Zrsr2 Knockout mouse models

Minor spliceosome function requires Zrsr2, the mouse ortholog of human ZRSR2, a zinc finger and RS domain protein that serves as the U2AF1-like 3 prime splice site recognition factor for the U11 and U12 dependent spliceosome, enabling excision of the roughly seven hundred U12-type introns found in genes such as Mapk1 and Parp1. Loss-of-function mutations and deletions, rather than hotspot missense changes, characterize its role in myelodysplastic syndrome and chronic myelomonocytic leukemia, where the consequence is selective U12-type intron retention and, unusually among spliceosome genes, a strong male predominance because the locus is X-linked and escapes X inactivation. Allele design therefore favors conditional nulls rather than knockins, with Vav1-cre or Mx1-cre induction and explicit attention to sex and dosage. Notably, real redundancy exists in mouse through the intronless autosomal retrogene Zrsr1, whose expression can mask intron retention phenotypes, so compound Zrsr1 and Zrsr2 conditional genetics is advisable before concluding minor spliceosome output is intact.

Global Zrsr2 deletion answers broad mechanism questions quickly. If timing or site matters, conditional alleles are a natural next step after the null is characterized.