HIF1A: A Putative Modifier of Hemochromatosis.

Sara Pelucchi,Alberto Piperno,Mario Mauri,Raffaella Mariani,Rocco Piazza,Giulia Ravasi,Cristina Arosio

doi:10.3390/ijms22031245

Abstract

HFE-related hereditary hemochromatosis (HH) is characterized by marked phenotypic heterogeneity. Homozygosity for p.C282Y is a low penetrance genotype suggesting that the HFE-HH is a multifactorial disease resulting from a complex interaction involving a major gene defect, genetic background and environmental factors. We performed a targeted NGS-based gene panel to identify new candidate modifiers by using an extreme phenotype sampling study based on serum ferritin and iron removed/age ratio. We found an increased prevalence of the HIF1A p.Phe582Ser and p.Ala588Thr variants in patients with a severe iron and clinical phenotype. Accordingly, Huh-7 cells transfected with both variants showed significantly lower HAMP promoter activity by luciferase assay. The qRT-PCR assays showed a downregulation of hepcidin and an upregulation of the HIF1A target genes (VEGF, HMOX, FUR, TMPRSS6) in cells transfected with the HIF1A-P582S vector. We identified mutations in other genes (e.g., Serpina1) that might have some relevance in single cases in aggravating or mitigating disease manifestation. In conclusion, the present study identified HIF1A as a possible modifier of the HFE-HH phenotype cooperating with the genetic defect in downregulating hepcidin synthesis. In addition, this study highlights that an NGS-based approach could broaden our knowledge and help in characterizing the genetic complexity of HFE-HH patients with a severe phenotype expression.

Highlights

Type 1 hemochromatosis (HH) is the most common inherited iron overload disorders in Caucasians, and homozygosity for the p.Cys282Tyr mutation of the HFE gene is the most frequent disease-causing genotype
Acquired factors may influence the HH phenotypes [2,3] and there is evidence that variants in genes involved in hepcidin regulation, iron uptake and transport, and other genes not directly linked to iron metabolism, e.g., SERPINA1, HP, GNPAT
Were obtained from three independent experiments conducted in triplicate

Summary

Introduction

Type 1 hemochromatosis (HH) is the most common inherited iron overload disorders in Caucasians, and homozygosity for the p.Cys282Tyr mutation of the HFE gene is the most frequent disease-causing genotype. Acquired factors may influence the HH phenotypes [2,3] and there is evidence that variants in genes involved in hepcidin regulation, iron uptake and transport, and other genes not directly linked to iron metabolism, e.g., SERPINA1, HP, GNPAT and PCSK7 might modulate the expression of the disease [4,5,6,7,8,9,10,11]. None of the polymorphic variants identified to date in candidate-gene and genome-wide association studies emerged as major modifiers of HH phenotype.

Methods

Results

Conclusion