Early-onset behavioral and neurochemical deficits in the genetic mouse model of phenylketonuria

Abstract

Phenylketonuria (PKU) is one of the most common human inborn errors of metabolism, caused by phenylalanine hydroxylase deficiency, leading to high phenylalanine and low tyrosine levels in blood and brain causing profound cognitive disability, if untreated. Since 1960, population is screened for hyperphenylalaninemia shortly after birth and submitted to early treatment in order to prevent the major manifestations of the disease. However, the dietetic regimen (phenylalanine free diet) is difficult to maintain, and despite the recommendation to a strict and lifelong compliance, up to 60% of adolescents partially or totally abandons the treatment. The development and the study of new treatments continue to be sought, taking advantage of preclinical models, the most used of which is the PAHenu2 (BTBR ENU2), the genetic murine model of PKU. To date, adult behavioral and neurochemical alterations have been mainly investigated in ENU2 mice, whereas there are no clear indications about the onset of these deficiencies. Here we investigated and report, for the first time, a comprehensive behavioral and neurochemical assay of the developing ENU2 mice. Overall, our findings demonstrate that ENU2 mice are significantly smaller than WT until pnd 24, present a significant delay in the acquisition of tested developmental reflexes, impaired communicative, motor and social skills, and have early reduced biogenic amine levels in several brain areas. Our results extend the understanding of behavioral and cerebral abnormalities in PKU mice, providing instruments to an early preclinical evaluation of the effects of new treatments.

Long-term dietary intervention with low Phe and/or a specific nutrient combination improve certain aspects of brain functioning in phenylketonuria (PKU)

“…In our current study, we introduced the SNC supplementation and low-Phe conditions at PND 31. At this time point, the maturation of the brain and the characteristic behavior in mice is thought to represent the early adolescent stage in humans [ 19 ] and, in BTBR PKU mice, this time point is after the onset of the behavioral and neurochemical deficits [ 20 ]. The introduction of our nutritional intervention would, therefore, surpass the early prevention window of PKU treatment to prevent cognitive disabilities, which is inherent to the PKU mouse model where early intervention would be complex, as the pups continue to drink with their dam until weaning and any nutritional intervention to the pups would be highly stressful.…”

AAV-Mediated CRISPR/Cas9 Gene Editing in Murine Phenylketonuria

“…Pah enu2/enu2 homozygotes exhibit all of the symptoms of classical untreated human PKU, including a blood phenylalanine concentration > 2,000 mM while consuming normal mouse chow, hypopigmentation, and associated neuropathology, resulting in cognitive and behavioral deficits. [25][26][27]…”

The Pah-R261Q mouse reveals oxidative stress associated with amyloid-like hepatic aggregation of mutant phenylalanine hydroxylase

“…The blood L-Phe level in Pah-R261Q corresponds to very mild HPA in human subjects. In contrast to the Enu2 PKU mouse model, which presents weight and length reduction, hypopigmentation, behavioral, and neurological problems 26 , Pah-R261Q were no different from their heterozygote and WT counterparts in length, pigmentation, and behavior. Three-month-old male Pah-R261Q mice, however, were weightier than their WT counterparts (27.8 ± 0.4 vs. 25.1 ± 0.3 g, respectively) (Fig.…”