Figure 21-27 Molecular Biology of the Cell (© Garland Science 2008)

教科書 9.2.1

無駄をそぎ落とした細胞：リボソームも、小胞体も、ゴルジ体もない（復習：図1.3)。つまり、蛋白質は合成されない。

核（DNAが詰まっている。しかし、DNAの転写は止められている。 ）

ATP（エネルギー）合成装置：ミトコンDNAは消滅する運命

1

Figure 21-32 Molecular Biology of the Cell (© Garland Science 2008)

教科書 9.2.1

実際の受精は1/300,000,000

（3億分の1）

ハムスター卵とヒト精子：生殖能力診断

10%以上進入すれば正常

2

21.3 Calcium Wave During Fertilization

When a sperm cell fuses with this sea urchin egg cell, calcium ions begin rushing

into the cell at the site of fusion.

In these experiments, calcium concentrations are visualized and measured

with a fluorescent dye that becomes increasingly brighter the more calcium is

present.

Brightness is then translated into a color scale, and, in this three-dimensional

display, into peak heights, where red and high peaks represent the highest

calcium concentrations.

A second rise of the calcium concentration can be observed after fertilization.

It occurs during the movement

教科書 9.2.1

カルシウム濃度の上昇が引き金となって酵素を包んでいる顆粒がポップコーンのようにはじける。→酵素が働き、2つ目の精子が入らないようにバリアを作る。（次の動画で詳しく。）

カルシウムイメージング：本学では白川英樹先生がご専門。

3

21.4 Sea Urchin FertilizationA sea urchin egg during fertilization is visualized here simultaneously by phase

contrast microscopy and by fluorescence microscopy. The egg contains a fluorescent

dye that becomes brighter in the presence of calcium ions.

When a sperm cell fuses with the egg, the fluorescence image shows a wave

of calcium ions that sweeps through the cytosol, starting from the initial point of

sperm–egg fusion. Following the path of the calcium wave, we see a membrane,

called the fertilization envelope, rising from the cell surface. The fertilization

envelope protects the fertilized egg from the outside environment, and prevents

the entry of additional sperm. The rise in cytosolic calcium triggers an elevation

of the fertilization envelope through the process of exocytosis.

Exocytosis releases hydrolytic enzymes stored in vesicles. Action of the

released hydrolases causes a swelling of material surrounding the cell,

which in turn elevates the fertilization envelope.

Exocytosis can be visualized directly in this system. For this purpose, the

plasma membrane is labeled with a fluorescent dye, seen on the right. Each time

a vesicle fuses, it leaves a depression in the plasma membrane which, in the

optical sections shown, appears as a ring of increased fluorescent staining.

On the left, differential interference contrast microscopy is used to directly

view the exocytic vesicles that underlie the plasma membrane. The vesicles are

visible here, because they are densely packed with protein and consequently

have a different refractive index from the surrounding material. Each time a

vesicle exocytoses, it disperses its contents and disappears from the image. This

effect is best seen when we step back and forth between adjacent frames of the movie.

発展 教科書 9.2.1

4

Figure 22-3 (part 1 of 3) Molecular Biology of the Cell (© Garland Science 2008)

教科書 9.2.2

と図9.1ウニの胞胚

原腸↑

5

Figure 22-3 (part 2 of 3) Molecular Biology of the Cell (© Garland Science 2008)

教科書 9.2と図9.1と9.2

中胚葉細胞

腸管

骨

お尻の穴

内胚葉

口

6

Figure 22-3 (part 3 of 3) Molecular Biology of the Cell (© Garland Science 2008)

教科書 9.2.3動物の体の基本設計図：口とお尻が貫通した図

（外胚葉） （内胚葉）

（中胚葉）

口

お尻の穴7

22.3 Gastrulation （原腸胚形成）

During gastrulation, cells of this developing frog embryo rearrange in a dramatic

ballet of orchestrated cell movements. In a continuous motion, cells from the

outer layer of the embryo (胚) sweep towards the vegetal pole and start invaginating,

forming a deep cavity in the interior.

The paths of the cells and the topology of these rearrangements are best

seen in this animation of an embryo that has been sliced open. The different cell

layers that are formed in this way have very different fates.

Cells that line the newly formed cavity, called the endoderm, develop into

the lining of the gut(腸) and many internal organs such as liver, pancreas, and lung.

Cells in the middle layer, called the mesoderm, give rise to muscle and connective

tissue. Cells remaining on the outside, called the ectoderm, go on to form

the outer layer of the skin, as well as the nervous system.

教科書 9.2.3

と図9.2

8

22.2 Developing Egg Cells

This frog egg cell has been fertilized and starts dividing. The first cell divisions

occur very rapidly. Cells divide every thirty minutes.

This timing is very precise. Egg cells that have been fertilized at the same

time divide and develop in almost perfect synchrony.

After a day or two, embryonic development （胚発生）is completed and tadpoles

hatch from the eggs.

教科書 図9.1と9.2

ここまでのまとめの動画

9

Figure 22-6b Molecular Biology of the Cell (© Garland Science 2008)

教科書 9.2.4

細胞塊

（宿主となる）胚に移植

発生途上の体構造を再編成

オーガナイザーを切り取って、別の胚に移植する実験

10

22.4 Spemann’s OrganizerHans Spemann and Hilde Mangold were pioneers of developmental biology.

They showed how the pattern of the embryo is created by interactions between

one group of cells and another. In 1924 they made a famous discovery. They

found that a small piece of tissue called the Organiser, taken from a specific site

in the early frog embryo and transplanted to another embryo, could control the

behavior of neighboring cells and direct the formation of an entire body axis.

The key experiment is re-enacted here by a modern developmental biologist,

using the frog Xenopus Lavis.

Two Xenopus embryos are maneuvered under the dissecting microscope.

The embryos are beginning to gastrulate. The blastopore, where cells are tucking

into the interior, is visible as a dark crescent in the embryo on the left. The

dorsal lip of the blastopore contains the Organizer cells.

With a pair of forceps and a fine tungsten needle, a block of Organizer tissue

is cut from the embryo on the left. Using a hair plucked from a human eyebrow,

the block of tissue is gently pushed into a site on the ventral side of the other

embryo.

An hour later, the graft has healed into the host embryo and the organizer

cells have been integrated at an atopic site.

Two days later, the host embryo has developed into conjoined twins. The

grafted Organizer has caused the host cells around the graft to form a second

body axis, complete with central nervous system, eyes, somites, and other structures.

教科書 9.2.4

11

Figure 22-32 Molecular Biology of the Cell (© Garland Science 2008)

教科書 9.3.1

前うしろ 末端 背と腹

発生の一番最初には、大雑把に前後・左右・上下を決めるための遺伝子が働き、それぞれの場所に別々の蛋白質を合成して、目印とする。

セントラルドグマの復習：うしろ遺伝子（うしろDNA)→うしろmRNA(Nanos)→うしろ蛋白質

12

Figure 22-26 Molecular Biology of the Cell (© Garland Science 2008)

教科書 9.3頭 胸 お腹

13

Figure 22-38 Molecular Biology of the Cell (© Garland Science 2008)

教科書 9.3.2

前 うしろ

ホメオティック遺伝子は体節間の違いを決める。

まずはおおまかに体の前後・左右・上下を決めてから細部（節）を決める。

14

Figure 22-44 Molecular Biology of the Cell (© Garland Science 2008)

教科書 9.3.2と9.3.3

遺伝子の並んでいる順番と翻訳されてできる蛋白質の空間的位置とは対応している。

15

Figure 22-46 Molecular Biology of the Cell (© Garland Science 2008)

教科書 9.3.2と9.3.3・昆虫と哺乳類それぞれのHox遺伝子群・体の領域への対応付け

ハエも人間も、対応するHox遺伝子の配列や順番は似ている。

ハエのDNA

共通祖先のDNA

人間のDNA

16

22.5 Drosophila Development(発生)

During development, a Drosophila embryo(胚) undergoes many complex

morphological changes. We first see migration of pole cells from the posterior end. These

cells are destined to become the germ cells of the fly. A crest develops which separates

a region that will develop into the head, mouth parts, and fore gut. At this

stage, the future tail end of the body is folded over on the dorsal side. Body segments

then become defined.

The first three segments will give rise to the head and mouth parts, the next three to the thorax,

and the remaining ones to the abdomen. Eventually, the rear end of the embryo will retract back

onto the ventral side and straighten out the

embryo. Development to this stage takes about 10 hours.

We can appreciate the complexity of these events by morphing a series of individual scanning

electron micrographs into a continuous temporal sequence: migration of pole cells;

development of various surface indentations, including openings to the air ducts, or tracheal tubes;

segmentation, and tail retraction.

A similar sequence viewed from the top—or the dorsal side. Pole cells migrate and then move into

the interior as the hind gut invaginates. The rear end is temporarily folded over onto the dorsal side

and eventually starts retracting to straighten out the embryo.

Early in development when seen from the bottom—or ventral side—a deep

groove forms during gastrulation(原腸胚形成), as mesodermal cells migrate inward, where

they become the precursor cells for many internal organs. The groove then seals

off as the cells that remain exterior zipper up.

教科書 9.3ここまでのまとめの動画

17

Figure 23-6 Molecular Biology of the Cell (© Garland Science 2008)

教科書 9.4と図9.3

外因的要因（細胞外で特定の分子が偏る）

非対称分裂

幹細胞 幹細胞

内因的要因（細胞内で特定の分子が偏る）

18

Figure 23-42 Molecular Biology of the Cell (© Garland Science 2008)

教科書 9.5.3造血系：（ほぼ）骨髄でのできごと

(例外：胸腺で)

(例外)

造血幹細胞

リンパ球前駆細胞

骨髄球前駆細胞

造血前駆細胞

巨核球

赤血球

好酸球

好中球

リンパ球★リンパ球も赤血球も、元々は同じ幹細胞から分裂したもの！

19

Figure 23-39b Molecular Biology of the Cell (© Garland Science 2008)

教科書 9.5.1骨髄

好酸球（未熟） 単球（未熟）

赤血球リンパ球（未熟）

巨核球（未熟）

赤血球の前駆細胞

好中球（未熟）

20

Figure 23-2 Molecular Biology of the Cell (© Garland Science 2008)

教科書 9.5.2と図9.4

皮脂腺

←幹細胞

21

Figure 23-68 Molecular Biology of the Cell (© Garland Science 2008)

教科書 9.5.5

ES細胞：受精卵からできた胚を壊して作ることが倫理的に問題とされている。

脂肪細胞

神経細胞

白血球

筋肉細胞

22

23.14 Embryonic Stem Cells

Embryonic stem cells, or ES cells, are able to differentiate into any cell type in

the body.

ES cells derived from an embryo can be grown in culture. Upon exposure to

an appropriate cocktail of signal molecules, the cells differentiate into specific

cell types.

In this experiment, ES cells were exposed to signal molecules, inducing the

differentiation program that specifies the development of heart muscle cells.

After a few days in culture, the previously homogeneous, undifferentiated cells,

organize into groups of highly specialized cells. Remarkably, the cells in these

groups start contracting rhythmically, indicating they have formed a fully functional

contractile apparatus, characteristic of muscle cells.

Examining GFP that has been expressed from a heart-muscle specific promoter,

shows that the appropriate gene expression programs have been activated

selectively in the beating cells.

教科書 9.5.5

23

本日のまとめ：

1.受精→初期胚形成→胚発生→個体。2. もともと１つの細胞（受精卵）が分化して別々の細胞になる。3.分化し切った細胞を補充するのが再生。例：皮膚のけががなおる、など。この場合、皮膚幹細胞が分化することで補充している。

4.個体をまるごと作れる全能性幹細胞（ES細胞など）がある。

24朝日新聞 2012.07.21