The IFNL1 gene encodes Interferon-Lambda 1, a type III interferon belonging to the helical cytokine family. As an interferon, IFNL1 has antiviral, antitumor and immunomodulatory activities. Specifically, the interferon acts as a ligand for a cytokine receptor thereby activating the JAK/STAT signal cascade and promoting the expression of IFN-stimulated genes. It promotes the production of MHC class I antigens and interferon-gamma, and inhibits the production of interleukin-5 and interleukin-13.
However, the activities of IFNL1 are limited to certain targets due to the restricted distribution of its receptor IFNLR1. The IFNLR1 receptor is expressed specifically in epithelial cells and hence IFNL1 activity is primarily seen in these cells.
The IFNL1 gene, located on the long arm of chromosome 19, spans a length of just 2.3 kb of DNA. Its coding sequence is contained within 5 exons and it encodes a 21.8 kDa protein product composed of 200 amino acids. Expression of the gene is highly upregulated in virus-infected cells.
Monies et al. (2017) reported the findings of 1000 diagnostic panels and exomes carried out at a next generation sequencing lab in Saudi Arabia. One patient, a 2-year-old female, presented with a failure to thrive, microcephaly, fine and gross motor delay, speech delay, agenesis of the corpus callosum, migration disorder, hypotonia, scoliosis, absent thumb, IUGR, external ear malformation, epilepsy and skeletal abnormalities. Using whole exome sequencing, a mutation (c.305T>C, p.L102P) was identified in exon 3 of the patient’s IFNL1 gene. This gene mutation was considered a candidate for pathogenicity as it was a novel variant located within a run of homozygosity and was predicted to be deleterious; and the IFNL1 protein was involved in DNA damage repair. The authors hoped that further studies would help confirm this association.
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