Lecture 22: Progenitor Regulation

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What happens if there is excessive differentiation of progenitor cells without sufficient self-renewal?

There will be a depletion of the progenitor cell pool. (correct)

Nephron development will happen more efficiently.

The nephron formation process will accelerate.

Progenitor cells will multiply rapidly.

What marks the end of the organogenesis phase in nephron formation?

Increased self-renewal of progenitor cells.

Completion of mesenchymal-to-epithelial transition.

Generation of new progenitor cells.

Depletion of progenitor cells with no further generation. (correct)

Which transcription factor is crucial in the regulation of nephron progenitor cells?

Sox2

Six2 (correct)

Nanog

Oct4

What was the outcome when Six2 gene expression was knocked out?

Loss of nephron formation and kidney development. Signup and view all the answers

What methodology was used to trace the lineage of nephron progenitor cells?

Lineage tracing with Cre recombinase. Signup and view all the answers

Which observation indicates the morphological state of nephron progenitor cells?

Progenitor clusters around epithelial tips. Signup and view all the answers

What do Six2+ cells give rise to during nephron development?

Nephrons Signup and view all the answers

What does the movement of nephron progenitor cells suggest about their fate?

Cell fate can be influenced by location and external signals. Signup and view all the answers

What technique was used to track the movements of nephron progenitor cells in real-time?

Fluorescent reporters with a Cre driver Signup and view all the answers

What was observed about the positional behavior of nephron progenitor cells within the niche?

They move dynamically between different realms of the niche. Signup and view all the answers

What happens to early nephron cells that migrate back into the progenitor population?

They re-express progenitor markers and revert to a progenitor state. Signup and view all the answers

What does the dynamic behavior of nephron progenitor cells indicate about the traditional understanding of cell differentiation?

It challenges the view that progenitor cells are static and predetermined. Signup and view all the answers

What characterizes the growth pattern of the kidney during development?

Early growth rates are significantly higher than later rates. Signup and view all the answers

How does progenitor cell regulation affect nephron formation?

Decreased self-renewal results in reduced nephron number. Signup and view all the answers

What significant percentage of nephrons is formed shortly after birth in mice?

50% Signup and view all the answers

What is the significance of precise phenotypic analysis in kidney growth?

It provides objective data for understanding growth patterns related to progenitor cells. Signup and view all the answers

What happens to the number of nephron progenitor cells during kidney development?

It decreases as development progresses, influenced by signaling changes. Signup and view all the answers

What imaging modalities are employed in kidney development analysis?

3D imaging at both organ and cellular scales. Signup and view all the answers

What is a direct consequence of decreased nephron progenitor proliferation?

Reduced kidney size and nephron number. Signup and view all the answers

What characterizes the dynamics of progenitor and epithelial tip development?

Epithelial tips increase while progenitor cells decrease in later development. Signup and view all the answers

What is a prime area affected by kidney growth analysis?

The relationship between kidney growth and progenitor cell numbers. Signup and view all the answers

Why is kidney growth analysis crucial for understanding nephron number regulation?

It provides insight into the critical periods affecting nephron formation. Signup and view all the answers

What role do nephron progenitors play in the nephrogenic niche?

They self-renew and differentiate while interacting with stroma and epithelium. Signup and view all the answers

What is indicated by higher levels of Wnt9b in nephron progenitors?

Induction of mesenchymal-to-epithelial transition. Signup and view all the answers

What indicates the cessation of nephrogenesis after birth?

Loss of ureteric tip identity before nephron progenitor identity. Signup and view all the answers

Which signals are essential for nephron progenitor self-renewal and differentiation?

Wnt9b, Wnt11, FGF, and BMP ligands Signup and view all the answers

Which component of the nephron niche is NOT interdependent with nephron progenitors?

Mature nephrons Signup and view all the answers

Which of the following is a consequence of losing nephron progenitor identity?

Disruption of the nephrogenic niche architecture. Signup and view all the answers

What primarily drives kidney development?

Interdependence of multiple progenitor populations. Signup and view all the answers

What effect do signals from the underlying epithelium have on nephron progenitors?

Enhance nephron progenitor self-renewal. Signup and view all the answers

What is the primary role of nephron progenitor cells in kidney development?

To self-renew and differentiate into nephrons. Signup and view all the answers

What is the consequence of reducing FGF signaling in nephron progenitors?

Fewer nephron progenitors and nephrons Signup and view all the answers

How does unrestrained nephron progenitor proliferation impact health?

Delays cessation and causes pediatric cancer Signup and view all the answers

What is the role of Lin28 in progenitor cells during kidney development?

Inhibits Let7 and promotes nephron progenitor maintenance Signup and view all the answers

What happens when Lin28 overexpression is restricted to a narrow developmental window?

Expansion of nephron progenitors with positive outcomes Signup and view all the answers

What physiological changes are observed as a result of doubling nephron number?

Improved kidney function despite kidney distension Signup and view all the answers

What is the result of ablation of nephron progenitors?

Reduction in overall nephron number Signup and view all the answers

What complication arises from transient overexpression of Lin28b during kidney development?

Kidney distension resulting from fluid buildup Signup and view all the answers

What is a potential pathological consequence of increased nephron progenitor proliferation?

Risk of developing Wilms tumor Signup and view all the answers

Which of the following statements about the balance of nephron progenitor proliferation is correct?

Controlled proliferation is important for maintaining kidney health. Signup and view all the answers

Which statement about Lin28 expression and nephron number is true?

Increased Lin28 expression can prolong the nephron progenitor phase. Signup and view all the answers

Study Notes

Progenitor Stem Cell Regulation

Pluripotent Stem Cells (ES, IPS): Capable of long-term self-renewal in culture. Can differentiate into all three germ layers (endoderm, mesoderm, ectoderm) except the placenta.
Adult Stem Cells: Maintained for the majority of the lifespan. Can differentiate into tissue-specific cell types. Have the capacity to self-renew.
Transient Progenitor Cells: Exist within a limited timeframe during development (e.g., in the developing kidney), present from partway through gestation until birth. Not maintained long term. Can differentiate into a limited number of tissue-specific cell types.

Kidney Function and Disease

Kidney Role: Regulates fluid homeostasis, removes waste from blood, regulates acid-base and electrolyte balance. Produces hormones that control blood pressure, bone density, and red blood cell count.
Nephron: Specialized filtration units, composed of segmented tubular epithelium with different functions (filtration and handling of fluid and solute).
Chronic Kidney Disease: Affects about 10% of the world's population, associated with high morbidity and mortality. Involves progressive nephron loss.

Nephron Number and Development

Low nephron number increases kidney disease risk. Nephron numbers vary substantially (200,000- 2,000,000 per individual).
Premature birth is often associated with lower nephron number.
Existing nephrons have limited capacity for repair; gradual decline in nephron number occurs over time.
Importance of nephron endowment: high/normal endowment leads to slower progression towards CKD, while low endowment leads to faster progression exacerbated by comorbidities.
Nephron formation occurs during kidney development. All nephrons are formed during kidney development.
50% of nephrons are formed shortly after birth. This period is critical for regulating nephron number.

Formation of Renal Precursors (Progenitor Specification)

Initial stage where renal progenitor cells are specified.
Nephrons form at this stage.
Kidney organoids model the early kidney development phase.

Organogenesis (Nephron Formation)

Bulk of nephron formation occurs during this stage.
Involves progenitor self-renewal and differentiation into nephrons.

Maturation

Final stage where formed nephrons mature and become fully functional.
Progenitor depletion can occur during kidney development stages.

Self-Renewal and Differentiation Phase

Progenitor cells are actively dividing to both self-renew and differentiate into nephrons.
Depletion can occur from excessive differentiation without sufficient self-renewal, resulting in reduced progenitor cells.

End of Organogenesis (Transition to Maturation)

Progenitor cells are gradually used up as they form the final set of nephrons.
Progenitor depletion becomes complete as no new progenitors are formed.

Morphological and Molecular Evidence of Nephron Progenitor Cell

Observations of progenitors clustering around epithelial tips.
Mesenchymal-to-epithelial transition noted in nephron formation..
Six2 expressed in mesenchymal regions surrounding epithelial tips. Six2 knockout halts nephron formation and kidney development; proposed as a marker and regulator.

Lineage tracing

Six2 gene used to drive Cre recombinase expression.
Cre recombinase crossed with a reporter line to mark cells expressing Six2 and their descendants.
Lineage tracing showed yellow cells showing green Cre expression and red lineage marking.

Kidney Development

Interactions between three progenitor populations drive kidney development.
Components of the nephron niche include: nephron progenitor, ureteric epithelium, and stroma. These populations are interdependent.
Signal interactions between nephron progenitors and epithelium promote branching and organ growth and signals from the epithelium promote nephron progenitors' self-renewal.
Wnt9b, Wnt11, FGF, and BMP ligands promote nephron progenitor self-renewal.

Cessation of nephrogenesis

Nephron formation stops after birth due to loss of progenitor populations.
Loss of nephron progenitor identity occurs first.
Nephron progenitor cells play a crucial role in maintaining progenitor populations.

Imaging Development in 3D

Widefield imaging provides surface images but lacks accurate quantification of 3D structures.
Sectioning approach allows for analysis but loses important 3D relationships between cells, such as epithelial tips.

3D Imaging +/- Clearing

Primary antibody binds to a specific protein of interest.
Secondary antibody binds to primary antibody for fluorescent molecule tagging for visualization.
Chemical or electrical treatments enhance tissue transparency.

Multiscale Imaging

Addresses questions about kidney development, progenitor populations, and final organ formation in 3D.
Whole Mount Immunofluorescence visualizes proteins across the entire organ.

Growth Patterns

Kidney growth is not continuous; higher growth rates occur early.
Number of progenitor cells and reciprocal signaling changes dramatically across time.
Large number of progenitor cells and epithelial tips exist during early development.
Progenitor numbers decrease during late stages, potentially due to changes in signaling environment.

Nephron Formation and Timing

50% of nephrons are formed shortly after birth (mice).

Precise Phenotypic Analysis

Instead of subjective descriptions, precise measurements are taken to quantify kidney growth.
This analysis reveals differences related to progenitor populations and nephron formation.

Nephron Progenitor Regulation

Decreased progenitor proliferation results in decreased nephron number (smaller kidneys, increased risk of CKD).
Increased progenitor expansion leads to increased nephrons.
Nephron progenitor expansion improves kidney function, but regulation is needed to avoid disease.

Potential Effects of Migration on Cell Fate

Progenitor fate is not fixed but influenced by location and the encountered signals; challenging the static model.
Back-and-forth movement of cells between niches may impact self-renewal capacity of the progenitor pool.

Single Cell RNA Sequencing (scRNA-seq)

Examines nucleic acid sequence information from individual cells.
Enables detailed transcriptional profiles for each cell and identification of active genes and pathways.
Dissociation or nuclei extraction isolates individual cells
RNA from each cell is captured and barcoded
Pooled RNA is sequenced, replicates removed, and bioinformatics performs quality control
Results are detailed transcriptional profiles identifying active genes and pathways.

High Throughput Single Cell RNA-seq

Enables comparisons to bulk RNA-seq.
Achieves identification of expected cell types, including clusters.

Pathway Activity Analysis

Differential expression within cell types is analyzed for pathway activity.
Pathways are identified by the expression of pathway targets or components.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the intricate processes of nephron development, focusing on the role of progenitor cells and the factors that influence their differentiation and self-renewal. This quiz covers key transcription factors, methodologies used in research, and the significance of cellular dynamics in organogenesis.