Arhgap36 Gene and Orange Coat in Cats

GS3 – S&T

Context:

A recent study has found that an ancient mutation on the X chromosome activates the Arhgap36 gene, causing the orange coat color in domestic cats.

Key Details:

• Location: Arhgap36 gene is on the X chromosome in mammals (cats and humans).
• Function: Regulates cellular processes related to pigmentation; active in skin, brain, and hormone-producing tissues.
• X-Linked Inheritance:
  • Males (XY) need only one mutated X chromosome to be orange.
  • Females (XX) need mutations on both X chromosomes for full orange fur; otherwise, they display calico or tortoiseshell patterns.
  • This explains why orange cats are predominantly male.
• Mutation Specifics:
  • A very small (0.005%) deletion outside the known pigment genes activates Arhgap36.
  • This deletion is in a non-coding regulatory region, not altering the gene’s structure.
  • Activation suppresses black pigment production, promoting orange fur pigment instead.
• Unique Mechanism:
  • This mutation mechanism is unique to domestic cats and absent in wild felines.
  • The deletion shifts pigmentation toward lighter, orange hues.