Mouse models for the study of SPO11 splicing isoforms

Abstract

Meiotic recombination is initiated by the formation of programmed DNA double‐strand breaks (DSB) catalyzed by the SPO11 protein. This protein is widely conserved and homologs have been isolated from mouse and human. There are many alternatively spliced variants of SPO11 and two major forms (α and β) are readily detected in testes.In males, the two major isoforms have distinct expression kinetics. Spo11 β transcripts (including all 13 exons) are found in early stages of prophase I whereas Spo11 α transcripts (exon 2 skipped) are mainly synthesized past pachytene stage. Since breaks are introduced in early prophase, the simplest model suggests that the larger form of SPO11 is the catalytic form that generates the DSB, while the smaller form has an alternative role in late prophase.To address the role of SPO11 α we have generated an isoform specific transgenic mouse by deleting exon 2 in a BAC containing a genomic region that includes the SPO11 locus. We were able to detect overexpression of SPO11 α in a wild type mouse carrying 7 copies of the transgene and found that overepression does not affect meiotic progression.We found that even though SPO11 α is expressed in a Spo11−/−Spo11α+/− transgenic mouse, it fails to rescue the meiotic arrest characteristic of the Spo11 KO mouse. This favors the notion of SPO11 β as the isoform responsible of introducing the breaks.Supported by the Intramural Research Program of the NIDDK, NIH.