PLA2G5 — Phospholipase A2 Group V

The PLA2G5 gene provides instructions for making an enzyme called phospholipase A2 group V. This enzyme is involved in breaking down certain fats (phospholipids) in cell membranes, which helps produce molecules important for inflammation and other cellular processes. It plays a role in maintaining the normal function and health of various tissues, including the retina in the eye. When there are mutations in the PLA2G5 gene, it can lead to a condition known as benign familial fleck retina. In this condition, small, yellow-white spots or "flecks" appear in the back of the eye (the retina). These flecks are thought to be caused by an abnormal buildup of certain fats due to the enzyme not working properly. Fortunately, despite the unusual appearance of the retina, people with benign familial fleck retina typically do not experience any vision loss or other eye problems. The condition is considered "benign" because it does not usually affect a person's ability to see clearly or cause other health issues. Therefore, while the gene mutation changes how the retina looks, it generally does not impact overall vision or health.

Gene description: The PLA2G5 gene encodes a secretory calcium-dependent phospholipase A2 enzyme that hydrolyzes membrane phospholipids to generate lysophospholipids and free fatty acids. Mutations in this gene are associated with benign familial fleck retina, a condition characterized by distinctive retinal lesions without significant visual impairment.

Patient and family guide: The PLA2G5 gene provides instructions for making an enzyme called phospholipase A2 group V. This enzyme is involved in breaking down certain fats (phospholipids) in cell membranes, which helps produce molecules important for inflammation and other cellular processes. It plays a role in maintaining the normal function and health of various tissues, including the retina in the eye. When there are mutations in the PLA2G5 gene, it can lead to a condition known as benign familial fleck retina. In this condition, small, yellow-white spots or "flecks" appear in the back of the eye (the retina). These flecks are thought to be caused by an abnormal buildup of certain fats due to the enzyme not working properly. Fortunately, despite the unusual appearance of the retina, people with benign familial fleck retina typically do not experience any vision loss or other eye problems. The condition is considered "benign" because it does not usually affect a person's ability to see clearly or cause other health issues. Therefore, while the gene mutation changes how the retina looks, it generally does not impact overall vision or health.

Gene function: The PLA2G5 gene encodes a secretory calcium-dependent phospholipase A2 that primarily targets extracellular phospholipids. It catalyzes the hydrolysis of the ester bond of the fatty acyl group attached at the sn-2 position of phospholipids, preferentially releasing fatty acyl groups such as arachidonic acid. This enzyme plays a role in various cellular processes, including lipid metabolism, inflammation, and macrophage polarization.

Protein structure: The PLA2G5 protein is a secretory phospholipase A2 that contains a catalytic domain characteristic of this enzyme family. Its structure includes several alpha-helices and beta-sheets, forming a stable fold that accommodates a calcium ion essential for its catalytic activity. The active site is highly conserved among secreted phospholipase A2s.

Molecular function: The encoded protein, phospholipase A2 group V, functions as a calcium-dependent hydrolase. It specifically targets the sn-2 position of glycerophospholipids, catalyzing the release of free fatty acids (such as arachidonic acid) and lysophospholipids. This enzymatic activity is crucial for the production of lipid mediators involved in inflammatory responses and cellular signaling. The protein also exhibits calcium ion binding and lipid binding capabilities, which are essential for its interaction with cell membranes and subsequent catalytic function.

Mutation spectrum: The mutation spectrum for PLA2G5 includes missense and nonsense mutations. For example, a homozygous missense mutation (c.133G>T, p.Gly45Cys) and a homozygous nonsense mutation (c.185G>A, p.Trp62X) have been identified in patients with benign fleck retina. Compound heterozygous mutations have also been reported.

Clinical significance: Mutations in the PLA2G5 gene are responsible for benign familial fleck retina, an autosomal recessive condition. The disease is characterized by a striking pattern of diffuse, yellow-white, fleck-like lesions extending to the far periphery of the retina but sparing the foveal region. Despite the abnormal retinal appearance, affected individuals are typically asymptomatic and show no apparent visual or electrophysiological deficits. The exact mechanism by which PLA2G5 mutations lead to these retinal flecks is not fully understood, but it is believed to involve abnormal lipid metabolism and accumulation in the retinal pigment epithelium.

Inheritance: Autosomal Recessive

Chromosomal location: 1p36.13

Research and therapeutic approaches: Currently, there are no specific gene therapies or targeted treatments available for benign familial fleck retina caused by PLA2G5 mutations. Because the condition is benign and patients are typically asymptomatic with normal vision, treatment is generally not necessary. Management primarily involves routine eye examinations to monitor the retinal appearance and ensure no other vision issues develop.