Questions and Answers to aid studying vertebrate development
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Course
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University Of Southampton (UOS)
Questions and answers based on BIOL2045 Vertebrate Development lectures. Covering topics: Stem cells, Vertebrate Gastrulation, Neural tube formation and neural crest development, Gametogenesis/Sex determination, fertilisation, cleavage to implantation and implantation
Vertebrate Development
questions
Stem cells
1. Describe the fundamental features of stem cells?
2. Compare the origin of embryonic, adult and induced pluripotent stem cells, and
contrast the differences in their developmental potential?
3. Explain the mechanisms that govern stem cell divisions, self-renewal, potency and
differentiation?
4. Explain the different experimental strategies used by researchers to study the
development, treatment and cure of diseases?
5. Evaluate the main advantages and limitations of the different types of stem cells for
researchers?
1. To be a stem cell, three criteria must be covered: undifferentiated or unspecified,
have the ability to self-renew and mature and differentiate. Stem cells have 3 modes
of division: asymmetric self-renewing division, Symmetric differentiating division,
and Symmetric self-renewing division.
2. Totipotency – the single-celled zygote and the 4-8 cell embryo can generate the
embryo and the extraembryonic tissue. Pluripotency – inner cell mass/ embryonic
stem cells generate the embryo proper. Multipotency – adult or somatic stem cells,
fuel organogenesis in the embryo and regeneration in the embryo and regeneration
in the adult tissue
3. The stem cell niche is the microenvironment that influences how the stem cells
function and behave. ICM is dependent on asymmetric cell divisions, with
symmetrical divisions leading to equal segregation and asymmetric divisions leading
to unequal segregation of fate determinants, in the trophectoderm. Oct4, Sox2 and
Nanog drive a pluripotent gene expression network to maintain ICM. They must be
differentially repressed during development to allow ICM cells to give the epiblast.
The scaffold protein AMOT is phosphorylated and interacts with the E-cadherin-
Catenin adherens junction complex. Hippo signalling kinase Lats1/2 is recruited and
activated, leading to repression of Yap-Taz-Tead transcriptional complex. Cdx2
repression and Oct4 activation, which promote pluripotency.
4. Embryonic stem cells are undifferentiated/non-committed, self-renewing,
pluripotent cells. ES cells were incorporated into embryos, creating animals carrying
genetic mutations. Offspring produced by the union of the eggs and sperm held the
ES cells’ chromosomes in every cell of their bodies. Scientists have since created and
studied ‘designer’ animals, many of which mimic aspects of human disorders.
Cerebral organoids can be used to understand the mechanisms underlying human
brain expansion: from an evolutionary perspective, shed light on the pathogenesis of
neurodevelopmental disorders that affect brain size determination and tackle
difficult questions pertaining to a number of debilitating neurological diseases. hES
cells are used in research to model human disease and design customised therapies.
However, ethical and ethical limitations hamper their widespread use.
, 5. iPS cells are somatic cells that can be reprogrammed into pluripotent stem cells by
overexpression of pluripotency genes (Oct4-Sox2-Nanog). Patient-specific iPS cells
represent a powerful tool to model disease and design personalised therapies.
However, iPS cells can generate tumours. Multipotent adult stem cells naturally exist
in our bodies, and they provide a natural repair mechanism for many tissues. In
regenerative therapy adult stem cells ‘remember’ the history of their
microenvironment “niche”, so they tend less than ES or iPS to cause tumours. HSCs
are specialised adult multipotent stem cells that give rise to the myriad of cell types
that compromise our blood. They arise and differentiate following 3 important
processes during development: primitive haematopoiesis, definitive haematopoieses
and homing. HSCs are located in two niches in bone marrow (endosteal and
perivascular) where several mechanisms control their self-renewal and
differentiation potential.
Vertebrate Gastrulation
1. Describe the mechanisms of gastrulation and contrast the morphogenic cell
movements underlying amphibian and human gastrulation
2. Understand the importance of morphogenic cell movements for the specification of
the three germ cell layers during gastrulation
3. Describe the mechanisms of symmetry breaking in the fertilized amphibian egg and
understand the importance of that for gastrulation
1. Invagination starts with an epithelial sheet which forms an inpoket towards the basal
side. Involution starts with epithelium expanding and turning over on itself, tissue
then rolls over like a conveyer belt. Delamination starts by splitting of one cellular
sheet into two parallel sheets. Ingression starts with the epithelium having individual
cells undergoing epithelial-to-mesenchymal transition (EMT). They lose adhesion,
alter their shape and become migrating mesenchyme cells. Primary mesenchymal
cells (PMCs) loose cadherin complex components such as E-cadherin, beta- and
alpha-catenin, at their surface. Epiboly starts with the movement of epithelial
sheets, spreading out of an overlying sheet of cells over an underlying mass of
stationary tissue
2. Gastrulation begins with the formation of the primitive streak (groove) on the dorsal
surface of the epiblast. Invagination of the epiblast, invading and displacing the
hypoblast cells to become endoderm. Ingression of epiblast cells form the third layer
of mesoderm cells. Driven by epithelial-to-mesenchymal transition through loss of
the cell-cell adhesion molecule E-cadherin. The epiblast cells remaining on the
surface become the ectoderm.
3. Gastrulation begins the gray crescent – the region opposite the point of sperm entry.
At this point, the cortical cytoplasm rotates relative to the internal cytoplasm. This is
facilitated by the formation of parallel arrays of microtubules in the vegetal
hemisphere. The cleavage division after fertilisation must go through the gray
crescent. First visible sign of blastopore formation is a depression in a dorsal vegetal
position to form dorsal blastopore lip, where gastrulation begins. Marginal zone
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