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Induction of Pluripotency: : ? Y) s+ A5 v$ a6 m& u
From Mouse to Human( e8 X# `2 z$ `; o) U$ ~# { S/ p
Holm Zaehres1! _6 |. P/ b$ P8 _" t6 A
and Hans R. Schöler1,
9 H, w' `' @) S7 f# J*
! [( s* S1 D6 P1, C3 N. m# b8 S5 `* B. X5 h [
Max Planck Institute for Molecular Biomedicine, Department of Cell and Developmental Biology, Münster, NRW 48149, Germany
/ O) M6 Z8 x8 K$ s*Correspondence: schoeler@mpi-muenster.mpg.de( j6 ]0 X3 d9 D; ^1 o
DOI 10.1016/j.cell.2007.11.020
: [7 S8 S% @0 A1 S1 OIn this issue of Cell, Takahashi et al. (2007) transfer their seminal work on somatic cell
2 h7 d+ B( D7 v( L6 Y$ `- Mreprogramming from the mouse to human. By overexpressing the transcription factor 2 w" ?' s8 y) R2 X; X# P
quartet of Oct4, Sox2, Klf4, and c-Myc in adult human fbroblasts, they successfully
: k( a( h* b R/ P7 c9 A4 Sisolate human pluripotent stem cells that resemble human embryonic stem cells by all 4 M* A( B3 y" \9 Z# ?( n# U) Q- x
measured criteria. This is a signifcant turning point in nuclear reprogramming research 8 I% u7 x0 ]6 j
with broad implications for generating patient-specifc pluripotent stem cells for research
/ E5 a% T' r' |/ D; xand therapeutic applications.8 K: w1 O9 _* U; Y& U- O& v) ^
This year’s three Physiology or Medi-
- U/ b; B$ w# W6 J' l0 B. rcine Nobel Laureates—Martin Evans, * D. ?. {. J; h/ M1 `# y
Mario Capecchi, and Oliver Smithies—
8 I! W! \2 p' ?6 N: _4 @2 ?3 Twill be honored in Stockholm in 10 4 L+ D* m6 f% R9 {" f& m
days time for their discovery of DNA
' F2 ?% M/ n6 |+ f6 crecombination and the development
7 |, _( J2 W* Aof mouse embryonic stem (ES) cell & |% [4 g* M! C7 _* @
technology. It was Martin Evans who 5 R: w; \6 @+ M9 A; }0 M7 N
discovered how to make mouse ES 0 B8 u' }3 F2 h; T- g# h
cells, enabling any genetic alteration
$ @2 t: u' I/ Q( J% e+ Oto be transferred to the germline and ' Z; G( _+ B; p% v S
hence to the next generation (Evans $ ~3 ]; U" l/ W1 L
and Kaufman, 1981; Martin, 1981). 4 s4 x" l( Y6 K/ Z- i
Before this breakthrough, researchers $ l8 C7 f$ m0 i+ K$ ?3 H' x. X
studied mouse embryonal carcinoma
8 R, s) ^; x0 s Tcells derived from tumors, which
* l, T; P( f* B' d/ xcould form every mouse cell lineage
. @' }* V9 q& R# `except the germline. Combining DNA
1 y( Z: i7 B: `6 Urecombination and mouse ES cell
$ \0 ]' B% I( A% \$ k2 a0 d3 Gtechnology revolutionized an entire % b( S3 {4 J) y N
feld of research, forming the basis for . V1 J; \+ U- \
studying and understanding the roles
# a& B. W5 A$ Y' Gof numerous genes in embryonic 2 x# f' ?: z: k3 ^7 }7 r! g# p
development, adult physiology, dis-
X+ X8 \/ o$ ?! Eease, and aging. To date, more than
. v# E1 i9 h; H# \500 mouse models of human disor-
8 Z% S5 J/ V9 t, L! [" }' [ders have been generated. Now, with
$ v. _. C3 Q( }; Vthe study by Takahashi et al. (2007)
8 [- k7 C9 o- h- I) q" n0 q- _7 Ppublished in this issue of Cell, another ' ]7 u, Z7 c* d- q' X$ i
important revolution is taking place.' d, `6 H; y9 V* t
Last summer, Takahashi and
% ^1 ^; r0 y" G) t | p8 [, m' ZYamanaka (2006) stunned the scientifc 7 U! z4 L2 m, ]4 }
community with their study showing
7 t/ ^3 s; h0 f; w+ Q, R9 P) wmolecular reprogramming of mouse ! ^0 V1 i; J9 S7 a- r# z
somatic cells into induced pluripotent % z9 t3 V$ h, z
stem (iPS) cells using just four factors: ( W$ ]! ^0 H4 D2 A @
Oct4, Sox2, Klf4, and c-Myc. Their
, I, Q3 u% L, S' @/ z# a1 celegant but demanding approach of 7 @) c5 f* \) G5 r1 K$ d
screening for a cocktail of factors that
' e; Q; v1 W9 K. X* _ t. ^- Ycould reprogram mouse fbroblasts
7 Y( h' T5 [( }9 `4 F: jstarting from 24 candidate genes paid
2 l7 N* k" E0 E8 d' Moff with their detailed description of iPS
# R! I& t) N# `) Ncells, which are almost indistinguish-
; u* z0 r3 K4 t" s) K2 P F( I- Pable from mouse ES cells. As with all
5 M4 |5 ~) Q/ k* L$ v" yscientifc discoveries, these exciting
5 t% [5 ]; B. y6 r: bfndings had to be reproduced. Sev-1 G- W/ d; x" y5 s# P
eral studies published this year not
# R: h2 U* A8 H+ t4 X5 Aonly reproduced but also extended $ l1 }& }* {7 S F
the Takahashi and Yamanaka fndings 6 c% `5 M& D6 p% ^: @
by demonstrating the pluripotency and ! Y' O* E$ s1 |% ^( b% a( \, K
differentiation potential of mouse iPS - }) ]2 j" j0 W# T
cells in rigorous developmental assays & Y( C" G N" P
(Maherali et al., 2007; Okita et al., 2007; & W9 _$ L' E4 h0 ^
Wernig et al., 2007).
6 T% c2 w* f: Z$ U4 Z* m4 bIn their new study, Takahashi,
: n1 Z" x8 g1 J3 z" D1 eYamanaka, and their colleagues
' F2 ~* W# {: k; w4 a(Takahashi et al., 2007) now translate ' l% P. o+ c/ A, m3 R$ u3 Q
their remarkable fndings from mouse 9 K$ L) v1 `5 }# x! B+ k! @ _
to human (see Figure 1). They selected
( w u- K: B5 {. d3 Sadult human dermal fbroblasts and
7 W! z; q& G7 W0 o1 T( ~1 Q9 ttwo other human fbroblast popula-
' G4 `9 j8 i ktions (from synovial tissue and neo-
1 |4 f& C+ u3 g/ f" m( unatal foreskin) from different human ) C8 L) O0 f) J* o/ P* w
donors as their reprogramming target k7 V3 ]* ^' Y8 h- S" C' a
cell populations. They then trans-0 Z+ i8 S( q5 b* i
duced the human fbroblast cultures
4 ~& L) t$ Z6 H" B3 @with retroviral vectors carrying trans-" E% u4 u& `7 Y6 U! X: Z
genes for the human versions of Oct4, : C* G2 f, |0 u
Sox2, Klf4, and c-Myc and cultured
( C- h U' V n" M0 athe cells under human ES cell culture : ?1 V) f* g- L* s
conditions. Thirty days after transduc-
: Z+ y: f- u0 Mtion, the culture plates were covered * o$ e, _: E m8 K
with human ES cell-like iPS colonies
0 w( T* x# U8 x, S* L) S8 e(among other colonies), which could / e$ g& v( B. V" O
be further propagated and expanded. 3 n0 n, T* m' P4 r3 ~9 s9 a4 N( ]; Z
The retroviral vectors enabled silenc-
$ W2 ^' B. y" ^9 G0 Sing of all four transgenes after human
# ?4 b% N( y( o' k; C4 ]iPS formation (as found in the mouse
7 n% A1 O+ g# q+ bsystem) indicating that the iPS cells ' H6 o8 Z+ u& F: [- L5 _0 G9 h) F( i
are fully reprogrammed and no longer 0 M0 z% x& U$ O& z2 e- B9 G) [
depend on transgene expression.( j7 t2 U, t" }( t+ _2 e
Unlike the mouse study, human
3 ]" |2 z) u. ?& liPS cells were generated without any 1 o4 R1 G; H, k( V
genetic selection procedures. Given
! V: K$ O' z" G) T: E6 uthe lower mitotic index of human ES
5 k& H: t. c4 X5 j- U4 xcells, it is not surprising that the gen-, y1 V. J; g+ e4 o
eration of human iPS cells takes nota-" B3 U7 G6 i. _& \ b6 g( c) O
bly longer than in the mouse system. # ~+ @" q3 F4 B/ L
The authors subjected their human 9 t+ M$ @( j2 p) J# c+ d, g
iPS cells to a panel of assays to com-
8 s* C6 u" l- R1 t4 D2 w: \+ \$ npare them with human ES cells. These
. E5 z3 c/ O% G& R% I- x' }assays included morphological stud-
" T) t: }5 ^4 M) x3 e9 ?- eies, surface-marker expression, epi-
% Q1 [/ n7 j# E% qgenetic status, formation of embryoid s6 S. K. g9 h6 v. R
bodies in vitro, directed differentia-
) U' P! v) s" {# T4 f7 Ytion into neural cells and beating car-8 Z, d: d% s! V! s
diomyocytes (according to human
, |# a1 O d8 S# mES cell differentiation protocols), and 9 K. m' ?& a# s" w0 O/ J" J# \5 n
fnally teratoma formation in vivo. . f9 ? B. G- V# W" K
DNA microarray analysis revealed + Q% t2 M5 v8 e9 ~+ h
the remarkable degree of similar-3 V# p3 j' F: b: V& ?) E) `3 ^" L
ity between the global gene expres-
6 \; P5 }5 o) w7 v& j/ ~sion patterns of human iPS cells and
. p6 t7 z8 j0 V6 m) E0 j* fhuman ES cells. Notably, genomic
8 K# C* C& d* D. k/ E2 a t8 fDNA analysis as well as analysis of & J% C0 N7 Q8 R: h, y5 g& g' e0 T8 B
short tandem repeats demonstrated
0 M0 S6 |. d3 d) ], rthe genetic origin of independent 9 c/ U6 j/ y- i& i% K; Z+ P3 N
human iPS clones from their parental
0 M! p4 {4 F# l9 Qfbroblast populations.
& V( D$ D. @+ |( x% a$ G* mThe derivation of mouse and then + n- v9 w3 f, P2 d' o2 s5 K
human ES cells (Thomson et al., 1998) - n% \# L, n, \5 }3 h( L" B
as the gold standard of pluripotent ' |4 b# o, c9 Y' G i, N. x+ z
stem cell populations has necessarily : d, J- S" u3 e- I' _
led to emphasis on differences in the
# z1 ~" j2 Z3 z( F+ k0 E% ]+ Qregulation of self-renewal between & `# p+ V) j0 A. Q
mouse and human ES cells. For
+ z$ x( G" W. Q( O0 e5 E% uexample, human ES cells depend on / ]& T$ {, [' W9 V% }3 A
bFGF for self-renewal, whereas their
C9 w5 E; k6 T5 H: c2 r; Ymouse counterparts depend on the " k& R/ t2 H/ j$ ^9 a2 t
Lif/Stat3 pathway; BMP is involved in
# `+ i: h8 _, A0 S- q6 S, C: A; Ymouse ES cell self-renewal, whereas 1 j* T% A/ r+ x' [
in human ES cells it induces differen-: M2 g' R( c7 {3 t/ `9 m
tiation. Extrinsic factors and signals ; |' x9 d# q1 X
for maintaining pluripotency may dif-. {8 D2 x& R3 @! G* Y
fer between mouse and human. How-
* J; K$ |9 Y/ ]5 P5 cever, the ability to translate somatic 9 y5 z% }6 J% l% a) q5 C# q8 v) w
cell reprogramming from mouse to
* L0 A- c) |* c; [, }5 m8 r+ p4 shuman using the same transcription
4 }3 G9 ]' [0 B. t9 h/ O5 s! kfactor quartet further emphasizes the
- ^* k T. T1 Y% k9 |4 qconserved nature of the Oct4/Sox2
4 |0 g9 \, m) i4 d4 \. p) \$ ]6 \transcription factor network that 3 d1 d- o6 K# ?2 `; m
controls self-renewal of mouse and
) B" G( x5 ~& o, m* z* uhuman ES cells (Boyer et al., 2005).
- H R' n7 r+ t3 S$ e9 xGiven that Klf4 and c-Myc are chro-
! X2 ]4 F6 L: ^% ]. S0 mmatin modifers and can immortal-
' M/ S3 @9 J* F$ y8 ?3 size cells, one might be able to fnd ) z: `+ C5 h, y- ?+ l I* _
other factors or small molecules that
. e5 y( h$ k2 w0 y6 s$ Jcould replace these two factors in the
; A1 J; G! ~0 R% v$ |, m5 I. H3 ~: Icocktail (Yamanaka, 2007). In these
6 }& y/ l, |2 x0 S T. astudies, the possibility of retroviral 6 U8 N/ }! S |2 V( Y8 n1 a
insertional mutagenesis, resulting
- _7 s0 s6 \5 N$ N- y! l2 ein the activation of other genes con-) B" B6 c" k5 k' S( f8 v
tributing to reprogramming, cannot % A8 Z& D. X4 B# l! D! G( S
be excluded, providing an opportu-7 j2 h- j$ o v: f9 B
nity to potentially identify new repro-
$ x* K; Y/ o- q% Agramming factors beyond the cur-
2 u- ~- L/ G c! f5 grent quartet. Also, taking a broader % S2 c4 @" }; g) y# l: @0 F
screening approach for reprogram-. e9 f/ L1 M3 H7 R
ming human fbroblasts (as Takahashi 4 `4 Q s2 R- P# ]- \
and Yamanaka did for their mouse
- p5 z$ B, W- {: f: A) B) h gstudy) might yield other combinations 1 u' n1 b5 Z3 [. r3 \
of reprogramming factors.
* r( T2 N0 Q# f% P' tDirect reprogramming of somatic
* s' k1 U8 R. i: g" ^cells to a pluripotent state, thus revers-0 p# ?( @. M ~+ y2 f5 i
ing the developmental arrow of time,
, f! h* W- f+ @% q5 R/ v6 X1 p( ris considered by some to be the “holy
+ ]0 a( f w: ugrail” of stem cell research. Once the
# o) f1 p6 V, p2 [9 b1 f2 Aresults in human cells are confrmed,
, }3 S7 X* `% \' [" k; mthese advances will enable the cre-
/ c2 M4 l$ I2 yation of patient-specifc stem cell lines & s* `) E& U" w8 G
to study different disease mechanisms 7 y: m! A" I4 n) _
in the laboratory. Such cellular models 2 V; i7 T! B& A- a
also have the potential to dramatically 9 q2 Y9 _' V( j! R( ~
increase the effciency of drug discov-5 K+ O+ Y! l6 s' Q, D* t- r8 h2 d
ery and to provide valuable tools for ' m$ h! m4 y# ~3 u6 G V' Z1 w
toxicology testing. Furthermore, this 7 L; p3 W1 V8 M2 n
reprogramming system could make - b" x; A5 o" L+ W& d4 i3 _
the idea of customized patient-specifc ; p* o5 v t3 }% [/ o
screening and therapy both possible
' A: }5 `+ u" H o5 Mand economically feasible. Finally, the
9 H% k6 n- Z- e9 y% S& F9 `- qwork will have a powerful impact on ' u) K* i" w2 U/ D! b# m' E
the intense debate regarding the moral,
7 N! W- J/ @& i" dreligious, and political aspects of ES cell
! L7 ~8 u: s# |& Aresearch. However, a big mistake now
- K& |9 j6 j! @6 b: lwould be to consider human ES cells
7 B) r1 V0 D* ~/ _3 O) Hobsolete. There are still many hurdles ! @! R' p9 D+ ^$ e: \2 L
to overcome before we ful ly understand ) s4 v, ?) o3 g: v! ?8 o9 [
pluripotency and before we have human 4 L7 ~1 ^3 K- a$ f) j0 `
iPS cells in hand that are suitable for 7 A8 x5 t/ Y8 n6 e) V- e9 _9 x
therapeutic application. For example, 1 n: K2 `8 l1 i) O" q6 }1 ]8 v7 ~" j
a signifcant proportion of mice derived
4 x8 W# K- B9 [+ Hfrom mouse iPS cells develop tumors & F( T. j$ c9 ^8 p; S/ N; c3 S, v
due to reactivation of the c-Myc retro-
2 A# I& i8 k- Q% y3 R3 J, O: }8 nvirus (Okita et al., 2007) compared to
% ^0 N% n' _' ]& P! [- Gmice derived from ES cells, which are , }+ q9 P' s9 J* s& m, h
normal. The search is now on to fnd a
' I( p( r% p6 A* z" z! Hway to reprogram somatic cells without 9 Z! W* |' i) a/ D4 s
retroviruses and maybe even using a
: L" x' E: O5 {* x* B' R3 Y# jcocktail of small molecules. Given this, 2 ^! W6 e7 ~9 q4 P
it should be emphasized that human 2 B% \0 Z2 n- ~6 L
ES cell research is more important than 7 K$ I" c6 K$ ?. h% ]# m
ever for it will shed light on how iPS
) d4 y$ {/ g7 C$ D" f. v2 l$ ]6 Lcells can best be maintained in their " W. c* ]9 v1 W4 A7 P, m
pluripotent state and how they can be ! U6 z$ {% _! t! i9 p: Q
induced to differentiate into the cell
0 z5 A2 W1 O1 E2 i) E6 jlineage of interest. The feld of nuclear
8 N% J6 P; j$ H3 hreprogramming has come a long way
, ~% ?1 x2 `2 m- h/ sfrom the initial nuclear transplantation
+ }* P/ e4 ]9 x" ^4 B# N' p. tstudies in frogs 50 years ago, to the $ o7 {3 ^- B7 H, Q0 n* ]9 y7 G' {
birth of Dolly, the frst mammal cloned 5 p: f8 ^' W. s2 F; k% V: h! E7 O
from adult somatic cells (Wilmut et al., 9 K ^4 {! b9 ]0 c# v- ?" B+ L7 R" g) |
1997), to the fallout from the fabricated / E: w6 T" d- E. C! B: G
human nuclear transfer experiments & B1 n1 x7 p& ^, Q3 a% Z8 L
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their colleagues, frst in mice and now
3 s# `3 r- l1 U+ v+ R9 zin humans.6 t# D$ r& h9 y/ H6 Z8 D- K8 n' T
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发表于 2009-4-28 21:35
发表于 2009-5-16 10:41
