The PKD2 gene encodes a membrane protein that functions as a large-conductance nonselective calcium-permeable cation channel. In renal epithelial cells, this channel is involved in calcium ion transport and calcium signaling. The protein is also found in primary cilia, where it functions in mechanosensation of fluid flow and in response, stimulates an increase in intracellular calcium. By carrying out its functions, the PKD2 protein is found to be involved in cell proliferation, tubule development and normal kidney functioning.
The gene has been implicated in Polycystic Kidney Disease 2 (PKD2), a progressive renal disorder characterized by cysts on the kidney and liver, renal insufficiency and urinary tract infections.
The PKD2 gene is located on the short arm of chromosome 19. It spans a length of 70.1 kb of DNA and its coding sequence is spread across 16 exons. The gene encodes a 109.6 kDa protein product composed of 968 amino acids. Several isoforms of the PKD2 gene exist due to alternatively spliced transcript variants. The gene is strongly expressed in the ovary, testis, small intestine as well as the fetal and adult kidney. Heterozygous mutations in the gene are associated with PKD2. More than 75 PKD2 gene mutations have been identified in affected patients, including transitions, insertions and deletions that result in a truncated non-functional PKD2 protein.
Monies et al. (2017) discussed 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 male, presented with bilateral nephrolithiasis. He also reported a family history of this phenotype. Using a multigene panel for renal disorders, a heterozygous mutation (c.567G>A, p.W189X) was identified in exon 1 of the patient’s PKD2 gene, associated with polycystic kidney disease 2. The case highlighted the importance of molecular testing, as identification of the PKD2 variant led to a highly altered course of disease management. Also, given his unusually early presentation, the case helped in the phenotypic expansion of polycystic kidney disease.
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