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本帖最后由 细胞海洋 于 2010-11-30 12:27 编辑 4 U, f( Q$ b: t) V
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Developmental Genetics, or What Can Genetics and Genomics Tell Us About Evolution, Development, Stem Cells, Human Birth Defects, and Disease?
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The ability of researchers to answer experimental questions greatly depends/ B1 Y" Q. X2 B S% s4 k: Q6 g6 @
on the available technologies. New technologies lead to novel observations
% H. l2 J7 H2 `( O% o7 Iand field-changing discoveries and influence the types of questions that can
, l1 P" N7 E. F: T$ _8 S" G# wbe asked. Today’s recently available technologies include sequencing and analyzing# b! m$ W' |+ |3 g. x0 R
the genomes of human and model organisms, genome-wide expression
: G2 y- }# J6 @# O) f$ Iprofiling, and high-throughput genomic and genetic analyses. The information
4 a1 t0 L# x' l/ V. L+ rprovided by these approaches is enabling us to begin to understand the; T/ H6 M4 o F' p& ]- i
complexity of many biological processes through the elucidation of gene regulatory
, k( `$ H z K! n6 m3 M+ dnetworks, signaling pathway networks, and epigenetic modifications.
- }+ ^; k( D1 X; M" {2 _( w. EThis book describes many lines of research that are being impacting by these0 M D" u+ c# G _. R1 i
new technologies, including developmental genetics and the related fields of
: k/ Q! N- L* U3 h& e" z* u7 D0 hclinical genetics, birth defects research, stem cell biology, regenerative medicine,
! ~! \& @7 B2 z" F1 wand evolutionary biology.
( y! r. }4 `. Q p( gThe field of developmental genetics, or the study of how genes influence; M: Z3 A, ?" ~& I l
the developmental processes of an organism, has been influenced by new technologies5 A* \' o" d: t7 S
and by interactions with other fields of study throughout its history.
7 O8 r* Q* v1 z& g6 IThe concept of a genetic basis of development began in “modern” times at the
" X( k- l, A w# e# b! { dintersection of descriptive embryology and cytology. Modern histological
5 t; }6 W1 ?& y- M" f1 p Atechniques were developed in the mid-19th century, largely by Wilhelm His
4 `, P t O1 E @! ~so that he could study cell division in the neural tube, which enabled visualization
5 j) J/ H8 [7 U5 D: c- Uof the cell nucleus, chromosomes, and the discrete steps of mitosis.5 d' J q8 D, Q: B) V5 u+ ^
Theodor Boveri cleverly applied these improved microscopic techniques to- P7 a0 s! c0 ^: e8 m( k' _
transparent marine embryos to demonstrate that each parent contributes" k3 L/ p4 P/ \: g3 m# e
equivalent groups of chromosomes to the zygote, and that each chromosome2 H; a, E$ V& ?! [' E& e% h- }4 o
is an independently inherited unit. Importantly, he noted that if an embryo5 X" y5 t; h. z5 T6 ~/ Q8 y. O: L
contains the incorrect number or improper combination of chromosomes, it
7 S) \4 G L5 {, ]1 ]+ U& [$ e1 I* L) xdevelops abnormally.
# Q* R- a9 `8 |. x6 jHowever, many early embryologists rejected the idea that development is
5 i( H. `: j2 Q6 o6 R) X5 ~: ]$ Ydriven by prepackaged heritable particles because it seemed too similar to the
) P& P0 h: E; d! F6 b7 |( Z/ aidea of “preformation”: the concept that development is driven by predetermined
- {5 v7 |/ n" k6 i9 s. c! p8 Y8 u" L4 xfactors or “forces” (sometimes described in rather mystical terms).4 o, n5 h5 o) x" Z& m, B
Wilhelm Roux, an advocate of studying the embryo from a mechanistic point
. {+ U9 S* y( Uof view, was a leader in the approach of manipulating the embryo with microsurgical
1 S7 Q* X' z& e- U) y1 Dtechniques to elucidate cause and effects between component parts7 Y* O6 h. t( H
(experimental embryology). By using an animal model whose embryos were i; E' L$ }0 ~* U, L
large, developed external to the mother, could be surgically manipulated with
8 b- I: D' D2 Isharpened forceps and cultured in simple salt media (i.e., amphibians), he
. l7 \* C. }% j0 nrejected the role of predetermined factors and demonstrated the importance
8 i" @% W) h' d2 ^0 N fof external (epigenetic) influences and cell–cell interactions in regulating( E k0 H6 J! h; L
developmental programs. Experimental embryologists further refined their
' d9 E: Q9 |6 r* u- eskills at dissecting small bits of tissue from the embryo, recombining them9 o- Z) ~$ P* g
with other tissues in culture or transplanting them to ectopic regions in the& Y* w4 V+ j2 D8 N, r9 N% }: X: x) I/ s( j
embryo. This work led to the invention of tissue culture by Ross Harrison- r! N9 u# u# _ a9 O
and the discovery of tissue inductions by Hans Spemann./ N2 m3 o) Y& o7 V
While experimental embryology was thriving, T. H. Morgan founded the
4 y% Y, P6 u, L# d- u9 {5 lfield of Drosophila genetics. Also trained as an embryologist, Morgan was
* C0 Q5 l4 ^1 o+ r# d- Z _) m5 Vskeptical of Boveri’s idea of heritable packets, and directed his studies towards% f9 Y& Y% M/ S8 P2 V7 C
understanding the principles of inheritance. For several decades, the two fields
& F- K; s2 S+ ]had little impact on one another. Interestingly, however, after a few decades of* n0 v8 L1 c; B; r
study of the fruit fly, Morgan’s work supported the idea of discrete intracellular
. Z% m8 L0 y* \5 c0 `" Aparticles that directed heritable traits, which he named “genes.” Nonetheless,( ~, F1 w9 R$ ?7 V5 [
the fields of experimental embryology and genetics remained fairly$ d9 g: ?, ~8 X; }: {1 o1 y/ P
separate entities with distinct goals and points of view. Embryologists were
5 @% C% f# o V9 ?5 \$ r; }: ielucidating the interactions that are important for the development of numerous
# o' ]3 D3 S6 h/ [tissues and organs, whereas geneticists were focused on the fundamentals
) B8 h' f; a0 j0 }of gene inheritance, regulation of expression, and discovering the genetic( q, s5 P: D: D1 X$ _5 B
code. Indeed, elucidating the genetic basis of vertebrate development was
' |7 J( Q% S! C8 e. vdelayed until new technologies in molecular biology and cloning were devised.6 R% |# A/ a* x$ b$ \" G- k
From the field of bacterial and viral genetics came the techniques for cloning
8 C ^, E0 O+ J" r0 n5 R T5 Reukaryotic genes and constructing vectors for controlling expression. From! T9 M$ k/ E P$ K1 X2 N
the classical genetic studies in fly and nematode came the rationale for mutagenizing( Z/ n) _" Q3 P0 `% ?
the entire genome and screening for developmental abnormalities.5 O. Y' X% _7 A! \3 S
Important regulatory genes were discovered in these invertebrates, and their
3 @# h) c0 v4 N4 }# Gcounterparts were discovered in many other animals by homology cloning& a8 z. T4 c2 h/ D. z9 J- a3 R5 M5 V
approaches. Thus was born the modern field that we call developmental; e: L) d' r. |+ |
genetics.
7 h) V" ?% w$ H8 FAn important advance in the past decade is the demonstration that genes! M9 o1 o. O1 Z2 I, V4 r/ }+ ~
that regulate developmental processes in invertebrate species have important8 S# p( n) m8 ^) Z, c) _
developmental functions in vertebrates. The wealth of information concerning3 A2 |7 Q) U5 ?
the molecular genetic processes that regulate development in various animals
! g1 O4 e) R% hdemonstrates that developmental programs and biological processes are highly
2 h8 m1 I+ C! y% L- ?conserved, albeit not identical, from yeast to human. Indeed, the Human9 Z8 r& N1 d% o& Q0 I5 f. }
Genome Project has made it possible to identify the homologues in humans$ n" W7 g- ^! z5 D' ^) Y
and demonstrate that many of these regulatory genes underlie human developmental! `7 H3 `' f$ B. O# m+ o# ?
disorders and aspects of adult diseases in which differentiation processes
! c3 B+ |( `& y4 |. r- D& ?go awry. Currently, researchers are studying the fundamentals of
% M% k# [7 G0 e4 J) O" idevelopmental processes in the appropriate animal model and screening
/ x: x9 L2 R" t& k; j8 S( ohumans for mutations in the genes identified by the basic research to be likely+ M- h* l8 e: c4 a5 d" \
causative candidates. Researchers are mutagenizing vertebrate animal models
$ w4 E0 s; @$ c5 B& {8 iand screening for mutants that resemble known human syndromes. This
- M# ~2 k( R- Zcross-fertilization of fields is also impacting concepts in evolutionary biology,
8 `0 V; d5 m$ `6 @( a+ Z' n# Qxii PREFACE
* Z6 k; g- O, T& c% A8 N' Yleading to a better understanding of “ancestral” species via gene expression3 L6 v0 e+ D/ h7 b
profiles, and paradigms in stem cell biology in which naı¨ve cells may be directed+ X; a$ i1 I5 ]/ ?6 g' g
to “designer” lineages. l2 |9 Z" f4 C3 R" E+ \
Most recently, there have been significant technological advances in
" o0 d# Y6 [4 R; {; Z3 _6 E* B( Igenetic, genomic, and protein expression analyses that are having a major* S/ n: s0 t/ `; t6 o
impact on experimental approaches and analytic design. The intersection of, z% H+ y; V4 }5 u
developmental biology with these technologies offers a new view of developmental
( ~3 [3 \, p% I5 Sgenetics that is only beginning to be exploited. It is this new intersection1 c+ \1 p, Q' U
at the onset of the genomic era that is the focus of this book. The book is
; B4 C9 m y' a; zorganized into sections focused on different aspects of developmental genetics.2 s+ F0 h W; `% B
Section I discusses the impact of new genetic and genomic technologies on
, F5 _: l* k, Y" bdevelopment, stem cell biology, evolutionary biology, and understanding7 }% I/ S5 h0 n1 M7 P$ ~8 A
human birth defects. Section II discusses several major events in early embryogenesis,
! ?; @- ?/ d; U! }& Cfate determination, and patterning, including cellular determinants' {( L+ m" Y* Z0 }: c+ W
(Boveri revisited?), gene cascades regulating embryonic axis formation, signaling
$ u" a6 d$ ?3 p4 Tmolecules and transcription factors that regulate pattern formation, and
2 q! O5 y& A/ d3 Rthe induction of the primary germ layers (ectoderm, mesoderm, and endoderm).. U) k) S1 y2 y- ?
Section III describes the reorganization of the embryo via different$ e7 E/ A; g: g
types of morphogenetic and cellular movements that result in the foundation
7 g8 I1 @( \& i) S# s; K" O/ s6 Kof organ systems, and discusses the many signaling and adhesion molecules$ R8 V0 l/ E2 v6 D- ~4 s0 \+ o
that are involved in regulating these complex processes. The final three sections+ o0 ^# O' b* Y) \! A
focus on the signaling cascades and transcriptional pathways that regulate
3 Y+ B9 ^0 D# I6 c: ~organogenesis in representative systems derived from the embryonic
. ?5 b8 a9 {* k" q" n+ t2 T1 Oectoderm, mesoderm, and endoderm. These chapters illustrate how embryonic. S3 B7 `$ Y% W8 U
rudiments become organized into adult tissues, and how defects in these processes( i/ p) B( T9 i; t. E/ B
can result in congenital defects or disease. Each chapter demonstrates2 k3 ]6 ?. T) d& P9 b
the usefulness of studying model organisms and discusses how this information
( q I# q6 }5 O. _$ G2 M0 Y( `applies to normal human development and clinical disorders. Several3 ~4 \6 }0 p, |+ P& W# ]: m
chapters also discuss the utility of stem cells to repair damaged organs and
2 m$ O, Y: a0 c. U, O5 sthe application of developmental genetics to the manipulation of stem cells8 z$ e! W2 J7 x) U& s9 l
for regenerative medicine.
% o" a* X% I- Z5 p5 ^: z0 CThe goal of this book is to provide a resource for understanding the critical
& U# N: D0 T X2 n3 {1 fembryonic and prenatal developmental processes that are fundamental to* H7 O, j. E- K \4 j' t+ u, h6 B! p
the normal development of animals, including humans. It highlights new+ ?4 k f% K+ f; [! C: N1 V3 V, F
technologies to be used, new questions to be answered, and the important1 t" i3 w* ~1 |- N8 a) `& V
roles that invertebrate and vertebrate animal models have had in elucidating
2 o$ t) ^8 p. W' e" o V; gthe genetic basis of human development. Developmental genetics has reemerged; l1 m2 g3 L; g j4 w3 c# f
from its birth a century ago as a nexus of diverse fields that are using/ E7 v5 Z0 S @; i; s, N
the common language of gene sequence and function. This is influencing
- S, N1 p4 p" ]+ P9 z# O fwhat questions are posed and how the answers are used. New technologies
) x- o" T, m( D/ X' f. J/ t. Care making it relatively easy to study gene expression and regulation at single
1 }2 `/ c$ ]! \8 i; ~cell, tissue, and embryonic levels. The conservation between the genomes
' d4 t+ A; o9 `8 n( Y$ u- Kof species that are separated by vast evolutionary time encourages us to
( P% K8 B! T" j; G- Imore fully utilize animal models to gain important insights into the clinical
) q- d0 g( o9 t% _/ Grelevance of the animal model data. It is our hope that this book will stimulate- j$ g1 B& @5 @ G" o
even more cross-fertilization and interactions between evolutionary biology,
- Y1 b! z$ Y' H, q' G$ B. zdevelopmental biology, stem cell biology, basic scientists, and clinical
+ D, Y# j1 u _* f$ y* i% Uscientists.8 r) |1 c" H- Z0 Y! y5 l
I wish to thank all of the authors for contributing such exciting and
2 t6 E8 Z0 K, t7 ^3 W& mexcellent chapters, and Pat Gonzalez for keeping all of us on schedule.
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