shani mutation in mouse affects splicing of Spata22 and leads to impaired meiotic recombination

Recombination is crucial for chromosome pairing and segregation during meiosis. SPATA22, along with its direct binding partner and functional collaborator, MEIOB, is essential for the proper repair of double-strand breaks (DSBs) during meiotic recombination. Here, we describe a novel point-mutated allele (shani) of mouse Spata22 that we isolated in a forward genetic screen. shani mutant mice phenocopy Spata22-null and Meiob-null mice: mutant cells appear to form DSBs and initiate meiotic recombination, but are unable to complete DSB repair, leading to meiotic prophase arrest, apoptosis and sterility. shani mutants show precocious loss of DMC1 foci and improper accumulation of BLM-positive recombination foci, reinforcing the requirement of SPATA22-MEIOB for the proper progression of meiotic recombination events. The shani mutation lies within a Spata22 coding exon and molecular characterization shows that it leads to incorrect splicing of the Spata22 mRNA, ultimately resulting in no detectable SPATA22 protein. We propose that the shani mutation alters an exonic splicing enhancer element (ESE) within the Spata22 transcript. The affected DNA nucleotide is conserved in most tetrapods examined, suggesting that the splicing regulation we describe here may be a conserved feature of Spata22 regulation.