请教畸胎瘤和四倍体补偿

zhaoyan1983

请教为什么用畸胎瘤实验和四倍体补偿实验可以用来证明ES的全能性？希望高手们可以说的详细一点，我是新手，说的太简略我理解起来比较吃力，谢谢！
% ^5 ~, B8 b6 B' P, r- @另外畸胎瘤在有关ES的实验中主要是用来证明什么的？

flydayzhu

畸胎瘤实验的话是说明ES能够分化成三个胚层的细胞，具有多向分化能力，四倍体互补的话是用四倍体支持ES的发育，使其能发育成一个完整的个体，证明其具有全能性

zhaoyan1983

回复 2# flydayzhu " H. h- W6 ~7 K7 ^7 L1 \
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# d& N; D9 P" q: r1 T5 E    能说的具体点吗

lixiaodong

Nagy和Rossant的一篇较早文章对四倍体补偿实验的原理和背景资料有较好的介绍。Introduction部分就讲解了很多问题。参考文献里也有很好的早期工作。另篇93年PNAS文章介绍了ES细胞的tetraploid complementation（是关于ES的类似实验的较早报道，）$ c, e$ o& H2 H
Embryonic stem cells alone are able to support fetal development in the8 P3 b; D2 b% n& p$ A' z  _* O! ^
mouse
+ k% W  D% O7 X% x. P: {3 P, HANDRAS NAGY1-2. ELEN GOCZA2. ELIZABETH MERENTES DIAZ2. VALERIE R. PRIDEAUX10 g- f( e1 e8 x; t5 j/ N
ESZTER IVANYI2. MERJA MARKKL'LA2 and JANET ROSSANT1 3, y1 n& j, ~4 r/ T, g4 D
Introduction
* |9 Y% ?7 ?8 D5 K. BMouse embryonic stem (ES) cells are the most
% U2 S: \5 e1 r+ M, m7 K1 R. ppluripotent cultured animal cells known. When ES cells
5 T& c, o1 L8 |: B9 r  tare injected into host blastoeysts they are capable of
3 O6 H; z6 _- v$ M. Z# icontributing to a wide variety of somatic tissues and the
; z0 I* r0 t. Q* feermline in resulting chimeras. However, their contributions
: X% g8 i1 t" E) N6 ato different lineages are not necessarily equal.  u+ u; [! n6 k  c' R! N
ES cells are able to contribute extensively to the fetus# f' M! F  o) c: `
and extraembryonic mesoderm. but their ability to
0 j+ q, S1 N* Rcolonize primitive endoderm and trophectoderm derivatives# E6 Z0 X' z8 ?* p6 J9 \+ d: \* b9 o
is poor (Beddington and Robertson. 1989). ES
. j8 }* x3 d, c' e5 O/ z) Pcells may thus have restricted potential in certain! D6 K" n* I) M2 W1 s- t2 H. C. k
extraembryonic lineages, suggesting that functional+ f# V5 J9 M& r( M0 D* r% ]
complementation by host cells is required during early
3 c0 U) H" D" v; D* }8 O' zstaues of development in chimeras. In this study, we2 c/ n4 E7 }; y7 R
asked whether this functional complementation is
4 ^' k9 w5 z# e' brequired at later stages within the embryonic lineages,6 S6 a% v8 E# j- t
or whether ES cells can support complete fetal and
7 q( L; |1 _9 F2 wpostnatal development. To test the full developmental
; l* |: [& S6 ]% k" C3 i4 [% j) U- fpotential of ES cells, they were aggregated with
; m  Y+ x$ k& S' L5 S7 Z% Q5 Pcleavage stage embryos that had been placed at a
# \! p+ o8 H( Y& ]" F5 E7 ?9 adevelopmental disadvantage by doubling their ploidy.* I' C# ?) `7 u, H3 Q& V4 K
The development of these aggregates was compared
8 E6 Y* d* v: b+ f! O" Xwith similar aggregates made with ICV1 cells.
9 ~6 f4 g* t0 w) NTetraploid embryos can implant at high frequency,2 T6 p1 t1 s/ U+ I* k
but rarely form embryonic structures (Snow. 1975.
$ `+ G3 k/ V' ?4 p& Q7 g1976; Tarkowski et a!. 1977). although occasional
8 K! v. T, e9 gembryos proceed through organogenesis and reach) D! U5 G2 E! o5 i+ E& [2 B0 p
term (Snow. 1973). Postnatal survival of tetraploid
# I- h1 d0 g; a) N. xembryos has not been reported. If blaslomere stage
8 c1 B' I0 h' |- @8 {tetraploid embryos are aggregated with diploid embryos,6 J+ H9 z! r$ E
the tetraploid cells are selected against durinti! C. O8 p& d) C; s- N. E
development of fetal tissues in most cases (Lu and
) J& s; f( g. YMarkert. 19X0). but persist in extraembryonal membranes
5 r- e# S; u: `1 i(Tarkowski et al. 1977). Thus, we reasoned thai# a3 b. G  B- q1 O& B4 G
tetraploid cells might complement the deficient
) e. m* P, o: J5 Eextraembryonal differentiation of ES cells while allowing
- f* ~/ b. E( Rfull expression of their potential for fetal development.
, |- r* Y$ m6 p, I+ c6 e. @Production of live fetuses that were entirely ES in
' \4 g; j% p% b( O( rgenotype was achieved from such aggregates, showinu- Z% M% h) V4 c# \
that ES cells have the potential to form all fetal cell
" ^$ k' i2 P, a" {0 T  _% n7 wI incases.

cony

粗略来说，四倍体只能发育成胎盘组织，不能发育成个体，而将ES注入四倍体胚胎后，如能产生个体，这个个体是完全从ES发育而来，从而证明ES的发育全能性。

懵懂干细胞

回复 5# cony
8 v4 ?* X" A5 f2 `) f9 @简短明了！谢谢

flydayzhu

回复 3# zhaoyan1983 - Y" }% O) O+ [0 P0 a; N- i& Q# t$ |
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6 T& L. n7 V5 P9 F. \    关于四倍体互补，可参考http://www.stemcell8.cn/viewthre ... 6%CC%E5%BB%A5%B2%B9

zhaoyan1983

回复 2# flydayzhu & X' Y0 I- J7 v- s0 y! `$ p! h
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    那畸胎瘤实验呢？一定要让ES成瘤才能证明它能够分化成三个胚层吗？我只是不明白为什么很多实验都涉及到畸胎瘤的部分，有点晕。

flydayzhu

回复 8# zhaoyan1983
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+ V$ [, R& S/ @6 ~0 N    体内注射后会形成畸胎瘤，畸胎瘤在体内能分化形成来自三个胚层的多种分化细胞，说明其具有亚全能性，因为这样才被拿来证明全能性，全能性的一个特点是能够分化成三个胚层的衍生物

张也行

这两个实验都是证明ES的多能性的。所谓多能性就是说ES必须要能分化为各种胚层才行，就像体内的ICM将来分化整个个体一样。他们具体的机制前面说的很好了，我就不赘述了。' N1 a% {7 c0 B2 G4 y
+ j  C- i7 e. Q# U6 A% M& S" t
畸胎瘤和四倍体补偿都是证明多能性的方法，但是显然后者更严谨一些，更有说服力一些。还可以用已经建立的体外诱导为多种细胞的方法证明多能性，但严谨性又比畸胎瘤弱一些，因为体外诱导的细胞种类有限。还有一种证明多能性的方法就是嵌合体（特别是生殖性嵌合）了。比畸胎瘤更严谨，比四倍体弱些。但一般做成生殖性嵌合体就足够了。