# Discovering Intron Gain Events in Humans Through Large-Scale Evolutionary Comparisons

## TL;DR

This study identifies new introns in human genes by comparing genomes across vertebrates, revealing recent evolutionary changes.

## Contribution

The paper introduces a method to trace recent intron gain events in humans using large-scale genomic comparisons.

## Key findings

- 342 intron gain events were identified in 293 human genes, all relatively recent in evolutionary terms.
- Three cases of intronization were found, where exonic sequences in other vertebrates became introns in humans.
- The study compares human protein sequences and structures with homologous genes lacking the introns.

## Abstract

The rapid growth in the number of sequenced genomes makes it possible to search for the appearance of entirely new introns in the human lineage. In this study, we compared the genomic sequences for 19,120 human protein-coding genes to a collection of 3,493 vertebrate genomes, mapping the patterns of intron alignments onto a phylogenetic tree. This mapping allowed us to trace many intron gain events to precise locations in the tree, corresponding to distinct points in evolutionary history. We discovered 342 intron gain events, all of them relatively recent, in 293 distinct human genes. Among these events, we explored the hypothesis that intronization was the mechanism responsible for intron gain. Intronization events were identified by locating instances where human introns correspond to exonic sequences in homologous vertebrate genes. Although apparently rare, we found three compelling cases of intronization, and for each of those, we compared the human protein sequence and structure to homologous genes that lack the introns.