GTP cyclohydrolase 1 gene 3′-UTR C+243T variant predicts worsening outcome in patients with first-onset ischemic stroke

Genetics of ischemic stroke functional outcome

Ischemic stroke, which accounts for 87% of cerebrovascular accidents, is responsible for massive global burden both in terms of economic cost and personal hardship. Many stroke survivors face long-term disability-a phenotype associated with an increasing number of genetic variants. While clinical variables such as stroke severity greatly impact recovery, genetic polymorphisms linked to functional outcome may offer physicians a unique opportunity to deliver personalized care based on their patient's genetic makeup, leading to improved outcomes. A comprehensive catalogue of the variants at play is required for such an approach. In this review, we compile and describe the polymorphisms associated with outcome scores such as modified Rankin Scale and Barthel Index. Our search identified 74 known genetic polymorphisms spread across 48 features associated with various poststroke disability metrics. The known variants span diverse biological systems and are related to inflammation, vascular homeostasis, growth factors, metabolism, the p53 regulatory pathway, and mitochondrial variation. Understanding how these variants influence functional outcome may be helpful in maximizing poststroke recovery.

Molecular and metabolic bases of tetrahydrobiopterin (BH4) deficiencies

Tetrahydrobiopterin (BH4) deficiency is caused by genetic variants in the three genes involved in de novo cofactor biosynthesis, GTP cyclohydrolase I (GTPCH/GCH1), 6-pyruvoyl-tetrahydropterin synthase (PTPS/PTS), sepiapterin reductase (SR/SPR), and the two genes involved in cofactor recycling, carbinolamine-4α-dehydratase (PCD/PCBD1) and dihydropteridine reductase (DHPR/QDPR). Dysfunction in BH4 metabolism leads to reduced cofactor levels and may result in systemic hyperphenylalaninemia and/or neurological sequelae due to secondary deficiency in monoamine neurotransmitters in the central nervous system. More than 1100 patients with BH4 deficiency and 800 different allelic variants distributed throughout the individual genes are tabulated in database of pediatric neurotransmitter disorders PNDdb. Here we provide an update on the molecular-genetic analysis and structural considerations of these variants, including the clinical courses of the genotypes. From a total of 324 alleles, 11 are associated with the autosomal recessive form of GTPCH deficiency presenting with hyperphenylalaninemia (HPA) and neurotransmitter deficiency, 295 GCH1 variant alleles are detected in the dominant form of L-dopa-responsive dystonia (DRD or Segawa disease) while phenotypes of 18 alleles remained undefined. Autosomal recessive variants observed in the PTS (199 variants), PCBD1 (32 variants), and QDPR (141 variants) genes lead to HPA concomitant with central monoamine neurotransmitter deficiency, while SPR deficiency (104 variants) presents without hyperphenylalaninemia. The clinical impact of reported variants is essential for genetic counseling and important for development of precision medicine.

Nucleotide Variants of the BH4 Biosynthesis Pathway Gene GCH1 and the Risk of Orofacial Clefts

A deficiency of GTP cyclohydrolase, encoded by the GCH1 gene, results in two neurological diseases: hyperphenylalaninaemia type HPABH4B and DOPA-responsive dystonia. Genes involved in neurotransmitter metabolism and motor systems may contribute to palatogenesis. The purpose of the study was to analyse polymorphic variants of the GCH1 gene as risk factors for non-syndromic cleft lip with or without cleft palate (NSCL/P). Genotyping of nine polymorphisms was conducted in a group of 281 NSCL/P patients and 574 controls. The GCH1 variant rs17128077 was associated with a 1.7-fold higher risk for NSCL/P (95 %CI = 1.224-2.325; p = 0.001). We also found a significant correlation between the rs8004018 and rs17128050 variants and an increased risk of oral clefts (p trend = 0.003 and 0.004, respectively). The best evidence of the global haplotype association was observed for rs17128050 and rs8004018 (p corr = 0.0152). This study demonstrates that the risk of NSCL/P is associated with variants of the GCH1 gene related to BH4 metabolism and provides some evidence of the relationships between morphological/functional shifts in the central nervous system and orofacial clefts.