Lipin 1 deficiency causes adult-onset myasthenia with motor neuron dysfunction in humans and neuromuscular junction defects in zebrafish
Journal
Theranostics
Journal Volume
11
Journal Issue
6
Pages
2788-2805
Date Issued
2021
Author(s)
Lu S
Abstract
Lipin 1 is an intracellular protein acting as a phosphatidic acid phosphohydrolase enzyme controlling lipid metabolism. Human recessive mutations in LPIN1 cause recurrent, early-onset myoglobinuria, a condition normally associated with muscle pain and weakness. Whether and how lipin 1 deficiency in humans leads to peripheral neuropathy is yet unclear. Herein, two novel compound heterozygous mutations in LPIN1 with neurological disorders, but no myoglobinuria were identified in an adult-onset syndromic myasthenia family. The present study sought to explore the pathogenic mechanism of LPIN1 in muscular and neural development. Methods: The clinical diagnosis of the proband was compared to the known 48 cases of LPIN1 recessive homozygous mutations. Whole-exome sequencing was carried out on the syndromic myasthenia family to identify the causative gene. The pathogenesis of lipin 1 deficiency during somitogenesis and neurogenesis was investigated using the zebrafish model. Whole-mount in situ hybridization, immunohistochemistry, birefringence analysis, touch-evoke escape response and locomotion assays were performed to observe in vivo the changes in muscles and neurons. The conservatism of the molecular pathways regulated by lipin 1 was evaluated in human primary glioblastoma and mouse myoblast cells by siRNA knockdown, drug treatment, qRT-PCR and Western blotting analysis. Results: The patient exhibited adult-onset myasthenia accompanied by muscle fiber atrophy and nerve demyelination without myoglobinuria. Two novel heterozygous mutations, c.2047A>C (p.I683L) and c.2201G>A (p.R734Q) in LPIN1, were identified in the family and predicted to alter the tertiary structure of LPIN1 protein. Lipin 1 deficiency in zebrafish embryos generated by lpin1 morpholino knockdown or human LPIN1 mutant mRNA injections reproduced the myotomes defects, a reduction both in primary motor neurons and secondary motor neurons projections, morphological changes of post-synaptic clusters of acetylcholine receptors, and myelination defects, which led to reduced touch-evoked response and abnormalities of swimming behaviors. Loss of lipin 1 function in zebrafish and mammalian cells also exhibited altered expression levels of muscle and neuron markers, as well as abnormally enhanced Notch signaling, which was partially rescued by the specific Notch pathway inhibitor DAPT. Conclusions: These findings pointed out that the compound heterozygous mutations in human LPIN1 caused adult-onset syndromic myasthenia with peripheral neuropathy. Moreover, zebrafish could be used to model the neuromuscular phenotypes due to the lipin 1 deficiency, where a novel pathological role of over-activated Notch signaling was discovered and further confirmed in mammalian cell lines. ? The author(s).
Subjects
cell protein; cholinergic receptor; messenger RNA; small interfering RNA; adult; adult onset myasthenia; animal behavior; animal tissue; Article; birefringence; C2C12 cell line; clinical article; demyelination; embryo; embryo development; gene identification; gene knockdown; gene mutation; glioblastoma cell line; heterozygote; human; human cell; immunohistochemistry; in situ hybridization; in vivo study; lipin 1 deficiency; locomotion; LPIN1 gene; motor neuron disease; muscle atrophy; muscle development; muscle function; myasthenia; myoglobinuria; nervous system development; neurologic disease; neuromuscular junction disorder; nonhuman; Notch signaling; pathogenesis; protein deficiency; protein expression; protein tertiary structure; reverse transcription polymerase chain reaction; somitogenesis; swimming; touch evoke escape response; U87 cell line; Western blotting; whole exome sequencing; zebra fish
SDGs
Other Subjects
cell protein; cholinergic receptor; messenger RNA; small interfering RNA; biological marker; LPIN1 protein, human; Notch receptor; phosphatidate phosphatase; adult; adult onset myasthenia; animal behavior; animal tissue; Article; birefringence; C2C12 cell line; clinical article; demyelination; embryo; embryo development; gene identification; gene knockdown; gene mutation; glioblastoma cell line; heterozygote; human; human cell; immunohistochemistry; in situ hybridization; in vivo study; lipin 1 deficiency; locomotion; LPIN1 gene; motor neuron disease; muscle atrophy; muscle development; muscle function; myasthenia; myoglobinuria; nervous system development; neurologic disease; neuromuscular junction disorder; nonhuman; Notch signaling; pathogenesis; protein deficiency; protein expression; protein tertiary structure; reverse transcription polymerase chain reaction; somitogenesis; swimming; touch evoke escape response; U87 cell line; Western blotting; whole exome sequencing; zebra fish; animal; cell line; genetics; glioblastoma; HEK293 cell line; metabolism; motoneuron; mouse; mutation; myoblast; nerve cell; neuromuscular junction; signal transduction; skeletal muscle; tumor cell line; zebra fish; Animals; Biomarkers; Cell Line; Cell Line, Tumor; Glioblastoma; HEK293 Cells; Humans; Mice; Motor Neurons; Muscle, Skeletal; Mutation; Myoblasts; Myoglobinuria; Neuromuscular Junction; Neurons; Phosphatidate Phosphatase; Receptors, Notch; Signal Transduction; Zebrafish
Type
journal article