A mutation in the endonuclease domain of mouse MLH3 reveals novel roles for MutLγ during crossover formation in meiotic prophase I

Melissa Toledo, Xianfei Sun, Miguel A. Brieño-Enríquez, Vandana Raghavan, Stephen Gray, Jeffrey Pea, Anita Venkatesh, Lekha Patel, Peter L. Borst, Eric Alani, Paula E. Cohen
2019 · doi:10.1101/517748
preprint OA: closed CC-BY-NC-ND-4.0
📄 Open PDF View at publisher

Abstract

ABSTRACT During meiotic prophase I, double-strand breaks (DSBs) initiate homologous recombination leading to non-crossovers (NCOs) and crossovers (COs). In mouse, 10% of DSBs are designated to become COs, primarily through a pathway dependent on the MLH1-MLH3 heterodimer (MutLγ). Mlh3 contains an endonuclease domain that is critical for resolving COs in yeast. We generated a mouse ( Mlh3 DN/DN ) harboring a mutation within this conserved domain that is predicted to generate a protein that is catalytically inert. Mlh3 DN/DN males, like fully null Mlh3 -/- males, have no spermatozoa and are infertile, yet spermatocytes have normal DSBs and undergo normal synapsis events in early prophase I. Unlike Mlh3 -/- males, mutation of the endonuclease domain within MLH3 permits normal loading and frequency of MutLγ in pachynema. However, key DSB repair factors (RAD51) and mediators of CO pathway choice (BLM helicase) persist into pachynema in Mlh3 DN/DN males, indicating a temporal delay in repair events and revealing a mechanism by which alternative DSB repair pathways may be selected. While Mlh3 DN/DN spermatocytes retain only 22% of wildtype chiasmata counts, this frequency is greater than observed in Mlh3 -/- males (10%), suggesting that the allele may permit partial endonuclease activity, or that other pathways can generate COs from these MutLγ-defined repair intermediates in Mlh3 DN/DN males. Double mutant mice homozygous for the Mlh3 DN/DN and Mus81 -/- mutations show losses in chiasmata that approach levels observed in Mlh3 -/- males, indicating that the MUS81-EME1-regulated crossover pathway accounts for some of the increased residual chiasmata observed in Mlh3 DN/DN spermatocytes. Our data demonstrate that mouse spermatocytes bearing the MLH1-MLH3 DN/DN complex display the proper loading of factors essential for CO resolution (MutSγ, CDK2, HEI10, MutLγ). Despite these functions, mice bearing the Mlh3 DN/DN allele show defects in the repair of meiotic recombination intermediates and a loss of most chiasmata. SUMMARY The MLH1-MLH3 complex is essential for crossing over in mammalian meiosis. We generated a mutation in mouse MLH3 that alters its conserved endonuclease domain and show that it disrupts crossing over in a manner distinct from the full null Mlh3 mouse, but also results in male infertility.

My notes (saved in your browser only)

Citation neighborhood (no data yet)

We don't have any in-corpus citations linked to this paper yet. The paper's references may be in our DB but unresolved to ``paper_id`` (resolution happens at ingest when the cited DOI matches a row we already have). Run the cross-source citation reconcile pass to retry.

References (66)

Source provenance

crossref
last seen: 2026-06-21T06:39:34.607279+00:00
europepmc
last seen: 2026-05-19T01:45:01.086888+00:00
unpaywall
last seen: 2026-05-22T02:00:06.705733+00:00
License: CC-BY-NC-ND-4.0