Establishment Of Mouse CSAD And TauT Gene Knockout Models And The Effects Of Taurine On Male Mouse Fertility

Taurine is rich in most tissues and plays important roles in regualing physiological functions.It has been documented that mammals gets taurine through dietary and biosynthesis,which relays on taurine transporter(TauT)and two key rate-limiting enzymes,cysteine dioxygenase(CDO),and cysteine sulfinic acid decarboxylase(CSAD).Functions of taurine are often closely related to taurine content in animal cells.However,there are few data about the expressions of CDO,CSAD and TauT,their functions and the related mechanisms in animal reproductive system.The aims of the present study were to assay the the expression of CDO,CSAD and TauT in male reproductive organs,establish the CSAD knockout(KO)and and TauT KO mouse model using TALEN(transcription active like effector nuclease)and CRISPR/Cas9(Clustered,regularly interspaced,short palindromic repeats,CRISPR-associated 9),and then investigate the effects of taurine on male fertility.The most important results include the following points.1.Expression of CDO,CSAD and TauT in mouse testis and epidydimisWestern Blot showed that CDO and CSAD were highly expressed in the caput epididymis,TauT highly expressed in testis and epididymis relatively.Immunohistochemical results showed that CDO and CSAD expresses in variety of cell types in epididymis.Immunofluorescence results showed that TauT expresses in testicular Leydig cells and epididymal sperm.Sperm TauT immunofluorescence signal located in acrosome.2.Established CSAD KO and TauT KO mouse modelHere,we developed taurine deficiency mouse model by disrupting the key synthase for taurine biosynthesis,CSAD and taurine transporter TauT.The CSAD KO and TauT KO mice showed severely declined taurine level in serum,and organs compare with wild type(WT)mice.3.Declined fertility of taurine deficient male miceDietary taurine restricted CSAD KO male mice showed further decreased taurine level in the serum and organs compare with WT control mice,and these animals were used to investigate the relationship between taurine and male fertility.The CSAD KO males showed declined fertility compared with WT control.Sperm assay showed that CSAD KO male had poor sperm motility,reduced sperm production and impaired sperm morphology compare with WT control.In vivo and in vitro fertilization assay of sperm released from cauda epidydimis showed that the sperm from CSAD KO male had lower fertilizing ability compare with WT control.Reproductive hormone assay showed that circulation testosterone significant decreased in CSAD KO male.In conclusion,CDO,CSAD and TauT highly express in testis and epidydimis,which influence taurine contents in these organs.Knockout of the mouse CSAD and TauT results in severe impairment in taurine synthesis and transportation.Restricting dietary taurine intake can further decrease taurine levels in CSAD KO male mice.Taurine deplete in male mice lead to impaired fertility which was due to multiple aspect of reproductive,including sperm motility,sperm production,sperm morphology,sperm fertilizing ability and testosterone secretion.These results suggest that taurine may play an important role in the male reproductive process.