The myometrium, composed of the inner circular muscle (CM) and outer longitudinal muscle (LM), is crucial in establishing and maintaining early pregnancy. However, the molecular mechanisms involved are not well understood. In this study, we identified the transcriptomic features of the CM and LM collected from the mesometrial (M) and anti-mesometrial (AM) sides of the pig uterus on day 18 of pregnancy during the placentation initiation phase. Some genes in the cellular zinc ion level regulatory pathways (MT-1A, MT-1D, MT-2B, SLC30A2, and SLC39A2) were spatially and highly enriched in uterine CM at the mesometrial side. In addition, the histone modification profiles of H3K27ac and H3K4me3 in uterine CM and LM collected from the mesometrial side were characterized. Genomic regions associated with the expression of genes regulating the cellular zinc ion level were detected. Moreover, six highly linked variants in the H3K27ac-enriched region of the pig SLC30A2 gene were identified and found to be significantly associated with the total number born at the second parity (P < 0.05). In conclusion, the genes in the pathways of cellular zinc homeostasis and their regulatory elements identified have implications for pig reproduction trait improvement and warrant further investigations.

子宫肌层由内环肌（CM）和外纵肌（LM）组成，对于建立和维持早期妊娠至关重要。然而，所涉及的分子机制尚不清楚。在这项研究中，我们鉴定了在胎盘启动阶段妊娠第 18 天从猪子宫的系膜 (M) 和抗系膜 (AM) 侧收集的 CM 和 LM 的转录组特征。细胞锌离子水平调节途径中的一些基因（MT-1A、MT-1D、MT-2B、SLC30A2和SLC39A2）在子宫CM的系膜侧空间上高度富集。此外，还对从子宫系膜侧收集的子宫 CM 和 LM 中 H3K27ac 和 H3K4me3 的组蛋白修饰谱进行了表征。检测到与调节细胞锌离子水平的基因表达相关的基因组区域。此外，在猪SLC30A2基因的H3K27ac富集区中鉴定出6个高度连锁的变异，并发现它们与第二胎的出生总数显着相关（P  <0.05）。总之，细胞锌稳态通路中的基因及其调控元件对猪繁殖性状的改善具有重要意义，值得进一步研究。