Being Merle: The Molecular Genetic Background of the Canine Merle Mutation

Area of Science:

• Genetics
• Molecular Biology
• Coat Color Genetics

Background:

• The merle pattern in canine coat color is a complex trait.
• The PMEL17 gene plays a crucial role in melanogenesis and pigment production.
• Understanding the genetic basis of coat color variation is important for breed standards and genetic research.

Purpose of the Study:

• To elucidate the molecular mechanism determining the intensity of the merle pattern.
• To investigate the role of a specific repeat element and its poly(A) tail in PMEL17 gene regulation.
• To correlate poly(A) tail length with PMEL protein function and eumelanin deposition.

Main Methods:

• Analysis of a repeat element inserted at the intron 10-exon 11 boundary of the PMEL17 locus.
• Investigation of poly(A) tail length variation as a microsatellite.
• Examination of alternative splicing events regulated by poly(A) tail length.
• Correlation of protein structure with eumelanin production and coat color.

Main Results:

• The intensity of the merle pattern is directly influenced by the length of a poly(A) tail associated with a repeat element in the PMEL17 gene.
• Longer poly(A) tails lead to aberrant splicing, resulting in abnormal PMEL protein and reduced eumelanin, causing lighter coat colors.
• Shorter poly(A) tails permit normal splicing and PMEL production, contributing to darker coat colors.
• Somatic mutations in this locus can create patterned clones, while germline mutations can lead to unexpected offspring color variations.

Conclusions:

• The length of the poly(A) tail of the PMEL17 repeat element is a key determinant of merle pattern intensity.
• Replication slippage and alternative splicing are critical mechanisms underlying coat color variation.
• This finding provides a molecular explanation for the merle phenotype and its variability.