Nephrogenesis,

1. EMBRYOLOGY OF THE KIDNEY
DR RAVIKUMAR G N
SENIOR RESIDENT
DEPT OF NEPHROLOGY
GMC TVM

2. INTRODUCTION
STAGES OF KIDNEY DEVELOPMENT
METANEPHRIC KIDNEY DEVELOPMENT
TIMELINE OF KIDNEY DEVELOPMENT
GENETIC ASPECTS
DEVELOPMENTAL ANOMALIES

3. INTRODUCTION

4. Basic concepts
Embryonic Disc= 3 germ layers.
Courtesy: osmosis.org

6. During late 1950s= The method of growing mouse embryonic kidneys as floating cultures on top of
filters.
Clifford Grobstein Lauri Saxen

8. INTERMEDIATE MESODERM
After folding of embryonic disc.
Intermediate Mesoderm form bulging on posterior abdominal wall
Nephrogenic cord/urogenital ridge.
Extension=cervical region to the sacral region.
Saxen L. Organogenesis of the Kidney. Cambridge: Cambridge University Press; 1987.

9. Nephrogenic cord
Structures formed in relation to Nephrogenic cord are:
1. Excretory tubules of the kidney.
2. Nephric duct which becomes mesonephric duct.
3. Paramesonephric duct formed lateral to nephric duct.
4. Gonads(testis and ovary).

10. STAGES OF KIDNEY DEVELOPMENT

11. Kidneys develop in three successive stages
Generating three distinct excretory structures
Pronephros
Mesonephros
Metanephros
Rostral to caudal
Aligned adjacent to the Wolffian / Mesonephric Duct.

12. PRONEPHROS
Greek-first kidney.
Develops - cranial part of Nephrogenic cord-Cervical region.
Appears on 22nd day.
Consists of pronephric tubules and pronephric duct.

13. PRONEPHROS
Principal excretory organ -larval stages of fishes and amphibians.
It is non excretory in humans.
It is transitory in mammals-Vestigial.
Induces development of mesonephros.
Disappears completely - 5 weeks of gestation (apoptosis).

15. MESONEPHROS
Greek-MIDDLE KIDNEY
Develops caudal to the pronephros.
Thoraco-lumbar region.
Appears on 24th day.

16. MESONEPHROS
It consists of a series of tubules.
Drain into the nephric duct = mesonephric duct.
Functional excretory apparatus in lower vertebrates (adult fish and amphibians)
Mammals -Acts as excretory organ for embryo until metanephros takes over.
Completely disappears by 4th month of gestation.

17. MESONEPHROS
Endothelial/peritubular myoid/steroidogenic cells of mesonephros
Migrate to adreno gonadal primordia.
Which ultimately forms the adrenal gland and gonads.
Abnormal mesonephric migration leads to gonadal dysgenesis.
Explains the common association of gonadal and renal defects in congenital syndromes ..VHL

19. METANEPHROS
Greek- Definitive /Permanent.
Third / final stage of kidney development.
Caudal end of the Nephrogenic cord.
Lumbo-sacral region.
Appears on 32nd day.

20. METANEPHROS
It results from reciprocal inductive signals.
Between metanephric mesenchyme (MM) and the
ureteric bud (UB).

22. METANEPHRIC KIDNEY DEVELOPMENT

23. Definitive kidney develops from 2 sources
1. Meta nephric diverticulum <– Ureteric bud (UB) = Collecting
2. Meta nephric blastema –> Metanephric mesenchyme (MM) = Excretory

24. The development of the kidney
1) Reciprocal signalling-
Metanephric mesenchyme(MM) & Epithelial ureteric bud (UB).
1) Inductive interactions between neighbouring Stromal cells.

25. Reciprocal inductive signals
Reciprocal induction - retinoic acid dependent.
1.METANEPHRIC BLASTEMA secretes growth factors that induce
growth of the URETERIC BUD from the caudal portion of the
mesonephric duct.
2.URETERIC BUD proliferates and responds by secreting growth factors
that stimulates proliferation and then differentiation of the
metanephric blastema into glomeruli and kidney tubules.

26. J Toxicol Pathol 2017; 30: 125–133 Review A brief review of kidney development, maturation, developmental abnormalities, and drug toxicity: juvenile animal relevancy John Curtis Seely1*

27. Metanephric blastema
Origin=Caudal part of the nephrogenic cord
Gives rise to Metanephric mesenchyme
Induced to undergo a mesenchymal-to epithelial transformation(MET).
Leads to the nephron formation from the epithelial glomerulus to the distal tubule.
Nephrons: on average 900,000–1 million in humans

28. https://www.researchgate.net/profile/Aswin_Menke/publication/9000665/figure/fig1/AS:277733436346369@1443228219134/Fig-2-Schematic-diagrams-representing-stages-of-
nephrogenesis-Upon-induction-by-the.png

29. Ureteric bud
Ureteric bud – outgrowth from the mesonephric duct near its entrance in
the cloaca (Endoderm)
Ureteric bud- elongates and penetrates the blastema

30. CRANIAL PART
Forms the urinary collecting tubule system.
Undergoes a number of dichotomous branching (symmetric -->asymmetric).
First 4 generations of tubules enlarge to form the major calyces.
Second 4 generations fuse to form the minor calyces.
The end of arched tubule induces clusters of blastema cells to form small
metanephric vesicles.
CAUDAL PART
 Forms ureter.

32. Kidney development
DEVELOPMENT OF NEPHRON -NEPHROGENESIS
DEVELOPMENT OF THE COLLECTING SYSTEM
RENAL STROMA AND INTERSTITIAL CELL
DEVELOPMENT OF VASCULATURE
RENAL ASCENT

33. Nephron is an individual unit separately induced and originating from a distinct pretubular
aggregate, the collecting ducts are the product of branching morphogenesis from the UB.
MM becomes histologically distinct from the surrounding mesenchyme and is found adjacent to the
UB.
Signals from UB induce the MM to condense along the surface
of UB.
NEPHROGENESIS

34. After condensation, a subset of the MM aggregates inferior and adjacent to the tips of
the branching ureteric bud, forming the PERITUBULAR AGREGATES (Mesenchymal
cap).
These undergo mesenchyme to epithelial transformation(MET) and form the RENAL
VESICLE .
Renal vesicle ultimately forms
o Glomerulus - glomerulogenesis
o Proximal Convoluted tubule
o Loop of Henle
o Distal Convoluted tubule Renal Vesicle

35. https://embryology.med.unsw.edu.au/embryology/index.php?title=Renal_System_Development

36. Gradual recruitment of progenitor cells during nephrogenesis
Brenner & Rector’s THE KIDNEY 11th edition

37. Renal vesicles undergo differentiation with morphologically distinct stages starting from the
comma-shaped and proceeding to the S-shaped body, capillary loop, and mature stage.
Each step involving precise proximal-to-distal patterning and structural transformations.
This process is repeated 600,000 to 1 million times in each developing human kidney.
New nephrons are sequentially born at the tips of the UB throughout fetal life.

38. GLOMERULOGENESIS
Glomerulus develops from the proximal end of renal vesicle that is furthest from the UB tip.
Glomerulus can first be identified in the S-shaped stage.
As presumptive podocytes Which appear as a columnar-shaped epithelial cell layer.
Kreidberg JA. Podocyte differentiation and glomerulogenesis. J Am Soc Nephrol. 2003;14:806–814.

39. vascular cleft develops & separates the presumptive podocyte layer from the proximal tubule.
Endothelial cells migrate into the vascular cleft.
Podocytes & endothelial cells produce the glomerular basement membrane.
Parietal epithelial cells differentiate and flatten to form the Bowman capsule.

40.  Pericytes or Mesangial cell ingrowth follows the migration of endothelial cells
 Capillary lumens are formed due to apoptosis of a subset of endothelial cells.
 At the capillary loop stage, glomerular endothelial cells develop fenestrae.
 which are semipermeable transcellular pores.
 Exposed to high hemodynamic flux.

41. TUBULAR PORTION
The tubular portion of the nephron becomes segmented in a proximal–distal order.
Leads formation :
 Proximal convoluted tubule.
 Descending and ascending loops of Henle.
 Distal convoluted tubule.

42. Overview of nephrogenesis
Brenner & Rector’s THE KIDNEY 11th edition

43. DEVELOPMENT OF THE COLLECTING SYSTEM
Derived from the Ureteric Bud.
 Initially it penetrates the metanephric mesoderm=Ampulla (Dilated tip).
Upon invasion of UB in the loose MM, signals from MM cause UB to branch
into a T – tubule.
 UB undergoes repeated branching to form :
Ureters/renal pelvis/major calyces/minor calyces/collecting ducts.
The mouse kidney has a single papilla and calyx, whereas a human kidney has 8 to 10 papillae.

44. Branching is highly patterned (Symmetrical  Asymmetrical).
After few rounds of branching of the UB with concomitant induction of nephrons from the MM.
Kidney subdivides : outer region - cortex and inner region - medulla.
Successive groups of nephrons are induced at the peripheral regions of the kidney.
known as the Nephrogenic zone.

45. THE NEPHROGENIC ZONE
Nephrogenic zone is a narrow band beneath the renal capsule.
Where the branching UB tips are found together with nascent nephrons
and self-renewing nephron progenitors.
Kidney growth and nephrogenesis occurs in a radial fashion.

46. Mature nephrons- innermost layers of the cortex and immature nephrons in -peripheral regions
Represents an active site of nephrogenesis.
Nephrogenic zone progressively thins out with the gradual depletion of nephrogenic precursors
Disappears once the remaining nephron progenitors have completely epithelialized.

47. Epithelial cells of tubules are derived from two distinct
cell lineages:
Branches
collecting part
Collecting duct, Minor
Calyx, major calyx
,pelvis, ureter.
URETERIC
EPITHELIA
LINEAGE Mesenchyme to
epithelial
Transition
Excretory part
Distal tubules, the
loop of Henle,
proximal tubules,
parietal epithelial
cells, and podocytes.
NEPHROGENI
C
MESENCHYM
E LINEAGE

48. RENAL STROMA AND INTERSTITIAL CELL
Stromal cells also derive from the MM but are not induced to condense by the UB.
Two distinct populations of stromal cells:
Cortical stromal cells -thin layer beneath the renal capsule
Medullary stromal cells -interstitial space between the collecting ducts and tubules.
Bard J. A new role for the stromal cells in kidney development. Bioessays. 1996;18:705–707.

49. Stromal cells and their derivatives coregulate ureteric branching morphogenesis,
nephrogenesis and vascular development.
Embryologic studies of kidney development.
Past emphasis on reciprocal inductive signals between MM and UB.
Recent years interest in the stromal cell as a key regulator of nephrogenesis has Researched.
RECIPROCAL SIGNALS---- INTERACTING STROMAL CELLS

50. RENIN CELLS AND THE JUXTAGLOMERULARAPPARATUS
Renin-expressing cells seen in arterioles in metanephric kidneys by week 8.
Are derived from Foxd1-expressing stromal mesenchyme.
Renin-expressing cells reside within the MM.
Give rise to juxtaglomerular cells / mesangial cells.
Starke C, Betz H, Hickmann L, et al. Renin lineage cells repopulate the glomerular mesangium after injury. J Am Soc

51. DEVELOPMENT OF VASCULATURE
Involves macro circulation and microcirculation.
By Vasculogenesis and angiogenesis.
 Develops by Branching.

52. VASCULOGENESIS – is the de novo differentiation of previously nonvascular endothelial cell
precursors into structures that resemble capillary beds.
ANGIOGENESIS – refers to sprouting from these early beds to form mature vessel structures,
including arteries veins, and capillaries.
Endothelial progenitors withing the MM give rise to renal vessels in situ, these capillaries form
a rich network around the developing nephric tubules

53. Microcirculations
of the kidney
Glomerular
capillary system
Production of the
ultrafiltrate
Vasa recta
bundles
& Peritubular
capillaries
Countercurrent
mechanism for urine
osmoregulation

54. RENAL ASCENT
Fetal metanephros =S1--S2
Adult kidney = T12--L3.
From 6th to 9th weeks: kidneys ascend to a lumbar site.
Initially the kidneys face anteriorly, but during the ascent.
the kidneys rotate 90°causing the hilum to finally face medially.

55. A: 5th -6th wk the mature kidneys lie in the pelvis with their hila pointed anteriorly
B: 7th wk the hilum points medially , kidneys in the abdomen.
C: 9th wk kidneys in the retroperitoneal position at level of L1 , complete rotation , anteromedially.

57. PRODUCTION OF URINE
Production of urine starts at the age of 10-12 weeks of gestation:
1. very dilute urine
2. small amount of urine
Filtration occurs prior to birth, maturation of tubules continues in the postnatal period.
Fetal urine is a major constituent of amniotic fluid.

58. Urinary flow rate
increases from 12ml/hr at 32 weeks gestation to 28ml/hr at 40 weeks gestation.
kidney function will reach adult level at the age of 2 years.
kidney size will reach the adult size at the age of 9 years.

59. GFR
Age GFR (ml/min/1,73m2
) Serum creatinine (mg/dl)
Premature
<30wks
30-
34wks
5-8ml
5-10 ml
<1,6
<1,2
Full term
<24 hrs
3 days to 3 wks
1-2 months
3-4 months
6months to 1 yr
15-25 ml
30-50 ml
60-70 ml
70-80 ml
80-100 ml
0,6-1,0
0,5-0,6
0,4-0,5
0,3-0,4
0,4-0,5
Adults 12020 0,6-1,1 (f)
0,6- 1,4 (m)

60. Nephron Number
Mouse kidney may contain up to 12,000–16,000 nephrons.
Humans on average have 1 million nephrons per adult kidney.
Range of total nephrons is highly variable across human populations.
Wide range in nephron number is influenced by
Genetic background,
Fetal nutrition and Environment
Maturity at birth.
Reduced nephronnumbers raises the susceptibility risk to hypertension and CKD.
Bertram JF, Douglas-Denton RN, Diouf B, et al. Human nephronnumber: implications for health and disease. Pediatr Nephrol. 2011;26:1529–

61. TIMELINE

62. Brenner & Rector’s THE KIDNEY 11th edition

63. LINEAGE RELATIONSHIPS WITHIN THE DEVELOPING MAMMALIAN METANEPHROS.
Melissa H. Little, and Andrew P. McMahon Cold Spring Harb Perspect Biol 2012;4:a008300

64. THANK YOU

65. EMBRYOLOGY-2

66. INTRODUCTION
STAGES OF KIDNEY DEVELOPMENT
METANEPHRIC KIDNEY DEVELOPMENT
TIMELINE OF KIDNEY DEVELOPMENT
GENETIC ASPECTS
DEVELOPMENTAL ANOMALIES
EMBRYOLOGY-1
EMBRYOLOGY-2

67. GENETIC
ASPECTS

68. NEPHROGENESIS
CELL PROLIFERATION
DIFFERENTIATION
APOPTOSIS
REGULATED BY GENE EXPRESSION

69. CELL PROLIFERATION
Extensive cell proliferation.
Thousand cells ------- > Millions in the mature organ.
Confined to the narrow rim of cortex – NZ.
Where actively branching ureteric bud tips and adjacent
condensing mesenchyme present.
(Winyard et al., 1996a and b)

70. APOPTOSIS
Fine tuning of cell numbers.
50% of the cells produced in the developing kidney deleted via this process.
In Cortex – seen early nephron precursors such as comma and s-shaped bodies
In Medulla-help to facilitate collecting duct remodelling.
Markedly increased apoptosis occurs in major diseases such as polycystic kidney
disease
(stewart and bouchard, 2011)

71. DIFFERENTIATION
Several levels of differentiation occur.
Early :Mesenchymal–epithelial differentiation to form renal vesicles.
Terminal :Differentiation where different cells in the same nephron
segments acquire different functions
(e.g. the α- and β-intercalated versus principal cells in collecting ducts).

72. GENES CONTROLLING NEPHROGENESIS
Outgrowth of the ureteric bud into a pre-specified area of metanephric mesenchyme.
Must occur just once @ right time / place for normal development.
The kidney may not form without it.
Slight deviation from the regular programme leads to lower urinary tract anomalies.
Genes control better studied in mice and other animals than in humans.

73. GENES INVOLVED IN NEPHROGENESIS
Harrison Textbook of internal medicine 21st edition

74. GENE FAMILIES AND SIGNALLING PATHWAYS

75. Factors from Pronephros
• Earliest determinants of pronephric fate.
• Both are under control of RA signaling.
• Depletion leads to a complete absence of pronephric tubule.
• pax8 overexpression leads to an enlargement of pronephros.
Pax8 (Paired box gene 8)
• Early pronephric marker.
• Direct target of the RA signaling.
• Essential factor for pronephric specification.
Pteg (Proximal tubules-expressed gene protein)

76. Metanephric Nephrogenesis
Nephrogenesis can be divided into the following
stages:
1. Ureteric bud induction
2. Mesenchymal-to-epithelial transition (MET)
3. Renal branching morphogenesis
4. Nephron patterning and elongation (Tubule
morphogenesis and glomerulogenesis)

77. This is complex process
 Is controlled by a large number of genes and signaling pathways
Alterations in the genes will cause CAKUT.
The various genes implicated in the different developmental stage of
nephrogenesis in mice models and human beings. (Vivante et al., 2014)

78. Nephrogenesis and human genes implicated in various stages

80. RECIPROCAL INDUCTIVE SIGNALS
METANEPHRIC MESENCHYME
Glial derived neurotrophic factor(GDNF) & RET
WT 1
Hepatocyte Nuclear Factor(HNF)
URETERIC BUD
PAX-2
WNT-4
Bone morphogenic protein(BMP)

81. J Toxicol Pathol 2017; 30: 125–133 Review A brief review of kidney development, maturation, developmental abnormalities, and drug toxicity: juvenile animal relevancy John Curtis Seely1*

82. METANEPHROS
GDNF/RET SIGNALLING
PAX–EYA–SIX CASCADE
WT1
HEPATOCYTE NUCLEAR FACTOR 1B
WNT GENES

83. GDNF/RET SIGNALLING
Glial cell line-derived neurotrophic factor (GDNF)/RET pathway
Critical for ureteric outgrowth and bud branching
Is the most important initiator.
Tyrosine kinase receptor-RET and co receptor,-GDNF alpha 1 (GDNFA1) are expressed in the
mesonephric duct.
when GDNF binds to RET /GDNFA1 ureteric bud is formed (Puri et al., 2011).
(costantini, 2010)

85. Involves positive inducers signals counterbalanced against negative repressor
molecules.
Negative regulation of GDNF is important to ensure a single ureteric bud.
Negative regulators mutations leads to multiple ureteric buds.

86. Positive regulators
• PAX2
• GATA3
• EYA1
• SIX1
• SALL1
• HOX11
Negative regulators
• FOXC1/FOXC2
• SLIT2–ROBO2
• Sprouty1 (SPRY1)

87. Transforming growth factor β1 (TGFB1) and bone morphogenic protein 4 (BMP4)
Are endogenous inhibitors of the GDNF/RET signaling pathway
Restrict the outgrowth of the ureteric bud to a single location.

90. FGFR2, independent of the GDNF/RET pathway, stimulates
ureteric budding
WT1 also induces ureteric bud formation in an independent
manner.
Angiotensin type II receptor (AGT2R) is essential for early
stages of ureteric bud morphogenesis.

91. PAX–EYA–SIX CASCADE
Part of GDNF expression
Consists of interlinked transcription factors : PAX2, EYA1, and
several SIX and SALL genes
 Coordinated expression of a cascade of several of these
factors is required for development of many organs including
the ear, eyes, and branchial arches.
(Costantini, 2010; Reidy and Rosenblum, 2009).

92. PAX genes
Are well preserved from drosophila through zebrafish to human.
Only PAX2, -3, and -8 are expressed in the developing kidney.
Pax2 was identified early because it is absolutely essential for kidney development
There is a direct correlation between expression and kidney phenotype
(Harshman and Brophy, 2011; Winyard et al., 1996a).

93. Mice & Pax2
Decreased Pax2 have aberrant kidney development
Heterozygous mutations cause hypoplasia
Pax2 knockouts lack mesonephric tubules
Metanephrons fail to form because the ureteric buds are absent.
Overexpression of Pax2 causes cystic kidneys with proteinuria and renal failure.

94. Human & Pax2
Frank human PAX2 mutations generate the ‘renal coloboma’ syndrome
Consists of optic nerve colobomas, renal anomalies, and vesicoureteric reflux
Polymorphisms with reduced PAX2 expression are associated with smaller kidneys
(Quinlan et al. 2007)

95. PAX2 regulators
PAX2 expression is upregulated by factors such as Yin Yang 1 and
VEGF
key downregulator in the kidney is the Wilms tumour gene(WT1).
 PAX2 binds to two sites in the WT1 promoter sequence and causes up
to a 35-fold increase in WT1 expression which acts in a negative
feedback loop to decrease PAX2 levels.
(Gao et al., 2005; Patel and Dressler, 2004),

96. PAX8 and PAX3
PAX8 and PAX3 are also expressed in nephrogenesis
PAX8 appears to be a co-factor in very early kidney development
Double PAX8/PAX2 mutation leads to failure of mesenchymal–epithelial transformation
(Hueber et al., 2009).

97. SIX GENES
Are important as part of developmental complexes with PAX.
SIX1 forms a developmental pathway comprising SIX1–EYA1–PAX2
Important for upregulating GDNF
Mediates ureteral smooth muscle formation
SIX2 expression Maintains a proportion of self-renewing progenitors
throughout nephrogenesis.
(Nie et al. 2010). (Self et al. 2006).

98. EYA1
Mammalian homologue of the Drosophila transcriptional co-activator ‘eyes absent’
gene
EYA1 mutations occur in a quarter of branchio-oto-renal syndrome patients
Homozygous EYA1 null mutant mice die at birth with multiple abnormalities
It can be renal agenesis because of defective ureteric bud outgrowth and
metanephric induction

99. WILMS TUMOUR GENE- WT1
Transcription factor
Originally identified as a gene involved in Wilms tumor.
More important for kidney development than tumours.
only mutated in 15% of these cancers
several other mutant genes implicated in a greater proportion
Eg: wtx, ctnnb1, and igf2 (md et al. 2011).

100. Expressed in the kidney, gonads and mesothelium.
Expressed in the metanephric mesenchyme but not in the ureteric
bud.
Makes MM tissue to respond to ureteric bud induction.
Later part , wt1 expression is lost in the cells of the proximal/distal
tubules.
Retained only in the glomerular podocytes.

102. Complete lack of WT1 is incompatible with life because of heart and lung defects.
Renal defects are
o Reduced numbers of mesonephric tubules
o Failure of ureteric bud branching
o Death of the presumptive metanephric blastema.

103. WT1 MUTATIONS SYNDROMES
1. DENYS–DRASH SYNDROME
Consists of genitourinary abnormalities, nephrotic syndrome with mesangial sclerosis.
Predisposition to Wilms tumour.
This is caused by point mutations of WT1
Predominantly affecting the zinc finger DNA-binding domains.

104. 2. WAGR SYNDROME
consists of Wilms tumour, aniridia, genitourinary abnormalities and mental retardation.
Deletion of 11q13 (WT1 &PAX6).
3. FRASIER SYNDROME
Consists of Focal glomerular sclerosis with progressive renal failure and gonadal dysgenesis.
Intronic point mutations of WT1
which affect the balance between different WT1 splice isoform.

105. HEPATOCYTE NUCLEAR FACTOR 1B
Commonest known genetic cause of congenital renal malformations
Mutations
TCF2 gene –encodes the hepatocyte nuclear factor 1B (HNF1B).
Mutations of the TCF2 gene-Renal cysts and diabetes syndrome (RCADS)
Eg: MODY
Renal malformations in RCAD are cystic dysplasia , hypoplasia , unilateral
agenesis.
In females may have uterine abnormalities.
(Adalat et al., 2009; Decramer et al., 2007)

106. WNT genes
Important for both early differentiation and later cell specification.
WNT family comprises > 20 genes.
Many expressed in normal nephrogenesis
Play key roles in both mesenchymal and epithelial lineages. (Schmidt-Ott and Barasch, 2008)
WNT signalling occurs via canonical or non-canonical pathways. (Grumolato et al.,)
Canonical WNT signalling results in activation of β-catenin-mediated transcription
 Non-canonical pathways mediated through WNT/ Ca2+ or WNT/planar cell polarity (PCP).

107. WNT4
Upregulated during mesenchymal–epithelial differentiation
Stimulated by PAX2
Mice lacking WNT4 do not progress beyond the condensate stage.
Wnt4 alone can induce tubulogenesis in isolated metanephric mesenchyme.
Loss-of-function WNT4 mutation result in mayer–rokitansky–kuster–hauser syndrome.
Which comprises defects in mullerian-derived structures and renal agenesis.
(Biason-Lauber et al., 2004).

109. WNT11
 Expressed at the tips of the ureteric bud.
Helps in ureteric branching morphogenesis
Not sufficient to induce tubulogenesis .
WNT11 mutation leads to kidney hypoplasia, perhaps by disrupting WNT11/GDNF/RET feedback.
Dickkopf-1 :Canonical inhibitor, disrupts ureteric bud branching in a similar pattern.
SALL1: Activates canonical WNT signalling and ureteric bud tip differentiation.
Mutations in SALL1 Townes–Brocks syndrome (ear, limb, heart, and renal anomalies). (Kiefer et al., 2010)

110. WNT9b
Expressed by the ureteric bud, and
Involved in both canonical and PCP signalling. (Karner et al., 2011)
Stimulate WNT4 expression leading to mesenchymal–epithelial transformation.
Both WNTs can be replaced by activating the Notch pathway.
which helps in specifying proximal epithelial and principal cells differentiation.(Sirin and Susztak, 2012)

111. PAX-2
-Causes mesenchyme epithelialisation for excretory tubule differentiation.
-Production of Laminin and Type 4 Collagen to form basement membrane.
Bone morphogenic protein(BMP)
-Stimulate proliferation of metanephric mesenchyme
-Maintain production of WT 1.

114. DEVELOPMENTAL
ANOMALIES

115. TYPES
• Congenital anomalies of the kidney and
the urinary tract (CAKUT)
Anatomic disruptions
• Congenital nephrotic syndrome
• Renal tubular acidosis
Functional disorders
• Low nephron number
• Risk for SHTN CKD
Oligomeganehronia
• ADPKD
• ARPKD
Inherited cystic disorders

116. Congenital Abnormalities of Kidney
and Urinary Tract (CAKUT)
Encompass a wide range of structural
malformations, which occur due to a defect in the
morphogenesis of the kidney and urinary tract.

117. Introduction
CAKUT are amongst the most common malformations in
humans.
CAKUT are among the most common birth defects (20-30%
of all birth defects)
Incidence is 3 to 6 per 1000 live births (Nicolaou et al., 2015).
CAKUT are the most frequent malformations detected by
antenatal ultrasound scan
(Wiesel et al., 2005) (Loane et al., 2011).

118. Understanding the genetics of CAKUT is essential
Early diagnosis and early initiation of treatment.
Prevention of end stage renal disease, especially in children.
CAKUT account for 40-50% of children with chronic kidney disease (Vivante et al., 2014).
Majority of CAKUT are sporadic and cannot be explained by monogenic inheritance.
Some single gene mutations have been identified in syndromic / non-syndromic CAKUT.
Autosomal dominant inheritance with reduced penetrance.

119. CAKUT-CLASSIFICATION
Classified into syndromic and non-syndromic types
Syndromic CAKUT -- congenital abnormalities outside the
urinary tract.
Non-syndromic CAKUT structural abnormalities are limited
to the kidney and urinary tract.

121. Evidence for a genetic etiology in CAKUT
Monogenic mouse models indicate a genetic basis for these
disorders.
Suspected because of familial segregation of renal anomalies.
Many such families have been described in literature.
Known syndromes with CAKUT and other extra-renal manifestations
with a single gene etiology also point to the existence of a genetic
basis for CAKUT.
(Monn & Nordshus, 1984; McPherson et al.,1987; Kalpan et al., 1989).

122. Etiopathogenesis of CAKUT
GENETIC
FACTORS
EPIGENETIC
FACTORS
ENVIRONMEN
TAL FACTORS

123. Environmental factors
Renal agenesis linked with pre-gestational maternal diabetes
mellitus.(dart et al., 2015)
Taking angiotensin converting enzyme inhibitors (ACEi)
during the first trimester is associated with an increased risk of
renal dysplasia. (Cooper et al., 2006)
Alcohol and cocaine exposure have been linked to a higher
occurrence of CAKUT. (Yosipiv., 2012)

124. Epigenetic factors
Epigenetic phenomena could influence
nephrogenesis.
Predetermine disease susceptibility.
Account for the variable penetrance seen in cakut.

125. Genetic factors
Etiopathogenesis of CAKUT
The classical anatomy theory- highlighted the importance
of the position of ureteric bud.
The New Understanding- advent of molecular diagnostic
techniques- Gives insights to the molecular mechanism of
development of CAKUT

126. Clinical presentation
Highly variable -asymptomatic to chronic kidney disease
requiring RRT
Can present anytime from newborn period to adulthood.
In Newborn period CAKUT can present as
Part of other malformation syndromes
Palpable abdominal mass
Respiratory distress (due to pulmonary hypoplasia.

127. Antenatal ultrasound scan- sensitivity of around 80%
Many malformations of kidney/urinary tract are
recognized as early as 20 weeks of gestation
Oligohydramnios and altered morphology of kidney or
urinary tract could indicate CAKUT.
Abnormalities of the outer ear and single umbilical
artery - increased risk of CAKUT.

128. Genetics of non-syndromic CAKUT
Identification of genes in non-syndromic forms of CAKUT has been difficult.
First single gene defect identified as causing CAKUT was a deletion in PAX2 gene
(family with optic coloboma, renal hypoplasia and VUR) (Nicolaou et al., 2015)
The second gene to be implicated in CAKUT was HNF1B
(family with two children with diabetes and renal cysts)
 PAX2 and HNF1B were two most common genes implicated in CAKUT
Contributing to 15% of all patients with CAKU. (Nicolaou et al., 2015)

129. Other Mutations identified in CAKUT patients are BMP4,
RET, DSTYK, WNT4 and SIX2.
UMOD gene has been implicated in familial juvenile
hyperuricemic nephropathy (FJHN), glomerulocystic kidney
disease (GCKD) and autosomal dominant medullary cystic
kidney disease 2.

133. Anomalies of renal form
Illustration shows structural anomalies of the kidney

134. Anomalies of renal form
Illustration shows fusion anomalies of the kidneys.

135. Illustration shows the different types of renal malrotation
Anomalies of renal position.

136. Anomalies of renal position.
Illustration shows simple and crossed renal ectopia

137. Anomalies of renal number
Illustration shows renal agenesis and a supernumerary kidney.

138. LINEAGE RELATIONSHIPS WITHIN THE DEVELOPING MAMMALIAN METANEPHROS.
Melissa H. Little, and Andrew P. McMahon Cold Spring Harb Perspect Biol 2012;4:a008300

139. THANK YOU

149. J Toxicol Pathol 2017; 30: 125–133ReviewA brief review of kidney development, maturation, developmentalabnormalities, and drug
toxicity: juvenile animal relevancyJohn Curtis Seely1*1 Experimental Pathology Laboratories, Inc., P.O. Box 12766, Research Triangle Park,