Paraxial and Intermediate Mesoderm. Mesodermal Regions Into what five regions do we subdivide the mesoderm? –prechordal plate mesoderm –chordamesoderm

Paraxial and Intermediate Paraxial and Intermediate MesodermMesoderm

Mesodermal RegionsMesodermal Regions

Into what five regions do we subdivide the Into what five regions do we subdivide the mesoderm?mesoderm?– prechordal plate mesodermprechordal plate mesoderm– chordamesodermchordamesoderm– paraxial mesoderm (somitic dorsal)paraxial mesoderm (somitic dorsal)– intermediate mesodermintermediate mesoderm– lateral plate mesodermlateral plate mesoderm

Mesodermal RegionsMesodermal Regions

Somite FormationSomite Formation

What substance What substance appears to be critical appears to be critical to the specificaton of to the specificaton of of somites from of somites from paraxial mesoderm?paraxial mesoderm?


Somites are formed in a periodic manner. What Somites are formed in a periodic manner. What appears to control this periodicity?appears to control this periodicity?


What role does the What role does the Hairy1Hairy1 gene play in somite gene play in somite formation?formation?


What factors influence the What factors influence the conversion of developing somite conversion of developing somite from mesenchyme to a block of from mesenchyme to a block of epithelial tissue?epithelial tissue?


What determines specification of somites along What determines specification of somites along anterior-posterior axis?anterior-posterior axis?


What structures are formed from the What structures are formed from the somite?somite?– cartilage of vertebrae and ribscartilage of vertebrae and ribs– dermis of dorsal skindermis of dorsal skin– muscles of rib cage, back, limbs, abdominal muscles of rib cage, back, limbs, abdominal

wall and tonguewall and tongue


As the somite differentiates what regions As the somite differentiates what regions become distinctive?become distinctive?


What factors cause differentiation of What factors cause differentiation of sclerotome?sclerotome?– sonic hedgehogsonic hedgehog– Pax1Pax1

What factors are responsible for What factors are responsible for differentiation of dermatome?differentiation of dermatome?– neurotropin 3neurotropin 3– wnt1wnt1


What factors influence the determination What factors influence the determination of the myotome?of the myotome?– epaxial myoblasts – wnt1 and 3epaxial myoblasts – wnt1 and 3– hypaxial myoblasts – wnt and BMPhypaxial myoblasts – wnt and BMP

shh inhibits BMP signal from converting shh inhibits BMP signal from converting sclerotome to myoblastssclerotome to myoblasts


MyogenesisMyogenesis

What are myogenic bHLH proteins?What are myogenic bHLH proteins?

OsteogenesisOsteogenesis

What are the three lineages giving rise to What are the three lineages giving rise to the skeleton?the skeleton?– somites – axial skeletonsomites – axial skeleton– lateral plate mesoderm – limbslateral plate mesoderm – limbs– cranial neural crest - craniofacialcranial neural crest - craniofacial


How is endochondrial ossification different How is endochondrial ossification different from intramembranous ossification?from intramembranous ossification?


What are the different stages of bone formation What are the different stages of bone formation in endochondrial ossification?in endochondrial ossification?

Intermediate Mesoderm and Kidney Intermediate Mesoderm and Kidney FormationFormation

What appears to be What appears to be needed for kidney needed for kidney formation?formation?


What are the three major stages of mammalian What are the three major stages of mammalian kidney development?kidney development?


How does the pronephros form?How does the pronephros form?– pronephric duct forms from intermediate pronephric duct forms from intermediate

mesodermmesoderm– duct cells migrate caudallyduct cells migrate caudally– anterior part of duct induces mesenchyme to anterior part of duct induces mesenchyme to

form pronephric tubulesform pronephric tubules


How does mesonephros form?How does mesonephros form?– Wolffian duct induces tubules to form from Wolffian duct induces tubules to form from

adjacent mesenchymeadjacent mesenchyme– as posterior tubules form anterior ones begin as posterior tubules form anterior ones begin

to regressto regress– source of blood forming stem cellssource of blood forming stem cells– some tubules persist in males to become vas some tubules persist in males to become vas

deferens and efferent ductdeferens and efferent duct


How does the metanephric kidney form?How does the metanephric kidney form?– in posterior part of intermediate mesoderm in posterior part of intermediate mesoderm

mesenchyme induces branching of nephric mesenchyme induces branching of nephric ductsducts

uretic buds – form uretersuretic buds – form ureters

– uretic buds induce mesenchyme to uretic buds induce mesenchyme to differentiate into nephronsdifferentiate into nephrons


Interactions of Developing KidneyInteractions of Developing Kidney

Specification of metanephric mesenchyme Specification of metanephric mesenchyme requires two sets of transcription factorsrequires two sets of transcription factors– Hoxa, Hoxc, & Hoxd 11 proteinsHoxa, Hoxc, & Hoxd 11 proteins– WT1WT1

metanephric mesenchyme can only form metanephric mesenchyme can only form kidney tubuleskidney tubules


Glial derived neurotropic factor (GDNF) causes Glial derived neurotropic factor (GDNF) causes growth of uretic budsgrowth of uretic buds


FGF2 and BMP7 secreted by uretic bud FGF2 and BMP7 secreted by uretic bud prevents apoptosis of mesenchymal cellsprevents apoptosis of mesenchymal cells

Three factors from uretic bud induce Three factors from uretic bud induce mesenchymal cells to condense and form mesenchymal cells to condense and form epithelial cellsepithelial cells– FGF2FGF2– leukemia inhibitory factor (LIF)leukemia inhibitory factor (LIF)– wnt6wnt6


Wnt4 from mesenchyme completes Wnt4 from mesenchyme completes conversion into epithelia of nephronconversion into epithelia of nephron– autocrine factorautocrine factor– may also involve Lim-1may also involve Lim-1– polycystins 1 and 2 may also be involvedpolycystins 1 and 2 may also be involved


Several different Several different mesenchymal signals mesenchymal signals affect branching of affect branching of uretic buduretic bud– GDNFGDNF– TGFTGFββ-1-1– BMP4BMP4– collagen XVIIIcollagen XVIII

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Paraxial and Intermediate Mesoderm. Mesodermal Regions Into what five regions do we subdivide the mesoderm? –prechordal plate mesoderm –chordamesoderm