# Phenotypic study of humanized mice carrying the PAH deep intronic variant c.1199+502A>T

## TL;DR

Scientists created the first mouse model with a specific genetic mutation linked to phenylketonuria (PKU), showing classic PKU traits and cognitive issues.

## Contribution

The first humanized mouse model with a deep intronic PAH variant causing PKU is developed and characterized.

## Key findings

- Mice with the c.1199+502A>T mutation showed classical PKU traits like high phenylalanine and yellow fur.
- The mutant mice had impaired spatial learning and memory compared to wild-type controls.
- This model provides a new tool for studying PKU pathogenesis and treatment.

## Abstract

The c.1199 + 502 A > T variant of the phenylalanine hydroxylase (PAH) gene, which is the most frequently reported deep intronic variant involved in phenylketonuria (PKU), is mainly observed in patients with classical or mild PKU. Prior to this study, no mouse models of PKU featuring deep intronic variants of PAH had been reported.

To phenotypically simulate the pathogenicity of this variant, we used CRISPR/Cas9 genome editing technology and homologous recombination to generate homozygous PKU model mice with a partially humanized Pah gene incorporating human PAH exons 11–12 carrying c.1199 + 502 A > T or wild-type (c.1199 + 502WT) control sequences.

Humanized homozygous Pah c.1199 + 502 A > T mice exhibited a classical PKU phenotype, including a higher serum phenylalanine concentration, yellowing of the fur, and other traits. The homozygous mutant group had poorer spatial learning and spatial memory compared with the wild-type group.

This construction of the first humanized mice carrying a deep intronic variant of PAH provides a new animal model for the pathogenesis and treatment of PKU, and may serve as a reference for future research on the pathogenicity of deep intronic variation.