SEPT12 phosphorylation results in loss of the septin ring/sperm annulus, defective sperm motility and poor male fertility

PLoS Genet. 2017 Mar 27;13(3):e1006631. doi: 10.1371/journal.pgen.1006631. eCollection 2017 Mar.

Abstract

Septins are critical for numerous cellular processes through the formation of heteromeric filaments and rings indicating the importance of structural regulators in septin assembly. Several posttranslational modifications (PTMs) mediate the dynamics of septin filaments in yeast. However, little is known about the role of PTMs in regulating mammalian septin assembly, and the in vivo significance of PTMs on mammalian septin assembly and function remains unknown. Here, we showed that SEPT12 was phosphorylated on Ser198 using mass spectrometry, and we generated SEPT12 phosphomimetic knock-in (KI) mice to study its biological significance. The homozygous KI mice displayed poor male fertility due to deformed sperm with defective motility and loss of annulus, a septin-based ring structure. Immunohistochemistry of KI testicular sections suggested that SEPT12 phosphorylation inhibits septin ring assembly during annulus biogenesis. We also observed that SEPT12 was phosphorylated via PKA, and its phosphorylation interfered with SEPT12 polymerization into complexes and filaments. Collectively, our data indicate that SEPT12 phosphorylation inhibits SEPT12 filament formation, leading to loss of the sperm annulus/septin ring and poor male fertility. Thus, we provide the first in vivo genetic evidence characterizing importance of septin phosphorylation in the assembly, cellular function and physiological significance of septins.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Blotting, Western
  • HEK293 Cells
  • Humans
  • Immunohistochemistry
  • Infertility, Male / genetics*
  • Male
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Microscopy, Electron, Transmission
  • Mutation
  • Phosphorylation
  • Septins / genetics*
  • Septins / metabolism
  • Sequence Homology, Amino Acid
  • Serine / genetics
  • Serine / metabolism
  • Sperm Motility / genetics*
  • Spermatozoa / metabolism*
  • Spermatozoa / ultrastructure

Substances

  • Serine
  • SEPT12 protein, mouse
  • Septins

Grants and funding

This study was supported by grants to PLK (MOST 103-2314-B-006-036, MOST 104-2314-B-006-001 and MOST 105-2314-B-006-001) from the Ministry of Science and Technology, and grants to CYW (MOST 103-2314-B-006-037, MOST 104-2314-B-006-002 and MOST 105-2314-B-006-002) from the Ministry of Science and Technology. The funder had no role in study design,data collection and analysis, decision to publish, or preparation of the manuscript.