The Janus kinase (JAK)–signal transducer and activator of transcription (STAT) (JAK–STAT) pathway is shown to restrain the hair follicles in catagen and telogen and prevent anagen reentry in murine hair follicle cycling. The early roles of JAK-STAT pathway genes in skin development remain uncharacterized in mouse and chicken models. Here, we revealed the expression patterns of three JAK-STAT pathway genes (JAK1, JAK2, and TYK2) in chicken embryonic skin at E6–E10 stages which are key to feather follicle morphogenesis. Multiple sequence alignment of the three genes from chicken and other species all showed a closely related homology with birds like quail and goose. Whole mount in situ hybridization (WISH) revealed weak expression of JAK1, JAK2, and TYK2 in chicken skin at E6 and E7, and followed with the focally restricted signals in the feather follicles of neck and body skin located dorsally at E8 for JAK1, E9 for TYK2 and E10 for JAK2 gene. All three genes displayed stronger expression in feather follicles of neck skin than that of body skin. The expression levels of JAK1 and TYK2 were much stronger than those of JAK2. Quantitative real-time PCR (qRT-PCR) analysis revealed the increased expression tendency for JAK2 both in the neck and body skin from E6 to E10, and the much stronger expression in neck and body skin at later stages (E8-E10) than earlier stages (E6 and E7) for JAK1 and TYK2. Overall, these findings suggest that JAK1 and TYK2, not JAK2 are important to specify the feather follicle primordia, and to arrange the proximal–distal axis of feather follicles, respectively, during the morphogenesis of feather follicles in embryonic chicken skin.

Janus激酶（JAK）–信号转导子和转录激活剂（STAT）（JAK–STAT）通路显示出可抑制毛囊中的毛发生长和端粒，并防止鼠毛囊循环中的生长期再进入。在小鼠和鸡模型中，JAK-STAT途径基因在皮肤发育中的早期作用仍未表征。在这里，我们揭示了E6–E10阶段鸡胚皮肤中三个JAK-STAT通路基因（JAK1，JAK2和TYK2）的表达模式，这是羽毛卵泡形态发生的关键。来自鸡和其他物种的三个基因的多序列比对均显示与鹌鹑和鹅等鸟类密切相关的同源性。整个原位杂交（WISH）显示JAK1的弱表达，JAK2和TYK2在鸡皮中分别位于E6和E7，JAK1，J9和TYK2分别位于E8和E10，JAK2基因位于E10背侧位于颈部和身体皮肤的羽毛毛囊中。这三个基因在颈部皮肤的毛囊中均显示出比人体皮肤更强的表达。JAK1和TYK2的表达水平明显高于JAK2。实时定量PCR（qRT-PCR）分析显示JAK2表达趋势增加从E6到E10在颈部和身体皮肤中的表达，并且对于JAK1和TYK2在后期（E8-E10）中的脖子和身体皮肤的表达要强于早期阶段（E6和E7）。总体而言，这些发现表明，JAK1和TYK2而不是JAK2对于指定鸡胚毛囊的形成过程中的毛囊原基和分别排列毛囊的近端-远端轴很重要。