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FTO Adipocyte Fate Simulator

FTO Mechanism Simulator

Interactive model of Claussnitzer et al., NEJM 2015

CRISPR-Cas9 Intervention

Edit rs1421085 C → T to rescue phenotype

1. The Genetic Switch rs1421085
...GTCA
C
GATC...
ARID5B
Repressor Bound
Super-Enhancer Active
2. Long-Range Circuitry Chrom 16
FTO
Intron
Targets IRX3
IRX5
Expression Level
Unbound enhancer loops over to IRX3/IRX5 (distant genes), driving their overexpression.

Adipocyte Type

White

Energy Storage

Mitochondria

Depleted

UCP1 Levels: 10%

Lipid Storage

Hypertrophic

Size: 90 µm

Simulated Seahorse Assay (O₂ Consumption)

Comparing metabolic rates of risk vs. protective genotypes. Based on Figure 3D.

OCR (pmol/min)
Basal
Stimulated

Risk (Reference)

Low Basal
No Response

Current Subject

Interpretation: The subject shows low basal respiration and fails to respond to adrenergic stimulation. This indicates a loss of thermogenic capacity, leading to energy storage (obesity).

Why this paper is a breakthrough

From Correlation to Causality

For years, Genome-Wide Association Studies (GWAS) flagged the FTO region as the strongest genetic risk factor for obesity, but no one knew why. This paper solved the puzzle by showing the risk variants don't affect the FTO protein itself. Instead, they act as a distant control switch for two entirely different genes, IRX3 and IRX5, located over a million base pairs away.

A Cellular Switch for Obesity

The study revealed a fundamental developmental fork in the road: precursor cells can either become White Adipocytes (storage) or Beige Adipocytes (burning). The risk variant (C) breaks the binding site for the ARID5B repressor, forcing cells down the storage path. By editing a single nucleotide with CRISPR, the researchers could flip this switch, turning human fat cells from "storers" into "burners."

Visualization inspired by: FTO Obesity Variant Circuitry and Adipocyte Browning in Humans (Claussnitzer et al., 2015)

https://www.dyetnutrition.com/fto