Knockdown of pnpla6 protein results in motor neuron defects in zebrafish

Abstract

SUMMARYMutations in patatin-like phospholipase domain containing 6 (PNPLA6), also known as neuropathy target esterase (NTE) or SPG39, cause hereditary spastic paraplegia (HSP). Although studies on animal models, including mice and Drosophila, have extended our understanding of PNPLA6, its roles in neural development and in HSP are not clearly understood. Here, we describe the generation of a vertebrate model of PNPLA6 insufficiency using morpholino oligonucleotide knockdown in zebrafish (Danio rerio). Pnpla6 knockdown resulted in developmental abnormalities and motor neuron defects, including axon truncation and branching. The phenotypes in pnpla6 knockdown morphants were rescued by the introduction of wild-type, but not mutant, human PNPLA6 mRNA. Our results also revealed the involvement of BMP signaling in pnpla6 knockdown phenotypes. Taken together, these results demonstrate an important role of PNPLA6 in motor neuron development and implicate overexpression of BMP signaling as a possible mechanism underlying the developmental defects in pnpla6 morphants.

Neuropathy target esterase impairments cause Oliver–McFarlane and Laurence–Moon syndromes

“…Injection of pnpla6 MO in single cells postfertilisation resulted in larvae with curved tails as well as small heads and eyes as previously described 29. The phenotypes were grossly scored in 48 h posthatching zebrafish embryos into four categories: (i) normal, (ii) mild with small head and eyes, (iii) intermediate additionally had distal tail curvature and (iv) severe had full tail and body curvature in addition to small head and eyes (figure 4A–D).…”

“…Control and PNPLA6 translation blocking (5′-ctgtgtccgatgtgctctgtcccat-3′)29 morpholinos (MOs) were injected in WT zebrafish embryos at one-to-two-cell stage. Rescue experiments were conducted with 100 pg human PNPLA6 mRNA and 2.5 ng MO.…”

Compound heterozygous PNPLA6 mutations cause Boucher–Neuhäuser syndrome with late-onset ataxia

“…Interestingly, while PLA2G6 mutations have been reported to cause infantile neuroaxonal dystrophy, atypical parkinsonism, and neurodegeneration with brain iron accumulation, PNPLA6 mutations have been typically related to hereditary spastic paraplegia, and, more recently, ataxia [6, 8, 15, 16]. Although these phenotypic heterogeneities are often seen in genes involved in diseases of the central nervous system [17], it is likely that this broad clinical spectrum relates to the complex role of the patatin-like domain within the brain, which is involved in brain lipid metabolism, neuronal development, intracellular membrane trafficking, and axon maintenance, among others [18, 19]. Given that lipid metabolism is a highly preserved function among species and tissue types, the multisystem effects of PNPLA6 mutations are not surprising.…”

Swiss Cheese, Drosophila Ortholog of Hereditary Spastic Paraplegia Gene NTE, Maintains Neuromuscular Junction Development and Microtubule Network

“…Mice without NTE neuronal expression develop a phenotype similar to sws mutants, including vacuolization, myelin production, and neuronal death [11]. NTE knockdown in zebra ish leads to development defects, axon shortening, and reduction of axonal arborization [12]. There have been many studies dedicated to NTE/sws; however, we still do not know much about their exact roles in the development and functioning of the nervous system.…”