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发信人: centuribob (缘定), 信区: Biology 标题: -1 发信站: BBS 珞珈山水站 (Fri Oct 13 23:59:21 2006) In late 1962, Francis Crick and I began a long series of conversations about t he next steps to be taken in our research. Both of us felt very strongly that most of the classical problems of molecular biology had been solved and that t he future lay in tackling more complex biological problems. I remember that we decided against working on animal viruses, on the structure of ribosomes, on membranes, and other similar trivial problems in molecular biology. I had come to believe that most of molecular biology had become inevitable and that, as I put it in a draft paper, "we must move on to other problems of biology which are new, mysterious and exciting. Broadly speaking, the fields which we shoul d now enter are development and the nervous system." At that time, there were extensive discussions with the Medical Research Council on building an extensi on to the Laboratory, and Max Perutz, the head of our laboratory, had been exp loring the ground with the Council. I have recently found the correspondence o n this topic, and in a letter dated 5 June, 1963 (see below), I wrote to Max and explai ned my views to him. Nematodes have not yet made their appearance, because I h ad only just started to read about them and had not yet formulated any ideas. Some people thought that our approach was too "biological" and would lead us a way from molecular biology, but, in any event, we were asked to make a formal proposal, and a document was accordingly submitted to the Council in October, 1963. During the summer I had formulated my ideas, and as you will see from th e document and the Appendix referred to, the now familiar lines of the project had emerged. Note that the paper refers to C. briggsae; it was some time befo re C. elegans was selected in preference. I hope readers will enjoy the last, brief paragraph of the Appendix. They shou ld understand that it has expanded into the contents of this book, and achievi ng it has taken more than 20 years and the labors of a large number of people. Sydney Brenner September 1987 From The Nematode Caenorhabditis elegans, WB Wood and the community of C elega ns researchers, eds., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, 1988. Letter to Max Perutz 5 June, 1963 Dear Max, These notes record and extend our discussions on the possible expansion of res earch activities in the Molecular Biology Laboratory. First, some general remarks. It is now widely realized that nearly all the "cl assical" problems of molecular biology have either been solved or will be solv ed in the next decade. The entry of large numbers of American and other bioche mists into the field will ensure that all the chemical details of replication and transcription will be elucidated. Because of this, I have long felt that t he future of molecular biology lies in the extension of research to other fiel ds of biology, notably development and the nervous system. This is not an orig inal thought because, as you well know, many other molecular biologists are th inking in the same way. The great difficulty about these fields is that the na ture of the problem has not yet been clearly defined, and hence the right expe rimental approach is not known. There is a lot of talk about control mechanism s, and very little more than that. It seems to me that, both in development and in the nervous system, one of the serious problems is our inability to define unitary steps of any given proces s. Molecular biology succeeded in its analysis of genetic mechanisms partly be cause geneticists had generated the idea of one gene-one enzyme, and the appar ently complicated expressions of genes in terms of eye color, wing length and so on could be reduced to simple units which were capable of being analyzed. M olecular biology succeeded also because there were simple model systems such a s phages which exhibited all the essential features of higher organisms so far as replication and expression of the genetic material were concerned, and whi ch simplified the experimental work considerably. And, of course, there were t he central ideas about DNA and protein structure. In the study of development and the nervous system, there is nothing approachi ng these ideas at the present time. It is possible that the repressor/operator theory of Jacob and Monod will be the central clue, but there is not very muc h to suggest that this is so, at least in its simple form. There may well be i nsufficient information of the right kind to generate a central idea, and what we may require at the present is experimentation into these problems. The experimental approach I would like to follow is to attempt to define the u nitary steps of development using the techniques of genetic analysis. At prese nt, we are producing and analyzing conditional lethal mutants of bacteria. The se are mutants which are unable to grow at 44C but do grow normally at 37C. Th e mutations affect genes controlling the more sophisticated processes of the b acterial cell, and some work which we have already done indicates that it will be possible to dissect the process of cell division into its unitary steps. W e have mutants in which neither a cell membrane septum nor a cell wall is made , others in which a septum is made but not a cell wall septum and so on. We ha ve mutants in which the control of DNA replication is affected. I intend to ex pand this research activity in the near future. Our success with bacteria has suggested to me that we could use the same appro ach to study the specification and control of more complex processes in cells of higher organisms. As a first stage, I would like to initiate studies into t he control of cell division in higher cells, in particular to try to find out what determines meiosis and mitosis. In this work there is a great need to "mi crobiologize" the material so that one can handle the cells as one handles bac teria and viruses. Hence, like in the case of replication and transcription, o ne wants a model system. For cell division, in particular meiosis, the ciliate s seem the likely candidates. Already, in these cells, the basic plan of meios is is present and there is no doubt that the controlling elements must be the same in ciliates as they are in the oocytes of mammals. Another possibility is to study the control of flagellation and ciliation. Thi s again is a differentiation in higher cells and its control must resemble the control in amoebo-flagellates. As a more long term possibility, I would like to tame a small metazoan organis m to study development directly. My ideas on this are still fluid and I cannot specify this in greater detail at the present time. As an even more long term project, I would like to explore the possibilities o f studying the development of the nervous system using insects... Excerpts from Proposal to the Medical Research Council, October, 1963 In summary, it is probably true to say that no major discovery comparable in i mportance to that of, say, messenger RNA, now lies ahead in this field, but th e detailed elucidation of the mechanisms already discovered is nevertheless vi tal. The new major problem in molecular biology is the genetics and biochemistry of control mechanisms in cellular development. We propose to start work in this field and gradually make it the Division's main research. In the first place, control mechanisms can be studied most easily in micro-org anisms, and this work has already begun. In addition we should like to start e xploratory work on one of two model systems. We have in mind small metazoa, ch osen because they would be suitable for rapid genetic and biochemical analysis . Proposals for such work, which we plan to begin within the next few months, are set out in Appendix I. APPENDIX I Differentiation in a Nematode Worm Part of the success of molecular genetics was due to the use of extremely simp le organisms which could be handled in large numbers: bacteria and bacterial v iruses. The processes of genetic replication and transcription, of genetic rec ombination and mutagenesis, and the synthesis of enzymes could be studied ther e in their most elementary form, and, having once been discovered, their appli cability to the higher forms of life could be tested afterwards. We should lik e to attack the problem of cellular development in a similar fashion, choosing the simplest possible differentiated organism and subjecting it to the analyt ical methods of microbial genetics. Thus we want a multicellular organism which has a short life cycle, can be eas ily cultivated, and is small enough to be handled in large numbers, like a mic ro-organism. It should have relatively few cells, so that exhaustive studies o f lineage and patterns can be made, and should be amenable to genetic analysis . We think we have a good candidate in the form of a small nematode worm, Caenor habditis briggsae, which has the following properties. It is a self-fertilizin g hermaphrodite, and sexual propagation is therefore independent of population size. Males are also found (0.1%), which can fertilize the hermaphrodites, al lowing stocks to be constructed by genetic crosses. Each worm lays up to 200 e ggs which hatch in buffer in twelve hours, producing larvae 80 microns in leng th. These larvae grow to a length of 1 mm in three and a half days, and reach sexual maturity. However, there is no increase in cell number, only in cell ma ss. The number of nuclei becomes constant at a late stage in development, and divisions occur only in the germ line. Although the total number of cells is o nly about a thousand, the organism is differentiated and has an epidermis, int estine, excretory system, nerve and muscle cells. Reports in the literature de scribe the approximate number of cells as follows: 200 cells in the gut, 200 e pidermal cells, 60 muscle cells, 200 nerve cells. The organism normally feeds on bacter ia, but can also be grown in large quantities in liver extract broth. It has n ot yet been grown in a defined synthetic medium. To start with we propose to identify every cell in the worm and trace lineages . We shall also investigate the constancy of development and study its control by looking for mutants. -- 尽人事,安天命. You will when you believe. ※ 来源:·珞珈山水BBS站 http://bbs.whu.edu.cn·[FROM: 128.146.132.*]
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发信人: centuribob (缘定), 信区: Biology
标  题: -1
发信站: BBS 珞珈山水站 (Fri Oct 13 23:59:21 2006)

In late 1962, Francis Crick and I began a long series of conversations about t
he next steps to be taken in our research. Both of us felt very strongly that
most of the classical problems of molecular biology had been solved and that t
he future lay in tackling more complex biological problems. I remember that we
decided against working on animal viruses, on the structure of ribosomes, on
membranes, and other similar trivial problems in molecular biology. I had come
to believe that most of molecular biology had become inevitable and that, as
I put it in a draft paper, "we must move on to other problems of biology which
are new, mysterious and exciting. Broadly speaking, the fields which we shoul
d now enter are development and the nervous system." At that time, there were
extensive discussions with the Medical Research Council on building an extensi
on to the Laboratory, and Max Perutz, the head of our laboratory, had been exp
loring the ground with the Council. I have recently found the correspondence o
n this topic, and in a letter dated 5 June, 1963 (see below), I wrote to Max and explai
ned my views to him. Nematodes have not yet made their appearance, because I h
ad only just started to read about them and had not yet formulated any ideas.
Some people thought that our approach was too "biological" and would lead us a
way from molecular biology, but, in any event, we were asked to make a formal
proposal, and a document was accordingly submitted to the Council in October,
1963. During the summer I had formulated my ideas, and as you will see from th
e document and the Appendix referred to, the now familiar lines of the project
had emerged. Note that the paper refers to C. briggsae; it was some time befo
re C. elegans was selected in preference.
I hope readers will enjoy the last, brief paragraph of the Appendix. They shou
ld understand that it has expanded into the contents of this book, and achievi
ng it has taken more than 20 years and the labors of a large number of people.

Sydney Brenner
September 1987
From The Nematode Caenorhabditis elegans, WB Wood and the community of C elega
ns researchers, eds., Cold Spring Harbor Laboratory Press, Cold Spring Harbor,
1988.

Letter to Max Perutz
5 June, 1963
Dear Max,

These notes record and extend our discussions on the possible expansion of res
earch activities in the Molecular Biology Laboratory.

First, some general remarks. It is now widely realized that nearly all the "cl
assical" problems of molecular biology have either been solved or will be solv
ed in the next decade. The entry of large numbers of American and other bioche
mists into the field will ensure that all the chemical details of replication
and transcription will be elucidated. Because of this, I have long felt that t
he future of molecular biology lies in the extension of research to other fiel
ds of biology, notably development and the nervous system. This is not an orig
inal thought because, as you well know, many other molecular biologists are th
inking in the same way. The great difficulty about these fields is that the na
ture of the problem has not yet been clearly defined, and hence the right expe
rimental approach is not known. There is a lot of talk about control mechanism
s, and very little more than that.

It seems to me that, both in development and in the nervous system, one of the
serious problems is our inability to define unitary steps of any given proces
s. Molecular biology succeeded in its analysis of genetic mechanisms partly be
cause geneticists had generated the idea of one gene-one enzyme, and the appar
ently complicated expressions of genes in terms of eye color, wing length and
so on could be reduced to simple units which were capable of being analyzed. M
olecular biology succeeded also because there were simple model systems such a
s phages which exhibited all the essential features of higher organisms so far
as replication and expression of the genetic material were concerned, and whi
ch simplified the experimental work considerably. And, of course, there were t
he central ideas about DNA and protein structure.

In the study of development and the nervous system, there is nothing approachi
ng these ideas at the present time. It is possible that the repressor/operator
theory of Jacob and Monod will be the central clue, but there is not very muc
h to suggest that this is so, at least in its simple form. There may well be i
nsufficient information of the right kind to generate a central idea, and what
we may require at the present is experimentation into these problems.

The experimental approach I would like to follow is to attempt to define the u
nitary steps of development using the techniques of genetic analysis. At prese
nt, we are producing and analyzing conditional lethal mutants of bacteria. The
se are mutants which are unable to grow at 44C but do grow normally at 37C. Th
e mutations affect genes controlling the more sophisticated processes of the b
acterial cell, and some work which we have already done indicates that it will
be possible to dissect the process of cell division into its unitary steps. W
e have mutants in which neither a cell membrane septum nor a cell wall is made
, others in which a septum is made but not a cell wall septum and so on. We ha
ve mutants in which the control of DNA replication is affected. I intend to ex
pand this research activity in the near future.

Our success with bacteria has suggested to me that we could use the same appro
ach to study the specification and control of more complex processes in cells
of higher organisms. As a first stage, I would like to initiate studies into t
he control of cell division in higher cells, in particular to try to find out
what determines meiosis and mitosis. In this work there is a great need to "mi
crobiologize" the material so that one can handle the cells as one handles bac
teria and viruses. Hence, like in the case of replication and transcription, o
ne wants a model system. For cell division, in particular meiosis, the ciliate
s seem the likely candidates. Already, in these cells, the basic plan of meios
is is present and there is no doubt that the controlling elements must be the
same in ciliates as they are in the oocytes of mammals.

Another possibility is to study the control of flagellation and ciliation. Thi
s again is a differentiation in higher cells and its control must resemble the
control in amoebo-flagellates.

As a more long term possibility, I would like to tame a small metazoan organis
m to study development directly. My ideas on this are still fluid and I cannot
specify this in greater detail at the present time.

As an even more long term project, I would like to explore the possibilities o
f studying the development of the nervous system using insects...

Excerpts from Proposal to the Medical Research Council, October, 1963
In summary, it is probably true to say that no major discovery comparable in i
mportance to that of, say, messenger RNA, now lies ahead in this field, but th
e detailed elucidation of the mechanisms already discovered is nevertheless vi
tal.
The new major problem in molecular biology is the genetics and biochemistry of
control mechanisms in cellular development. We propose to start work in this
field and gradually make it the Division's main research.

In the first place, control mechanisms can be studied most easily in micro-org
anisms, and this work has already begun. In addition we should like to start e
xploratory work on one of two model systems. We have in mind small metazoa, ch
osen because they would be suitable for rapid genetic and biochemical analysis
. Proposals for such work, which we plan to begin within the next few months,
are set out in Appendix I.

APPENDIX I
Differentiation in a Nematode Worm
Part of the success of molecular genetics was due to the use of extremely simp
le organisms which could be handled in large numbers: bacteria and bacterial v
iruses. The processes of genetic replication and transcription, of genetic rec
ombination and mutagenesis, and the synthesis of enzymes could be studied ther
e in their most elementary form, and, having once been discovered, their appli
cability to the higher forms of life could be tested afterwards. We should lik
e to attack the problem of cellular development in a similar fashion, choosing
the simplest possible differentiated organism and subjecting it to the analyt
ical methods of microbial genetics.
Thus we want a multicellular organism which has a short life cycle, can be eas
ily cultivated, and is small enough to be handled in large numbers, like a mic
ro-organism. It should have relatively few cells, so that exhaustive studies o
f lineage and patterns can be made, and should be amenable to genetic analysis
.

We think we have a good candidate in the form of a small nematode worm, Caenor
habditis briggsae, which has the following properties. It is a self-fertilizin
g hermaphrodite, and sexual propagation is therefore independent of population
size. Males are also found (0.1%), which can fertilize the hermaphrodites, al
lowing stocks to be constructed by genetic crosses. Each worm lays up to 200 e
ggs which hatch in buffer in twelve hours, producing larvae 80 microns in leng
th. These larvae grow to a length of 1 mm in three and a half days, and reach
sexual maturity. However, there is no increase in cell number, only in cell ma
ss. The number of nuclei becomes constant at a late stage in development, and
divisions occur only in the germ line. Although the total number of cells is o
nly about a thousand, the organism is differentiated and has an epidermis, int
estine, excretory system, nerve and muscle cells. Reports in the literature de
scribe the approximate number of cells as follows: 200 cells in the gut, 200 e
pidermal cells, 60 muscle cells, 200 nerve cells. The organism normally feeds on bacter
ia, but can also be grown in large quantities in liver extract broth. It has n
ot yet been grown in a defined synthetic medium.

To start with we propose to identify every cell in the worm and trace lineages
. We shall also investigate the constancy of development and study its control
by looking for mutants.

--
            尽人事,安天命.
          You will when you believe.

※ 来源:·珞珈山水BBS站

http://bbs.whu.edu.cn·[FROM: 128.146.132.*]

[返回单文区目录]