Genomic coordinate (human 13:27,920,001 IPF1).
Cytoband (human 13q12.2 IPF1).
OMIM’ genes @ 13q12.2 = 6 genes.
ClinVar = 350 IPF1 variants reported.
PANTHER Classification is “transcription factor” PC00218.
Swallowtail chromosome-13 is 308 genes.
Chromosome-13 Cytobands: WCWCCWG6BGBGB2GB2
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Here I present: “Pancreatic Agenesis”, Victor McKusick, Mendelian Inheritance in Man’, 1966. (PDX1)
The diagram BELOW illustrates a cusp catastrophe model showing how continuous changes in PDX1 gene activity and environmental signaling create sudden, discontinuous shifts in pancreatic development.
📊 Core Mechanics of the Model
The model maps how three distinct variables interact to determine whether a pancreas develops normally or fails to form.
Pancreatic Developmental State: The vertical axis measures the final outcome, ranging from high (normal development) to low (complete absence of the organ, or agenesis).
Tissue Structural Parameter: Represents the biological competence or readiness of the initial tissue area (pancreatic primordium).
Paracrine Signal Gradient: Represents the strength of external developmental signals interacting with the PDX1 gene program.
🧬 Phenotypic Outcomes & Attractors.
Depending on where an individual falls on these parameter scales, the system settles into one of three stable states or “attractors”:
Normal Pancreas (Lower Sheet): Achieved with adequate PDX1 activity and tissue competence, resulting in proper endocrine and exocrine organ function.
MODY4 / Diabetes Susceptibility (Lower Sheet Edge): Caused by mild or heterozygous PDX1 variants. The pancreas forms, but has impaired beta-cell function, leading to Maturity-Onset Diabetes of the Young type 4 or an elevated risk for Type-II diabetes.
Pancreatic Agenesis 1 / PAGEN1 (Upper Sheet): Caused by severe, biallelic PDX1 disruptions. This results in a complete failure of the pancreas to form, causing neonatal diabetes and exocrine insufficiency.
⚠️ The “Catastrophe” (Sudden Switch).
The core takeaway of the model is the fold line and cusp. While a person can experience a “smooth, gradual change” in their signaling environment or gene activity (yellow sphere pathway), crossing a critical threshold causes a sudden, catastrophic jump (dashed line) directly from the lower sheet to the upper sheet. This explains why minor variations in underlying parameters can sometimes trigger a drastic, all-or-nothing developmental failure rather than a partial defect.
