Phenylketonuria Zebrafish Model
Phenylketonuria Disease Pathology
Phenylketonuria also called PKU, is a rare inherited disorder which is caused by build up of amino acid called phenylalanine in the body. The disease is caused by a defective gene that helps create the enzyme required to break down phenylalanine
Drug development for Phenylketonuria (PKU) has been a challenge due to the heterogeneity of the disease. Several allele specific mutations on a single gene, makes it difficult to identify an effective therapeutic dosage that would be successful in a large patient population. The primary progress of the PKU pathology is an excessive buildup of phenylalanine in the brain causing neuronal damage evident at synaptic-dendritic regions with associated demyelination. It carries wide pathological profile such as cognitive disability, seizures, heart defects and behavioral problems making it difficult to identify a single drug that can address all symptoms. Additionally, large amino acid transport into the brain is impaired leading to impairment of neuronal cellular metabolism.
Overall outcomes of a PKU pathology can be observed as neurobehavioral toxicity with a wide range of cognitive dysfunctions such as depression, anxiety, irritability, poor memory, social disorders, psychosis and attention deficit disorders among others. Therefore, screening PKU models for neuro-behavior toxicity rescue can help identify a potential drug that addresses the wide range of pathology.
Zebrafish as a model for PKU
Zebrafish is a proven animal model for neurobehavioral research because of its ability to accurately replicate human pathophysiology. The enzyme phenylalanine hydroxylase (PAH) is conserved between humans and zebrafish with PAH zebrafish mutants displaying moderate to severe pathology based on the severity of the mutation. Since the prevalence of PKU is a compound heterogenous mutation, scientific team at Pentagrit identified several established mutations in humans and replicated the same heterozygous compound mutant genotypes in the zebrafish larvae. Below are 3 reasons why zebrafish is a validated model for PKU studies
Sequence match between human & zebrafish
Same Mutations in human sequence can be replicated in zebrafish
Enzyme structure and activity is similar between humans & zebrafish
Zebrafish Model Design for Therapeutic Strategies
Heterozygous mutants are created by the CRISPR Cas9 method and local field potential (LFP) screens for brain activity is performed for HIT identification. LFP Signature based HIT identification creates a high-resolution funnel enabling to focus only on promising candidates. Promising candidates can then be screened through a full pathology screen to understand mechanism of action and range of therapeutic rescue.