Nephrogenesis and WT1 Lecture Flashcards

A set of 65 flashcards covering kidney development, molecular signaling (GDNF/Ret, WNT, BMP4), and WT1-related diseases such as Wilms Tumour, based on the lecture notes.

What tissue induces the outgrowth and branching of the ureteric bud?

Metanephric mesenchyme (MM)

Who performed co-culture experiments in 1955 showing the ureteric bud branches when placed with spinal cord?

Grobstein

What did Saxen's trans-filter experiments in the 1960s-70s indicate about the signal from the MM?

A soluble factor from the metanephric mesenchyme induced ureteric bud outgrowth and branching.

What is the key paracrine signal produced by the metanephric mesenchyme for ureteric bud outgrowth?

Glial derived neurotrophic factor ($GDNF$)

Where is the specific receptor tyrosine kinase $Ret$ expressed during nephrogenesis?

In the ureteric bud ($UB$)

Which transcription factors are required for the induction of $GDNF$ in the metanephric mesenchyme?

$Pax2$ and $Hoxb11$

What is the typical phenotype of $Gdnf$ or $Ret$ knockout mouse models?

Kidney agenesis (no, or very rudimentary, kidneys)

In $Gdnf$ heterozygous ($+/-$) animals, which kidney specifically tends to exhibit agenesis?

The right kidney

Which transcription factors initiate the successive stages of pronephros, mesonephros, and metanephros?

$Odd-1$, $Pax2$, $Pax8$, and $Lim1$

What structure facilitates waste removal from glomerular capillaries into the Bowman's space?

Pedicels (podocyte foot processes)

How many times is the process of nephrogenesis repeated to generate a full nephron complement?

$100,000s$ of times

Which factor is first secreted by the mesenchyme to induce $Ret$ expression in the nephric duct?

Retinoic acid

What transition do metanephric mesenchyme cells undergo to form a nephron?

Mesenchyme to epithelial transition ($MET$)

Which factors secreted by the ureteric bud promote the survival and proliferation of the metanephric mesenchyme?

$FGF2$, $FGF9$, and $BMP7$

What happens to metanephric mesenchymal cells if they are left uninduced?

They undergo apoptosis.

What is the role of $WT1$ in the metanephric mesenchyme?

It promotes survival, proliferation, and the mesenchymal to epithelial transition ($MET$).

Which signaling molecule from the ureteric bud acts 'upstream' of $WNT4$ to promote MM survival and aggregation?

$$WNT9B$$

What transcription factor determines whether metanephric mesenchyme cells remain as progenitors or differentiate?

$$Six2$$

High expression of which transcription factor maintains metanephric mesenchyme as progenitors?

$$Six2+$$

Which cell adhesion protein is induced during epithelialisation of the metanephric mesenchyme by $WNT6$?

$$E-cadherin$$

What type of signaling is required for the autocrine initiation of the mesenchyme to epithelial transition ($MET$)?

$WNT4$ signaling

What is the phenotype of $Wnt4$ knockout mice?

They have condensed cap mesenchyme but do not form epithelium, leading to kidney agenesis.

How do newly formed epithelial cells break down the basal lamina of the ureteric bud tip for fusion?

By secreting metalloproteases

Which transcription factor is expressed in newly synthesized comma- and s-shaped bodies?

$$Lim1$$

Lack of which proteins leads to polycystic kidney disease?

Polycystin proteins $1$ and $2$

What factor is produced by podocytes to promote the differentiation of angioblasts into glomerular endothelium?

Vascular endothelial growth factor ($VEGF$)

Which pathway coordinates the balance between branching and cell division in the ureteric bud?

$GDNF/Ret$ and $WNT$ signaling pathways

Which factor stabilizes ureteric bud branches by promoting the synthesis of matrix proteins?

TGFeta1

What is the role of $BMP4$ in ureteric bud development?

It antagonizes branching, restricting it to appropriate sites.

Which molecule specifies the branching pattern and is expressed in branches but not in tips?

Collagen type $XVIII$

What is the function of Gremlin ($Grem1$) in kidney development?

It is an inhibitor of $BMP4$ signaling, preventing the suppression of bud outgrowth.

Deletion of which direct inhibitors of $GDNF$ leads to supernumerary bud phenotypes?

$Foxc1/2$ (transcription factors), $Slit2$ (ligand), and $Robo2$ (receptor)

Where does the receptor for $BMP4$ reside in the developing kidney?

In the 'stalk' regions of the epithelium

Which RTK antagonist acts in the nephric duct to refine the $GDNF-Ret$ signaling domain?

$$Sprouty$$

What does $WT1$ stand for?

Wilms tumour suppressor protein $1$

According to Knudson’s 2-hit hypothesis, how many $WT1$ alleles must be inactivated for tumors to develop?

Both ($2$)

What kind of ectopic tissue is often found in Wilms’ tumours?

Skeletal muscle

Wilms’ tumours frequently show activating mutations in which gene?

$CTNNB1$ (encoding beta-catenin)

Which imprinted gene frequently has a 'double dose' in Wilms’ tumours?

$$IGF2$$

What is the genetic cause of WAGR syndrome?

Deletion of one $WT1$ allele

What does the 'W' in WAGR syndrome stand for?

Wilms Tumour

What mutation type typically causes Denys-Drash syndrome?

A missense mutation in the zinc finger ($ZF$) of one $WT1$ allele

What are two clinical features of Denys-Drash syndrome besides Wilms tumour risk?

Glomerular sclerosis and gonadal abnormalities

What specific genetic disruption causes Frasier syndrome?

Exon $9$ splice donor disruption of one $WT1$ allele

Does Frasier syndrome typically involve a high frequency of Wilms tumours?

No

What are the two specific isoforms of $WT1$ mentioned as necessary for proper kidney development?

$WT1+KTS$ and $WT1-KTS$

What is the result of deleting both $WT1$ alleles in a mouse (null phenotype)?

Metanephric mesenchyme ($MM$) apoptosis and kidney agenesis

Adult renal-cell carcinoma is closely related to which specific subset of normal kidney cells?

Proximal tubule cells

According to single-cell transcriptomic studies, Wilms tumor cells are related to which fetal kidney cells?

Ureteric bud ($UB$) and pretubular aggregate ($PV$) cells

What is one role of $WT1$ in the mature kidney?

Maintenance of podocytes

What is the effect of $BMP4$ knockout on ureteric bud development?

It reliefs inhibition of bud outgrowth, leading to supernumerary buds.

What signaling pathway does $WNT9B$ use in combination with $WNT6$?

The canonical beta-catenin signaling pathway

What characterizes the 'cap mesenchyme'?

Aggregated metanephric mesenchyme around the tips of the ureteric bud with increased $WT1$ expression.

How many nephrons are generated in a human kidney?

$$100,000s$$

Which factor promotes cell division in the elongating tips of ureteric bud branches and induces $Wnt11$ expression?

$$GDNF$$

What does LOH stand for in the context of Chr. 11 mutations in Wilms’ tumours?

Loss of heterozygosity

What does LOI stand for regarding $IGF2$ in Wilms' tumours?

Loss of imprinting

At what stage of human development can developing structures/cells be seen in the kidney?

$15-16$ weeks

What is the function of the Bowman’s capsule?

It surrounds the renal corpuscle and collects waste dumped by podocytes.

What is the source of the cells that form the glomerular endothelium?

The metanephric mesenchyme ($MM$)

Which molecules are involved in the transcription factor cocktail that initiates the metanephros?

$Odd-1$, $Pax2$, $Pax8$, and $Lim1$

What type of stem cells are metanephric mesenchymal cells?

Multipotent stem cells

What is the consequence of $Hoxb11$ knockout in the MM?

No $GDNF$ is produced, resulting in no ureteric bud induction.

What is the effect of $WT1$ Cre-deletion in combination with $Ctnnb1$ mutations?

A defect in the mesenchyme to epithelial transition ($MET$) which is key for Wilms' tumour.

Name one application of kidney development knowledge in regenerative medicine.

Nephrotoxicity screening (or patient-derived stem cell disease modeling/functional tissue generation)