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M2M2 > Sex Development > Flashcards

Sex Development Flashcards

1
Q

Why Sex?

A

Allows for introduction of genetic variation to propagate new genetic traits

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2
Q

Sexual reproduction benefits organisms who live in what type of environment

A

Exist in a constantly changing environment

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3
Q

Sexual reproduction benefits organisms who encounter what? And need to what?

A

Encounter bacteria, viruses, and parasites, and need to fend off disease

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4
Q

Sexual reproduction benefits organisms who need to purge what?

A

Deleterious mutations

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5
Q

Sexual reproduction - 2 levels of variation

A
  • each parent share’s half genome via independent assortment
  • recombination during meiosis

*note also that specific point mutations can occur that can confer advantage (or disadvantage) evolutionarily

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6
Q

What is sexual dimorphism?

A

The phenotypic difference between males and females -

includes reproductive organs as well as body habitus

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7
Q

Sex chromosomes anueploidy leads to

A

Disorders that don’t have the normal number of X or Y chromosomes

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8
Q

Now matter how many X chromosomes you have, how many X chromosomes are active?

A 
There is only one active X chromosome, no matter how many X chromosomes you have... 
Thus, 
46,XX
47,XXX
47,XXY
48,XXYY 
all only have one active X chromosome
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9
Q

Turner Syndrome

Chromosome constitution

A

45, XO

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10
Q

Turner Syndrome

Signs at birth

A 
Prenatal cystic hygroma - cyst-like cavity filled with lymph
Webbed neck
Puffy hands and feet
Head defects
Coarctation of the aorta
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11
Q

Turner Syndrome

Stature?

A

Short Stature

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12
Q

Turner Syndrome - intelligence?

A

Normal - sometime targeted learning disabilities

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13
Q

Turner Syndrome - fertility?

A

Infertile due to non-functioning ovaries

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14
Q

Turner Syndrome - hormones?

A

Hormone dysfunction - need hormone treatment for secondary puberty

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15
Q

Turner Syndrome - distinctive features?

A

Low set ears - broad chest

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16
Q

Turner Syndrome - incidence?

A

1/2,500 newborn girls

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17
Q

Kleinfelter Syndrome

Chromosome Constitution

A

47, XXY

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18
Q

Kleinfelter Syndrome - childhood and learning?

A

Can be seen –>
Learning disabilities
Delayed speech and language
Tendency toward being quiet

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19
Q

When does Kleinfelter become obvious?

A

Becomes more obvious as puberty - sometimes not even detected until infertility issues arise?

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20
Q

Kleinfelter statures?

A

Tall

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21
Q

Kleinfelter genital issues?

A

Small testes

Hypospadias - opening of urethra is on underside of penis

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22
Q

Kleinfelter - body habitus and hair?

A

Reduced facial and body hair
Gynecomastia
Feminized body habitus

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23
Q

Kleinfelter - incidence?

A

1/500 - 1/1000 newborn boys

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24
Q

What is 47, XYY?

A

Jacobs Syndrome

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25
Q

What is Klinefelters chromosome constitution?

A

47, XXY

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26
Q

Jacobs syndrome clinical features (6)

A 
Learning disabilities 
Speech delays
Developmental delays
Behavioral and emotional difficulties
Autism Spectrum disorders
Tall stature
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27
Q

Incidence of Jacobs Syndrome?

A

1/1000 newborn boys

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28
Q

So what is Jacobs vs. what is Klinefelters?

A 
Jacobs = 47, XYY
Klinefelters = 47, XXY
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29
Q

What is 47,XXX called?

A

Triple X syndrome

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30
Q

What kind of stature do Triple X syndrome people have?

A

May have tall stature

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31
Q

Triple X syndrome increases risk of? (5)

A 
Learning disabilities 
Delayed speech 
Delayed motor milestones
Seizures
Kidney abnormalities
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32
Q

Incidence of Triple X syndrome?

A

1/1000 newborn girls

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33
Q

So, if we know that only one X is expressed regardless of the number of Xs, what sense does it make that these variations in Xs manifest phenotypes?

A

Apparently there is a pseudoautosomal region on the X chromosome which is expressed in both Xs - this is why we see variation in phenotype from 45X, 46XX and 47XXX

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34
Q

Genetic regulation of sex development

Primary sex determination =

A

Determination of the gonads

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35
Q

Gonad determination is ______________

A

Chromosomal

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36
Q

What results in a male individual?

A

Generally the presence of a normal Y choromosom

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37
Q

What results in a female individual?

A

The presence of a normal X chromosome and the absence of a Y choromosome

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38
Q

Are there exceptions to the X Y rule and Sex differentiation?

A

Of course! But, these exceptions are due to genetic variants not on x or y

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39
Q

Do we still say that “female” is the default sex?

A

Not really.
Our current understanding is that both ovaries and testes result from a common bipotential gonad
Both are active, gene-directed processes

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40
Q

Secondary sex determination is determined by?

A

Gonadal development determines secondary sex characteristics

and recall that it was the chromosomes that determined gonads (primary sex determination)

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41
Q

What is included in secondary sex characteristics?

A

Includes sex-specific organs

  • penis, seminal vesicles, prostate
  • vagina, cervix, uterus, fallopian tubes, mammary gland

Includes other phenotypic features

  • body habitus and musculature
  • hair growth
  • vocal cartilage
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42
Q

Embryology - what happens in the 4th week?

A

Primordial germ cells form in wall of yolk sac

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43
Q

At what week in development do primary germ cells form in the wall of yolk sac?

A

4th week

44
Q

Embryology - what happens in the 5th week?

A

Coelomic epithelium becomes genital ridge

45
Q

At what week in development does the coelomic epithelium become the genital ridge?

A

5TH

46
Q

What happens at six week of conception with the primordial germ cells?
with the epithelial cells of the gonadal ridge?

A

They migrate to the dorsal mesentary of the hindgut and enter the undifferentiated gonad

The epithelial cells of the gonadal ridge proliferate and form primitive sex cords

47
Q

At which week in development do the primordial germ cells migrate to the dorsal mesentary of the hindgut and enter the undifferentiated gonad? and the epithelial cells of the gonadal ridge proliferate to form primitive sex cords?

A

6th week

48
Q

In males, what happen in the 7th week of conception?

A

Differentiation of genital ridge into sertoli cells and leydig cells

49
Q

What do sertoli cells do?

A

They will eventually produce sperm

50
Q

What do Leydig cells do?

A

The are intersitital cells that produce testosterone

51
Q

In males, what happens in the 8th week of conception?

A

Leydig cells begin producing testosterone
Sertoli cells begin producing AMH
Primitive sex cords differentiate into testis and rete testis - eventually to become seminipherous tubules during puberty

52
Q

What does Testosterone tell the male fetus to do?

A

start forming male structures

53
Q

What week does male fetus start pumping out T?

A

Leydig cells begin producing T at 8th week

54
Q

Which week do the cells of the genital ridge differentiate into Leydig and Sertoli?

A

7th

55
Q

What do Sertoli cells produce?

A

AMH

56
Q

What do Leydig cells produce?

A

T

57
Q

At the 8th week of conception what do sex cords in male differentiate into?

A

Rete testis and testis cord - which will eventually become seminipherous tubules during puberty

58
Q

What happens in the 7th - 8th week of female sex development?

A

With absence of SRY –>

Primitive cords dissociate into irregular clusters –>

Medullary (primitive) cords regress and cortical (secondary) cords are formed

secondary cords are destined to become follicular cells in the ovary

follicular cells will eventually surround and oogonium which together are the primary ovarian follicle

59
Q

In female reproductive development, which week do the cortical cords form?

A

They form in the 7-8th week when the medullary (primitive) cords regress

60
Q

In female repro, what are the cortical (secodary) cords destined to become?

A

follicular cells in the ovary

61
Q

Genital Ducts - what is initially present (6 weeks)?

A

Initially, 2 pairs of genital ducts in both males and females

  • Mesonephric (Wolffian)
  • Paramesonephric (Mullerian)
62
Q

Mesonephric Duct

Results in?

A 
Male Structures 
Under the influence of T --> elongate to form
- Epididymis
- Seminal Vesicles
- Vas deferens
63
Q

SRY gene and SOX9
What are they
What do they do?

A

Both are transcription factors

Responsible for the production of AMH

Causes regression of the Mullerian duct

64
Q

FGF9
What is it
What does it do?

A

Chemotactic factor that causes tubule from mesonephric (Wolffian) duct to penetrate the gonadal ridge

Essential for differentiation of testis

65
Q

SNF1/NRFA1

What do they do?

A

Simulate differentiate of Sertoli and Leydig cells

66
Q

Paramesonephric (Mullerian) Ducts - result in?

A 
Female Structures 
Under the influence of E (from maternal and placental sources) -->
Uterus
Cervix
Broad ligament
Fallopian Tubes 
Upper 1/3 of the vagina
67
Q

Female development

What is WNT4?

A

Extracellular signalling factor responsible for the differentiation of ovary
Inhibited by SOX9

68
Q

Female development

What is DHH gene?

A

A nuclear hormone receptor
Up-regulates WNT4
Downregulates SOX9

69
Q

Female development

What is RSPO1?

A

Coactivator in WNT pathway - which differentiates ovary :)

70
Q

Development of external genitalia - what happens at 3 weeks?

A

Cells that originate from mesenchymal cells in the primitive streak migrate to form a genital tubercle and genital swellings

71
Q

Male, what does genital tubercle become?

A

Glans of penis

72
Q

Female, what does genital tubercle become?

A

Clitoris

73
Q

Male, what do genital folds become?

A

Shaft of penis

74
Q

Female, what do genital folds become?

A

Labia

75
Q

External genitalia in both males and females originate from what?

A

Urogenital sinus

76
Q

External genitalia - what signal in males to become what structures?

A

Androgen exposure (DHT) from the testis –>
penis
scrotum
urethral opening at tip

77
Q

External genitalia - what signal in females to become what structures?

A

Estrogen from maternal and placenta –>
clitoris
labia majora and minora
lower 2/3 vagina

78
Q

So to review

The first determinant is sex is

A

Chromosome and the genes on them

79
Q

So to review… the chromosomes and genes on them determine what you gonads will be (primary sex determination)… what is secondary?

A

Once your gonads form, they will produce signals that tell your body what it is going to look like both internally (tracts) and externally (2sexChar)

80
Q

What is the Prader scale?

A

Scale of virilization used to describe the external appearance of genitalia -
No virilization - female
100% virilization - male

81
Q

If we are uncertain about sex… what are tests we can run to probe further?

A

FISH for sex chromosomes and a Karyotype (or microarray) ?SRY?

Hormone studies (important early) (LH/FSH/DHT/AMH)

Consider Ultrasound study (gonads?)

82
Q

Teams to consult with disorders of sexual differentiation

A

Endocrinology
Genetics
Urology
Psychology

83
Q

Issues to consider with sex differentiation disorders (7)

A 
Underlying genetics
Family/cultural perspective
Medical/surgical outcomes
Risk for tumor
Fetal brain and hormone exp
Future sexuality
Future fertility
84
Q

DIAGNOSTIC ALGORITHM

A

SLIDE 37 LOOK AT IT!

85
Q

Androgen Insensivity Syndrome

Chromosome constitution?

A

46,XY

86
Q

AIS mode of inheritance?

A

X-linked gene,

AR is apparently X-linked

87
Q

Androgen insensitivity syndrome, what’s the problem?

A

Mutation causes abnormality of the androgen receptor

- even though the body makes androgens (T), it does not recognize or respond

88
Q

AIS - phenotype

A

Ranges from mild under-virilization (partial AIS) to full sex reversal (Complete AIS)

89
Q

What was AIS called in the past?

A

Testicular feminization

90
Q

Disorder - 5-Alpha Reductase Deficiency

Chromosome constitution

A

46, XY

Mutation causes decreased ability to convert T to DHT
Phenotype = undervirilized male with increased virilization at puberty

91
Q

What specific disorder is characterized by undervirilization in youth but then starting to look more masculine at puberty?

A

5-alpha reductase deficiency

92
Q

What is the chromosomal constitution of disorders associated with the SRY gene?

A

Can be
46, XY
46, XX

93
Q

SRY is on which Chromosome

A

Y-linked

94
Q

What happens if SRY is deleted?

A

Full sex reversal and phenotypically normal female (even though 46XY)

95
Q

What happens if there is ectopic presence of SRY gene in 46XX

A

Phenotypically normal male

96
Q

What happens if there is a mutation in the SRY of 46XY?

A

Decreased or absent production of AMH and undervirilization

97
Q

Denys-Drash and Frasier Syndrome

A

Sex reversal with 46XY

Due to mutations in WT1 gene

98
Q

Denys-Drash and Frasier Syndrome

What kind of disease do both cause

A

Chronic kidney disease

  • diffuse mesangial sclerosis (nephrotic disease)
  • focal segmental glomerulosclerosis
99
Q

Denys-Drash and Frasier Syndrome

Increased risk for what?

A

Wilms tumor (malignant tumor of kidney)

100
Q

What is WT1?

A

Transcription factor for SRY gene

101
Q

Mutation in WT1 that causes sex reversal in XY … syndrome name?

A

Denys Drash and Frasier Syndrome

102
Q

Does Mutation in WT1 effect XX?

A

Not sexually, but causes other problems

103
Q

Congenital adrenal hyperplasia

A 
Ambiguous genitalia in 46XX
21 hydroxylase deficiency
Complicated by salt wasting in first weeks of life and when stressed
- decreased Na/Cl
- Increased K
104
Q

FISH for XY –> 46XY DSD
T and DHT normal
Possiblitiles?

A

AIS

5-Alpha reductase deficiency

105
Q

FISH fOR XY –> 46XY DSD
T and DHS low
Possiblities?

A

WT1 associated disease (Frasier and Denys Drash)

SRY Mutation/Deletion

106
Q

FISH for XY –> 46XX DSD

Possiblities?

A

CAH
Ectopic SRY
Wnt4 Mutations

107
Q

AIS and risk for gonadoblastoma?

A

Only if the testes are in the abdomen - not applicable if inguinal

M2M2 (27 decks)

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