Zrsr2, zinc finger CCCH-type, RNA binding motif and serine/arginine rich 2, is an essential splicing factor. It is part of both the major and minor spliceosomes, recognizing 3'-intron splice sites, especially crucial for U12-type introns which represent a small fraction of human introns. It is involved in RNA and protein processing pathways, and its proper function is of great biological importance [2].

Zrsr2 mutant mouse lines showed blood cell anomalies, and in some lines, oogenesis was blocked at the secondary follicle stage. RNA-seq indicated aberrant gene expression and alternative splicing events, with enrichment of U12-type intron retention in Zrsr2 mutant secondary follicles [1]. In zebrafish, zrsr2-knockout embryos displayed multiple developmental defects and died after 8 days post-fertilization, along with down-regulation of essential metabolic pathways and aberrant retention of minor introns in many genes [2]. In mice, concurrent Zrsr2 mutation and Tet2 loss promoted myelodysplastic neoplasm (MDS), presenting with peripheral blood cytopenia, splenomegaly, and multi-lineage dysplasia [3].

In conclusion, Zrsr2 is vital for splicing, especially of U12-type introns, and plays a significant role in follicular development, embryonic development, and hematopoiesis. The study of Zrsr2 using knockout mouse models has provided insights into its functions in these processes and its association with diseases like MDS [1,2,3].