Although the clinical presentation of PLA2G6-associated neurodegeneration was reported to be homogeneous, our findings suggest patients with PLA2G6 mutation could show heterogeneous phenotype such as dystonia-parkinsonism, dementia, frontotemporal atrophy/hypoperfusion, with or without brain iron accumulation.
The 2 major types of neurodegeneration with brain iron accumulation (NBIA) are the pantothenate kinase type 2 (PANK2)-associated neurodegeneration (PKAN) and NBIA2 or infantile neuroaxonal dystrophy (INAD) due to mutations in the phospholipase A2, group VI (PLA2G6) gene.
Phospholipase A2 group VI (PLA2G6)-associated neurodegeneration (PLAN) includes a series of neurodegenerative diseases that result from the mutations in <i>PLA2G6</i>.
Therefore, we investigate glutamate (Glu)-evoked Ca<sup>2+</sup> signals in neurons and astrocytes in co-culture obtained from three INAD mouse model strains with Pla2g6 mutations, (i) hypomorphic Pla2g6 allele with reduced transcript levels, (ii) knocked-out Pla2g6, and (iii) (G373R)-point mutation with inactive VIA iPLA<sub>2</sub> enzyme.
About 85% of INAD patients carry mutations in the PLA2G6 gene that encodes for a Ca(2+)-independent phospholipase A(2) (VIA iPLA(2)), but how these mutations lead to disease is unknown.
We describe the clinical phenotypes, neuroimaging features and PLA2G6 mutations in 5 children, of whom 4 presented with infantile neuroaxonal dystrophy (INAD).
Mutations in PLA2G6 have been associated with disorders such as infantile neuroaxonal dystrophy, neurodegeneration with brain iron accumulation type II and Karak syndrome.
We mapped a locus for infantile neuroaxonal dystrophy (INAD) and neurodegeneration with brain iron accumulation (NBIA) to chromosome 22q12-q13 and identified mutations in PLA2G6, encoding a calcium-independent group VI phospholipase A2, in NBIA, INAD and the related Karak syndrome.
Thus, our findings bring new insight into molecular mechanism affected in INAD and highlight the non-canonical function of VIA iPLA2 in regulation of mitochondrial Ca(2+) handling.
In the PLA2G6 knockout (KO) mouse, which is an excellent PLAN model, specific membrane degeneration takes place in neurons and their axons, and this is followed by axonal spheroid formation.