CXXC1 is not essential for normal DNA double-strand break formation and meiotic recombination in mouse

Abstract

In most mammals, including mice and humans, meiotic recombination is determined by the meiosis specific histone methytransferase PRDM9, which binds to specific DNA sequences and trimethylates histone 3 at lysine-4 and lysine-36 at the adjacent nucleosomes. These actions ensure successful DNA double strand break formation and repair that occur on the proteinaceous structure forming the chromosome axis. The process of hotspot association with the axis after their activation by PRDM9 is poorly understood. Previously, we and others have identified CXXC1, an ortholog of S. cerevisiae Spp1 in mammals, as a PRDM9 interactor. In yeast, Spp1 is a histone methyl reader that links H3K4me3 sites with the recombination machinery, promoting DSB formation. Here, we investigated whether CXXC1 has a similar function in mouse meiosis. We created two Cxxc1 conditional knockout mouse models to deplete CXXC1 generally in germ cells, and before the onset of meiosis. Surprisingly, male knockout mice were fertile, and the loss of CXXC1 in spermatocytes had no effect on PRDM9 hotspot trimethylation, double strand break formation or repair. Our results demonstrate that CXXC1 is not an essential link between PRDM9-activated recombination hotspot sites and DSB machinery and that the hotspot recognition pathway in mouse is independent of CXXC1.

Histone H3 Lysine 56 Acetylation Is Required for Formation of Normal Levels of Meiotic DNA Breaks in S. cerevisiae

“…In the current model, H3K4me3 is deposited by Set1C and becomes recognized by Spp1 (the PHD finger subunit of Set1C), which leads to tethering of DSB sites to the chromosome axis that undergo Spo11-mediated cleavage (Acquaviva et al, 2013;Sommermeyer et al, 2013;Karányi et al, 2018). A similar mechanism has been proposed in mammals involving the meiosis-specific H3K4 methylase Prdm9 (Baudat et al, 2010;Parpanov et al, 2010), however, CXXC1 (the yeast ortholog of Spp1) is apparently not essential for the association of H3K4 tri-methylated recombination sites with the DSB machinery (Tian et al, 2018).…”

Function and Regulation of Histone H3 Lysine-4 Methylation During Oocyte Meiosis and Maternal-to-Zygotic Transition

“…Studies in yeasts have shown that CXXC1 recruits chromatin regions with H3K4me3 to the chromosome axis for DNA double-strand break generation and crossover formation in the prophase of meiosis ( Parvanov et al, 2017 ). To investigate whether CXXC1 also plays a comparable role in the meiotic prophase of mammalian germ cells, researchers from two groups independently knocked out Cxxc1 in germ cells before the onset of meiosis with Stra8-Cre ( Tian et al, 2018 ; Jiang et al, 2020 ). While the knockout of Cxxc1 in male germ cells using transgenic Stra8-Cre did not affect spermatogenesis and male fertility, the deletion of Cxxc1 in a Stra8-Cre knockin mouse strain resulted in male and female infertility.…”

CxxC finger protein 1-mediated histone H3 lysine-4 trimethylation is essential for proper meiotic crossover formation in mice

“…In mammals, meiotic recombination occurs at 1-to 2-kb genomic regions termed hotspots (de Massy, 2013a; Paigen and Petkov, 2010), the positions and activities of which are determined by another DNA-binding histone methyltransferase, PRDM9 (Baudat et al, 2010;Berg et al, 2010;Diagouraga et al, 2018;Parvanov et al, 2010). Hypothetically, PRDM9 forms complexes with additional proteins, including CXXC finger protein 1 (CXXC1; also known as CFP1), thereby bringing hotspot DNA to the chromosomal axis, and providing the appropriate environment to allow hotspots to proceed into the next phase of recombination (Parvanov et al, 2017;Tian et al, 2018). However, in vivo evidence is lacking to support the role of CXXC1 in homologous chromosomal recombination.…”

“…Deficiency of Cxxc1 in mice leads to peri-implantation lethality (Carlone and Skalnik, 2001). To study the in vivo functions of CXXC1, several groups have independently generated Cxxc1 flox/flox mouse strains for CRE recombinasemediated conditional knockout (Cao et al, 2016;Chun et al, 2014;Tian et al, 2018). Deletion of Cxxc1 in oocytes blocks the accumulation of H3K4me3 on chromatin during oogenesis and significantly impairs meiotic maturation and the subsequent maternal-to-zygotic transition (MZT) (Yu et al, 2017).…”