Re-visiting the Protamine-2 locus: deletion, but not haploinsufficiency, renders male mice infertile.
Protamines are arginine-rich DNA-binding proteins that replace histones in elongating spermatids. This leads to hypercondensation of chromatin and ensures physiological sperm morphology, thereby protecting DNA integrity. In mice and humans, two protamines, protamine-1 (Prm1) and protamine-2 (Prm2) are expressed in a species-specific ratio. In humans, alterations of this PRM1/PRM2 ratio is associated with subfertility. By applying CRISPR/Cas9 mediated gene-editing in oocytes, we established Prm2-deficient mice. Surprisingly, heterozygous males remained fertile with sperm displaying normal head morphology and motility. In Prm2-deficient sperm, however, DNA-hypercondensation and acrosome formation was severely impaired. Further, the sperm displayed severe membrane defects resulting in immotility. Thus, lack of Prm2 leads not only to impaired histone to protamine exchange and disturbed DNA-hypercondensation, but also to severe membrane defects resulting in immotility. Interestingly, previous attempts using a regular gene-targeting approach failed to establish Prm2-deficient mice. This was due to the fact that already chimeric animals generated with Prm2+/-ES cells were sterile. However, the Prm2-deficient mouse lines established here clearly demonstrate that mice tolerate loss of one Prm2 allele. As such they present an ideal model for further studies on protamine function and chromatin organization in murine sperm.
Institute of Pathology, Department of Developmental Pathology, University of Bonn Medical School, Bonn, Germany.
Simon
S
Schneider
Minerva Max Planck Research Group - Molecular Physiology, Center of Advanced European Studies and Research, Bonn, Germany.
Melanie
M
Balbach
Minerva Max Planck Research Group - Molecular Physiology, Center of Advanced European Studies and Research, Bonn, Germany.
Jan F Jikeli
Institute of Veterinary-Anatomy, -Histology and -Embryology, Justus-Liebig University, Giessen, Germany.
Daniela
D
Fietz
Institute of Pathology, Department of Developmental Pathology, University of Bonn Medical School, Bonn, Germany.
Daniel
D
Nettersheim
Institute of Pathology, Department of Developmental Pathology, University of Bonn Medical School, Bonn, Germany.
Sina
S
Jostes
Institute of Veterinary-Anatomy, -Histology and -Embryology, Justus-Liebig University, Giessen, Germany.
Rovenna
R
Schmidt
Institute of Veterinary-Anatomy, -Histology and -Embryology, Justus-Liebig University, Giessen, Germany.
Monika
M
Kressin
Institute of Veterinary-Anatomy, -Histology and -Embryology, Justus-Liebig University, Giessen, Germany.
Martin
M
Bergmann
Minerva Max Planck Research Group - Molecular Physiology, Center of Advanced European Studies and Research, Bonn, Germany.
Dagmar
D
Wachten
Department of Urology, Pediatric Urology and Andrology, Section Molecular Andrology, Biomedical Research Center of the Justus-Liebig University, Giessen, Germany.
Klaus
K
Steger
Institute of Pathology, Department of Developmental Pathology, University of Bonn Medical School, Bonn, Germany.
Hubert
H
Schorle
D000818:Animals; D001483:Base Sequence; D064113:CRISPR-Cas Systems; D005091:Exons; D005260:Female; D056726:Genetic Association Studies; D056426:Genetic Loci; D057895:Haploinsufficiency; D006657:Histones / Q000378:metabolism; D007248:Infertility, Male / Q000235:genetics*; D008297:Male; D051379:Mice; D011479:Protamines / Q000235:genetics* / Q000378:metabolism; D017384:Sequence Deletion; D013081:Sperm Motility; D013091:Spermatogenesis; D013094:Spermatozoa / Q000473:pathology; D013737:Testis / Q000378:metabolism / Q000473:pathology
D006657:Histones; C513176:Prm1 protein, mouse; D011479:Protamines; C068621:protamine 2