The fate of neural crest cells The mesoderm Sex determination Primordial germ cells 세포생물학 3 (임현정) March 26, 2010

Specification of the NC cells “중간” 정도의 농도로 BMP, Wnt, FGF 류의 paracrine factor들이 존재할 때 neural plate border specifiers라 불리우는 전사요소들이 유도된다. 이들은 neural crest specifiers라 불리우는 전사요소인 Slug와 FoxD3를 유도한다. Slug는 neural crest cell들이 epithelium을 떠나 이동해 가는데 필요한 것으로 보임.

NC is a transient structure. Cranial NC Trunk NC Vagal and sacral NC Cardiac NC devbio8e-fig-13-02-0.jpg Regions of the chick neural crest. The cranial neural crest migrates into the pharyngeal arches and the face to form the bones and cartilage of the face and neck. It also produces cranial nerves. The vagal neural crest (near somites 1-7) and the sacral neural crest (posterior to somite 28) form the parasympathetic nerves of the gut. The cardiac neural crest cells arise near somites 1-3; they are critical in making the division between the aorta and the pulmonary artery. Neural crest cells of the trunk (about somite 6 through the tail) make sympathetic neurons and pigment cells (melanocytes), and a subset of these (at the level of somites 18-24) form the medulla portion of the adrenal gland.

devbio8e-table-13-01-0.jpg

Neural crest cell migration in the trunk of the chick embryo (Part 1) devbio8e-fig-13-03-1.jpg Path 1 (Ventral pathway): ventrally 이동해 sclerotome의 anterior half 부분 통과 (ganglia, adrenomedullary cells, etc) Path 2 (Dorsolateral pathway): epidermis와 dermis 사이 통과 (pigment-producing melanocytes) * Sclerotome: somite의 일부로 vertebral cartilage를 만듬

13.3 Neural crest cell migration in the trunk of the chick embryo (Part 2) devbio8e-fig-13-03-2.jpg Anti-HNK1으로 염색 (NC marker)

Segmental restriction of neural crest cells and motor neurons by the ephrin proteins of the sclerotome (Part 1) devbio8e-fig-13-05-1.jpg (HNK1 staining)

Segmental restriction of neural crest cells and motor neurons by the ephrin proteins of the sclerotome (Part 2) devbio8e-fig-13-05-2.jpg

The major lineages of the amniote mesoderm (Part 1) The mesoderm The major lineages of the amniote mesoderm (Part 1) devbio8e-fig-14-01-1.jpg

The major lineages of the amniote mesoderm (Part 2) * Trunk mesoderm 1. Chordamesoderm: notochord 형성 일시적 구조로 neural tube 유도 2. Paraxial mesoderm: somite 형성 등쪽의 connective tissue 형성 (bone, muscle, cartilage, dermis) 3. Intermediate mesoderm: urogenital system (kidney, gonads) 4. Lateral plate mesoderm: notochord에서 가장 멀다 Heart, blood vessels, blood cells Limb(사지)의 중배엽성 구조 형성 devbio8e-fig-14-01-2.jpg

Gastrulation and neurulation in the chick embryo, focusing on the mesodermal component devbio8e-fig-14-02-1.jpg

* Paraxial mesoderm은 neural fold 시기에 somite 형성 (block of cells) Mature somite: a. Sclerotome – vertebrae와 rib cartilage 형성 b. Myotome – 등쪽의 musculature, ribs, limbs c. Dermatome – 등쪽의 dermis (진피) devbio8e-fig-14-02-2.jpg (Surface ectoderm 을 벗긴 상태)

14.3 Specification of somites Pax3 staining (somite의 marker) Noggin: BMP antagonist devbio8e-fig-14-03-0.jpg Specification of somites: chick의 lateral plate mesoderm이 형성될 곳에 Noggin-secreting cell들을 넣어 주니 paraxial mesoderm (somite-like)이 유도되는 것을 보여줌 (bracket 친 곳 )

Notch signaling and somite formation (Part 1) devbio8e-fig-14-05-1.jpg

Notch signaling and somite formation (Part 2) Somitogenesis Periodicity Fissure formation Epithelialization Specification Differentiation Somite의 A/P axis에는 Hox gene들이 관여 devbio8e-fig-14-05-2.jpg

Somite formation correlates with the wavelike expression of the hairy1 gene in the chick devbio8e-fig-14-06-0.jpg Somite 수: chick은 50개, mouse는 65개 (Embryonic development 과정 중 현재 몇 개의 somite가 형성이 되어 있는지 보는 것은 발달단계의 좋은 indicator)

Epithelialization and de-epithelialization in somites of a chick embryo devbio8e-fig-14-09-0.jpg

Segmental plate mesoderm transplanted into a different region in a younger embryo differentiates according to its original position devbio8e-fig-14-10-0.jpg Thoracic somite로 분화했을 segmental plate mesoderm부분을 younger embryo의 cervical somite가 될 부분으로 transplant하면 grafted mesoderm이 원래의 성격을 따라 rib을 만든다.

Intermediate mesoderm Signals from the paraxial mesoderm induce pronephros formation in the intermediate mesoderm of the chick embryo devbio8e-fig-14-20-1.jpg (A) The paraxial mesoderm was surgically separated from the intermediate mesoderm on the right side of the body. (B) As a result, a pronephric kidney (Pax-2-stained duct) developed only on the left side. (C) Lim1 expression in an 8-day mouse embryo, showing the prospective intermediate mesoderm.

General scheme of development in the vertebrate kidney devbio8e-fig-14-21-1.jpg (A) The original tubules, constituting the pronephros, are induced from the nephrogenic mesenchyme by the pronephros by the pronephric duct as it migrates caudally. (B) As the pronephros degenerates, the mesonephric tubules form. (C) The final mammalian kidney, the metanephros, is induced by the ureteric bud, which branches from the nephric duct. (D) The intermediate mesoderm of a 13-day mouse embryo showing the initiation of the metanephric kidney while the mesonephros is still apparent. The duct tissue is stained with a cytokeratin antibody.

Sex determination Chromosomal sex determination in mammals 1. Primary sex determination: chromosomes, gonads Y chromosome: testis-determining factor 2. Secondary sex determination: gonad 이외의 phenotype 결정 대부분 gonad에서 나오는 hormone들에 의해 결정

Y chromosome X chromosome

Sex determination in mammals devbio8e-fig-17-01-2.jpg

Differentiation of human gonads shown in transverse section (Part 1) devbio8e-fig-17-02-1.jpg

Differentiation of human gonads shown in transverse section (Part 2) devbio8e-fig-17-02-2.jpg

Differentiation of human gonads shown in transverse section (Part 3) devbio8e-fig-17-02-3.jpg

The development of the gonads and their ducts in mammals (Part 1) devbio8e-fig-17-03-1.jpg

The development of the gonads and their ducts in mammals (Part 2) devbio8e-fig-17-03-2.jpg

The development of the gonads and their ducts in mammals (Part 3) devbio8e-fig-17-03-3.jpg

An XX mouse transgenic for Sry is male devbio8e-fig-17-04-0.jpg

Ability of Sox9 to generate testes devbio8e-fig-17-05-0.jpg

Migration of the mesonephric cells into Sry+ gonadal rudiments (Part 1) devbio8e-fig-17-06-1.jpg

Migration of the mesonephric cells into Sry+ gonadal rudiments (Part 2) devbio8e-fig-17-06-2.jpg

Phenotypic sex reversal in humans having two copies of the DAX1 locus devbio8e-fig-17-07-0.jpg

Dax1 expression in the mouse genital ridge devbio8e-fig-17-08-0.jpg

Possible mechanism for primary sex determination in mammals devbio8e-fig-17-09-0.jpg

Primordial Germ Cells 1. All gametes arise from PGCs. 2. Frogs, nematodes, flies, etc.: PGCs are autonomously specified by cytoplasmic determinants (Germ Plasm) during cleavage. 3. Mammals, etc.: PGCs are specified by interactions among neighboring cells. Chromosome diminution (roundworm Parascaris) 이로 인해 많은 유전자가 사라지나 germ cell이 될 세포에서는 모든 유전정보가 유지된다 devbio8e-fig-19-01-0.jpg 원심분리로 인해 germ plasm이 두 개의 세포에 나뉘게 되어 두 개의 stem cell이 생긴다 “Germ plasm”: 특정 RNA나 protein이 이를 specify 한다

19.3 The pole plasm of Drosophila devbio8e-fig-19-03-0.jpg

19.6 Germ plasm at the vegetal pole of frog embryos Xcat2 mRNA의 localization devbio8e-fig-19-06-0.jpg

Day 7 mouse embryo 포유류에서는 germ plasm이 없다. 그대신 embryo에서 유도되어 만들어진다. (요막) (Epiblast)

19.7 Specification and migration of mammalian primordial germ cells Day 7 mouse embryo Morphogens devbio8e-fig-19-07-0.jpg fragilis (+) stella (+) blimp1 (+) Extraembryonic ectoderm과 epiblast junction에서 germ cell들이 유도되어 나온다. Posterior epiblast 부분으로 PGC가 들어온다.

Spermatogonia Oogonia Expression of Oct4 mRNA correlates with totipotency and ability to form germ cells Posterior Epiblast (8.5) Migrating PGCs (10.5) Inner cell mass devbio8e-fig-19-08-0.jpg Spermatogonia Oogonia

19.14 Primoridal germ cell migration in the mouse (Part 1) Hindgut devbio8e-fig-19-14-1.jpg

19.14 Primoridal germ cell migration in the mouse (Part 2) devbio8e-fig-19-14-2.jpg