Supplementary Material for: Comparative Organization and Gene Expression Profiles of the Porcine Pseudoautosomal Region

The pseudoautosomal region (PAR) has important biological functions in spermatogenesis, male fertility and early development. Even though pig (<i>Sus scrofa</i>, SSC) is an agriculturally and biomedically important species, and its genome is sequenced, current knowledge about the porcine PAR is sparse. Here we defined the PAR in SSCXp/Yp by demarcating the sequence of the pseudoautosomal boundary at X:6,743,567 bp in intron 3-4 of <i>SHROOM2</i> and showed that <i>SHROOM2</i> is truncated in SSCY. Cytogenetic mapping of 20 BAC clones containing 15 PAR and X-specific genes revealed that the pig PAR is largely collinear with other mammalian PARs or Xp terminal regions. The results improved the current SSCX sequence assembly and facilitated distinction between the PAR and X-specific genes to study their expression in adult and embryonic tissues. A pilot analysis showed that the PAR genes are expressed at higher levels than X-specific genes during early development, whereas the expression of PAR genes was higher at day 60 compared to day 26, and higher in embryonic tissues compared to placenta. The findings advance the knowledge about the comparative organization of the PAR in mammals and suggest that the region might have important functions in early development in pigs.

假常染色体区域（pseudoautosomal region, PAR）在精子发生、雄性生育及早期发育过程中具有重要生物学功能。尽管猪（家猪，Sus scrofa，SSC）是兼具重要农业与生物医药价值的物种，且其基因组已完成测序，但目前学界对猪假常染色体区域的认知仍较为匮乏。本研究通过划定位于SHROOM2基因第3-4内含子中X染色体坐标6,743,567 bp处的假常染色体边界序列，明确了猪X/Y染色体短臂（SSCXp/Yp）上的假常染色体区域，并证实SHROOM2基因在猪Y染色体上存在截短变异。对包含15个假常染色体区域基因及X染色体特异性基因的20个细菌人工染色体（Bacterial Artificial Chromosome, BAC）克隆进行细胞遗传学定位后发现，猪假常染色体区域与其他哺乳动物的假常染色体区域或X染色体短臂末端区域具有高度共线性。本研究结果优化了当前猪X染色体的序列组装，并有助于区分假常染色体区域与X染色体特异性基因，以研究二者在成年及胚胎组织中的表达模式。初步分析显示，在早期发育阶段，假常染色体区域基因的表达水平高于X染色体特异性基因；与妊娠第26天相比，妊娠第60天的假常染色体区域基因表达量更高，且胚胎组织中的表达水平显著高于胎盘组织。本研究成果拓展了学界对哺乳动物假常染色体区域比较基因组组织的认知，并提示该区域可能在猪的早期发育过程中发挥关键生物学功能。