本帖最后由 细胞海洋 于 2010-5-4 20:47 编辑 " e% x1 R# c/ Z
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The mammary gland represents a unique model 2 h3 `. T, r3 X1 E2 E* A1 Msystem to study gene functions in adult stem cells.5 w( V) S* b: Z7 V* [. p
Mammary stem cells (MaSCs) can regenerate a ; n* `( g7 h6 l ]! A% n7 H6 ?8 f+ Q7 rfunctional epithelium upon transplantation into % k- {% ~6 m2 R/ K) W& Dcleared fat pads. We studied the consequences of/ U; K4 w' K: A6 u- y0 H# ~( ~+ F
distinct genetic modifications of MaSCs on their 2 w, W4 ?5 F( F% Q' Vrepopulation and differentiation ability. The ( @3 L$ f: Y/ { t. {reconstitution of ductal trees was used as a stem cell' w. t; e( N! ?4 N5 C" m) ^
selection procedure and the nearly quantitative& G- N" f- s2 Y( L
lentiviral infection efficiency of the primary + K f; ?: G( Z5 ?6 }5 ]3 fmammary epithelial cells (MECs) rendered the + Y* O% j( b- v6 r6 g' Eenrichment of MaSCs prior to their transplantation * p: D, Z. ?, R2 ~4 E; R8 N% [- Yunnecessary. The repopulation frequency of1 U* J, A W. |; P F# h
transduced MaSCs was nearly 100% in" V6 p; J9 c* O
immunodeficient recipients and the resulting 5 ]* D& g2 z4 o/ l8 _transgenic ducts homogeneously expressed the virally - Z6 s- h1 H- E M) I9 f; L. xencoded fluorescent marker proteins.3 I8 R7 c7 x i
Transplantation of a mixture of MECs, expressing- W6 L8 L3 j z" c5 B
different fluorescent proteins, resulted in a distinct $ l3 X: q. s' H1 N* |$ o0 T3 f7 \pattern of ductal outgrowths originating from a small ! r+ {- z+ f/ cnumber of individually transduced MaSCs. We used : f5 s/ c+ C: t" z% a; v7 lgenetically modified MECs to define multiple , @8 j. ~. ?4 e( i# afunctions of Stat5 during mammary gland 5 M/ x/ x5 Y; K% r: _development and differentiation. Stat5-1 v4 G8 p* J( X2 D7 ` _0 ?6 u
downregulation in MaSCs did not affect primary : z0 `9 Z3 A7 ]' S% Mductal outgrowth, but impaired side-branching and ' K6 K/ f% b U9 N& Gthe emergence of mature alveolar cells from luminal / B: O& U4 \8 b$ l' zprogenitors during pregnancy. Conversely, the 7 f$ o) r d" q/ ^expression of a constitutively active variant of Stat5,) T7 _/ n; K5 R7 a4 A
cS5-F, caused epithelial hyperproliferation,. U4 I% [8 T0 r) z
thickening of the ducts and precocious, functional # W8 Q+ q4 D$ F5 A }) q' oalveoli formation in virgin mice. Expression of cS5-F7 B5 E/ j1 H5 a; G( N* P
also prevented involution and caused the formation : J9 e+ V5 w* C4 P( uof ER+PR+ adenocarcinomas. The tumors expressed 5 J" [' e! Q, F! e- |activated Stat5 and Stat3 and contained a small+ c' t' L6 K8 r2 O
fraction of CD44+ cells, possibly indicative of cancer6 K d$ r/ m9 h" g8 r' S) q
stem cells (CSCs)作者: tuanzi 时间: 2015-5-29 20:58