Figures
Meiotic Cas9 expression mediates gene conversion in the male and female mouse germline
Highly efficient gene conversion systems have the potential to facilitate the study of complex genetic traits using laboratory mice and, if implemented as a "gene drive," to limit loss of biodiversity and disease transmission caused by wild rodent populations. It has previous been shown that such a system of gene conversion from heterozygous to homozygous after a sequence targeted CRISPR/Cas9 double-strand DNA break (DSB) is feasible in the female mouse germline. In the male germline, however, all DSBs were instead repaired by end joining (EJ) mechanisms to form an "insertion/deletion" (indel) mutation, suggesting that timing Cas9 expression to coincide with meiosis I is critical to favor conditions when homologous chromosomes are aligned and interchromosomal homology-directed repair (HDR) mechanisms predominate. Using a Cas9 knock-in allele at the Spo11 locus, Weitzel et al. show that meiotic expression of Cas9 does indeed mediate gene conversion in the male as well as in the female germline. The image shows male germline stem cells (magenta only) and expression of Cas9 in meiotic spermatocytes marked by the overlap of magenta and green.
Image Credit: Alexander Weitzel
Citation: (2021) PLoS Biology Issue Image | Vol. 19(12) December 2021. PLoS Biol 19(12): ev19.i12. https://doi.org/10.1371/image.pbio.v19.i12
Published: December 31, 2021
This is an open-access article distributed under the terms of the Creative Commons Public Domain declaration which stipulates that, once placed in the public domain, this work may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose.
Highly efficient gene conversion systems have the potential to facilitate the study of complex genetic traits using laboratory mice and, if implemented as a "gene drive," to limit loss of biodiversity and disease transmission caused by wild rodent populations. It has previous been shown that such a system of gene conversion from heterozygous to homozygous after a sequence targeted CRISPR/Cas9 double-strand DNA break (DSB) is feasible in the female mouse germline. In the male germline, however, all DSBs were instead repaired by end joining (EJ) mechanisms to form an "insertion/deletion" (indel) mutation, suggesting that timing Cas9 expression to coincide with meiosis I is critical to favor conditions when homologous chromosomes are aligned and interchromosomal homology-directed repair (HDR) mechanisms predominate. Using a Cas9 knock-in allele at the Spo11 locus, Weitzel et al. show that meiotic expression of Cas9 does indeed mediate gene conversion in the male as well as in the female germline. The image shows male germline stem cells (magenta only) and expression of Cas9 in meiotic spermatocytes marked by the overlap of magenta and green.
Image Credit: Alexander Weitzel