Cloning, Bioinformatics Analysis And Expression Of Fas And FasL Gene In Yak

Fas/FasL system-mediated apotosis has been shown to be existed in varietiestissues of mammals, implicated in the peripheral clone deletion of auto reactive T cell,activation induced T cell death, cytolytic function of cytotoxic T cells, thephenomenon of “immune privilege”, the mechanism of the tumour escape and thecyclical remodeling of female reproductive organs. In this study, the Fas and FasLgenes of yak were cloned by RT-PCR method and their bioinformatics were analysisby relate softwares and network resources; In order tofurther understand the functionof Fas/FasL system, their expression were analyzed by combination of RT-PCR andimmunohistochemistry. A complete cDNA sequence in2605bp of Fas gene of yakwas obtained, which contained a969bp coding region that coded a protein whichconsisted of323amino acids. Bioinformatics analysis of the amino acids indicated asignal sequences (22amino acids) presented at the N-terminal, and a transmembranedoma in of20amino acids divided the Fas antigen into an extracellular domain and acytoplasmic domain; the extracellular domain mainly consisted of random coil andextended strand, and approximate100amino acids of cytoplasmic domain consist aα-helix domain. A complete cDNA sequence in1572bp of FasL gene of yak wasobtained, which contained114bp of5’URT,831bp of coding region that encoded aprotein of277amino acids and627bp of3’UTR. The FasL protein of yak consisted ofan extracellular region of179amino acids from99th to277th amino acid and amembrane region of23amino acids from76th to98th amino acid and a cytoplasmicregion of75amino acids from1th to75th amino acid. Both cDNA sequences anddeduced amino acids of these two genes showed highly homology with theircounterpart of other species. Fas and FasL mRNA were coexpressed in all analyzedtissues except heart, which expressed Fas mRNA alone. Noticeably, these two genesstrongly coexpressed in liver, spleen, kidney, lymphonodus, thymus, testis andplacentome. A cytoplasmic form of FasL protein was detected in several cell types ofvarious organs. The results suggested that Fas and FasL more conservative inevolution. These two genes expression in various tissues in yak and their expression had a relative relationship, they strongly expressed together or weakly expressedtogether. Otherwise, in addition to st rongly coexpressing in lymphoid organs andimmune privilege sites, Fas and FasL were also strongly coexpressed in kidney andliver that were neither lymphoid nor immune privilege site, suggested that Fas/FasLsystem was more complicated than previously thought. In addition, the cytoplasmicform of FasL existed in several cell types of various organs of yak and its’ exactlyfunction need further investigations.