Meiotic and epigenetic defects in Dnmt3L-knockout mouse spermatogenesis

doi:10.1073/pnas.0500702102

Meiotic and epigenetic defects in Dnmt3L-knockout mouse spermatogenesis

^*Genetics and Bioinformatics Division, The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3050, Australia; ^‡Centre for Molecular Reproduction and Endocrinology, Monash Institute of Reproduction and Development, Australian Research Council Centre of Excellencein Biotechnology and Development, Monash University, Clayton, Victoria 3168, Australia; ^§Schools of Molecular and Microbial Sciences and Land and Food Sciences and ^§§Australian Research Council Centre of Excellence for Integrative Legume Research and Institute of Molecular Bioscience, University of Queensland, Brisbane 4072, Australia; ^¶Institute of Medical Technology and Department of Pathology, Biokatu 6, Tampere University Hospital, 33014 University of Tampere, Fin-33521, Tampere, Finland; ^∥Chromosome Research Group, The Murdoch Children's Research Institute, Royal Children's Hospital, Flemington Road, Parkville, Victoria 3052, Australia; ^**Department of Genetic Medicine and Development, University of Geneva Medical School and University Hospitals of Geneva, CMU, 1, Rue Michel Servet, 1211 Geneva, Switzerland; ^††Prince Henry's Institute of Medical Research, Monash Medical Centre, Clayton, Victoria 3168, Australia; and ^‡‡Molecular Pathology, University of Tartu, Tartu 50414, Estonia

Communicated by Suzanne Cory, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia, January 26, 2005 (received for review September 9, 2004)

Abstract

The production of mature germ cells capable of generating totipotent zygotes is a highly specialized and sexually dimorphic process. The transition from diploid primordial germ cell to haploid spermatozoa requires genome-wide reprogramming of DNA methylation, stage- and testis-specific gene expression, mitotic and meiotic division, and the histone–protamine transition, all requiring unique epigenetic control. Dnmt3L, a DNA methyltransferase regulator, is expressed during gametogenesis, and its deletion results in sterility. We found that during spermatogenesis, Dnmt3L contributes to the acquisition of DNA methylation at paternally imprinted regions, unique nonpericentric heterochromatic sequences, and interspersed repeats, including autonomous transposable elements. We observed retrotransposition of an LTR-ERV1 element in the DNA from Dnmt3L–/^– germ cells, presumably as a result of hypomethylation. Later in development, in Dnmt3L ^–/– meiotic spermatocytes, we detected abnormalities in the status of biochemical markers of heterochromatin, implying aberrant chromatin packaging. Coincidentally, homologous chromosomes fail to align and form synaptonemal complexes, spermatogenesis arrests, and spermatocytes are lost by apoptosis and sloughing. Because Dnmt3L expression is restricted to gonocytes, the presence of defects in later stages reveals a mechanism whereby early genome reprogramming is linked inextricably to changes in chromatin structure required for completion of spermatogenesis.

Footnotes

↵ ¶¶ To whom correspondence should be addressed. E-mail: hscott{at}wehi.edu.au.
↵ † K.E.W. and M.K.O. contributed equally to this work.
Author contributions: K.E.W., M.K.O., S.F., P.E.C., U.A., J.C., D.K.H., R.L., S.E.A., D.M.d.K., M.P.H., P.P., B.J.C., and H.S.S. designed research; K.E.W., M.K.O., S.F., P.E.C., U.A., H.A., N.P., R.L., and M.P.H. performed research; S.F., J.C., D.K.H., H.A., N.P., B.J.C., and H.S.S. contributed new reagents/analytic tools; K.E.W., M.K.O., S.F., P.E.C., U.A., J.C., S.J.M., D.M.d.K., P.P., B.J.C., and H.S.S. analyzed data; and K.E.W., M.K.O., P.E.C., U.A., J.C., R.L., D.M.d.K., B.J.C., and H.S.S. wrote the paper.
Abbreviations: AMP, amplified methylation polymorphism; IHC, immunohistochemistry; KO, knockout; SC, synaptonemal complex; DMR, differentially methylated region; LINE, long interspersed nuclear element.
Note. While this work was under consideration, two related articles were published (7, 8).
Freely available online through the PNAS open access option.