Study On The Development And Regulatory Mechanism Of The Knob On Goose Forehead

The forehead knob is one of the head appearance features to distinguish between Hong Yan(with forehead knob)and gray goose(without forehead knob).It is found that the forehead knob is composed of skin and bones.However,the researches on the forehead knob of goose were mainly focused on adult geese,and there are few studies on the development and regulation of forehead knob.Therefore,in this study,Sichuan white goose(SW,Anser cygnoides)with forehead knob and Landes goose without forehead knob(LD,Anser anser)were used as experimental animal.Phenotypic determination and DR scanning were used to analyze the morphological changes of forehead knob of SW and LD.The bone tissues of forehead knob of LD/SW were collected and analyzed by HE staining and transcriptome sequencing(RNA-Seq).The differences of bone histology and transcriptome expression profiles at the forehead knob of the two breeds were compared to reveal the development laws of forehead knob and its regulation mechanism.The main results are as follows:(1)The morphological results showed that the forehead knob bone of SW gradually protruded at 10 ～ 30 W and formed a loose porous spherical structure at 30 W.In addition,the bone mineral density of the forehead knob of SW reached its peak at 20 W,while no protuberance was found in LD.The bone mineral density of the forehead knob increased significantly with the increase of age.(2)The analysis of forehead knob bone composition showed that the forehead knob bone of LD was mainly composed of bone,cartilage,dense layer,and bone marrow cavity at 0 W,6 W,10 W,and 30 W.SW was the same as LD at 0 W,6 W,and 10 W,but lost cartilage and dense layer at 30 W.The bone thickness of SW goose was significantly higher than that of LD at 0 W(P < 0.01),and significantly smaller than that of LD at 6 W(P < 0.01).The skeletal dense layer of SW was significantly thicker than that of LD at 0 W(P < 0.05),and extremely significantly thicker than that of LD at 6 and 10 W(P < 0.01).(3)Transcriptome sequencing analysis showed that 1904,1268,2413,998,947,and2303 differentially expressed genes(Differentially expressed genes,DEGs)were identified from 0 W vs.6 W,0 W vs.10 W,0 W vs.30 W,6 W vs.10 W,6 W vs.30 W,and 10 W vs.30 W in the bone tissue of SW forehead knob.The DEGs of these six groups were significantly enriched in cytokine-cytokine receptor interaction and Wnt signal pathway.In the bone tissue of LD forehead knob,376,638,3023,1428,2316,and 3153 DEGs were identified from 0 W vs.6 W,0 W vs.10 W,0 W vs.30 W,6 W vs.10 W,6 W vs.30 W,and10 W vs.30 W,respectively.Functional enrichment analysis showed that the DEGs of these six groups were significantly enriched in Wnt and TGF-β signal pathways except 0W vs.10 W.In addition,1065,1486,1037,and 2238 DEGs were detected in the bone tissue of forehead knob between SW and LD at their 0 W,6 W,10 W,and 30 W,respectively.Functional enrichment analysis showed that the DEGs of these four groups were significantly enriched in neuroactive receptor-ligand interaction,calcium signal,and metabolic pathway.(4)The results of weighted gene co-expression network(WGCNA)analysis showed that the genes in red,brown,blue,sky blue,and turquoise modules were all related to the bone development of goose forehead knob.The functional enrichment analysis of the genes in the five modules showed that the genes in red and brown modules were mainly involved in cell proliferation;the genes in blue module were mainly involved in transcriptional regulation;the genes in sky blue and turquoise modules were closely related to the forehead knob of bone development and cartilage destruction.Further proteinprotein interaction(PPI)analysis showed that PCNA,CCNB2,CCNB1,GSTO1,GSTA3,GPX1,GPX2,GPX3,and ACTB genes may play a key role in regulating the development of forehead knob bone.In summary,this study revealed the development law and molecular regulation of forehead knob bone in goose breeds with and without forehead knob,and cytokinecytokine receptor interaction,Wnt signal pathway,TGF-β signal pathway,neuroactive receptor-ligand interaction,calcium signal pathway,and metabolic pathway may be the key pathways to regulate the forehead knob in geese.These results provide a theoretical basis for the breeding of forehead knob in geese.