HFE Iron Loading Gene Linked to MN

Membranous Nephropathy (MN) is a kidney disease that is caused by an abnormal build up of immune proteins in the part of the kidney filter known as the glomerular “basement membrane.” This part of the glomerulus is the thin bit of tissue that helps separate the blood from the urine. In MN, the basement membrane becomes thick and damaged, allowing large amounts of protein to leak out of the blood and into the urine. Often the underlying cause of MN is not known (idiopathic), but it can be associated with other conditions.

High Fe (HFE) has been identified as one possible contributor to the damage of the basement membrane. HFE is a “protein coding” gene. Protein coding is nearly synonymous with “open reading frame” and “protein coding sequence.” Protein encoding genes are commonly described as structural or regulatory. Structural genes encode enzymes and structural proteins. Regulatory genes encode proteins that function to regulate the expression of other genes, often by binding specifically to short sequences of the DNA. A protein-coding gene consists of a promoter followed by the coding sequence for the protein and then a terminator. The promoter is a base-pair sequence that specifies where transcription begins. The coding sequence is a base-pair sequence that includes coding information for the polypeptide chain specified by the gene. The terminator is a sequence that specifies the end of the mRNA transcript.

Diseases associated with the HFE protein coding gene include microvascular complications of diabetes and hemochromatosis. Related pathways include removal of Cdc6 and CDK-mediated phosphorylation. The protein encoded by this gene is a membrane protein that is similar to major histocompatibility complex (MHC) class I-type proteins and associates with beta2-microglobulin (beta2M). It is thought that this protein functions to regulate iron absorption by regulating the interaction of the transferrin receptor with transferrin. The iron storage disorder, hereditary hemochromatosis, is a recessive genetic disorder that results from defects in this gene.

In a case study published in 2015, a 55-year-old man was found to have nephrotic range proteinuria (15.7 g/24 h). His renal biopsy demonstrated evidence of membranous glomerulonephritis and increased iron deposition. At this juncture, a serum ferritin was checked which showed an initial value 933 µg/L with transferrin saturation at 96.6%. A subsequent liver biopsy also showed evidence of iron overload but without fibrotic changes. He was subsequently treated with interval venesection which was associated with significant symptomatic and biochemical evidence of improvement in oedema and proteinuria.

The link between HFE and MN is being studied further and The Halpin Foundation is interested in receiving proposals from researchers and clinicians to advance our understanding the causation and possible treatments.

Sources:
rarediseasesnetwork.org/cms/neptune/Learn-More/Disorder-Definitions
nmpdr.org/FIG/wiki/view.cgi/FIG/ProteinEncodingGene
phschool.com/science/biology_place/biocoach/transcription/procodgn.html
genecards.org/cgi-bin/carddisp.pl?gene=HFE
casereports.bmj.com/content/2015/bcr-2014-204830