SYCP1 (synaptonemal complex protein 1) is a major structural component of the synaptonemal complex, a protein scaffold that assembles between homologous chr1 during meiotic prophase 1. As a key transverse filament protein, SYCP1 is essential for proper chromosome 1, homologous chromosome 1, and meiotic recombination during oocyte and spermatocyte development 2. SYCP1 exists as tetramers that form a protein lattice; the central element protein SYCE3 remodels this lattice by converting SYCP1 tetramers into heterotrimers, disrupting the original assembly interface and establishing a new integrated SYCP1-SYCE3 lattice that recruits additional central element complexes 3. SYCP1 transcription is stage-specifically regulated during meiosis, initiated at leptotene-zygotene stages with distinct regulatory mechanisms in male versus female gonads 4. Mutations in SYCP1 cause male infertility; a homozygous frameshift mutation (c.2892delA) resulted in severe oligozoospermia through impaired DNA binding and reduced capacity to repair meiotic double-strand breaks 1. Additionally, HSF5 regulates SYCP1 transcription during meiotic progression, and HSF5 deficiency causes spermatogenic arrest partly through reduced SYCP1 expression 2. Pathogenic SYCP1 variants are increasingly recognized as causes of non-obstructive azoospermia and spermatogenic arrest 5.