cells demonstrated that Nkapl induced changes in spermatogonial stem cell (SSC) markers and the reduction of differentiation factors through the Notch signaling pathway, whereas testes with Nkapl deleted showed inverse changes in those markers and factors. Therefore, Nkapl is indispensable because aberrantly elevated Notch signaling has negative effects on spermatogenesis, affecting SSC maintenance and differentiation factors. Notch signaling should be properly regulated through the transcriptional factor Nkapl.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Apoptosis
Basic Helix-Loop-Helix Transcription Factors / genetics
Basic Helix-Loop-Helix Transcription Factors / metabolism
Cell Differentiation
Cell Line
Cell Nucleus / metabolism
Co-Repressor Proteins / genetics
Co-Repressor Proteins / metabolism
Germ Cells / cytology
Germ Cells / metabolism
HEK293 Cells
Homeodomain Proteins / genetics
Homeodomain Proteins / metabolism
Humans
Male
Mice
Mice, Inbred ICR
Nuclear Proteins / deficiency
Nuclear Proteins / genetics
Nuclear Proteins / metabolism*
Phenotype
Protein Binding
RNA, Messenger / metabolism
Real-Time Polymerase Chain Reaction
Receptors, Notch / metabolism*
Repressor Proteins / genetics
Repressor Proteins / metabolism
Signal Transduction
Spermatogenesis
Spermatozoa / metabolism
Testis / metabolism*
Testis / pathology
Transcription Factor HES-1
Transfection

Substances

Basic Helix-Loop-Helix Transcription Factors
Co-Repressor Proteins
Hes1 protein, mouse
Hes5 protein, mouse
Homeodomain Proteins
NKAPL protein, human
Nuclear Proteins
RNA, Messenger
Receptors, Notch
Repressor Proteins
Transcription Factor HES-1

Grants and funding

A grant-in-aid from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan 24659713, (http://www.mext.go.jp/english/), the Research Fellowship for Young Scientists from the Japan Society for the Promotion of Science (JSPS), 11021 (http://www.jsps.go.jp/english/index.html). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.