Comparative transcriptomic analyses reveal key genes underlying melanin distribution during embryonic development in geese (<i>Anser anser</i>)

1. Melanin distribution typically exhibits a gradient dilution along the dorsal-ventral axis of the body, including in domestic geese. However, the specific genes and molecular mechanisms responsible for this melanin distribution pattern remain incompletely understood. 2. The transcriptomic comparisons were conducted at three embryonic stages, specifically on embryonic d 15 (E15), 22 (E22), and 29 (E29), between the pigmented dorsal skin and the depigmented distal foot. 3. Differentially expressed genes (DEGs) associated with melanin synthesis were identified, particularly <i>TYR</i>, <i>TYRP1</i>, and <i>EDNRB2</i>, which exhibited significantly higher expression levels in the dorsal skin at E15 and E22. However, expression levels significantly decreased in later stages (E29). 4. The <i>ASIP</i> gene showed remarkably high-expression levels in the distal feet compared to the dorsal skin post-E22 stage (log₂FC: 5.31/6.88 at E22/E29). Gene Ontology (GO) enrichment analysis detected eight terms associated with melanin synthesis and melanosome formation (<i>p</i> &lt; 0.05), including melanosome membrane (GO: 0033162) and melanin biosynthetic process (GO: 0042438). Additionally, KEGG pathway analysis showed significant enrichment of the melanogenesis pathway (hsa004916) at d 22 (E22).1. 黑色素分布通常沿躯体背-腹轴呈现梯度递减现象，家鹅亦不例外。然而，调控该黑色素分布模式的具体基因及分子机制尚未完全阐明。 2. 本研究选取三个胚胎阶段，即胚胎发育第15天（E15）、第22天（E22）与第29天（E29），对有色背侧皮肤与无色素的远端足部组织进行转录组比较分析。 3. 研究鉴定出与黑色素合成相关的差异表达基因（DEGs），其中以TYR、TYRP1与EDNRB2基因最为显著，这些基因在E15与E22阶段的背侧皮肤中表达水平显著更高，但在后续的E29阶段其表达水平显著下调。 4. ASIP基因在E22阶段之后的远端足部中，相较于背侧皮肤呈现显著高表达（E22、E29阶段的log₂折叠变化分别为5.31、6.88）。基因本体（Gene Ontology，GO）富集分析共筛选出8个与黑色素合成及黑素体形成相关的条目（P<0.05），包括黑素体膜（GO: 0033162）与黑色素生物合成过程（GO: 0042438）。此外，京都基因与基因组百科全书（Kyoto Encyclopedia of Genes and Genomes，KEGG）通路富集分析显示，在E22阶段黑色素生成通路（hsa004916）呈现显著富集。