The ASIP gene in the llama (Lama glama): Alternative transcripts, expression and relation with color phenotypes

Area of Science:

• Genetics
• Mammalian Genetics
• Molecular Biology

Background:

• The Agouti gene (ASIP) is crucial for mammalian coat color determination.
• ASIP exhibits complex transcriptional regulation via multiple promoters and alternative non-coding first exons, leading to diverse mRNA isoforms and pigmentation patterns.

Purpose of the Study:

• To investigate ASIP transcriptional variants and their expression in llamas with varying coat colors.
• To characterize the ASIP locus, including promoter utilization and splicing events, in llamas.

Main Methods:

• Utilized 5'RACE-PCR to identify ASIP transcripts and their 5' untranslated regions (5'UTRs).
• Analyzed ASIP expression levels in llama skin tissues representing different coat color phenotypes.
• Investigated novel splicing events and promoter usage within the ASIP locus.

Main Results:

• Identified seven ASIP transcripts with alternative 5'UTRs, including novel exon 1A", and new alternative spliced forms.
• Observed high ASIP expression in white and brown llamas, contrasting with very low expression in black llamas.
• Discovered a fusion transcript between ASIP and NCOA6 in white and brown llamas, absent in black llamas, identified as the primary driver of expression differences.

Conclusions:

• ASIP gene expression in llamas is predominantly regulated at the transcriptional level.
• The diversity of ASIP 5'UTRs suggests potential post-transcriptional regulation of protein synthesis.
• A novel ASIP-NCOA6 fusion transcript is a key determinant of coat color variation in llamas.