Quiz 12/6

Question 1

mesoderm segments

Answer 1

intermediate, axial, paraxial, and lateral plate

Question 2

axial mesoderm becomes

Answer 2

notochord

Question 3

intermediate mesoderm becomes

Answer 3

kidneys and gonads

Question 4

paraxial mesoderm becomes

Answer 4

somites

Question 5

lateral plate mesoderm becomes

Answer 5

circulatory system, body cavity, pelvis and limb bones

Question 6

somites give rise to

Answer 6

sclerotome (vertebrae/cartilage), dermomyotome (skeletal muscle and back dermis)

Question 7

what does the formation of somites result in?

Answer 7

segmentation of the vertebrate body plan where each vertebrae is a segment

Question 8

formation of somites

Answer 8

occurs in pairs of right and lefts along the neural tube through EMT. Early somites can become any somatic cell, but once they go through EMT, they become committed to forming certain cell types (sclerotomes or dermomyotomes)specification of somites

Question 9

specification of somites

Answer 9

gain identity through interactions with the surrounding neural tube, notochord, and ectoderm. sclerotomes form closest to the neural tube and dermomyotomes form from the remaining epithelial somites

Question 10

signaling that specifies somites

Answer 10

initially, BMP gradient from ectoderm but notochord and somitic mesoderm express noggin to repress BMP signal, resulting in a gradient of BMPs. Somites come from low BMP levels (Foxc1/Foxc2), lateral mesoderm come from high BMP levels (Foxf1)

Question 11

significance of Brachyury (T), Tbx6, and mesogenin

Answer 11

pioneer transcription factors for early specification of presomitic mesoderm, likely induced by Foxc1 and 2

Question 12

when Tbx6 is lost from a somite

Answer 12

results in neural identity so somite becomes NT, mesoderm expresses neural markers Sox2 and Pax6, so Tbx6 likely represses neural markers

Question 13

relationship between Mesogenin and Tbx6

Answer 13

mesogenin is upstream and necessary and sufficient for Tbx6 expression in presomitic mesoderm

Question 14

what induces stem cells of caudal (posterior) progenitor zone to become either meso or ectoderm?

Answer 14

High anterior gradient of RA, which forms somites and neural plate. RA represses Fgf8 and Tbx6, resulting in neural fates. High posterior gradient of Fgf8 and Wnt from the tailbud represses RA through Cyp26b, resulting in mesodermal fates in the middle

Question 15

how is early identity of somites along the trunk patterned?

Answer 15

Hox genes, more hox genes are posterior, fewer are anterior

Question 16

somitogenesis

Answer 16

formation of somites, occurs one pair at a time with the first somites forming right behind the otic vesicle. Somites bud-off from the anterior portion of presomitic mesoderm

Question 17

somite numbering

Answer 17

SI are most recently formed somites, S0 are somites being formed, and S-1 are the next somites to be made

Question 18

Nueromesodermal progenitor cells (NMPs)

Answer 18

cells along the most posteriormost region of the tail that have the ability to become neural tube (Sox6) or paraxial mesoderm Tbx6)

Question 19

where are NMPs found?

Answer 19

in the dorsal medial zone (DMZ), but eventually move posteriorly (collective migration) into the progenitor zone of the tailbud, reaching PSM

Question 20

maturation zone

Answer 20

area that NMPs move through that results in them expressing mesodermal markers Tbx6 and mesogenin, as well as Cdc25 which allows for one cell division

Question 21

main factors that drive axis elongation

Answer 21

cell proliferation, collective cell migration, and intertissue adhesion

Question 22

regions of zebrafish tailbud

Answer 22

dorsal medial zone, progenitor zone, maturation zone, and emerging PSM zone

Question 23

movements of neuromesodermal stem cells

Answer 23

start in the dorsal medial zone but then quickly collectively migrate into the progenitor zone where they slow and eventually migrate bilaterally into the maturation zones and then finally the PSM region

Question 24

mesenchymal to epithelial transition (MET)

Answer 24

upregulation of mesodermal posterior (Mesp) codes for a Txfactor that regulates MET, Mesp is only expressed in the anterior half of the somite

Question 25

role of Mesp

Answer 25

upregulates Eph in the anterior portion of the somites(S0) which triggers ephrin in the opposing posterior somite (S-1) and in the posterior half of it’s own somite

Question 26

when do somites bud from the PSM

Answer 26

when posterior (ephrin) half separates from the anterior (eph) half, inducing epithelializaiton

Question 27

Signaling of epithelialization

Answer 27

Cdc42 is inhibited by ephrin, which induces peripheral cells to become epithelial and surround mesenchymal somatic cell. Then, integrins are enhanced by eph-ephrin signaling which induces an ECM between the somites and promotes separation of somite SO from S-1