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本帖最后由 细胞海洋 于 2010-11-30 12:27 编辑 0 U; D- U' @- x; J* e, f m8 q: u
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& ^& I+ R2 p, t; @% k; ^) x1 _! pDevelopmental Genetics, or What Can Genetics and Genomics Tell Us About Evolution, Development, Stem Cells, Human Birth Defects, and Disease?
1 I& I0 Y: l- U
7 l2 T) i6 x! ~5 T$ K* H& B( [The ability of researchers to answer experimental questions greatly depends- ]9 F8 d& u: h0 v& ^
on the available technologies. New technologies lead to novel observations
; R( y0 f1 Y0 i$ u3 Tand field-changing discoveries and influence the types of questions that can0 ~" R- h5 N9 U s: j
be asked. Today’s recently available technologies include sequencing and analyzing
: M9 e X2 s' r- i( Nthe genomes of human and model organisms, genome-wide expression! r5 D5 N( |) L( q# g& ^8 Z6 M& `
profiling, and high-throughput genomic and genetic analyses. The information
! D# o, f. } v+ @& ~' P0 fprovided by these approaches is enabling us to begin to understand the
7 C% D8 |* M* v2 C: _# }4 zcomplexity of many biological processes through the elucidation of gene regulatory1 U i9 m5 ~+ Q E
networks, signaling pathway networks, and epigenetic modifications.6 }9 }# z8 d# H0 B0 u7 A/ L
This book describes many lines of research that are being impacting by these2 g7 P2 T7 |# s" H# F3 b6 u
new technologies, including developmental genetics and the related fields of4 @- L7 C/ P5 O+ o2 x; H
clinical genetics, birth defects research, stem cell biology, regenerative medicine,: J' x$ u& A8 m# b6 w2 F5 g" j
and evolutionary biology.
3 U- q7 k+ u0 jThe field of developmental genetics, or the study of how genes influence
/ u3 O: P$ Y& n0 i, k, jthe developmental processes of an organism, has been influenced by new technologies% }: }, q: C: z9 b0 o" U4 W' h
and by interactions with other fields of study throughout its history.
/ F- ?' T& x( p1 X8 UThe concept of a genetic basis of development began in “modern” times at the
) F8 ]% ~3 l% ]: N5 n$ Lintersection of descriptive embryology and cytology. Modern histological. w* ] d9 A3 R5 c
techniques were developed in the mid-19th century, largely by Wilhelm His+ W( h# h* ?. D, \& L
so that he could study cell division in the neural tube, which enabled visualization
8 J4 ~+ Q- V4 pof the cell nucleus, chromosomes, and the discrete steps of mitosis.
# k" h" t. x5 l8 a3 V XTheodor Boveri cleverly applied these improved microscopic techniques to; j( P% y6 i/ y2 `* \8 y7 z- A! t
transparent marine embryos to demonstrate that each parent contributes2 V/ e- f6 a: l4 _1 f
equivalent groups of chromosomes to the zygote, and that each chromosome
- C0 G0 D* e2 B- i) N! _- D! d" h- N- gis an independently inherited unit. Importantly, he noted that if an embryo
2 i2 t) q0 b0 zcontains the incorrect number or improper combination of chromosomes, it
0 c8 | m" F/ V. fdevelops abnormally.( ]! Y" D G6 W; A
However, many early embryologists rejected the idea that development is
3 }, [/ K3 l- i# K2 [: ydriven by prepackaged heritable particles because it seemed too similar to the- u1 v" O# S6 g" l! }0 f' }4 l
idea of “preformation”: the concept that development is driven by predetermined" C1 F Q t) n$ g4 i
factors or “forces” (sometimes described in rather mystical terms).: k' g7 I- W9 V1 n; |; q/ g
Wilhelm Roux, an advocate of studying the embryo from a mechanistic point
1 v, |. p5 ^ v- |of view, was a leader in the approach of manipulating the embryo with microsurgical
- S1 s6 o" K6 i7 Qtechniques to elucidate cause and effects between component parts: I* U0 l) P, l7 _* J, Z
(experimental embryology). By using an animal model whose embryos were$ V* m8 U6 R+ J
large, developed external to the mother, could be surgically manipulated with
" j. _/ z, C6 A! Hsharpened forceps and cultured in simple salt media (i.e., amphibians), he
. R& c4 z1 c% f# F u5 v9 prejected the role of predetermined factors and demonstrated the importance _2 y: a) t' P4 l; u8 p4 j B
of external (epigenetic) influences and cell–cell interactions in regulating! C! _8 M5 X" E! P
developmental programs. Experimental embryologists further refined their6 x+ j3 X6 F+ e
skills at dissecting small bits of tissue from the embryo, recombining them/ C% W1 b4 ?4 t
with other tissues in culture or transplanting them to ectopic regions in the2 c& R# V W# I2 C# y( h; v9 x
embryo. This work led to the invention of tissue culture by Ross Harrison
2 T: p; ?* X6 o1 yand the discovery of tissue inductions by Hans Spemann.& e( h0 j" D4 Q6 t# O
While experimental embryology was thriving, T. H. Morgan founded the
9 Z2 g* w+ _& sfield of Drosophila genetics. Also trained as an embryologist, Morgan was8 B3 K) ~8 ^& O0 ?7 u0 x
skeptical of Boveri’s idea of heritable packets, and directed his studies towards8 b. Z. A+ h7 U. A* s: R9 Y, {
understanding the principles of inheritance. For several decades, the two fields
1 ?+ x, h& n& X# W5 h% q, `had little impact on one another. Interestingly, however, after a few decades of
- ]6 q9 o; T; f2 E) R* _% R7 |study of the fruit fly, Morgan’s work supported the idea of discrete intracellular
/ y, s5 E& [0 M. f6 ~, X& k; Sparticles that directed heritable traits, which he named “genes.” Nonetheless,- A5 C- p0 V. H3 [) y9 O
the fields of experimental embryology and genetics remained fairly
( c& u. f+ p: z5 D% O2 z$ }& kseparate entities with distinct goals and points of view. Embryologists were
$ M$ _8 l; T" Q2 jelucidating the interactions that are important for the development of numerous
* J* e! V8 e2 n6 r$ W0 Y* ltissues and organs, whereas geneticists were focused on the fundamentals; [; [6 u5 Z* r7 G, W. ]! H
of gene inheritance, regulation of expression, and discovering the genetic+ L+ q3 V& T; q3 d) c5 q
code. Indeed, elucidating the genetic basis of vertebrate development was
* g1 w& h+ D9 J6 k4 G5 t0 Odelayed until new technologies in molecular biology and cloning were devised.* w) F2 }) c0 [% i- }
From the field of bacterial and viral genetics came the techniques for cloning: Q$ {& s0 ?9 s8 \4 R' y
eukaryotic genes and constructing vectors for controlling expression. From
& }, c( v1 I6 t$ I$ xthe classical genetic studies in fly and nematode came the rationale for mutagenizing' f! X" h7 ]* F6 ?# T
the entire genome and screening for developmental abnormalities.
) ^0 _" z7 F7 G* H2 cImportant regulatory genes were discovered in these invertebrates, and their
' y6 O, U! n: b& N. e$ Ycounterparts were discovered in many other animals by homology cloning
3 n7 P$ M3 F2 c% C9 Q# N: ?( eapproaches. Thus was born the modern field that we call developmental3 M1 w1 q( `) v
genetics.
$ D4 U! l# c* q1 D! oAn important advance in the past decade is the demonstration that genes
7 r; A1 R% m; B7 V8 l4 w/ p! c: R7 ethat regulate developmental processes in invertebrate species have important$ W* `) _$ T4 I
developmental functions in vertebrates. The wealth of information concerning# f+ ]& @2 M. l/ P% R3 w: G
the molecular genetic processes that regulate development in various animals
3 U7 x- f5 o8 q4 {demonstrates that developmental programs and biological processes are highly
& Y Z0 |6 l6 n/ v! d$ [ H4 a/ yconserved, albeit not identical, from yeast to human. Indeed, the Human) S: l, m4 D. M8 K2 J0 |
Genome Project has made it possible to identify the homologues in humans& s# L/ S" _8 i* x. E' f% _" S; q. a
and demonstrate that many of these regulatory genes underlie human developmental
4 E; ^, @, s/ f/ b( @5 Hdisorders and aspects of adult diseases in which differentiation processes! t- p V: t. m6 w
go awry. Currently, researchers are studying the fundamentals of
+ I; a6 N8 N& g' c2 Xdevelopmental processes in the appropriate animal model and screening, q' b$ V2 o3 O& _7 Y4 N
humans for mutations in the genes identified by the basic research to be likely
% B" u9 F' r# h# Jcausative candidates. Researchers are mutagenizing vertebrate animal models- g& O. j7 M8 [! F5 e
and screening for mutants that resemble known human syndromes. This
/ l) U6 ]! R+ ]7 Z% S+ O$ Ncross-fertilization of fields is also impacting concepts in evolutionary biology,
4 e! Y; N7 g% {0 N, x& Ixii PREFACE
' q' Z: ^5 D+ @) d$ ]leading to a better understanding of “ancestral” species via gene expression
" d" t% T# [7 h2 l# s ?profiles, and paradigms in stem cell biology in which naı¨ve cells may be directed
( u5 D4 g, b! D; `to “designer” lineages.
, O9 e. W1 _. [; RMost recently, there have been significant technological advances in8 C# p+ t E# T( b0 Z3 p7 J' D$ h6 V
genetic, genomic, and protein expression analyses that are having a major) h; @+ R/ b8 M% w. ]: \/ p# J3 U5 E
impact on experimental approaches and analytic design. The intersection of
" h. r& x" s( Mdevelopmental biology with these technologies offers a new view of developmental0 {8 R `- h2 B$ N& I
genetics that is only beginning to be exploited. It is this new intersection
$ |, A( @/ t; I7 Aat the onset of the genomic era that is the focus of this book. The book is# y5 H( ]+ H' K
organized into sections focused on different aspects of developmental genetics.
5 W) }1 g0 ?4 r% R& g8 X) w: fSection I discusses the impact of new genetic and genomic technologies on. t, u9 k7 c) H% [' `/ e. ^
development, stem cell biology, evolutionary biology, and understanding
0 [0 n7 H4 t1 `9 U* [9 ahuman birth defects. Section II discusses several major events in early embryogenesis,
! L) m$ Z; l# Zfate determination, and patterning, including cellular determinants' \8 y. }* l( F9 @* l4 F1 B
(Boveri revisited?), gene cascades regulating embryonic axis formation, signaling5 Z6 a2 i" ?& y/ e) |
molecules and transcription factors that regulate pattern formation, and
* `' k4 O5 L* w( ^) W7 O! q( ~0 ]9 Fthe induction of the primary germ layers (ectoderm, mesoderm, and endoderm).. X; i3 \0 G' K s9 T$ Y7 J
Section III describes the reorganization of the embryo via different" ~. a. ]# K7 Z. |
types of morphogenetic and cellular movements that result in the foundation
. p- t, ~4 D* s$ mof organ systems, and discusses the many signaling and adhesion molecules
' r9 [5 J6 k, {# R0 z Jthat are involved in regulating these complex processes. The final three sections. K; M* D8 M. g4 C! G* [. W7 [2 E
focus on the signaling cascades and transcriptional pathways that regulate7 p' |8 O( e& V7 ^
organogenesis in representative systems derived from the embryonic
# L% q7 q8 e. R( U! s$ eectoderm, mesoderm, and endoderm. These chapters illustrate how embryonic
# T3 o- i2 c! lrudiments become organized into adult tissues, and how defects in these processes
3 l5 `: u; _* w1 Q! Mcan result in congenital defects or disease. Each chapter demonstrates
C6 d/ z( F* U2 ~% l5 A7 I0 Tthe usefulness of studying model organisms and discusses how this information0 ?+ k5 T1 w9 x+ l3 x
applies to normal human development and clinical disorders. Several
8 F" q4 E/ c+ ^8 q; Nchapters also discuss the utility of stem cells to repair damaged organs and
3 p) l* Z1 ~! n3 J4 }/ X, ^the application of developmental genetics to the manipulation of stem cells
, g6 U, M: f- L6 |" Ufor regenerative medicine.
' L! |; x+ Y% {' Z* ^The goal of this book is to provide a resource for understanding the critical
`5 ^' c2 K' U/ Vembryonic and prenatal developmental processes that are fundamental to. ~ z) h% C5 |! k. e; A* E
the normal development of animals, including humans. It highlights new
5 P- v9 K! w8 a- C* ~technologies to be used, new questions to be answered, and the important+ o$ @) l& V1 a
roles that invertebrate and vertebrate animal models have had in elucidating
4 x% f w7 @4 G8 g6 D( ~the genetic basis of human development. Developmental genetics has reemerged" W& M, O, o5 u. T% P
from its birth a century ago as a nexus of diverse fields that are using! Y5 i7 b$ S5 ? {2 ~" r
the common language of gene sequence and function. This is influencing
+ ~1 X( P1 {8 Y- n& e; l" ~what questions are posed and how the answers are used. New technologies* Y# h* [7 j. C' P# X) h& S
are making it relatively easy to study gene expression and regulation at single$ x; L A z1 v- Q( f9 ?
cell, tissue, and embryonic levels. The conservation between the genomes
0 v9 g6 _0 N! `# \, Q' c% \of species that are separated by vast evolutionary time encourages us to: u9 L& z( j7 Q: l. R$ ^/ o
more fully utilize animal models to gain important insights into the clinical
6 }& @# ^! r1 S3 P4 mrelevance of the animal model data. It is our hope that this book will stimulate2 [7 d# Q. N1 x: |% G7 A. u- v! u
even more cross-fertilization and interactions between evolutionary biology,
- }: C( s) v) h& P: u+ L. B" ^! ldevelopmental biology, stem cell biology, basic scientists, and clinical
, D" _7 c" z2 m6 T( X! ^scientists.: z( d2 J/ y/ ]4 |6 W, a. p
I wish to thank all of the authors for contributing such exciting and5 i; a3 S" n+ y; C
excellent chapters, and Pat Gonzalez for keeping all of us on schedule.
$ q* `/ q- J: @! _
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