Developmental Bio Exam 2

multipotent

germ layer cells

level of most adult stem cells

totipotent

can form any cell in body and placenta

pluripotent

can form any cell except for placenta

cells in the inner cell mass

limited differentiation potential

progenitor cells

limited division cell

precursor

stem cell niche

where stem cells live in adults

low turn over adult stem cells

skeletal muscle and brain

high turnover adult stem cells

mesenchymal stem cells

intestine

hematopoietic

epidermis

how are stem cells regulated most of the time

extracellular mechanism →intracellular changes (epigenetic/transcription regulation)

(paracrine/endocrin/juxtacrine signaling, extracellular matrix adhesion (mechanical force), neurotransmitters)

what influences mesenchymal stem cell differentiation

elasticity of the matrices where it sits

low elasticity (0-3 kPa)

neuron

mid elasticity (4-60)

muscle

high elasticity

bone

where do embryonic stem cells come from

the inner cell mass of a blastocyst

oct3/4

acts on nanog, tells cell to remain pluripotent

c-Myc

opens up chromatin

Klf4

prevents cell death

yamanaka factors

oct 3/4, c-Myc, sox2, klf4

transcription factors given to induce pluripotent stem cells

organoid

cell cultures made in a lab that can mimic an organ, created by giving pluripotent stem cells transcription factors necessary for typical organ development

stem cell potential

range of cell types a stem cell can produce

mesenchymal stem cells

found in a variety of tissues as both stem cell and supportive cell

mullerian duct

persists through development in males, disappears in females

becomes vas deferens, epididymis, seminal vessicle

wolffian duct

persists through development in females, disappears in males

becomes oviduct, uterus, cervix, top of vagina

seminiferous tubules

where sperm is produced

follicles

contains/makes egg

how many chromosomes do humans have

46

44 autosomal, 2 sex

beta-catenin, rspo1, wnt4

important factors for development of female sex characteristics

granulosa and thecal cells

cells that make up the follicles in the ovaries

estrogen

important for development of female internal and external genitalia

sry

on the y chromosome, turns on sox9

sox9

kickstarts male sex development

sertoli cells

in the testes, release amh

amh

causes regression of the mullerian duct

leydig cells

in the testes, produce testosterone

testosterone

forms male internal genitalia and promotes dht

dht

important for development of external male genitalia

4 week development (sex determination)

bipotential gonads (could develop into male or female)

initial sex chords form

6 week development (sex determination)

primary sex chords formed, still bipotential

8 week male

testes development

20 week male

seminiferous tubule and spermatogonia formed in teste

8 week female

ovary development

20 week female

oogonium have formed (precursor to oocyte)

what happens when a female mouse in transgenic for sry

sox 9 is activated and the mouse exhibits male phenotypes

androgen insesitivity syndrome

people with xy chromosomes that present female

have internal testes and female secondary sex characteristics

what causes androgen insensitivity syndrome

loss of androgen receptor which plays a key role in the testosterone and male development pathway

barr bodies

an inactivated x chromosome to regulate dosage of genes on the chromosome

inactivated at random

temp dependent sex determination

heat affects ion channels which then activate a signaling pathway which acts on transcription factors to determine what sex is expressed in the animal

for reptiles

external fertilizaiton

egg is released into environment and is then fertilized

internal fertilization

fertilization happens inside the body

sea urchin egg

~10x larger than sperm

vitlline envelope

extracelluar matrix surrounding membrane

jelly coat

extracellular matrix around vitilline envelope

what is in externally fertilized eggs

nutritive proteins, ribosomes, tRNA, morphogenic factors, and protective chemicals

cortical granule

contains enzymes released after fertilization which prevents polyspermi

cumulus

folic that supports the egg

ovum

egg

zona pellucida

present in mammals, similar to vitalline envelope in sea urchins

sperm contacts jelly layer

first step of external fertilization

acrosome reaction

second step in external fertilization

acrosomal membrane dissolves and releases acrosomal enzymes, actin forms a needle like structure in their place at head of sperm and bindin coats the membrane around the actin

digestion of jelly layer

third step of external fertilization

binding to vitelline envelope

fourth step of external fertilization

fusion of acrosomal process and membrane of egg allowing sperm to fertilize

fifth step of external fertilization

how is cross species fertilization prevented in external fertilization

sulfated polysaccharides characterize the jelly coat and are specific to a species, these polysaccharides induce the acrosome reaction

sperm are attracted to eggs bases on proteins released by them that are species specific

bindin is species specific

bindin

binds sperm to egg surface and is species specific

polyspermi

egg is fertilized by multiple sperms

how do sea urchins prevent polyspermi

when a sperm makes contact with the egg there is a dramatic change in its charge due to influx of calcium. This positive charge prevents more sperm from binding to the egg

how do eggs get rid of excess sperm to prevent polyspermy

when sperm makes contact to egg, cortical granules containing digestive enzymes are released into the environment modifying zona pellucida so it can no longer bind to sperm

initiated by a wave of calcium across the egg

hyaline layer

formed by/after cortical granule exocytosis to prevent polyspermy

where does fertilization happen in mammals

in the oviduct

what role does progesterone play in fertilization

allows for rapid influx of calcium which generates hyperactive sperm

izumo protein

recognizes juno protein on microvilli of egg and allows for sperm-egg fusion and entry into cell

capacitation of sperm

recognize cues to be guided to egg, undergo acrosome reaction, fuse with egg cell membrane

thermotaxis

sperm swim towards warmer environment (further with into fillopian tube)

chemotaxis

sperm follow concentration gradient released by egg

e-cadherin

upregulated at 8 cell stage to induce compaction

implantation

embryo must ‘hatch’ from the zona pelllucida in order to implant into the endometrium of uterus

primitive groove/ primitive streak

homologous to blastula lip

organizer region

node

part of the primitive streak

causes neural induction and pattern the anterior-posterior axis

AVE

positions the primitive streak

what plays a role in activating hox genes

retinoic acid, wnt3, and fgf8 (posterior patterning)

nodal

regulates pitx2

pitx2

transcription factor that controls location of non-symmetrical structures (lung and heart)

what is the level of conjoined twins based on

where the primitive streak breaks

embryonic period

1-8 weeks

fetal period

9 weeks through the rest of them

how man pregnancies come to full term

~30%

how many pregnancies are born with congenital defect

~2.5%

syndrome

several symptoms that occur together

pleiotropy

idea that one gene has multiple effects

mosaic pleitropy

effects of the gene are produced independently

relational pleiotropy

defects in one part lead to other problems inderectly

genetic heterogeneity

mutations in different genes can result in the same phenotype

phenotypic heterogenity

mutation in the same gene can result in different phenotypes for different individuals because genes interact with eachother

smn gene

mutation causes spinal musclular atrophy

translocations

one piece of a chromosome breaks off and is translocated to another chromosome

preimplantation genetics

genetic tests are run on cells taken from the blastocyst

in vitro fertilization

egg fertilized outside of uterus then implanted in

teratogens

agents from outside the embryo that can effect it