山羊品种间体细胞核移植研究

萨能奶山羊是著名的奶用山羊品种,波尔山羊则是世界著名的肉用山羊品种.为了研究波尔山羊体细胞在奶山羊卵母细胞中的去分化,我们将成年波尔山羊的颗粒细胞或耳皮肤成纤维细胞作为供核细胞(试验组),移入奶山羊中Ⅱ期的去核卵母细胞透明带下,经电融合和离子霉素与6-二甲基氨基嘌呤(6-DMAP)激活,直接移入同期发情奶山羊输卵管或经体内培养,将发育的重构胚移人同期发情羊子宫内.妊娠早期作B超诊断,确立妊娠的观察至足月.同时将奶山羊的35日龄胎儿成纤维细胞作供核细胞(对照组),按试验组同样方法处理,将重构胚直接移入同期发情的奶山羊输卵管内.结果试验组,波尔羊颗粒粒细胞与耳皮肤成纤维细胞的融合率分别为78.2%(115/147)、57.4%(116/202),重构胚卵裂率为85.8%(115/134),桑椹胚、囊胚的发育率38.8%(52/134),早期妊娠三头,分别于妊娠40、60、60日龄终止妊娠.对照组,融合率为89.5%(136/152),早期妊娠率为42.9%(6/14),四头受体足月分娩,产四头公羊羔,其中三头存活,一头分娩时死于肺不扩张,并体重过大,显示胎儿过大综合症.经基因型鉴定证实,这四头克隆羔羊均源于同一胎儿成纤维细胞系.以上结果表明,波尔羊体细胞核在奶山羊卵母细胞中能够去分化,并维持一定程度的发育.     

继代核移植能成倍提高来自奶山羊卵胞质体的异种间核移植重构胚的发育率

为了提高异种间核移植重构胚的发育率,本研究以体内排放的奶山羊成熟卵为供胞质的受体细胞,以人、兔、波尔山羊等的异种或亚种体细胞的原代核移植（Primary Somatic Cell Nuclear Transfer,PSCNT）重构早胚（8-16细胞期）的卵裂球作供核体,观察经亚种或异种卵胞质体短期“修饰”的核再移植产生的继代（Secondary SCNT,SSCNT）重构胚的着床前发育潜能。结果：人、兔、波尔山羊的继代桑椹／囊胚发育率均显著地高于其PSCNT胚胎（人,14．81％VS．7．79％;兔,23．53％VS．12．50％;波尔羊,55．35％VS．24．53％）;这些早胚的各阶段发育时程仍遵循供核体动物正常受精卵的发育时程。结果启示：奶山羊成熟卵胞质对异种体细胞核亦具一定的去分化能力,能支持重构胚发育到囊胚;异种重构胚的发育特征是由供体核所决定的;继代核移植几乎能够成倍提高异种间重构胚的着床前发育率,提示核的去分化完全是在母型信息主导的调控之下完成的,而进一步发育的时序似乎是由核决定的：成倍延长在含母型信息主导调控环境中的时间能成倍提高SCNT重构胚的着床前发育率。     

奶山羊转基因供核细胞的再饥饿对核移植胚胎发育的影响

为提高转基因奶山羊体细胞核移植胚胎早期发育率,将经转染外源基因的山羊胎儿成纤维细胞经饥饿培养(含0．5％FCS的DMEM)5天后分成两部分：第一部分细胞-80℃或液氮冻存,试验前复苏后直接用作供核细胞(试验组Ⅰ),或复苏后恢复培养(含10％FCS的DMEM)2-5天后再饥饿5天用作供核细胞(试验组Ⅱ);第二部分细胞作传代培养(含10％FCS的DMEM)2天后再饥饿5天用作供核细胞(试验组Ⅲ)。将上述不同处理的供核细胞进行细胞周期与存活率的检测,并将该供核细胞移入去除遗传物质的山羊MⅡ期卵母细胞的卵周隙内,经电融合、化学激活后,将核移植(NT)胚胎经0．8％琼脂糖包理后移入临时寄母输卵管内,培养6天后回收并观察NT胚胎的早期发育。结果,试验组Ⅱ所用供核细胞中G0／G1期细胞所占比例及其存活率分别为95．68％、99．9％,均显著地高于试验组Ⅰ(88、66％、80％);试验组Ⅱ的桑椹及囊胚期NT胚胎的发育率(66．09％)显著地高于试验组Ⅰ(22．00％)与试验组Ⅲ(50．5l％)。将以上发育的NT胚胎分别移入同步发情的受体后,35天作B超妊娠诊断,试验组Ⅱ的受体妊娠率为45．83％,显著地高于试验组Ⅰ(20．00％)与试验组Ⅲ(29．58％)。流式细胞仪分析结果表明,饥饿后的供核细胞经冷冻,复苏后恢复培养2-5天,再经饥饿处理,能显著地提高G0／G1期细胞的比例及细胞存活率;应用该细胞所组建的NT胚不仅具有较高的桑椹与囊胚期发育率,而且具有较高的受体妊娠率。     

由成年转基因山羊体细胞而来的克隆山羊

在已经获得的乳腺特异性表达人促红细胞生成素 (rhEPO)成年转基因山羊 (Caprahircus)的基础上 ,取其耳尖成纤维细胞和卵巢颗粒细胞 ,进行体外传代培养 ,然后将这种培养的转基因山羊的体细胞移入去核的处于第Ⅱ次减数分裂中期的卵母细胞中 ,并进行电融合 ,构建重构胚胎 ,重构胚胎在体内培养 6d ,再将发育至囊胚或桑椹胚的重构胚胎移入同步情期的寄母羊子宫内。结果 ,有 2只寄母羊妊娠并最终产下 2只成活的克隆山羊。她们分别来自同一成年母羊的耳尖成纤维细胞和卵巢颗粒细胞。克隆羊经PCR RFLP图谱分析显示 :以克隆羊组织DNA为模板的PCR产物与相应的提供体细胞的基因羊的PCR产物的酶切图谱完全一致 ;并且经PCR对外源hEPO基因检测表明 2只克隆山羊均携带hEPO外源基因。由此证明获得了转基因成年体细胞的克隆山羊     

家兔供体细胞的发育周期与重构胚发育的关系

采用血清饥饿法处理体外培养的兔子胎儿成纤维细胞,并将其作为供体细胞移入去核卵母细胞内构建重构胚胎。检查供体细胞的细胞周期对重构胚的融合率、分裂率和着床率的影响。实验结果表明：培养基中血清含量在0．5％的情况下,G0／G1期的细胞比例由正常培养条件下(培乔液中含有10％FCS)的73．2％明显地增加到86％以上。饥饿1～3天的细胞作为供体细胞构建重构胚时,可明显提高重构胚的融合率,但是不同的饥饿时间其融合率并无显著的差异。饥饿处理可明显增加重构胚的分裂率,以饥饿处理3天为最佳。     

兔体细胞核移植的初步研究

实验以兔胎儿成纤维细胞为核供体,对兔体细胞核移植技术的融合,激活和发育等环节进行了初步研究。实验通过比较不同电场强度对兔2细胞胚胎卵裂球融合以及卵母细胞激活的影响,证实200和260V/mm的电场强度可有效地诱导2细胞胚胎的融合和兔卵母细胞的孤雌激活。然后将200和260V／mm电场强度用于体细胞核移植,融合率分别为44．4％和48．4％,卵裂率分别为58．8％和53．8％,桑椹胚／囊胚发育率分别为5．9％和5．5%。但112枚核移植胚胎移植到5只受体后没有幼子出生。结果表明,实验中所建立的程序至少可以支持兔体细胞克隆胚胎的早期发育。     

猪体细胞核移植重构胚的体外发育

以卵丘细胞为核供体细胞组成重构胚,卵裂率达到56．7％,发育至桑椹胚率达到11．7％,囊胚率为6．7％,显著高于成纤维细胞重构胚（P＜0．05）。本文还研究了卵母细胞的采集方法、激活程序和卵龄对卵丘细胞核移植重构胚体外发育的影响。以血清饥饿法将卵丘细胞诱导G0/G1期,抽吸法／解剖法采集卵母细胞,体外培养33－44h,将卵丘细胞放至去核卵母细胞的卵周隙中,重构胚以钙离子载体A23817或电脉冲结合6－DMAP激活处理,体外培养6d。研究表明,卵母细胞采集方法、激活液中细胞松驰素（CB）、激活程度并不影响重构胚的发育（以卵龄44h的卵母细胞为受体）;而以电脉冲结合6－DMAP激活处理能提高重构胚发育能力（以卵龄33h的卵母细胞为受体）（P＜0．05）。本研究显示,以电脉冲结合6－DMAP激活卵丘细胞重构胚,体外能发育至囊胚。     

影响猪体细胞核移植重构胚体外发育的若干因素

以卵丘细胞为核供体细胞组成重构胚,卵裂率达到56．7％,发育至桑椹胚达11．7％、孵化囊胚率为6．7％,显著高于成纤维细胞组成的重构胚（P＜0．05）。我们研究了卵母细胞的采集方法,激活方法和卵龄对卵丘细胞核移植重构胚体外发育的影响。以血清饥饿法将卵丘细胞诱导至G0或G1期,抽吸法／解剖法采集卵母细胞,体外培养33或44h,将卵丘细胞置于去核卵母细胞的卵周隙中,重构胚以钙离子载体A23817或电泳冲结合6－DMAP激活处理,体外培养6天,结果表明,卵 母细胞采集方法、激活液中细胞松弛素（CB）并不影响重构胚的发育（以卵龄44h的卵母细胞为受体）;而以电脉冲结合6－DMAP激活处理能提高重构胚发育能力（以卵龄33h的卵母细胞为受体）（P＜0．05）。本研究显示,以电脉冲结合6－DMAP激活卵丘细胞重构胚,能在体外发育至囊胚。     

成年耳细胞克隆山羊(Capra hircus)

繁殖季节采集关中奶山羊卵巢,采集获得可用卵母细胞5.5枚/卵巢(1815/330).经约20 h 成熟培养,第一极体排放率66.17%(1201/1815).将有类第二极体排出结构的成熟卵母细胞去核,去核率75.44%(906/1201).培养济宁青山羊耳部皮肤成纤维细胞传2代后液氮冷冻,解冻培养3~6代,用0.5% FBS饥饿2~10 d作为供体细胞.利用卵母细胞胞质内注射法将分离的供体细胞核胞体注入到去核卵母细胞内,注核成功率98.12%(889/906).克隆胚胎用5μmol/L 离子酶素激活4.5 min, 在含2 mmol/L 6-二甲氨基嘌呤(6 dime-thylaminopurine,6-DMAP)的培养液中培养3 h,然后在mCR1aaBF培养液中培养36 h,卵裂率76.69%(645/841).其中由未经冷藏处理供体细胞克隆得到308枚胚胎,激活后卵裂率、4-细胞发育率、囊胚发育率分别为68.5%(211/308),59.72%(126/211)和17.46% (22/126);另外,由4℃冷藏处理24h供体细胞获得的109枚克隆胚胎,激活率、4-细胞率、囊胚率分别为72.48%(79/109),53.16%(42/79)和19.05%(8/42).统计学分析表明,4℃处理供体细胞对克隆胚胎的早期发育没有显著影响.将102枚发育至4-细胞期的克隆胚胎移植到17只自然发情2~3 d 的受体山羊输卵管,其中非冷藏供体细胞克隆的84枚胚胎移植后没有产仔.18枚冷藏体细胞克隆的胚胎移植获得1只发育足月的克隆山羊.将冷藏或非冷藏处理供体细胞克隆得到的19枚体外发育囊胚移植到自然发情6~8 d 的受体山羊,结果无一产仔.未经冷藏处理供体细胞克隆得到的18枚体外发育桑椹胚移植到自然发情5 d受体山羊后获得1只足月羔羊.微卫星引物PCR扩增结果证实2只克隆山羊来源于同一供体细胞.     

奶山羊转基因供核细胞的再饥饿对核移植胚胎发育的影响

为提高转基因奶山羊体细胞核移植胚胎早期发育率,将经转染外源基因的山羊胎儿成纤维细胞经饥饿培养(含0.5?S的DMEM)5天后分成两部分:第一部分细胞-80℃或液氮冻存,试验前复苏后直接用作供核细胞(试验组Ⅰ),或复苏后恢复培养(含10% FCS的DMEM)2-5天后再饥饿5天用作供核细胞(试验组Ⅱ);第二部分细胞作传代培养(含10% FCS的DMEM)2天后再饥饿5 天用作供核细胞(试验组Ⅲ)。将上述不同处理的供核细胞进行细胞周期与存活率的检测,并将该供核细胞移入去除遗传物质的山羊MⅡ期卵母细胞的卵周隙内,经电融合、化学激活后,将核移植(NT)胚胎经0.8%琼脂糖包理后移入临时寄母输卵管内,培养6天后回收并观察NT胚胎的早期发育。结果,试验组Ⅱ所用供核细胞中G_0/G_1期细胞所占比例及其存活率分别为95.68%、99.9%,均显著地高于试验组Ⅰ(88.66%、80%);试验组Ⅱ的桑椹及囊胚期NT胚胎的发育率(66.09%)显著地高于试验组Ⅰ(22.00%)与试验组Ⅲ(50.51%)。将以上发育的NT胚胎分别移入同步发情的受体后,35 天作B超妊娠诊断,试验组Ⅱ的受体妊娠率为45.83%,显著地高于试验组Ⅰ(20.00%)与试验组Ⅲ(9.58%)。流式细胞仪分析结果表明,饥饿后的供核细胞经冷冻,复苏后恢复培养2-5天,再经饥饿处理,能显著地提高G_0/G_1期细胞的比例及细胞存活率;应用该细胞所组建的NT胚不仅具有较高的桑椹与囊胚期发育率,而且具有较高的受体妊娠率。     

Production of cloned goats after nuclear transfer using adult somatic cells.

The developmental potential of adult somatic nuclei after nuclear transfer (NT) into enucleated, in vitro-matured oocytes was evaluated in a dwarf breed of goat (BELE: Breed Early Lactate Early). Somatic donor cells were obtained from two different sources: 1) adult granulosa cells (GCs) and 2) fetal fibroblasts. Primary GCs were obtained from follicular aspirants after laparoscopic oocyte pick-up (LOPU) and were cryopreserved immediately. Frozen aliquots of cells were thawed and cultured until confluent and were then cultured in low serum for 4 days before use in NT. Immature oocytes were obtained by LOPU and matured before enucleation and NT. Ninety-one adult GC-derived NT embryos were transferred into eight recipients, four of which were confirmed pregnant (50%) at Day 30 by ultrasound. Fifty-four male fetal fibroblast-derived NT embryos were transferred into six recipients, one of which was confirmed pregnant (17%). All pregnancies were maintained through term. Four recipients delivered seven female kids (three sets of twins) derived from the GC cultures (7.7% of embryos transferred). The other recipient delivered two male kids (3.7% of embryos transferred). Birth weights were within the normal range for dwarf goats. One female twin and one male twin died at birth; the remaining kids appeared healthy and normal. DNA analysis confirmed that the kids were genetically identical to their respective donors. These results demonstrated that adult caprine somatic cells could direct normal development after NT.     

Viable Transgenic Goats Derived from Skin Cells

The current study was undertaken to evaluate the possibility of expanding transgenic goat herds by means of somatic cell nuclear transfer (NT) using transgenic goat cells as nucleus donors. Skin cells from adult, transgenic goats were first synchronized at quiescent stage (G0) by serum starvation and then induced to exit G0 and proceed into G1. Oocytes collected from superovulated donors were enucleated, karyoplast-cytoplast couplets were constructed, and then fused and activated simultaneously by a single electrical pulse. Fused couplets were either co-cultured with oviductal cells in TCM-199 medium (in vitro culture) or transferred to intermediate recipient goat oviducts (in vivo culture) until final transfer. The resulting morulae and blastocysts were transferred to the final recipients. Pregnancies were confirmed by ultrasonography 25-30 days after embryo transfer. In vitro cultured NT embryos developed to morulae and blastocyst stages but did not produce any pregnancies while 30% (6/20) of the in vivo derived morulae and blastocysts produced pregnancies. Two of these pregnancies were resorbed early in gestation. Of the four recipients that maintained pregnancies to term, two delivered dead fetuses 2-3 days after their due dates, and two recipients gave birth to healthy kids at term. Fluorescence in situ hybridization (FISH) analysis confirmed that both kids were transgenic and had integration sites consistent with those observed in the adult cell line.     

Improvement of the nuclear transfer efficiency by using the same genetic background of recipient oocytes as the somatic donor cells in goats

We have compared the effect of the genetic background of recipient oocytes on the in vitro and in vivo development of nuclear transfer reconstructed embryos in goats. Adult fibroblast cells from Boer goats were used as donor cells, and recipient oocytes were obtained from Boer goats and Boer cross-breeds (Boer♂×Huanghuai♀). Nuclear transfer reconstructed embryos were cultured in vitro, or transferred into recipient goats. The mitochondrial origin of 2 cloned Boer goats was investigated by analysing the D-loop region based on polymorphisms via DNA sequencing. There was no significant difference in the fusion rate and cleavage rate of reconstructed embryos (P>0.05), when using Boer and cross-breeding goat oocytes as recipient cytoplast respectively. However, in vitro morula development of reconstructed embryos from Boer oocytes was significantly higher than that of cross-breeding embryos (34.1% versus 19.1%, P<0.05). There was no significant difference in the rate of pregnancy and foetus loss between the 2 breeds. However, the live-birth rate was significantly higher with Boer goat oocyte recipients than the cross-breeds (3.1% versus 0.8%, P<0.05). Mitochondrial analysis showed that the 2 cloned goats were similar to their respective oocyte donor goats, and significantly different from the nucleus donor. In conclusion, genetic background of recipient oocytes affected in vitro and in vivo development of reconstructed embryos, with the homologous background of cytoplast and nuclear donor benefiting development of reconstructed embryos. The mitochondrial origin of the 2 cloned Boer goats came from recipient oocytes, not donors.     

Generation of dwarf goat (Capra hircus) clones following nuclear transfer with transfected and nontransfected fetal fibroblasts and in vitro-matured oocytes

The developmental potential of caprine fetal fibroblast nuclei after in vitro transfection and nuclear transfer (NT) into enucleated, in vitro-matured oocytes was evaluated. Fetal fibroblasts were isolated from Day 27 to Day 30 fetuses from a dwarf breed of goat (BELE: breed early lactate early). Cells were transfected with constructs containing the enhanced green fluorescent protein (eGFP) and neomycin resistance genes and were selected with G418. Three eGFP lines and one nontransfected line were used as donor cells in NT. Donor cells were cultured in Dulbecco minimum Eagle medium plus 0.5% fetal calf serum for 4-8 days prior to use in NT. Immature oocytes were recovered by laparoscopic ovum pick-up and matured for 24 h prior to enucleation and NT. Reconstructed embryos were transferred as cleaved embryos into synchronized recipients. A total of 27 embryos derived from transgenic cells and 70 embryos derived from nontransgenic cells were transferred into 13 recipients. Five recipients (38%) were confirmed pregnant at Day 35 by ultrasound. Of these, four recipients delivered five male kids (7.1% of embryos transferred) derived from the nontransfected line. One recipient delivered a female kid derived from an eGFP line (7.7% of embryos transferred for that cell line). Presence of the eGFP transgene was confirmed by polymerase chain reaction, Southern blotting, and fluorescent in situ hybridization analyses. Nuclear transfer derivation from the donor cells was confirmed by single-strand confirmation polymorphism analysis. These results demonstrate that both in vitro-transfected and nontransfected caprine fetal fibroblasts can direct full-term development following NT.     

人-山羊异种核移植胚胎发育的初步研究

以体外分离培养的人胚胎成纤维细胞为核供体,经血清饥饿培养后,通过显微操作技术移入山羊去核卵母细胞中,采用化学方法激活重组胚.通过体外培养观察,2-细胞胚胎发育率可达51.33%,4-细胞发育率为31.42%,但发育至桑椹胚阶段的胚胎数目大大减少,仅为9.73%.虽然目前尚未能获得异种核移植囊胚,但实验结果说明山羊成熟卵母细胞可以支持人体细胞核完成重编程,人-山羊异种体细胞核移植重组胚可在体外完成其早期发育.     

Effects of interval between fusion and activation, cytochalasin B treatment, and number of transferred embryos, on cloning efficiency in goats

To improve the efficiency of somatic cell nuclear transfer (SCNT) in goats, we evaluated the effects of the interval between fusion and activation (1 to 5 h), cytochalasin B (CB) treatment after electrofusion, and the number of transferred embryos on the in vivo and in vitro development of cloned caprine embryos. The majority of the reconstructed embryos had condensed chromosomes and metaphase-like chromosomes at 2 and 3 h after fusion; cleavage and blastocyst rates from those two groups were higher (P < 0.05) than those of embryos activated 1, 4, or 5 h after fusion. Treatment with CB between fusion and activation improved in vitro and in vivo development of nuclear transfer (NT) goat embryos by reducing the fragmentation rate (P < 0.05). Although there were no significant differences in NT efficiency, pregnancy rate and kids born per recipient were increased by transfer of 20 or 30 embryos per recipient compared with 10 embryos. We concluded that CB treatment for 2 to 3 h between fusion and activation was an efficient method for generating cloned goats by somatic cell NT. In addition, increasing the number of embryos transferred to each recipient resulted in more live offspring from fewer recipients.     

In vitro oocyte culture and somatic cell nuclear transfer used to produce a live-born cloned goat

The use of an in vitro culture system was examined for production of somatic cells suitable for nuclear transfer in the goat. Goat cumulus-oocyte complexes were incubated in tissue culture medium TCM-199 supplemented with 10% fetal bovine serum (FBS) for 20 h. In vitro matured (IVM) oocytes were enucleated and used as karyoplast recipients. Donor cells obtained from the anterior pituitary of an adult male were introduced into the perivitelline space of enucleated IVM oocytes and fused by an electrical pulse. Reconstituted oocytes were cultured in chemically defined medium for 9 days. Two hundred and twenty-eight oocytes (70%) were fused with donor cells. After in vitro culture, seven somatic cell nuclear transfer (SCNT) oocytes (3%) developed to the blastocyst stage. SCNT embryos were transferred to the oviducts of recipient females (four 8-cell embryos per female) or uterine horn (two blastocysts per female). One male clone (NT1) was produced at day 153 from an SCNT blastocyst and died 16 days after birth. This study demonstrates that nuclear transferred goat oocytes produced using an in vitro culture system could develop to term and that donor anterior pituitary cells have the developmental potential to produce term offspring. In this study, it suggested that the artificial control of endocrine system in domestic animal might become possible by the genetic modification to anterior pituitary cells.