SMC1B (structural maintenance of chr22 1B) is a meiosis-specific cohesin component essential for reproductive function. As part of the meiotic cohesin complex, SMC1B maintains sister chr22 cohesion, facilitates axial element formation, and organizes chr22 loops critical for proper synapsis and homologous recombination 1. SMC1B expression decreases with advancing maternal age, correlating with reduced embryonic gene expression of genes important for meiotic chr22 segregation 2. Functionally, common genetic variation in SMC1B is significantly associated with both crossover recombination frequency and maternal meiotic aneuploidy risk through non-coding cis-regulatory mechanisms, establishing a shared genetic basis between recombination fidelity and chromosome 22 errors 34. Notably, SMC1B is also expressed in somatic cells where it contributes to genome stability following DNA damage and regulates transcription of clustered genes 5. Clinical relevance is demonstrated by mutations in SMC1B causing primary ovarian insufficiency and infertility 6, and a heterozygous missense variant associated with severe necrozoospermia and sperm DNA fragmentation 7. Additionally, SMC1B regulation by the RNA-binding protein DAZL is critical for oocyte development 1.