A mouse TRAPP-related protein is involved in pigmentation

Area of Science:

• Genetics
• Cell Biology
• Developmental Biology

Background:

• Melanosome biogenesis is crucial for pigmentation and involves complex vesicle trafficking pathways.
• The TRAPP (transport protein particle) complexes are known regulators of intracellular vesicle transport.
• Understanding the specific roles of TRAPP subunits in mammalian systems, particularly in pigment cell development, remains an active area of research.

Purpose of the Study:

• To identify and characterize a novel spontaneous mouse mutation affecting coat and eye pigmentation.
• To elucidate the genetic basis of the mosaic hypopigmentation (mhyp) phenotype.
• To investigate the role of the identified gene in melanosome biogenesis and vesicle trafficking.

Main Methods:

• Forward genetic screen using a retroviral mutagenesis approach in mice.
• Positional cloning and gene sequencing to identify the mutated gene.
• Analysis of coat pigmentation, retinal histology, and melanosome morphology.
• Quantitative analysis of gene expression levels in mutant versus wild-type tissues.

Main Results:

• A novel recessive mutation, mhyp, causing mosaic coat and retinal hypopigmentation, was identified.
• The mhyp mutation was mapped to mouse chromosome 7 and found to be a defect in the Trappc6a gene.
• Expression of TRAPPC6A (trafficking protein particle complex subunit 6A) was significantly reduced in mhyp homozygotes, leading to abnormal melanosomes.
• TRAPPC6A is a subunit of the TRAPP I and II complexes, implicated in ER-to-Golgi and post-Golgi vesicle transport.

Conclusions:

• The study identifies a critical role for mammalian TRAPPC6A in the regulation of vesicle trafficking during melanosome biogenesis.
• The mhyp mouse model provides a valuable tool for studying pigment cell development and related disorders.
• These findings highlight the conserved and specialized functions of TRAPP complexes in eukaryotic intracellular transport.