# A Comprehensive Allele Specific Expression Resource for the Equine Transcriptome

## TL;DR

This study creates a detailed resource on gene expression differences in horse tissues, revealing how genetic variations affect gene activity.

## Contribution

The novel contribution is a comprehensive ASE resource for horses, highlighting regulatory variation across tissues.

## Key findings

- 635 allele-specific expression events were identified across 9 equine tissues.
- Liver tissue showed the highest proportion of ASE events.
- 97% of validated variants in liver samples demonstrated ASE.

## Abstract

Allele-specific expression (ASE) analysis provides a nuanced view of cis-regulatory mechanisms affecting gene expression.

An equine ASE analysis was performed, using integrated Iso-seq and short-read RNA sequencing data from four healthy Thoroughbreds (2 mares and 2 stallions) across 9 tissues from the Functional Annotation of Animal Genomes (FAANG) project. Allele expression was quantified by haplotypes from long-read data, with 42,900 allele expression events compared. Within these events, 635 (1.48%) demonstrated ASE, with liver tissue containing the highest proportion. Genetic variants within ASE events were in histone modified regions 64.2% of the time. Validation of allele-specific variants, using a set of 66 equine liver samples from multiple breeds, confirmed that 97% of variants demonstrated ASE.

This valuable publicly accessible resource is poised to facilitate investigations into regulatory variation in equine tissues. Our results highlight the tissue-specific nature of allelic imbalance in the equine genome.