Module 1 Flashcards
What determines which is the lead follicle pre-ovulation?
FSH sensitivity/ receptor density
What adaptation does the lead follicle undergo before ovulation?
It develops LH receptors on its granulosa cells
Give the two main effects of the LH surge on the lead follicle
Triggers ovulation
Releases oocyte of the dominant follicle from first meiotic prophase arrest
Which form of inhibin is not present in men?
A
Which cells in the woman produce androgens?
Which gonadotrophin are these cells sensitive to?
Thecal cells
LH
Which cells in the woman produce oestrogens?
Which gonadotrophin are these cells sensitive to?
Granulosa cells
FSH
What percentage of men are azoospermic?
1%
Give three genetic causes of male infertility
Autosomal recessive condition (e.g. cystic fibrosis)
Aneuploidy (e.g. Klinefelter’s syndrome)
Microdeletions (e.g. on Y chromosome)
Kallman syndrome
Give three signs of Klinefelter’s syndrome
Reduced IQ Tall stature Gynaecomastia Poor muscle development Infertility by early twenties
Why are cystic fibrosis patients almost always infertile?
Vas deferens fails to form
What method of assisted fertility is particularly effective in male cystic fibrosis patients?
Sperm aspiration
The sperm are still made and are normal, but there is an obstruction preventing them from being ejaculated
Which hormone programs male differentiation of the gonads?
Anti-Mullerian hormone
Which duct persist and develops in male gonads?
Wolffian duct
Which genetic abnormality would result in an infertile male phenotype with XX allosomes?
Translocation of the SRY gene.
This would trigger male differentiation, but the genes for manfacturing sperm would remain on the original Y chromosome, so the patient would be infertile
Microdeletions in which genes could lead to male infertility?
AZFa, b, and c genes
Why does opioid use reduce fertility?
Dynorphin is an endogenous opioid which counteracts the effects of kisspeptin on GnRH release in order to balance it. Opioids activate the same receptors as dynorphin and so reduce GnRH release, which silences the HPG axis
Describe the effect of oestrogen on the AVPV in rats
Oestrogen exerts positive feedback on Kiss1 neurons in the AVPV
Describe the sexual development of a child with a GnRH knockout
They will not go through puberty
What is the effect on male FSH/LH of Kisspeptin?
They will increase
What is the effect on female FSH/LH on kisspeptin?
There will be little if any effect in the follicular stage of the menstrual cycle. However in the pre-ovulatory stage administration of kisspeptin will cause a large rise in FSH and LH
What is the effect of oestrogen on kisspeptin neurons in the arcuate nucleus?
Negative feedback
What effect would administration of exogenous oestrogen to a female rat immediately post-natally have on the hypothalamus?
Masculinisation of the hypothalamus - the AVPV would not develop
Masculinisation of the AVPV is caused by oestrogen, testosterone only exerts an effect because it is aromatised to oestrogen
What triggers the LH surge?
An activational effect due to rising oestrogen which increases sensitivity of the pituitary to GnRH
What effect would knockout of TAC3R have?
TAC3R is the neurokinin B receptor, and KO would cause a failure to got through puberty and infertility
What effect does ghrelin secretion have on GnRH release?
Decreases - it is the hunger hormone
What effect does PYY have on GnRH release?
Increases - it is a satiety hormone
What effect does leptin release have on GnRH secretion?
Leptin is permissive to GnRH release - it is required
What two ways is leptin thought to exert its effects on GnRH neurons
Kisspeptin neurons
Glutamate neurons in ventral premamillary nucleus
What proportion of cancer can supposedly be attributed to lifestyle factors rather than chance?
1/3
What type of mutation usually creates an oncogene?
A gain of function mutation
What type of mutation usually causes cancer in a tumour suppressor gene?
A loss of function mutation
What are the ten hallmarks of cancer
Sustained proliferative signalling Evading growth suppressors Resisting cell death Replicative immortality Inducing angiogenesis Invasion and metastasis De-regulation of cellular genetics Immune evasion Genome instability and mutation Tumour-promoting inflammation
Which tumour suppressor mutation is associated with a worse breast cancer prognosis?
p53
Which receptor is the primary driver of growth in breast cancer?
Oestrogen receptor
What is the normal function of the BRCA gene?
DNA repair
What is the Warburg effect?
Cancer cells use anaerobic respiration (glycolysis) even in aerobic environments
How do cancer cells acquire replicative immortality?
Up-regulation of telomerase allows cells to continue dividing indefinitely, instead of reaching senescence after a certain number of divisions
How do cancer cells induce angiogenesis?
Hypoxia in cancer cells leads to a build-up of hypoxia inducible factor (HIF) which is degraded under normoxic conditions. HIF translocates to the nucleus and causes vascular endothelial growth factor (VEGF) production, which is then released from the cell and affects endothelial cells, promoting their survival, replication, and migration. Endothelial cells also release platelet-derived growth factor (PDGF) which promotes survival and replication of nearby pericytes which support endothelial cells when forming blood vessels
What type of cell transition occurs prior to invasion?
Give three cell changes that characterise this transition?
Epithelial to mesenchymal
Loss of cell polarity/ change in morphology, increased motility, loss of adherent junctions, expression of proteases
Which four terms are used to classify endometrial hyperplasia?
Simple vs. complex
Typical vs. atypical
Give three risk factors for endometrial cancer
Obesity T2DM Hypertension Nulliparity Unopposed oestrogen exposure (including tamoxifen and HRT use) Radiation PCOS Early menarche Late menopause
What are most cases of endometrial cancer in women under 40 due to?
PCOS
What proportion of endometrial cancer does type I account for?
70-80%
What mutation is characteristic of type I endomterial cancer?
PTEN mutation
What mutation is characteristic of type II endometrial cancer?
p53 mutation
WHat is the morphology and prognosis of type II endometrial cancer
Papillary serous or clear cell
Prognosis is poor with a high rate of recurrence and a generally poor response to hormone treatments
Which type of endometrial cancer occurs as a result of unopposed oestrogen exposure?
Type I
Which lymph nodes will endometrial cancer usually spread to first?
Pelvic and para-aortic
Which viral infection is a prerequisite for cervical cancer?
HPV
Which two HPV subtypes together cause 75% of cervical cancer
16 and 18
Which two HPV subtypes account for 90% of genital warts?
6 and 11
Which cells does HPV infect?
Keratinocytes in the basal layer of the epidermis
What is the most vulnerable area of the cervix to HPV infection?
The squamo-columnar junction
Also known as the transformation zone
What is the action of the HPV E6 gene?
Induces degradation of p53 proteins
What is the action of the HPV E7 gene?
Binds and inactivates pRB, leading to its degradation
What uses does a vaccine have in HPV?
Prophylactic only
They have no therapeutic value
Where do primordial germ cells originate?
Posterior wall of the yolk sac
Describe the migration of primordial germ cells
Along the hindgut and through the dorsal mesentary to the genital ridges
Which critical gene does the SRY gene up-regulate?
Sox-9
What embryological structure do the gonads originate from?
The mesonephros
Where do Sertoli cells originate from?
Cells of the coelomic epithelium
Through what mechanism does Sox-9 cause differentiation of coelomic epithelial cells into Sertoli cells?
Sox-9 is present in Sertoli cells and up-regulates PgD synthase and FGF9. PgD is released and induces Sox-9 expression in neighbouring cells, which then differentiate into Sertoli cells
Describe the action and expression of steroidogenic factor 1 (SF1)
SF1 activates AMH release to drive male differentiation. It is initially expressed in Leydig and Sertoli cells, but Sertoli cells later lose the expression
At what point are oocytes arrested?
Diplotene of prophase of the first meiotic division
At the time of menarche, how far towards their eventual height has a girl on average progressed
95%
What is usually the first sign of puberty in females?
Breast development
Usually precedes menarche by 2-3 years
Between what age ranges does puberty usually occur for boys and girls?
What are the mean ages for each?
Boys: 9-14
Girls: 8-14
Boys: 11.5
Girls: 10.5
How much does adrenarche precede puberty by?
1-2 years
Is precocious puberty concerning in males or females?
It is common and benign in females, but more often concerning in males
Give 5 factors that may influence puberty
Low body fat Exercise Thyroid issues Chronic inflammatory disease Genetics Nutrition Endocrinological disease e.g. Cushing's, hyperprolactinaemia, CAH Hypothalamic/ pituitary impairment
What testicular volume indicates a male has begun puberty?
What ovarian volume indicates a female has begun puberty?
What ovarian volume indicates a female has completed puberty?
4ml
1cm cubed
4cm cubed
How long after menarche is the first ovulation?
6-9 months
Which enzyme converts cholesterol to pregnenolone?
CYP11A1
What structure is aromatised to convert an androgen to an oestrogen?
The A ring (first carbon ring)
What is the effect of sulphonation of a steroid hormone?
It renders it inactive and water soluble so it may be excreted
Where is cholesterol transported for metabolism to hormones, and how?
Inside the mitochondria
Via a StAR protein
Give two characteristic biochemical features of PCOS
Raised androgens
Raised LH
How does IGF modulate gonadotrophin action?
It directly stimulates steroidogenesis through its own signalling pathway, but also stimulates the Akt signalling pathway of the gonadotrophin receptor.
IGF also increases the number and activity of gonadotrophin receptors
Through which pathway do gonadotrophins stimulate steroidogenesis?
Protein kinase A pathway
What are the four glycoprotein hormones?
FSh, LH, hCG, and TSH
Which subunit of glycoproteins does not vary?
Alpha
Give two effects of glycosylation on the beta subunit of glycoproteins?
Increased half-life
Altered activity
hCG has a ten-fold greater half-life than LH
Deglycosylated glycoprotein hormones can still bind their receptors, but fail to stimulate cAMP production
What frequency of GnRH pulse release favour FSH release?
Once every 90-120 minutes
What frequency of GnRH pulse release favour LH release?
Once every 30 minutes
Give two extra-HpG axis effects of FSH
Increases bone resorption
Decreases thermogenesis, and increases fat storage in adipocytes
What effect does an inactivating LH mutation have on male and female phenotypes?
Male: Disrupted puberty, micropenis, hypogonadism, azoospermia
Female: Normal puberty including gonadal development, antral follicles visible, oligomenorrhea
What effect does an inactivating FSH mutation have on male and female phenotypes?
Male: Normal puberty but subfertile with low sperm quality
Female: Infertile, arrested follicle maturation, primary hypergonadotrophic amenorrhea
Why does FSHR inactivating mutation render males totally infertile, but FSH inactivating mutations do not?
The FSHR has some constitutive activity that is preserved even if FSH is absent or mutated
Name the stages of spermatagonia development
A-dark, A-pale, A-transition (disputed), B
What process converts a spermatocyte into a spermatid?
Two rounds of meiosis
What change in DNA packaging allows DNA to be tightly packaged into the sperm head whilst remaining transcriptionally silent
Replacement of histones with protamines
Which layer of the antral follicle is vascularised?
Thecal cell layer
Describe proliferation of the granulosa cells in the primordial follicle
Initially they proliferate laterally, but as the cells become more crowded the cells change shape and become cuboidal to make room. Eventually the cells are forced to form layers, as the axis of mitosis become perpendicular
What important structure is synthesised by the oocyte as the granulosa cells divide?
The zona pellucida
What is secreted by the cumulus granulosa cells to form a blob that can be picked up by the fimbriae of the ovary?
Hyaluronan
Describe the events of follicle luteinisation
The remainder of the follicle post-ovulation is invaded by macrophages and leukocytes. The basal lamina breaks down allowing vascularisation of the follicle
What are the three main factors governing germ-cell entry into meiosis?
Retinoic acid
Dazl
Stra8
Describe the action of retinoic acid in males and females
In females it stimulates Stra8 expression
In males it is degraded by Cyp26b1
Describe the role of Dazl
Dazl regulates primordial germ cell progression to meiosis
During which part of prophase do chiasmata develop?
Pachytene
How is diplotene arrest maintained within oocytes?
GPCR on the membrane of oocytes are constitutively active and produce cAMP.
Granulosa cells produce cGMP which enters the oocyte through gap junctions and prevents the degradation of cAMP by the PDE3A enzyme. High levels of cAMP maintain meiotic arrest
Where is Kit-ligand expressed and what process is it crucial for?
It is expressed by granulosa cells (the receptors are on oocytes) and is crucial for oocyte maturation
How are oocytes released from meiotic arrest?
The LH surge triggers a shift in granulosa cells that causes them to withdraw their processes from the oocyte. cGMP in the oocyte decreases, allowing cAMP to be degraded and meiosis progresses
At what point is meiosis II arrested, and when is it resumed?
Metaphase
Fertilisation
Which species of bacterium is responsible for maintaining an acidic vaginal pH?
Lactobacillus
How does the sperm reach the Fallopian tube?
A combination of cilial wafting and peristalsis-like uterine contractions
Inert particles have been shown to be able to reach the Fallopian tube so its probably not that much to do with the sperm
How does cervical mucous influence the journey of the sperm (positively and negatively)?
Hydration of the mucous peaks during ovulation to make it permeable to sperm
The mucous provides a barrier so that malformed sperm are less able to reach the Fallopian tubes
Mucous prevents phagocytosis of sperm by maternal leukocytes
Give two major change seen in sperm after capacitation
Increase in motility and development of a ‘whiplashing’ tail beat
Surface molecules which interact with the zona pellucida are unmasked
What triggers capacitation?
What other function does this chemical serve relative to the sperm?
Progesterone
It provides a chemotactic gradient for sperm to move along
Describe the events that occur within the sperm upon capcitation
Progesterone increases the sperm membrane’s permeability to calcium (though there is no progesterone receptor on sperm). The influx of calcium triggers opening of CatSper channels within the flagellum (tail) which open to allow further calcium influx.
Give 5 key functions of the epididymis
Further maturation of sperm Concentration of fluid Induction of quiescence to prevent premature acrosome reaction or capacitation Storage of sperm Passage of sperm through peristalsis Removal of degenerating sperm
Which cells control pH in the epididymis and how?
Apical cells
ATPase and carbonic anhydrase II
Which segment of the epididymis is most heavily involved in concentrating fluid, and how?
Initial segment
Sodium-linked transporters
Which segment of the epididymis coats the sperm in the proteins that are removed at capcitation?
Corpus
Which region of the epididymis is most contractile and responsible for emission of sperm?
Cauda
What is the best treatment for a prolactin-secreting tumour
Dopamine agonists (e.g. bromocriptine, cabergoline) Surgery is rarely necessary
What characterises PCOS?
Anovulation with clinical and/or biochemical features of hyperandrogenism
Why is weight loss first-line treatment for a patient with PCOS and BMI >30?
Because obesity exacerbates the symptoms of PCOS, and fertility may improve sufficiently on weight loss alone
Why is FSH low in PCOS?
Multiple lead follicles develop instead of just one. As a consequence, oestrogen levels are unusually high which suppresses FSH, which prevents follicles from further progressing
Give two drug treatments for PCOS
Clomiphene: inhibits oestrogen receptors in hypothalamus so removes negative feedback and boosts GnRH and FSH
Letrozole: Aromatase inhibitor which decreases circulating oestrogen to allow FSH levels to return to normal
What is the biggest danger of exogenous FSH therapy?
Ovarian hyperstimulation syndrome
Which nucleic acids can become methylated, and at which position?
Cytosine
5th carbon
What proportion of methylated cytosine residues are found in CpG islands?
70-80%
Why are methylated cytosine residues under-represented in the genome?
Because methylated cytosine is vulnerable to losing its amide group to become 5-methyluracil, which is essentially analogous to thymine, and so is not registered as an error by DNA repair machinery
Where are CpG islands most commonly found within DNA?
Towards the end of gene promoter regions
What effect does CpG methylation have on residues in CpG islands, and how?
Gene silencing (It has the opposite effect on cytosine residues outside of CpG islands) CpG island methylation sterically inhibits factor recruitment to the promoter region, and recruits methyl-CpG-binding proteins which remodel chromatin to make it inaccessible for transcription
What overall methylation pattern is seen in genomes in cancer?
Global hypomethylation
In what genomic location would hypermethylation be associated with cancer?
Tumour suppressor genes
What percentage of p53 mutations occur at methylated cytosines (in sporadic colorectal cancer)?
50%
What effect does UV light exposure have on p53?
Causes pyrimidine dimers to form in its DNA sequence making mutations more common
Name two therapies that act by altering DNA or histone methylation or acetylation
DNA methyltransferase inhibitors - myelodysplatic syndrome
Histone deacetylase inhibitors - T-cell cutaneous lymphoma
Give two uses for epigenetics in cancer
Treatment therapies
Classifying populations based in methylation in the same way they are classified based on genes ([prognostic and diagnostic biomarkers)
Which disease does GSTP1 gene methylation correspond to?
Prostate cancer
Which hormone may be measured to diagnose and even predict menopause instead of FSH?
Anti-Mullerian hormone (not menstrual cycle dependent)
Why is FSH high in the build-up to menopause?
Ovarian ageing results in less Inhibin B secretion, so FSH rises
Why is heavy, erratic menstrual bleeding a symptom of menopause?
Anovulatory cycles become more common in the build-up to menopause. Without ovulation, there is no progesterone, so oestradiol remains high and the endometrium continues to grow until it finally sheds leaving to heavier than normal bleeding
Which is the main oestrogen during menopause?
Estrone
What is thought to be the cause of hot flushes?
Narrowing of the ‘thermoneutral zone’ in the temperature regulation part of the hypothalamus
Which functions are progesterone receptor A important for?
Ovulation and implantation
Which functions are the progesterone B receptor important for?
Breast development during puberty
Particularly branching/ proliferation and differentiation of alveolar buds in breast tissue
How do progestins affect oestrogen receptors?
They promote redistribution of oestrogen receptor binding away from pro-proliferative genes
What is the only point of difference between progesterone receptor A and B?
The presence of an activation function 3 domain on progesterone receptor B
Describe the 7 steps of the cancer-immunity cycle
Release of cancer cell antigens into circulation
Uptake and presentation of antigen on APC
Activation of T-cell
Trafficking of T-cell to tumour
Infiltration into tumour
Recognition of cancer cells
Killing
Describe two cytokine-based cancer therapies
Interferon-alpha: initiates response similar to anti-viral resposne. Used as an adjuvant in treating melanoma
IL-2: Triggers activation and expansion of t-cell populations. Used against metastatic melanoma and renal cell carcinoma
Name the four types of cancer vaccines
Tumour cell - tumour cells are extracted and modified to make them more immunogenic, then are re-transfused
Dendritic cell - dendritic cells are extracted from peripheral blood then expanded using IL-4 and GM-CSF and activated via exposure to tumour antigens. They re re-transfused to activate t-cells
Protein/ peptide
Infection - e.g. HPV vaccines which control the infection which causes the cancer, thereby limiting cancer rates
Give four ways in which a monoclonal antibody treatment can act on cancer
Signalling inhibition: e.g. Herceptin targets HER2 receptor causing it to internalise and degrade
Antibody-mediated cytotoxicity: e.g.Rituximab (anti-CD20)
Delivery of conjugates: not particularly common, but antibodies can be used to deliver more targeted chemotherapy. One type of conjugate involves fixing enzymes to tumour cells, then giving chemotherapy as a prodrug that is only metabolised to its active form where the enzyme it present
Blocking immunosuppression - one of the most successful recent breakthrough therapies. CTLA-4 and PD1 are the main immunosuppressive receptors for T-cells (PD1 had a broader role in negative regulation) and suppression of these receptors leads to a more vigorous t-cell response. Nivolumab is a PD1 blocker, and Ipilumumab is a CTLA-4 blocker
What is the advantage of using engineered t-cells over t-cell transfer?
Engneered t-cells can express chimeric antigen receptors which don’t require MHC stimulation, and so cna target cancer cells that have lost MHC
Give three down-sides to t-cell transfer
There is a dissapointing clinical response
Only 30-40% of tumour biopsies yield sufficient lymphocyte for the procedure to work
It takes 6 weeks
What triggers the LH surge?
Increased sensitivity to circulating GnRH levels
There is no increase in GnRH release that corresponds to the LH surge, instead there is increased gonadotrophin release in response to the same level of GnRH. This is why women have different reponses to kisspeptin at different stages of the menstrual cycle
