| Chinese Cashmere goat plays an important strategic role in the international market for producing cashmere as China is the world’s largest cashmere production and export country.Recently,the contradiction is increasingly among the demand of high quality and quantity,and intensified environmental desertification.It is urgent to uncover the mechanisms for cashmere hair follicle growth,and find an environmentally friendly technique to promote cashmere yield.It is a fast,low-cost and efficient technique by artificially shortened photoperiod increasing cashmere yield.However,the effect of the technology in different breeds of Cashmere goats is different and the molecular mechanism remains unclear.To investigate comprehensively the intrinsic molecular mechanisms of hair follice cycling and the effect of a short photoperiod on hair follicle,we measured cashmere length,yield and hormone level of Inner Mongolian Cashmere goats under different light conditions.Then,we compared with the hair follicle morphogenesis in different development phases under shortened photoperiod and natural condition.Moreover,we performed RNA-seq analysis of skin tissues from six Cashmere goats at seven time points,including three goats under shortened photoperiods versus three under natural conditions to identify the key factors related to cashmere growth.The aim of this project is to find theoretical basis for the increasing cashmere yeild technology by shortened photoperiod,and it is of great significance to the popularization and optimization of the main producing areas of Cashmere goats in China.Analysis of the skin morphology of Cashmere goats at different developmental stages showed that:(1)Under the natural photoperiod condition,the hair follicle development period of Inner Mongolia Arbas-type Cashmere goats can be subdivided accurately into four stages: proangen period(May-July),full growth period(August-December),categen(January)and telogen(Febrary-April).(2)Shortened photoperiod treatment promoted the anagen phase in June with two months ahead of natural photoperiod.And hair follicle entered the categen and telogen as the same time with the control group,indicating that shortened photoperiod can prolong the hair follicle growth period.The levels of melatonin and prolactin in the peripheral blood of different hair follicle development period showed that:(1)the melatonin level of the test group was slightly increased in June under the shortened photoperiod,while the control group decreased sharply.(2)The prolactin level is lower significantly for the test group than control group under shortened photoperiods.This may have a certain role in prolonging the growth of hair follicle cycle.(3)Melatonin and prolactin showed significant cyclical changes as the growth of secondary follicles cycles,but there was no significant difference in hormone levels between the test and control groups because of individual differences.Transcriptional analyses on 20 skin samples from the control group at seven time points during a complete secondary hair follicle(SHF)growth cycle showed that:(1)Principal component analysis analysis divided these twenty samples into four clusters,exactly matching the four stages of secondary hair follicle cycling(proanagen,anagen,catagen and telogen),suggesting that the transcriptional changes in secondary hair follicle cycling are consistent with the morphological alterations;(2)A total of 1,713 differentially expressed genes(DEGs)were identified between transitions I-IV,and the number of DEGs in transitions I and III were remarkably larger than those in II and IV(catagen-telogen transition: 962;early anagen-anagen transition: 744);(3)In transition I,332 out of 744 differentially expressed genes also showed differential expression in transition III,including 25 transcription factors,however,the direction of expression changes was mostly opposite for these differentially expressed genes;(4)The hierarchical clustering analysis on all 1,713 differentially expressed genes showed eight gene clusters(K1-K8),of which K1,K5 and K8 included 62% genes,and the expression pattern was periodical.Go ontology analysis found overrepresented categories including skin development,hair follicle cycle and cell proliferation suggesting those genes may play an important role in regulating hair follicle cycle growth.Transcriptional analyses on 40 skin samples from the test and control groups at seven time points during a complete secondary hair follicle growth cycle showed that:(1)Shortened photoperiod treatment promoted the anagen phase in June,which is consistent with the morphological observations;(2)A total of 951 differentially expressed genes were identified between the test and control groups at each of the seven time points,the largest divergence was identified in June(597),the majority of them(246/597)displayed periodic expression patterns,and go ontology analysis found overrepresented categories including hair molting and nail development.(3)Eight transcription factors displayed SHF-higher or specific expression,most of them have been confirmed to be essential regulators of hair follicle growth and development for humans and mice.(4)Csdc2 silencing in mouse fibroblast cells resulted in the decreased mRNA expression of two key hair follicle factors(p < 0.05),Foxn1 and Notch1 after 72 h of siRNA treatment,which led to decreased cell numbers and density(p < 0.01),suggesting that Csdc2 may be a new regulator in hair follicle cycling.In this study,from the histological morphology and molecular level,we studied systematically the mechanism of shortened photoperiod on cashmere in Inner Mongolia Cashmere goats,and found some key genes and new transcription factors to regulate hair follicle cycle.We classified the hair folliclle cycle much more accurate.This study provides a theoretical basis for short photoperiod increasing cashmere yield which is of great significance to improve cashmere yield of Cashmere goats. |
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